SAFETY IS THE PREVAILING DIRECTIVE (IEEE 1100-2005,3.1.5)

Dedication

To Dad and Mom and Lynda and Lindsey.For your Guidance, Influence, Inspiration and Memories.

Rich K., August 2006

But to him who's scientificThere is nothing more te"ijic

In the falling ofthe flight ofthunderbolts;Yes, in spite ofall my meekness

IfI have a little weaknessIt's a passion for a flight ofthunderbolts.

- GILBERT AND SULLIVAN, The Mikado

I "Lightning Protection for Engineers" was revised and updated in May 2007 I

INTRODUCTION

by Josephine Covino, PhDChairperson, Lightning Protection Review Committee

Department ofDefense Explosives Safety Boardhttp://www.hqda.army.mil/ddesb/esb.html

Washington DC

In 1926 lightning visited the Naval Ammunition Depot at Lake Denmark NJ. Theincident virtually destroyed the Depot and caused heavy damage to nearby PicatinnyArsenal and surrounding communities. Twenty one people were killed and fifty oneothers injured. Damage to the Navy area alone was $46 million in 1926 dollars.

The problem of lightning safety is not unique to the USA. In June 1998 lightningdestroyed a large Russian Army munitions depot in the Ural mountains, near the villageof Losiniy 30 kIn northeast of Yekaterinburg. At least 14 army personnel including thebase commander were killed and 1300 villagers were evacuated from the area. Sourcesreport that 240 tons ofstores were destroyed. In 2002 at a railyard in Beira, Mozambiquelightning insulted a military explosives depot with considerable damage and injuries.

As an outgrowth of the Lake Denmark event, in 1928 Congress established theDepartment ofDefense Explosives Safety Board (DDESB). 'Since then we have collected55 verifIable lightning-caused accidents in our database. The lightning safety complianceregulation DDESB 6055.9 is mandatory for military explosives installations.

While DDESB takes the lightning issue seriously, for the most part this is not thecase with the commercial and industrial workplace. In Denver in 1996, a refrigeratedwarehouse was struck by lightning and the loss was $55 million. Recent substantiateddata from the National Lightning Safety Institute places annual USA lightning costs andlosses at about $4-5 billion per year. The general public too does not fully appreciatelightning's hazards. Boaters, golfers, school children and people from most other walksoflife too often are victims of lightning.

Education and attention to detail are the keys to lightning safety. LightningProtection For Engineers makes a valuable contribution to the literature for such groupsas specifying architects and engineers, those Authorities Having Jurisdiction, educators,libraries and interested local, state, and federal officials. We all need to improve ourunderstanding oflightning safety issues.

••••••••••••••••••••••••tttttttttttt

•4•44

••

A FEW WORDS ABOUT THE USE OF THIS BOOK.

Lightning protection in an absolute sense is impossible because of the arbitrary,capricious, and stochastic nature of lightning strikes. Some twenty five million ofthem striking in the USA annually each have unique characteristics. The protectionapproach is highly site-specific, with many designs unique to individual facilities andstructures. Mitigation of lightning insults is attempted through the deployment of acombination of exterior and interior defenses. The purpose of this Workbook is todescribe and illustrate those defensive systems as they are applied in varioussituations. When employed in combination, the following sub-systems represent alayered defensive strategy, commonly called a Lightning Protection System (LPS).

Air Terminals - an exterior defense. Lightning usually terminates on grounded objectssticking up in the air. Franklin rods are air terminals. Overhead steel cables andmetal masts are air terminals. Steel towers are air terminals. Trees are air terminals.In the absence of taller objects, fences and blades of grass are air terminals. OldBen's design developed in 1752 carried lightning from rods in the air via conductorsto rods in the ground. This rod-configuration on buildings was and is based upon thePath of Least Resistance laws of physics. Nowadays, some vendors are promotingunconventional air terminal designs (ESE/DAS/CTS) seeking to gain advantage overcompetitors. Caveat Emptor. Of course, should lightning strike across the street froma protected facility center and couple into sensitive electronics via undergroundwiring, then no air terminals design of any classification has performed its role inprotection.

Grounding -an exterior defense. Low impedance and resistance grounding providesan efficient destination for the Lightning Beast. If site soils are composed of sand orrock they are resistive, not conductive. If surrounding soils are clays or dirt, they maybe conductive. "Good Grounds" are achieved with properly configured volumetricefficiencies. We recommend buried bare 4/0 copper wire - the so called ringelectrode or ring ground. Cadwelding© security fences, tower legs, and otheradjacent metallics to the buried ring will augment the earth electrode sub-system.NEC 250 describes other grounding designs such as rods, plates, water pipes(beware plastic pipes underground), metal frame of bUildings, and concrete-encasedelectrodes. Choose your grounding design based upon localized conditions and theamount of available real estate at your location. NEC 250.56 suggests a target earthresistivity number of 25 ohms. Lower is better.

Bonding - an interior defense. Without proper bonding, all other elements of the LPSare useless. Bonding of all facility incoming metallic penetrations - cables, conduits,pipes and wires - assures all of them are at equal potential. There are many interior"grounds" in modern buildings, such as computer grounds, AC power grounds,

lightning grounds, single point grounds, and multi-point grounds. All must be bondedso as to achieve the same potential. When lightning strikes, all grounded equipmentmust rise and fall equipotentially. This will eliminate the differential voltages inseparate sensitive signal and data systems. Bonding serves to connect all conductorsto the same "Mother Earth." Not convinced bonding is important? Check out NEC250.90 through 250.106 for more details.

Surge Suppression - an interior defense. Surge suppression devices (SPDs) allfunction either by absorbing the transient as heat or crowbaring the transient toground (or some combination thereof). SPDs should be installed at main panelentries, critical branch or secondary panels, and plug-in outlets where low voltagetransformers convert AC power to DC current and voltage. SPDs also ~hould beinstalled at signal and data line facility entry points and at electronic equipment.Telephone punch blocks should be Spo-protected. Beware the junk SPDs whichproliferate the marketplace. Beware counterfeit or false UL and IEEE labeling. Bewareof the "it sounds to good to be true" marketing hype employed by vendors. Insist onCertified Test Results to substantiate performance claims by manufacturers.Consider SPDs which have capabilities to remotely signal their operationalperformance. SPDs rank right behind Bonding in the hierarchy of important steps tomitigate the lightning hazard.

Codes and Standards. There are excellent codes and standards, helpful codes andstandards and superficial codes and standards. No one such document by itselfprovides comprehensive guidance for the lightning protection engineer. Familiaritywith, many recognized codes and standards is vital for competency in lightningproblem-solving.

NlSI Note about Sources: Some of this Workbook is original material and some isreproduced from other sources. Thanks to organizations such as Bellcore, IEEE,Erico, Dehn, MTL, IEC, NFPA, Polyphaser, lPC, MCG, Phoenix Contact, CITEl, APC,Telebyte, IEC, API, ICAE, NOAA, Vaisala, NASA, NCHRP, STC, Motorola, FAA, DOD, DOE,FAA, USGA, IClP, ILDC, ERA and others. Thanks also to individual friends worldwide inacademia, business, government, industry, and the private sector.

••••••••t•••••••••••••••••••••••••••••••I•••

TABLE OF CONTENTS

1. Lightning Physics, Lightning Behavior 1-22And Lightning Safety Overview

2. Risk Assessment 23-40

3. The Grounding and Bonding Imperative 41-76

4. Exterior Lightning Protection for Structures 77-94

5. Interior Lightning Protection for the Electrical 95-114System of a Complex Facility

6. Communications Facilities, Exterior Lightning 115-128Protection

7. Communications Facilities, Interior Lightning 129-150Protection

8. Lightning Protection for High Risk Installations 151-170Containing Sensitive Electronics, Explosives,Munitions or Volatile Fuels

9. International View ofUnconventional Air 171-194Terminals such as "ESE" and "DAS/CTS"

10. Lightning Safety for Outdoor Activities 195-214

11. References, Resources, Codes & Index 215-249

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter One

LIGHTNING PHYSICS,LIGHTNING BEHAVIOR AND

LIGHTNING SAFETY OVERVIEW

Early Creeks beli~ed that lightning W3S the weapon of 'Zeus.

1

Chapter One Overview

Lightning is arbitrary~ capricious~ rando~ stochastic and unpredictable.Science does not fully understand its phenomenology. However,investigations from today~s researchers is considerable.

While lightning creates major upsets and significant dollar losses to theeconomy~ safety from its effects is rarely employed proactively. Absoluteprotection is impossible but deployment of a holistic~ systematic approachcan mitigate the hazards.

In gene~ many errors and misunderstandings dominate lightningprotection efforts. "Lightning never strikes twice" is not correct. "Lightningrods provide safety for people" is not correct. New information slowly isaltering the 19th Centmy Conventional Wisdom.

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THUNDERSTORM CONVECTION PROCESS PRODUCES LIGHTNING

Simplified Version: The Sun evaporates surface moisture, transforming it intoclouds/gas/water vapor. Hot air causes clouds to rise over time. At about -15 C degrees,gas is transformed into solids/ice/hygrometeoriteslgraupuls. High winds (160 kmlhr)tumble the solids, with the collision process/.friction creating static electricity.

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T3: TIme for attaining 90% peak currentrB: Time to drop to 50% of peak current

(after readdng peak value)

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"COLD' LIGHTNING IS A LIGHTNING FLASH WHOSEMAIN RETURN STROKE IS OF INTENSE CURRENT BUT OFSHORT DURATION. "HOT' LIGHTNING INVOLVES LESSERCURRENTS BUT LONGER DURATION. HOT LIGHTNING ISMORE 'APT TO START FIRES. COLD LIGHTNINGGENERALLY HAS MECHANICAL AND/OR EXPLOSIVEEFFECTS.

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National lightningSafety Institute

891 N. Hoover Avelouisville CO 80027

LIGHTNINGLOGNORMALDISTRIBUTION

1% STROKES EXCEED 200,000 A

10% STROKES EXCEED 80,000 A

50% STROKES EXCEED 28,000 A

. .90 % STROKES EXCEED 8,000 A '

99 % STROKES EXCEED 3000 A

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79

SEQUENCE OF STEPS IN TYPICALCLOUD TO GROUND LIGHTNING FLASH

(from Uman, The Lightning Discharge)

PCloud Charge Preliminary SteppedDistribution Breakdown Leader

~~~~~~t= 0 1.00 ms 1.10 ms 1.15 ms 1.20 ms

~.19.00rns 20.10ms 20.15 ms

~20.20ms

60.00ms 61.00ms 62.00ms 62.05ms

National Lightningsafely Institute

891 N. Hoover Avelouisville CO 80027

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BEHAVIOR OF LIGHTNING - PART ONEAs downward Leaders approach earth they may induce electrical andmagnetic signatures upon grounded objects. Grounded objects may respondin stages: 1) accelerated electron behavior; 2) corona emissions; 3) launch ofupward Streamers. When Leaders and Streamers connect, a preferential pathto ground is established. Below are conditions for the Final Jump.

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BEHAVIOR OF LIGHTNING - PART TWOLeaders close to the ground enter a "Cone of Discrimination"where they may choose to strike one or more ground targets.Striking Distance is a function of Peak Current (below). Horvath(1969, 1971) concluded that ground corona current increases inresponse to elevated electric fields. A "glow-to-arc" transitionfrom point discharge (corona) to upward Streamer stage can occurat about 10 to 50 mAo Peak Current is the determining agency.

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11

ATMOSPHERIC CHARGE REDISTRIBUTION (ACR)

Before, during and after lightning strikes toground, highly mobile charged cloud centersredistribute themselves attempting to reachequilibrium with opposing polarity earth charges,including man-made (conductive) structures. ThisACR creates strong electromagnetic fields similar tothose of lightning. ACR can deliver voltage andcurrent surges into conductors similar to those causedby cloud-to-ground lightning.

Inler-planldUIa lines.

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The coupling of lightning transients into sensitive electronics can arise fromdifferent mechanisms as a result of direct and/or indirect (distant) lightning.

RESISTIVE, MAGNETIC FIELD &ELECTRIC FIELD COUPLING

II,IiI

Electric Field CouplingThe nearby lightning stroke contains ahigh electric field which charges electrically­conductive objects like a large capacitor.The air becomes a dielectric mediuni. Highvoltages arise in electrical and signal & dataconductors, even though the structure wasnot directly struck.

Resistive CouplingWhen a facility is struck by lightning,the current flow into the earth usuallygenerates high voltages between .the power supply and the remoteearth. Partial lightning currents thenflow in electrical and signal & dataconductors which are a part of thestructure and which are connected toremote earth.

Magnetic Field CouplingLightning current, flowing either in aconductor or in the lightning channelitself, produces a high magnetic field.Where the magnetic field attaches to-electrical and signal & data conductorsit causes -voltages in loops fonned bythese conductors.

THE LIGHTNING ATTACHMENT PROCESS

When lightning strikes at or nearby to a critical or high valuefacility, stroke currents will divide up among all parallelconductive paths between the attachment point(s) and earth.Division of current will be inversely proportional to the pathimpedance Z, (Z = R + XL, resistance plus inductive reactance).The resistance term will be very low, assuming effectively bondedmetallic conductors. The inductance and corresponding relatedinductive reactance presented to the total return current will bedetermined by the combination of all the individual inductive pathsin parallel-the more parallel paths, the lower the total impedance.

Lightning can be considered current source, Le. outputcurrent is independent of load impedance. A given stroke wi IIcontain a certain amount of charge (coulombs = amps x seconds)that must be neutralized during the discharge process. If the returnstroke is 50 kA, then that is the magnitude of current that will flow,whether it flows through one ohm or 1000 ohms. Therefore,achieving the lowest possible path impedance serves to minimizethe transient voltage developed across the path through which thecurrent is flowi~g [e(t) = I(t)R + L di/dt)].

..A risk management approach to lightning safety must assume

the facility will be struck by lightning. Now what? By adopting ajudicious combination of defenses, the lightning safety engineercan attempt to mitigate lightning's consequences. Since eachfacility is unique, as is each lightning flash, site-specific designsmust be applied. Application of integrated approaches for airterminals, ground terminals, conductors, bonding, shielding, surgeprotection devices, etc. will depend on the geographic location andthe perceived risk to the facility.

National Lightningsafety Institute

891 N. Hoover Ave .Louisville CO 80027

13

Thunderstorm Days Per Year .

Most of Europe 15-40England 5-10Argentina 30-80Colombia

Cerromatoso 275-320Brasil 40-200USA

Florida 90-110Colorado 65-100

Japan 35-50Australia 10-60Malaysia 180-·260Indonesia 180-260

Bogor (1988) 322Singapore 160-220

About 2000 global conti.nuonsThunderstorms deliver about·75-100 strikes/sec. to earth.

National LightningS8fe1Y Institute .

891 N. Hoover AveLouisville CO 80027

"14 ,

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USA FLASH DENSITY MAP "IIIe­liCIIillilltil.tiltil.~

A network of sensors record cloud-to-ground lightning flashes. Approx.efficiencies are: detection of flashes 90% ; distance (ranging) 400-500 ffi.

Operated by National Lightning Detection Network (NLDN) in USA and byother organizations in many other countries.

LITTLE-KNOWN LIGHlNING INFORMATION

1. LIGHTNING PROTECTION SYSTEMS PROVIDE LIMITED PROTECTION.

"What we found out was that the lightning protection system played a limited role in directing currentfrom a lightning strike... [instead] current traveled through the rebar, through concrete, through pipes,through cables, through vent stacks, and through the electrical system..." - Results of rocket­triggered testing sponsored by US Government.

Source: Marvin Morris, Electromagnetic Test and Analysis Dept., as quoted in Sandia Lab News,April 25, 1997, Sandia Natl Lab, Albuquerque NM

2. THE AVERAGE DISTANCE BETWEEN SUCCESSIVE FLASHES IS GREATER THANPREVIOUSLYKNOWN.

Old data said successive flashes were on the order of 3-4 Ian apart. New data shows half the flashesare some 9 Jan apart. The National Severe Storms Laboratory report concludes with arecommendation that: "It appears the safety rules need to be modified to increase the distance ::from aprevious flash which can be considered to be relatively safe, to at least 10 to 13 Ian (6 to 8 miles). Inthe past, 3 to 5 km (2-3 miles) was as used in lightning safety education."

Source: Separation Between Successive Lightning Flashes in Different Storms Systems: 1998, Lopez&Holle, from Proceedings 1998 Intl Lightning Detection Conference, Tucson AZ, November 1998.

3. A mGH PERCENTAGE OF LIGHTNING FLASHES ARE FORKED.

Many cloud-to-ground lightning flashes have forked or multiple attachment points to earth. Testscarried out in both the USA and Japan verify this in at least half of negative flashes and more thanseventy percent of positive flashes have forked characteristics. Many lightning detectors cannotacquire accurate information about these multiple ground lightning attachments.

Source: Termination ofMultiple Stroke Flashes Observed by Electro- Magnetic Field: 1998, Ishii, etal. Proceedings 1998 International Lightning Protection Conference, Birmingham UI< Sept. 1998.

4. LIGHTNING CAN SPREAD OUT SOME 60 FT. UPON STRIKING EARTH'S SURFACE.

Radial horizontal arcing has been measured at least 20 m. :from the point where lightning enters theearth. DePending upon soils characteristics, safe conditions for people and equipment near lightningtennination points (ground rods) may need to be re-evaluated.

Source: 1993 Triggered Lightning Test Program: Environments Within 20 meters of the LightningChannel and Small Are Temporary Protection Concepts: 1993, SAND94-0311, Sandia NationalLaboratory, Albuquerque NM

17

DevelopLightning

Model

DevelopLightningProtection

Requirements

·6-dB Electronics20-dB OrdinanceYes .

DevelopDesign

Requirements

Lightning ProtectionAdequate

Determine InternalEnvironment

(Threat levelsto EQui ment

LocateStrikePoints

Determine ExternalCurrent Paths byTest and Analysis

Implement Designfor Protection FromDirect and Indirect

Effects

DetermineSusceptibilityof Each Pieceof Equipment

Yes

No

THE LIGHTNING PROTECTION PROCESS,per NASA TM... 1999...209734

EquipmentDesign

Restrict OperationWhen Lightning is

Forecast

HOW TO GET TO LIGHTNING SAFETY?

FOR PERSONNEL PROTECTION:

1. LIGHTNING HAZARD ANALYSIS

2. LIGHTING SAFETY POLICY

3. LIGHTNING DETECTION & ACTIVITY SUSPENSION

4. POSTED WARNING SIGNAGE

FOR FACILITY PROTECTION:

1. AIR TERMINALS AND CONDUCTORS TO GROUND

2. GROUNDING DESIGNS FOR LOW IMPEDANCE ACCORDING TOLOCAL SITE REQUIREMENTS.

3. BONDING ALL EXTERIOR AND INTERIOR CONDUCTORS.

4. SURGE PROTECTION TO AC POWER, SIGNAL AND DATA LINES.

5. INSPECTION, MAINTENANCE AND TESTING.

National Lightningsafety Institute

891 N. fioover AveLouisville CO 80027

19

MATRIX OF LIGHTNING PROTECTION SUB-SYSTEMSApply these sub-systems as appropriate (YES or N/A) to specific facilities or structures.

DIRECT INDIRECT EXTERIOR INTERIOR PEOPLE STRUCTURESTRIKE STRIKE LOCATION LOCATION SAFETY SAFETY

AIR TERMINALS YES N/A YES N/A N/A YES

DOWN· YES N/A YES YES N/A YESCONDUCTORS

BONDING YES YES YES YES YES YES

GROUNDING YES YES YES YES YES YES

SHIELDING YES YES YES YES YES YES

SURGE YES YES YES YES YES YESPROTECTION

DETECTION YES . YES YES YES YES YES

POLICIES & YES YES N/A N/A YES YESPROCEDURES

LIGHTNING MITIGATION GUIDELINEThe premise of this Guideline is that lightning will strike our facility.

Lightning cannot be "stopped" or prevented, and in this sense absoluteprotection against it is impossible. A pro-active, systematic approach ofpreparedness is the best defense against lightning consequences.

1. Strike Probability Study.-Historic 5 year lightning data from archives.-Future strike estimates via simulation.

2. Site Inspection.- Identify IlSafeiNot Safe" personnel zones.- Identify potential coupling (DC, capacitiveand inductive) to critical and non-critical areas.

3. Lightning Detection & Personnel Notification.-Define criteria for cessation ofactivities.-Acquire appropriate lightning detectionand signaling devices.

-Integrate decisions into overall Safety Plan.

4. Comprehensive Employee Safety Education.-Provide all affected personnel withdefensive - preparedness information.

5. Grounding Analysis.-Complete e/ectrogeo/ogical model.-Review merits of various grounding options.-Ensure grounds meet target resistance.

6. Air Terminal/Downconductor/Bonding/Shielding.-Evaluate existing system.-Consider design options.-Select & install appropriate devices.

7. Transient Voltage Surge Suppression.-Study all conductive penetrations.-Identify vulnerabilities. Define protective zones.-Install power and signal protection devices.

8. Implement Recommendations.-Verify correct installation ofall devices.-Certify site as having adopted "bestavailable technology" for lightning safety.-Establish site inspection and maintenance programs.

©2006 National Lightning Safety Institute (NLSI), Tel. 303-666-8817.

21

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Two

RIS'K ASSESSMENT

J 01 N. or D I B.

by Benjamin FranklinPennsylvania Gazette May 9. 1754

23

Chapter Two Overview

Risk analysis is interesting. To quote Einstein: "Statistics are useful, so longas you don't believe them."

The risk of lightning to key structures is low, maybe 1:1,000,000. But theconsequences can be very high. Some examples: A cellular phone site istaken off line and revenues cease; A security system fails and critical data isstolen; A E911 call center drops off line and there is no response toemergency calls; AC power is interrupted to a process control operationresulting in wasted product; A data processing center suffers corrupted"One's and Zero's" due to transients causing power anomalies.

Assessing probabilities with lightning issues is a form of gambling. Pay themitigation costs up front, or pay them afterwards. Lightning doesn't care.

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of5

DETERMINING THE PROBABILITY OF LIGHTNINGSTRIKING A FACILITY

By R.T. Hasbrouck, PENational lightning Safety Institute

Revised 4/18/04

One objective of a facility lightning hazard mitigation study is to determine the likelihood of itsbeing struck by lightning. In this article, actual site-specific lightning strike data Is used tocalculate probability.

Estimating ProbabilityThe probablUty of lightning striking a particular object situated on the earth (ground) is found by multiplyingthe object's lightning-attractive area by the local ground-flash density (lightning strikes to ground per km2

per year). The following example considers a low structure surrounded by 12 tall, grounded metal light poles.

caveats: It must be understood that calculations used for determining strike probability are based uponempirical relationships, generally accepted by the research community as reasonably representing thelightning phenomenon. The method presented here provides a reasonable estimate but should not beconsidered the "final word." Other, more complicated geometric methods can be used but, considering thecapricious nature of lightning, it is unlikely they would provide significantly Improved results.

A complete cloud-to-ground lightning event, referred to as a flash, consists of one or more return strokes.Return strokes are hlgh-peak-amplltude (tens to hundreds of thousands of amperes) current pulses, eachlasting for a few hundred microseconds. Analysis of a large quantity of lightning flash data shows the averagenumber of strokes (multiplicity) per negative (the most common type of lightning) flash to be between threeand four. Approximately 25% of all negative flashes- also exhibit several hundred amperes of continuingcurrent during an interval lasting hundreds ofmilliseconds following at least one return stroke. In a givenflash, consecutive return strokes- may strike the ground Within several meters of each other, or as far apart aseight Ian. Analysis ~f data (as reported by Dr. Phil Krider) Indicates that flashes -exhibit- a "random walk,"having a mean interstroke distance of 1.8 km. Ground-flash density data used In this paper is based upon thefirst stroke of each flash-detected by the National Ughtnlng Detection Network (see below)-regardless ofstroke amplitude or flash multiplicity. The author is unaware of any strike probablUty estimates that take Intoaccount the area encompassed by a multi-stroke flash and/or the current-amplitude distribution of stroke~ Inthe flash. Anally, note that the statistically less frequent positive lightning flash usually consists of a singlestroke having average and maximum peak amplitudes that are significantly higher than for negativelightning. It Is accompanied by continuing current and has a total duration as long as one to two seconds.

Cumulative ProbabilityLightning Attractive AreaIf the earth's surface beneath a storm doud were perfectly flat, lightning could be expected to strike any

25

2of5

point on the earth with equal probability. For example, if an area of 0.1 krif experiences a ground-flashdensity of one flash per km2 per year, the probability of its being struck is 0.1 In any given year (a returnfrequency of 10 years per flash). However, a conductive object that is taller than the surrounding areaexhibits a lightning attractive area greater than the ground surface area it occupies. The probability of Itsbeing struck Is a function of its ground surface area, height, and the striking distance between the tip of thedownward-moving stepped leader and the object (Ref. 1). For negative lightning, the stepped leader Is anegatively charged channel that travels In discrete jumps from cloud to Earth,

Striking distance, the stepped leaders final jump to the conductive object, varies with the amount of chargecarried by the channel. (Note: For the sake of simplicity, striking distance calculations don't take Into accountupward-moving, positively-charged streamers. These streamers emanate from conductive objects under theinfluence of the stepped leaders strong electric field-much as hairs rise up toward a statically charged combheld over one's head.) Since the magnitude of this charge also determines return-stroke peak-currentamplitude, greater striking distances are associated with larger amplitude return strokes, i.e., they jumpfarther to reach the object (Ref. 2). Thus, for a given ground surface area and object height, the maximumlightning-attractive area will be associated with the stroke having the largest peak amplitude.

Ground-Flash DensityIn the United States, actual cloud-to.-ground lightning strike data Is detected and archived by the NationalLightning Detection Network (NLDN), Global Atmospherics, Inc. (GAl-Tucson, AZ) analyzes the data andproduces ground-flash density maps for user-specified areas. The map used for this study was based upon29,207 negative and positive flashes-five years (1990-1994) of site-specific data-detected In an area of1.3 x 104f km2• The average overall flash density was 0.45 flashes/km2/yr, ranging from < 0.25 to < 0.5flashes/km2/yr within a 4-km radius of the fadllty.

The following should be taken Into account when considering the GAl data. NLDN detection efficiency(DE)-I.e., the percentage of all lightning flashes that were detected and recorded-improved over thefive-year period during which our data was acquired. Initially, DE was reported as 65-700/0; the currently(1995) stated value is 85-90% (for Ipk > 5 kA). Assuming a five-year DE average of 75% (considered byGAl to be a reasonable estimate) gives a corrected facility flash-density range of < 0.33 to < 0.67. Themedian value of 0.5 flashes/km2/yr was used for our probability calculations.

Two points regarding this value of ground-flash density should be kept In mind. It Is based upon only fiveyears (1990-95) of actual NLDN data-the network was quite new at the time this study was carried out.Analysis of data collected since that time probably would indicate a different value, although It seems doubtfulthat it would differ by very much. Significantly different values of ground-flash density are found in otherparts of the country. However, even locations relatively dose to the area studied could have notably differentvalues because of variations In topography. That Is one of the benefits of NLDN data, the ability to Identifydifferences between wide-area flash-density estimates, and site-speclflc values.

Return-Stroke Peak-Current AmplitudeOver a number of decades, researchers have measured and recorded a variety of lightning parameters, withmuch of the data resulting from strikes to tall, instrumented steel towers. Along with current rate of rise andtotal charge transfer, peak return-stroke current Is considered to be one of lightning's most significant threatparameters. For the generally accepted frequency distribution of peak currents for negative lightning, thefirst-percentile value, 200 leA (I.e., 990/0 of all lightning Is of lower amplitude), Is generally considered toconstitute a severe negative stroke.

Although the NLDN detection efficiency Is less than 100%, GAl reports that it Is low-peak-current (i.e., < 5leA) events that are missed, Thus, had all flashes been detected, the distribution of peak-current amplitudeswould be expected to show a somewhat lower average value.

Facility Lightning Attractive Area

26 -.

t1It1I-.-.tiltiltil----I)--------------@@

fJ~@

~

ff,f

",fff-

ofS

Since the twelve 32-meter-tall perimeter light poles for our study appeared to be likely lightning strikepoints-at least for large-amplitude flashes-they were used In calculating the facility's lightning-attractivearea. For the sake of simplicity, structure height was not included in our equation. It is reasonable to expectthat some low-amplitude strokes will bypass the poles and attach to the structure.

As previously discussed, attractive area must take into account the peak amplitude of return-stroke current.Thus, an attractive area must be calculated for each current amplitude. The following method for dealing withthe distribution of return-stroke currents Is attributed to the late J. Stahmann of Boeing/Kennedy Spacecenter (Ref. 3). Stahmann assigned return-stroke peak currents from a large body of available data todeclles-i.e., 10% of the total number of flashes being considered were placed Into each of ten bins. Themean peak current per decile was then calculated.

Facility Strike ProbabilityStahmann's mean peak-current per decile values were used to find the per-decile attractive area. The effectof the tall light poles on attractive area CAe) can be seen In Table 1. Although the surface area encompassedby the poles is 45*103 m2, the lightning-attractive area is 77*103 m2 for a 6-kA stroke and 171*103 m2 fora 112-kA stroke. The product of attractive area times ground-flash density prOVided per-decile probability,the sum of which gave a cumulative probability. The reciprocal of cumulative probability is the mean returnperiod (average strike frequency). Our study determined that some point of the facility will be struck bylightning-of some amplitude-approximately once every 17 years.

Table 1. Cumulative Probability of Strike to Fadllty

Jpk D. r AA Po Pc R

Decile (leA) (m) (m) (m2) (yr/fI)#

1 6 33 33 76,764 3.8E-03

2 13 S3 48 93,489 4.7E-03

..

3. .18 ..65 56 101,496 s.1E-03

4 23 76 62 108,624 5.4E-03

5 28 88 68 115,399 s.8E-03

6 35 101 74 122,391 6.1E-03

:

7 45 118 81 130,658 6.5E-03

27

28

3. Stahmann, J.R., "Launch Pad Lightning Protection Enhancement by Induced Streamers," Boeing AerospaceOperations, Kennedy Space Center, Rorlda, september 1968.

References1. Golde, R.H., "Proteetlon of Structures Against Lightning," Proceedings of the Institute of ElectricalEngineers, Vol. 115, No. 10, pp. 1523-1529, 1968.

2. Golde, R.H., "The Ughtning Conductor," In Golde, Lightning, Vol. 2, p. 560, Academic Press, london, 1977(the striking distance equation attributed to E.R. love).

S 57 138 89 140,196 7.0E-03

9 77 168 99 153,061 7.6E-03

10 112 215 113 171,380 8.6E-03 6E·02 17

I

f

f

«ttt«~

••••~

t

••••••fifi

•••••••••••••"•..

- 'years/flash

-leA

-m

-m

-m

Area enclosed by light poles: I = 312 m, w =144 m (I x w = 44,928)

h == height of poles above ground level = 32

Ipk = average peak return-stroke current per decile

Os == lightning striking distance =10 x Ipko.65

r =radius of light pole's attractive area = (2 x Os x h - h2)o.5

M == attractive area/decile = (I + 2r) x (w + 2r) - 10 x [(4 • ")/4] x r2Fg = ground flash density =0.5 {using GAl flash density analvsls}

PO == strike probabiJity/dedle == AA x (0.1 x Fg) x 10-6

PC =cumulative probability =I PO

R == mea,n return period (i.e., average strike frequency) =1/PC

ConclusionReasonable strike probability estimates can be made using site-spedflc, ground-flash density values that arebased upon actual lightning data. Strike estimates are Interesting, and although their results provide anIndication of lightning strike return frequency, they should not be considered as absolutes. Perhaps their mostuseful funetlon Is to permit determination of the relative effects of changes made to a facility. Examples ofsuch changes are: increased lightning-attractive area-either by extending the fadlity's surface dimensionsand/or height (adding a vent stack or tower); plating an Identical fadllty In a location having a significantlydifferent ground-flash density.

of5

ANALYSIS OF NEED FOR PROTECTIONWith permission ftom Singapore Standards and Productivity Board

Reproduced from Singapore Standmd CP33: 1996 Lightning Protection

2.1 GENERAL

Before proceeding with the detailed design of a lightning protection system, the followingessential steps should be taken :

(a) It should be decided whether or not the structure needs protection and, if it does whatthe special requirements are (see Clause 2.2 and Section 3).

(b) A close liaison should be ensured between the architect, the builder, the lightningprotection system engineer and the appropriate authorities.

(c) The procedures for testing, commissioning and future maintenance should be agreed.

2.2 NEED FOR PROTECTION

2.2.1 General. Structures with inherent explosive risks, e.g. explosives factories, stores and dumpsand fuel tanks usuaJly need the highest possible class of lightning protection system andrecommendations for protecting such structures are given In Section 5.

For all other structures, the standard of protection recommended in the remainder of this Codeis applicable and the only question remaining is whether protection is necessary or not.

In many cases, the need for protection may be self--evident. for example:

(a) Where large numbers of people congregate;

(b) Where essential public services are concerned;

. (c) ·Where the area Is one In which lightning Is prevalent;

(d) .Wh~ there are very tall or isolated·Structures;·

(e) Where there are structures of historic or cultural importance;

(f) Where there are structures containing explosive or flammable ~ntents.

However, there are many cases for which it is not so easy to make a decision. In these areas,reference should be made to 2.2.2 to 2.2.8 where the various factors affecting the risk of being struckand the consequential effects of a strike are discussed.

However, some factors cannot be asseSSed ·and ·these may override all other considerations.For example, a desire that there should be no avoidable risk to life or that the occupants of a bUildingshould always feet safe may decide the question in favour of protection, even though it would normallybe accepted that there was no need. No gUidance can be given in such matters but an assessment can. _be made taking account of the-exposure risk· (that is. the· risk of the structure being· struck) and thefollowing factors:

(a) Use to which the structure is put;

(b) Nature of its construction;

29

CP33: 1996

2.2.3 Risks Associated With Everyday Uving. To help in viewing the risk from lightning in thecontext of the risks associated with everyday IMng, .Table 2.1 gives some figures based on 5S 6651 :1992. The risk of death or injury due to accidents is a condition of lMng and many human activitiesimply a judgement that the benefits outweigh the related risks. Table 2.1 is intended simply to give anappreciation of the scale of risk associated with different activities. Generally, risks greater than 10.3 (1in 1000) per year are considered unacceptable. With risks of 10'" (1 in 10000) per year, it will be normalfor public money to be spent to try to eliminate the causes or mitigate the effects. Risks less than 10.5

(1 in 100 000) are generally considered acceptable, although public money may still be spent oneducational campaign designed to reduce those risks Which are regarded as avoidable.

2.2.4 Suggested Acceptable Risk. On the basis of Subclause 2.2.3, the acceptable risk figure hasbeen taken as 10-5 per year,.l.e. 1 In 100 000 per year.

. "

Table 2.1. Comparative probability of death for an individual per year ofexposure (order of magnitude only)

Risk Activity

1 in 400 (2.5 x 10-3) Smoking(10 cigarettes per day)

1 in 2000 (5 x 10"') All accidents

1 in 8000 (1.3 x 10' Traffic accidents4)

1 in 20 000 (5 x 10~ Leukaemiafrom natural causes

1 In 30000 (3.3 x 1005) Work in industry, drowning

1 in 100 000 (1 x 10' Poisoning

1 in 500 000 (2 x 10~ Natural disasters

1 in 1 000 000 (1 x 10-, Rock climbing for 90 s..,-d~ng 50 mites by road*

1 in 2 000 000 (5 X 10.7) Being struck by lightning

* These risks are conventionally expressed In this form rather than In terms of exposurefor a year.

NOTE. The source 01 this table Is as 6651 : 1992

2.2.5 Overall Assessment Of Risk. Having established the value of P, the probable number ofstrikes to the structure per year (see Subclause 2.2.2), the next step is to apply the weighting factors'.as given in Tables 2.2 to 2.6. This Is done by multiplying P by the appropriate factors to determine

" whether the result, the overan risk factor, exceeds the acceptable risk of Po =10-5 per year.

2.2.6 Weighting Factors. In Tables 2.2 to 2.6, the weighting factor values are given under theheadings A to E"and denote a relative degree of importance or risk in each case. Tables 2.2 to 2.6 aremostly self-explanatory.

31

CP33: 1996

Figure 2.1 Plan of collection area

This is shown in Figure 2.1.

Q30 .-..........

"".......­.......­.­.­.­.­..•....••.,.,.,•.,.,".,.,.,""••••

t ,

-.-. ---

--- --

~----;'

Hm

"-'\

\I

II

!Wm II .

I --±. I Boundary ofI L-----------~1 ,----. collec tlon area

'7 I. Lm -l /~ /......--_.--

/I

f

I!

The probable number of strikes to the structure per year, P, is as follows:

Ac == LW + 2LH + 2WH + .~

The effective collection area of a structure is the area of the plan of the structure extended inall directions to take account of its height. The edge of the effective collection area is displaced fromthe edge of the structure by an amount equal to the height of the structure at that point. Hence. for asimple rectangular bullding of length L, width Wand height H On m), the collection area has length(L + 2 H) m and width (W + 2H)m with four rounded corners formed by quarter circles of radius H(in m). This gives a collection area, Ac frn m', of: .

2.2.2 Estimation Of Exposure Risk. The probable number of srikes to the structure per year is theproduct of the 'lightning flash density' and the 'effective collection area' of the structure. The lightningflash density, Ng is the number of flashes to ground per km2 per year. Values of Ng vary from place toplace. in Singapore the best estimate for the average annual density can be taken to be 12.6 flashesto ground per km2 per year.

(e) The height of the structure (in the case of the composite structures, the overall height).

(d) The location of the structure;

(c) Value of its contents or consequential effects;

It should first be decided whether this risk P is acceptable or whether some measure ofprotection is thought necessary.

CP33: 1996

Table 2.4 gives the weighting factor for contents or consequential effects. The effect of the valueof the contents of a structure Is clear, the term 'consequential effects' Is Intended to cover not onlymaterial risks to goods and property but also such aspects as the disruption of essential services of allkinds, particularly In hospitals.

The risk to life Is generally very small but, If a bUilding is struck, fire or panic can naturally result.All possible steps should therefore be taken to reduce these effects, especially among children, the oldand the sick.

For multiple use buRdlngs, the value of weighting factor A applicable to the most severe useshould be used.

Table 2.2. Weighting factor A (use of structure)

Use to which str.ucture Is put Value of factor A

Houses and other buirdlngs of comparable size 0.3

Houses and other buildings of comparable size with outside 0.7aerial

Factories, workshops and laboratories 1.0

Office blocks, hotels. blocks of flats and other residential 1.2buildings other than those InclUded below

Places of assembly, e.g., churches, halls, theatres, museums. 1.3eXhibitions, department stores, post offices, stations. airports,and stadium structures

Schools, hospitals, children's and other homes 1.7

Table 2.3 Weighting factor B (type of co~stru~ion)

Type of construction Value of factor B

Reinforced concrete or steel frame with metallic roof 0.4

Membrane structure with metallic frames 0.8

Reinforced concrete or steel frame with non-metallic roof 1.0

Timber or masonry with non-metallic roof 1.4

Timber or masonry with metallic roof 1.7

Any building with a thatched roof 2.0

NOTE. A structure of exposed metal which is electrically continuous down to ground level is excludedfrom the table as it requires no lightning proteCtion, beyond adequate earthing arrangements.

CP33: 1996

Table 2.4 Weighting factor C (contents or consequential effects)

Contents or consequential effects Value of factor C

Ordinary domestic or office buildings, factories and workshops not 0.3containing valuable or specially susceptible contents

Industrial and agricultural bundings with specially susceptible* contents 0.8

Power stations, gas Installations, telephone exchange, radio stations 1.0

Key Industrial plants, ancient monuments and historic buildings, 1.3museums, art galleries or other buildings with specially valuable contents

Schools, hospitals. children's and other homes, places of assembly 1.7

* This means specially valuable plant or materials vulnerable to fire or the result of fire.

Table 2.5 Weighting factor 0 (degree of isolation)

Degree of isolation Value of factor 0

Structure located in a large area of structures or trees of the same or 0.4greater height, e.g. in a large town or forest

Structure located in an area with few other structures or trees of similar 1.0height

Structures completely isolated or exceeding at least twice the height of 2.0surrounding structures or trees

Table 2.6 Weighting factor E (type of terrain)

Type of terrain . Value of factor E

Aat land at any level 0.3 . . .

On hillside 1.0

On hilltop 1.3

2.2.7 Interpretation Of Overall Risk Factor. The risk factor method given in this Code Is Intendedto give guidance on what can, in some cases. be a difficult problem. If the result obtained isconsiderably less ·than· 10-5 (1 in 100 000) then, in the absence of. other overriding considerations.protection does not appear necessary; if the result is greater than 10.5, say for example 10'" (1 in10000), then sound reasons would be needed to support a decision not to give protection.

When it is thought that the consequential effects will be small and that the effect of a lightningstrike will most probably be merely slight damage to the fabric of the structure. it may be economic notto Incur the cost of protection but·to accept the risk. Even though this decision is .made, it is suggestedthat the calculatIon is stm worthwhile as givIng some idea of the magnitUde of the risk being taken'"

33

CP33: 1996

Structures are so varied that any method of assessment may lead to anomalies and those whohave to decide on protection have to exercise judgement. For example, a steel framed buDding maybe found to have a low risk factor but, as the addition of an air tennlnation and earthing system will givegreatly improved protection, the cost of providing this may be consIdered worthwhile.

A low risk factor may result for chimneys made of brick or concrete. However, where chimneysare free-standing or where they project for more than 4.5 m above the adjoining structure, they willrequire protection regardless of the factor. Such chimneys are, therefore, not covered by the method

. of assessment. Similarly, structures containing explosives or flammable substances are sUbject toadditional consideration (see Section 5).

Results of calculations for different structures are given in Table 2.7 and a specific case isworked through in Subclause 2.2.8.

NOTE. Table 2.7 should be read in conjunction with Figure 2.2.

2.2.8 Sample Calculation Of Overall Risk Factor. A hospital is 10 mhigh and covers an area of70 m x 12 m. The hospital' is located on flat land and isolated from other structures. The constructionis of brick and concrete with a non·metallic roof.

To determine whether or not lightning protection is needed. the overall risk factor is calculated.as follows:

(a) Number of flashes per km2 per year. The value for Ng is 12.6 flashes per km2 per year.

(b) Collection area. Using the first equation in 2.2.2 the collection area, ~ in m2, is given by:

Ae = (70 x 12) + 2(70 x 10) + 2(12 x 10) + (~x 100)

A.c = 840 + 1400 + 240 + 314

(c) Probability of being struck. Using the second equation in 2.2.2 the probable number ofstrikes per year, P. is given by:

P = A x N x 100Ge 9

P = 2794 m2 x 12.6 x 100G

P =3.5 x 10.2 approximately

(d) Applying the weighting factors. The following weighting factors apply:

factor A = 1.7factor B = 1.0factor C = 1.7factor 0 = 2.0factor E = 0.3

The overall multiplying factor =A x B x C x D x E = 1.7

Therefore, the overall risk factor = 1.7 x 3.5 x 10.2 = 5.9510'2. The conclusion is, therefore. thatprotection is necessary.

CP33: 1996

2.3 NEED FOR PERSONAL PROTECTION

A hazard to persons exists dUring a thunderstorm. Each year. a number of persons are struckby lightning part.iculariy when outdoors in an open space such as an exposed location on a golf course,or when out on the water. Other receive electric shocks attributable to lightning when Indoors.

In built-up areas protection is frequently provided by nearby buftdlngs, trees. power lines orstreet lighting poles. Persons within a substantial structure are normally protected from direct strikes.but may be exposed to ahazard from conductive materials entering the structure (e.g. power. telephone,or TV antenna wires) or from conductive objects within the structure which may attain differentpotentials. Measures for the protection of persons within buildings or structures are set out in Section 7.

Ughtning strikes direct to a person or close by may cause death or serious injury. A persontouching or close to an object struck by lightning may be affected by a side flash. or receive a shockdue to step, touch or transferred potentials, as described in Appendix A.

When moderate to loud thunder is heard, persons out of doors shOUld avoid exposed locationsand should seek shelter or protection in accordance with the gUidance for personal safety provided inAppendix G, particutariy if thunder follows within 15 s of a lightning flash (corresponding to a distanceof less than 5 km).

2.4 NEED FOR PROTECTION OF PERSONS AND EQUIPMENT WITHIN BUILDINGS

As explained in Clause 2.3, persons and equipment within buildings can be at risk from lightningcurrents and associated voltages which may be conducted Into the b\Jildlng as a consequence of alightning strike to the building or associated services. Some equipment (e.g. electronic equipment,including computers) is especially susceptible to damage from overvoltages transferred from externalconnections caused by lightning and such damage may occur even when the lightning strike is remotefrom the building. e.g. from a surge conducted into the building via the power and telecommunicationcables.

Measures may therefore need to be taken to protect persons and equipment within buildingsand Section Seven provides further. advice on this SUbJect. Tt:t~~~sures recommended in· Section

. Seven can be implemented even when a lightning protection system for the building structure has notbeerl.provided. .

The decision as to Whether to provide protection specifically directed to equipment will dependon the value placed on that equipment and on the cost and inconvenience which might resuit from theequipment being out of service for an extended period.

The risk factor determined from Clause 2.2 will provide guidance on the likelihood of a buildingbeing subject to a lightning strike with consequent risk of damage occurring to equipment within thebUilding. However. since damage to equipment can result from lightning strikes to adjacent propertiesor to power or signal lines some distance away. the Index value may not be a sufficient indicator of therisk. The incidence of damage occurring to similar equipment within bundings in the vicinity may providea better guide to the need to protect. . .

35

CP33: 1996

Reference General arrangement Collection area and method of calculation

(a I 1S R15 , ... ----..,..~ A~ ·14 X 50 -t 2115 x 50) +

i~I- l I \ 1S +2(15X 14)+1115'---!-I I : 14 Ac " 3327 m2

L._ I ~i-~, I I I 1Sr ~-- ----t K-15 SO 15 R15

{bl 21R21---,. ..,--- -r..---. Ac • 15 X 40 + 2121 X 401 +

i--~..( , .... 2' +2(21 X 151 + ,,21 2

~-J [-'~,--tl~ Ac • 4296 m1

f " I- - -, . - - .,-tt ", I ~:: 21

......_--~~21 40 '21". I....I.. _1_ .., '--R21

Ie) 10" - - - - c;:--"[ Ac .. n 142 + 2(14 x 30)

~~ '--t-~'C. A e .. 1456 m2

( 1 r'- .' 14",._--t-14 8 ....JQ...; "-R1C.

ldl b R6--. ti"'o--~ A e .. 7 X 8 + 216 X 71 + IIS2 +W

1bf, ~~~6 + 10 tapprox.l (or areas in black

j" ~~ I R9 -' e Ac .. 405 m'yoV I ~9

, I j~6j "'-1_-

4 . i.lJ R6

(el 60 A c • 25 X 60 + 25 X 30 + 6 X 60 +R6 r- ""l 6r------'F + 6 X 50 + 6 X 25 + 6 x 25 +

~+ 6 X 30 + 6 X 24 + 5/411 6'

~ " .... , : Ll r-6 : 25 Ac " 3675 m2

(SO : W----lRb .

6 2S . ,, 6 I~. ,./

6..J 1--:to -j :tn 16

R'3~ 3If)

(~r', ..t A~=9+2(9) + 2(9} + 113

2

-~t3. Ac = 73.3 m2

:.i

All dimensions are in metres.NOTE. This fi9ure should be used in conjunction wilk lab Ie V

-"

Figure 2.2 Details of structures and collection areas

'lI!1II1!

36 ..

"""••­..fIlAfIlA

•......

Table 2.7 Examples of calculations for evaluating the need for protection

1 2 3 4 5 6 7 8 9 10 11 12 13

Ref. in Description of RIsk of being struok, P Weighting factors Overall Overall risk RecommendationFigure structure

;multiplying factor

2.2 factor (product of

Collection Rash P= A B C 0 E (prodUcts columns 5

area, Ate density, Use of Type of Contents or Degree of Type of of columns to 11)

Ng Acx Ng X 10-8 structure construction consequential Isolation country 6 to 10)

(Table 2.2) (Table 2.3) effects (Table 2.4) (Table 2.5) (Table 2.6)

(a) An apartment. 3327 12.6 41.9 x 10'" 1.2 1.0 0.3 0.4 0.3 0.043 1.8 x 10-3 Protectionbuilt with recommendedreinforced

concrete andbrick and Ishaving non-metallic roof

(b) An office 4296 12.6 54.1 x 10-3 1.2 1.0 0.3 0.4 0.3 0.043 2.3 x 10-3 ProtectIonbuilding, built recommendedwith reInforcedconcrete andIs havIng non-

.metallic roof

(c) A school, built 1456 12.6 18.3x 10'" 1.7 1.0 1.7 0.4 0.3 0.35 6.4 x 10-3 Protectionwith reinforced recommendedconcrete andbrick and Ishaving non~

metallic roof

Table 2.7 Examples of calculatIons for evaluating the need for protectIon

1 2 3 4 5 6 7 8 9 10 11 12 13

Ref. in Description of Risk of beIng struck, P Weighting factors Overall Overall risk RecommendationFigure structure multiplying factor

2.2 factor (product of

Collection Aash p= A B C 0 e (products columns 5

area, "c density, Use of Type of Contents or Degree of Type of of columns to 11)

Ng Ae x Ng X 10.8 structure construction consequential Isolation country 6 to 10)

(Table 2.2) (Table 2.3) effects {Table 2.4} (Table 2.5) (Table 2.6)

(d) A two storey 405 12.6 5.1 x 10.3 0.3 1.7 0.3 0.4 -0.3 0.02 1.02 x 10'4 Protectiondetached recommendedbungalow,built withreinforced .

concrete andbrick and ishaving non·metallic roof

(e) A factory, built 3675 12.6 46.3 x 10'3 1.2 0.4 0.3 0.4 0.3 0.017 7.9)( 10.3 Protectionwith reInforced recommendedconcrete andsteel framedencased and

is havingmetallic roof

(f) A security 73.3 , 12.6 9.24 x 10'4 0.3 0.4 0.3 0.4 0.3 0.00432 4 x 10.8 Protection notguard post of required3mx3mx

3m, built withreinforced

concrete andbrick and Is

havingmetallic roof

NOTE. The risk of being struck, P (column 5), is multiplied by the product of the weighting factors (columns 6 to 10) to yield an overall risk factor (column 12). This should becompared with the acceptable risk (10's) for guidance on whether or not to protect. Risks less than 10.5 do not generally require protection; risk greater than 10.4 require protection; forrisks between 10'5 and 10-4 protection is recommended (see Subclause 2.2.3 to 2.2.8)

Task: I Risk Analysis for Lightning Safe.ty - Example: Mining Activities

Analysis by: National Lightning Safety Institute Date:

Approved by: Date:

Uke/ihoodE u(OS :.Eu !! c.rz: l.': 15or:

0 C> ...Stil) "0 0

";'; I:: 0 "(;j>

..s ~ ::?Z ::?Z a. , . , .- N M "l:t <n

A - Certain H H R E BB - Likely M H H E BC - Possible L M H B· BD - Unlikely L L M H BE - Rare L L M H H

Job Steps Potential Hazards Level of Risk Control Measure

Mine control receives lightning detector alert Iwarning

Mine control contacts drill crew Unable to·make c~ntact, radio not working L(Ct) Geologist advised ofneed to notify drill crew. Ensurebase station radio. kept in working order

Delay in contacting drill crew H(C3) Drill crew to monitor weather conditions for themselves atall times

Drill crew receives alert . Accident on rig when distracted by radio L(D2) Ensure rig safe before moving to answer radio

Slip I trip when moving to answer radio L(D2) Ensure ongoing good housekeeping of rig site(particularly in. dark)

-_.-

Rig without base station not informed ofalert H(C3) Drill crew with base station to notify other crew andmaintain contact

Drill crew acts on alert Not shutting down rig properly L (01) Ensure rig crew knowledgeable on emergency shut downprocedures

Electrical activity Lightning strike of rig crew E(D5) Drill crew to be in safe location during electrical activity

Drill crew receives all clear No radio contact L(Cl) . Keep hand held radio charged and in working order andmonitor channel 2 for all clear

Electrical activity not finished in vicinity of rig H (C3) Drill crew to monitor electrical activity in vicinity of rig

Resume drilling activities Not fonowing correct start up procedures L(D!) Ensure drill crew knowledgeable on start up procedures

Further electrical activity in area H (C3) Drill crew to continue monitoring weather conditionsaround the rig and keep radio on channel 2

SHORT VERSION OF RISK ASSESSMENT(PERNLSI)

1. Lightning Behavior is not fully understood. In another100 years, science may roll back the "Unknown" to the"Known." Today we can only agree that it is arbitrary,capricious, random, stochastic and unpredictable.

2. From a perspective of statistical probability the likelihoodof lightning striking our facility or structure is remote.Perhaps one-in-a-million?

3. If lightning did strike our operations, damage from alightning strike is calculable. Consequences range from"mild" to "catastrophic."

4. Our options are:4.1 Do Nothing. Run with the Odds. Take our

Chances.4.2 Do Something. Get some information. Perform a

Safety Assessment. Install defenses for people andfor the facility.

5. Lightning doesn't care what we do.

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Three

THE GROUNDINGAND BONDING

IMPERATIVE

41

Chapter Three Overview

GrOlUlCling (aka Earthing) means using a low resistance and conductiveEarth Electrode Subsystem (BES) to provide a safe destination forlightning's energy. A suitable BES employs volumetric efficiencies, not just25 ohm or 10 ohm target resistance. BES designs are site-specific. Oftentimes to just drive a few ground rods is an error ofsimplification.

Bonding was recognized only recently as essential to good lightningprotection. All metallic conductors, intended or otherwise, must beinterconnected. Equalization of all potentials is mandated in the NationalElectrical Code. The US Air Force API 32-1065 says it all: "If you don'tbond, your lightning protection system wont work:."

•42 4

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~

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DEFINITION OF TERMS USED IN GROUNDING

by National Lightning Safety Institute (NLSI)www.lightnlngsafety.com

In order to promote a uniform understanding of grounding issues, thefollowing Glossary is presented.

Concrete Encased Electrodes: The rebar in concrete can be aneffective part of the grounding electrode subsystem. Since concrete is alkalineand hydroscopic (absorbent) in nature, this type ionizing and moist medium cancreate a large and effectiVe earth sink by using t"e foundation ground of any AFS.It is critical, however, that the rebar be connected to the primary groundelectrode, buried ring electrode and/or other ground points in keeping with theconcept of a wholly-unifonn and integrated single point ground for the entirefacility. Concrete encased electrodes are recognized as a beneficial component ofthe earth electrode system.

Current Magnitudes: Typical lightning current magnitudes peak in the20-30kA range. However, magnitudes over 400kA have been recorded.Approximately 3% of magnitudes measure above 100kA. IEEE recommends thatlightning protection engineers use 40kA as a design threshold for lightningprotection sys~ems.

Deep Wells: Due the typical high cost of deep wells, other ~Iternatives

first should be explored. These include: additional ground rods; connection ofperimeter security fences to augment the ground grid; radial buried ground wiresor ground ·straps .configured away from building corners;. treatment oraugmentation of soils with artificial backfills; and low-cosldrip irrigation systems.

. .Driven' Rods: 'CoPPer plated slee.l .rods are driven beloW grade andconneCted to ground wires. . .

Earth Electrode Subsystem: A network of electrically interconnectedrods, plates, mats, or grids installed for the purpose of establishing a lowresistance contact to earth.

Equipotential Plane: A grid, sheet, mass, or masses of conductingmaterial which, wh,n bo~de~ together, o~rs a negligible.impedance. to currentflow.

Facility Ground System: The electrically interconnected systems ofconductors and conductive elements that provide current paths to earth. Thefacility ground system includes the earth electrode subsystem, lightning

43

protection subsystem, signal reference subsystem, fault protection subsystem, aswell as the bUilding structure, equipment racks, cabinets, conduits, junctionboxes, raceways, duct work, pipes, towers, other antenna supports and othernormally non-current carrying metallic elements.

Frequency and Skin Effect: Lightning Is a high frequency, highcurrent pulse. At high frequencies and high currents, energy is transmitted alongconductors with high skin effect Skin effect limits current flow to the extremeouter surfaces of conductors.

Ground: Usually meaning the same as dirt or soil or earth.

Ground Conductor Connections: Exothermic connections providethe IQwest inductance and the highest reliability of all connection alternatives.Even a low inductance path in a lightning circuit can invite large voltagegradients, which in turn may facilitate arcing to alternative paths. Gradients over50kV/m are common in both air and earth situations. Such arcing, known as "sideflash", may be the result of tight bends in above-grade wire conductors.

Ground Electrode: A conductor (usually buried) for the purpose ofproviding an electrical connection to ground.

Ground Ring: A ground wire of No.2 size encircling or surrounding abuilding, tower or other above-ground structure. Usually the ground ring shouldbe installed to a minimum depth of 2.5 ft. and should consist of at least 20 ft. ofbare copper conductor. It should be installed beyond the building drip line.

Halo Grounded Ring: A grounded No.2 wire, installed around all fourwalls inside a small bUilding, at an elevation of approx. six inches below theceiling. There are drops installed from the halo to the equipment cabinets and towaveguide ports, Interior cable trays etc. Halo rings serve as connector points toachieve ground references of interior metallic objects. These, in tum, areconnected to the main ground bus bar.

Inductance and Voltage Poteotials: Lightning will follow the path oflowest inductance. The higher the frequency, the higher the inductive reactancevalue in calculating the total impedance of the circuit. Resistive values can beeliminated for all practical purposes in high frequency lightning conductorcalculations for distances approximately 2000 feet or less.

Impedance: The impedances of typical grounding electrode conductorwires linearly increase as a function of frequency.

Resistance of Electrode: Recommended NEC practice is to provide aresistance of less than 25 ohms for an earth ground. Local conditions will varythis target figure. Figures of 10 ohms or less are standard practice in several USGovernment standards. Volumetric efficiencies with large cross sectional areasmeans that impedance is more important than resistance. See IEEE 1100..1999,section 4.7 for more detailed information.

Shield: A housing, screen, or cover which substantially reduces thecoupling of electric and electro-magnetic fields into or out of circuits or preventsthe accidental contacts of objects or persons with parts or components operatingat hazardous voltage levels.

Spark Gap: A short air space (dielectric) between two conductors.

Types of Connectors: a} Mechanical, as in a threaded clamp; b)Pressure, as in a compression clamp; c) Thermal, as in CADWELO@, which resultsin a exothermic or molecular connection. Thermal connectors are said to bebonded, or electrically-joined.

45

46

7299

138

790300

3300

I\.csislivityohm-rn

1.3

1.0

".618.0

107.0

Rcsisrivicyohm·m

-5 23o 32 (ice)

10 5020 68

.15 14

TcmpcRNf\!·C F

5.0

1.00.10.0

20.010.0

Please note that, if your soiltcmpcr.ature decreases from +20oC to •SoC, the resistivity increases more thanten times.

When the ground becomes frozen. itsresistivity rises dr.amatically. An eanhthat may be effective during temperateweather may become ineffective inwinter.

ElfcCl orT~mpmNrt on ResiuivityFor sandy loam, IS,2% mouture

D) 'l'EMPERATUllE

Table 4

Note that although the addition ofsaltscan lower soil resistivity. they are notrecommended due to corrosionand leaching. (See section on soilconditioning on page 16).

Elfea orSalt on RcsislivilyFor laIIdy loam. 15.2% moiuure

Table 3

Certain minerals and salts can affect soilresistivity. Their levels can vary withtime due to r.ainfa1l or flowing water.

c) CHEMICAL COMPOSITION

4263

/85

105

430

1.000 II 104

Sandy Loam

2· 2.7... ISO

90 - 800060· 400

300· SOIl

/20

530310

1000 upwards

1650

2500I,OOlhl()l

TopSoil

/0

20

30

15

2.S5

o

MoUture I\.nillivicy ohm·mcontenl'K •by weight

B) MOlsnJRE

l'co.

RockSondy Grovel

Ch.lkSond

loom ~nd ClayManhy Ground

It is especially important to considermoisture content in areas of highseasonal variation in rain&ll.

Increased moisture content of theground can rapidly decrease itsresistivity.

Table 2

EfTm orSoil Type on Rcslslivicy

Wherever possible the earth electrodeshould be installed deep enough toreach the "water table" or "permanentmoisture level".

EfTecl orMobllne on Resilliv;ty

FACTORS AFFECTING SOIL RESISTIVITY

Soil TYl'" TypialllCliHivicyohllH1l

Table 1

Different soil compositions givedifferent avenge resistivities:

A) PHYSICAL COMPosmON

National LIgtltningsafety Institute

891 N. Hoover Avelouisville CO 80027

RELATIVE ADVANTAGEIDISADVANTAGEOF PRINCIPAL TYPES OF EARTH ELECTRODE SYSTEMS

47

Type

VerticalRods

Plates

Advantages

Simple design. Easy to installin good soils.Hardware readilyavailable. Can be extended toreach the water table.

Can achieve low resistancecontact in limited area.

Disadvantages

High impedance. Hardto install in rocky soil.Step voltage on earthsurface can be highunder large faultcurrents or during adirect lightning strike.

Most difficult toinstall. Should beinstalled vertically.

Horizontal Low impulse impedance.Bare Wires Good RF counterpoise(Radials) when laid in star pattern.

Incidental Can achieve very lowElectrodes resistance in certain(water pipes, applications.Ufer grounds, ....buried tanks.)

Ring Ground Straightforward design.Easy to install aroundexisting facility. Hardwarereadily available. Veryefficient due to volume.

Subject to resistancefluctuations with soilsdrying. Not recommendedwith unstable soils.

Little or no control overfuture alternations. Mustbe employed with other.e~ectrodes, not as soleelectrode.

Problems with asphaltand concrete around thefacility? Not desireablewhere large rocks arenear surface.

Note:.Engineered soils employing .various backfills and/or salts alsoshould he consideredfor difficult locations and situations.

•

48

.­4444444444444444444444444444

44

4

4

4

~

ffffff

l

l

~

Limited AreaEarthing - Use deepdrill hole. Reducesvoltage rise atthe surface.

Radial Earthing ­Ideal for medium soilresistivity. Current·split 6 ways.

II

Deep Drill Earthing­Required in dryareas whereJround water isvery low or rocky.

Multiple Rod. Earthing .'An effectivemethod. Spacing ofeach rod is 2 x depth.

EXAMPLES OF VARIOUS GROUNDING LAyours

Radial Earthing ­Ideal in areas ofhigher soil resistivity.Multiple paths forlightning current.

Single Rod Eaithing­Satisfactory for simpleapplications wherewater level is high.

49

SUPPLEMENTARY GROUNDINGFOR BUILDINGS WITH BASEMENTS

(C)

(B)

(C)

(C)

Building Plan A - Supplementary ground field for building withstructural steel columns or concrete columns using welded orwire-wrapped reinforcing bars .

(B) (B)

p (C)·

(A)

I~P

h

D

n

o

D

(e)

n·Building Plan B - Same as Plan A except thatground rods are located at every column

(A) OPGP Bus Bar

(B) #2 AWG Bare Tinned Copper Wire

(C) 5/8" x 8' Ground Rod

Building Plan C - Same as Plan A except thatcolumns lack reliable electrical continuityand are not bonded to the supplementary field

.-0- Exothermic Weld to Ground Rod

- Exofhermic Weld to #2 AWG, Bus Baror Building Steel

(f)

(a)

SUPPLEMENTARY GROUNDING,BUILDINGS WITHOUT BASEMENTS

p(e)

't;

U . U. U L

(f)

Ground ring is 2' to 6'from perimeter of building

0 0 D Lf\- H(C)

(a)Ir

b.(e)

"'I

h n· I

b.. ~ .I:.

(e)

(a) #2 AWG solid tinned copper conductor(b) Grounding Electrode Conductor run

between the main house service Paneland the main cold water pipe; sized perTable 2-2

(c) OPGP bus bar(d) PVC conduit(e) 5/8" X 8' copper clad steel ground rod(f) Exothermic weld connection

RECOMMENDED GROUND ROD BONDING.

1. WELD TO ROD IN GROUND2. OK TO BOLT TO ABOVE GROUND CONDUCTOR

Preferred O.K.Welded Bolted

51

Ground Rod

SOME IDEAS (not in any Codes) FORGROUNDING ADDITIVES AND BACKFILLS

THESE CONCEPTS WILL INCREASER VOLUMETRICEFFIQENCIES OF THE £ARmELECTRODESUBSYSTEMINRESlSTWEEARTH COWmON8- ASKALL VENDORS FOR MSDS & READ CAREFULLY.

SULPHUR CONTENT OFPRODUcrSSHOUW NOTEXCEED 5 %.

1. Coke Breeze - 85% carbon bound into a cinder-like matrix. Check MSDS forminimwn, lowest sulphur content variety. Use pebble size, not dust size. Should beinstalled in slurry form to encourage compaction.

.. Mid Continent Supply, Chicago IL tel.708-798-1110

.. Christianson Bros, Spanish Forks, UT tel. 801 ..798..9158.

2. Conductive Cements .... Carbon mixed into cement. Some types need residualmoistW'e. Not recommended where vehicle traffic may crack concrete or whereshifting or unstable soils exist. Should be installed in slurry form. Check MSDS.

- Electric Motion Co, tel. 860-379-8515;.. ERICO tel. 800-248-9353... Sankosha Corp., tel. 310-320..1661- Loresco Corp., 1-601-544-7490 www.loresco.com

3. Ground Augmentation Fill (GAF). Needs residual moisture. Avoid freezingconditions. Available from LEC, tel. 303-477-2828. Check MSDS.

4. Bentonite. Needs residual moisture. Not recommended in :freezing conditions.Available from Wyo-Ben Co., Billings MT, tel. 406..652-6351.

5. Drip Irrigation (as required). Use a leaky hose or a water container (an upside­down 5 gallon plastic jerry can on platform works well) and drip-irrigate a slowtrickle of 15% salts and 85% water onto the earth electrode area. Drip irrigation/leakyhose is available from Home Deport or equal.

6. Trenching. Deeper is better (to reach available moisture). Don't forget to do your"Locates" first !!!!! Install'backfill with 1/0 stranded copper or equivalent flat strapin below-grade trench approx. 30cm (12 in.) X 30cm, at least 1m (3 ft.) below gradenot exceeding 10m (30 ft.)in length. Install yellow "Warning Tape." Compact andbackfill with compacted native earth.

•52 ,,,t,,,,,,,,,,,,,,,,,,•••••••••••t~

~

~

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~

~..

53

TYPICAL DRIVE AND WALK GATE ENTRIES

-2/0 BARE COPPER CABLE

3'·0" BEYOND FAATHESTSWING OF GATE

CONNECTTO GATE

DRIVE GATE

CONNECTION<TYPJ

t12f-~"*"t-M7'~IN=SIDE PLANT'::....r-=-_....,.-<...-.-_-4It- --;~:::..-- -~OU~TSIDE PLANT

CN3LE EQUN..LY $PACED

FENCE PERIMETER .GROUND (SEE SECTION 15)

-2/0 BARE COPPER CABLE.CONNECTIONnyp.>

au SiOE PUNT'INSIDE PLANT

WAlK GATE

3'-0" BEYOND f/lRTHESTSWING OF GATE

CABLE EQUAlLY SPACED

2',0"

FENCE PERIMETER .IGROUND (SEE SECTION 15)

NOTE: WHEN THE DIRECTION OF THE GATE SWING IS TO THE INSIDE OF THE SITE FENCE PLACE THEGRID ON THE INSIDE. WHEN THE DIRECTION OF THE GATE SWING IS BOTH TO THE INSIDE ANDTO THE OUISIOE, PLACE THE GRID ON BOTH THE INSIDE N-ID OUTSIDE OF THE FENCE.OMIT THE GATE GRID WHEN THE FENCE GROUND IS ISOLATED fROM THE SITE GROUNDINGSYSTEM AS INDICATED ON THE GROUNDING Pl.AN DRAWINGS.·

II'-

54 f-.'­''­'­'­'-

BONDING TO FENCE SUPPORT POST DETAIL

unterpolse COndudor

or

,",

/. ,'", ''', :--

~"

/.~

~

Ba~Copper Conductor(stranCSed)

Ul Rated Mechanical Conned

410 awg CO&f:H!r Conductor(exothermic elel 80th Ends)

'.

~ l-

....'~ \,Grade,

~\ j 0' • -I" I' '.• 4. I"" I .

410 awg Bare Copper 00' ... -, I',f " . \' ,,,.., . ,.

I ' l.J' Yo. . ' '.10' Jt 314" copper Clad Steel Ground Rodthermic WeldExo

t#6 awg

NatiOnal UabtninDsafety aniitUte

891 N. Hoover Avelouisville CO 80021

55

"UFER GROUND" EMPLOYINGCONCRETE SUPPORTING FOUNDATION

CADWELDAt Or Near Unstre~ed End Of Rebars ~

CADWE!..OTo Copperbonded Rod

CopperbondedGround RodDriven 10 Feet

Bare Copper Conductor _

National Lightningsafety Institute

891 N. Hoover Avelouisville CO 80027

RECOMMENDED SEPARATION DISTANCEOF EARTH ELECTRODE SUBSYSTEM

FROM ENERGIZED CONDUCTORS(from MIL ST1J-419A)

GRADE LEVEL ~

1/0 AWG~ BARE GUARD WIRE

10 IN.

L --~ PROTECTED CABLESLO~OlOJ -(DIRECT BURIAL ORIN DUCT)

CABLE _-...... ....__SPREAD

(aJCABLE SPREAD L.ESS THAN 3 FEET

~%7////7///7//7///$///7/7/////?/?m/7/7//. 1/0 AWG

~ BARE GUARD WIRE

GREATER --1 ~ ~ rTHAN 12 IN. AT LEAST 10 IN.LESS THAN 18 IN. 12 IN. 1

0000- - - -- - - --000--1.-

lb) CABLE SPREAQ 3 FEET OR GREATER

National LightningSafety Institute

891 N. Hoover Avelouisville CO 80027

vr

56 ,.

fill"..,.,.,.,..,.,."."..,.f1".......-,

57

RECOMMENDED SERVICE GROUNDINGFOR TYPICAL BUILpING ENTRY

When steel conduit IS usedto protect grounding WIre,1-__..2Q..f8£lL__..1bOM all ends of the conduitto the grounding wire.

OptIonal method Is to use a UFERground. A 1/2 in. dla., 20 ft. longsteel rod or #4 AGW bare copperwlre encased In the concretefooting.

;:=~;;;;d:~r::::' Minimum;:: #14AWGwires.

2ft.Minimum

grade level'CO

metalliC water seN'

INTERSYSTEMBONDING POINT forconnection of telephone,television, and radio'antennae grounding wires.

#6 AGW bare copperwire jumper aroundwater meter, and thenAWG on to ground bus

I~

National Ughtningsafety InBtitute

891 N. Hoover Avelouisville CO 80027

FACILITY BONDING DETAIL ill

59

ItW, '

I ~ 4 4 l 4 I 41 .-'~ ,

-:- )

..~ ',:10;....~; ,...~, 1 11 1 1 l'"...' ....." ..."

.. ~

: ~I- '-I- '- .. '- '- .. '-

power cable,

220/380 V- \-rl.':;I'

EDP·cable

\r!~ ~

telecommunication cable I

.)'-'

..I r!,.-~~'... -

~ ( {

Z fl \~ ~water pipe \ 0.~~. W -- W C..~.

\?-

~~', 0'1

", a, ~.\,.J'

. l ~.~ ... -K gas pipe 1Z 1 'A

.' ,,~

II .~

. ":. - 0 . \,J . ..

". .'" . insulating piece',

,~~. ..~

. ,.' r1:'':' E-~....

r-heating pipe I

t-.' w" found ation earth electrode 'Fp:-.

.' ,. I" '

~ CJ ~~olrY: :~'·.~'~~~~~·jb~~~·~O.°r\C;~~;~~·6~,,~~~·~~~.::~U.()·D.·Ur1~' (S~~ D()~~ 0 I'~C'\)O~\f l\~I'IC,)Q .' /l

il

. C\~~ ()'. 7.o:0:on· ~:.!-l(\oYo'J·~~\J~~9··':,)\'n~'~O~Y'(\:U,?~~t)~~Oo~.~ ,vtir-'-Qo:'(\,..

--F:~ ~.protective device pro~ective device

energy technical network· for Information technical network

-e e-disconnection spark 9~P

POOR BONDING CREATES INDUCTIVE COUPLINGOF SURGE CURRENT TO ADJACENT CIRCUITS

DOWN CONDUCTOR CIRCUITIMPEDANCE

-..~

58 4.'­•".".".".,.,.,.".".,..,..,..,..,

SENSITIVE .)CIRCUIT .(LOqP)

AIRTERMINAL

(MIL-HDBK 419 (B41) lind MIWTD-laB·114A (B42)

THE PROBLEM...-.

d1 & d2 :1& DISTANCES FROM DOWN CONDUCTOR

National Ughtningsafety InstitUte

891 N. Hoover AveLoutsvHle CO 80027

--EARTH

.. ELECTRODESUBSYSTEM

60

One or ~""l:fal

grounding elecuodtslocated around perimeter

of ground plane(if on grade levc:l)

StructurAlJ buildingsteel

Metalcold-waterpipe withgroundingchlmp~ACpower

reeder to telecommunicationsequipment aR8

Protected "Ideofc:able{s)

Unprotected sideofcable(s)

FACILITY BONDING DETAIL a)

Frame is continuou!\bC'twcen Jocalion~

lmay be bonded betweensepaJ'Cue 5Cctions)

frame is bondedto the ground

plane (penelrUtionsand mounting 'eet)

Typical metillcable: ladde:r andequipment frame

=oI

N

BONDING BUILDING STEEL TO GROUND

Beware the insulating abilities ofoxide-reducing paints.Bolted connections across steel columns or plates may not

meet a low resistance bonding requirement. A bonding strapor tack-welds may be required.

Typical InstallationWeld At Column Base.

• First Floor

31-0-

\ .

Typical Down Conductor

61

National Ughtning.Safety Institute

891 N. Hoover AveLoulsvUle CO 80027

GROUND POTENTIAL EQUALIZTION

Creating an equipotential ground plane 'nDder lightningconditions is 'essential for the safety of equipment andpersonnel. All ground. electrodes must have a commonreference in order to minimize potential differences.

GROUNDELECfROOE

CONDUCTOR

OOWNCONDUcrOR EQUIPMENTGROUND PLATE

.~

National Lightningsafety ln$\ltute

891 N. Hoover AveLouisville CO 80021

BONDING SEPARATE GROUND RODS

63

Home Computer,TV Set, Stereo, etc.

Separated Ground Rods

National Lightning881etylnStltute

891 N. Hoover AvelouiSVille CO 80027

Failure 'to BondAC Power Ground Rodto Separate Cable TVand/or Telco GroundRods willcreate a voltage rise mismatch.,

BONDING OF GROUNDING CONDUCTORTO ITS ENCLOSED CONDUIT

Remove Insulationat Contact Point ----

Insulated Circuit _Grounding Conductor

.National LIghtning.. safety tnSttIute .8t1 N. HOover AveLouIBvUIe CO 80027

(]----- Split BoltConductor

~---- Ground Conductorto Busing

).J~.----- Ground Bushing

---Conduit

64 l

l

l

~

~

~

~

4444ff

•f•••••••••••••••••••••••,•....t

National LightningSafety Institute

891 N. Hoover Avelouisville CO 80027

BONDING TO PREVENT SIDE FLASHINGSHOWING LOCATIONS IN TYPICAL BUILDING

2

1. ~irTennination .2. Down Conductor3. Bond to Aerial °

4. Bond to Vent5. Bond to Re-Bar6. Bond the Metal

Staircase

7. Bond to Metal° Window Fnme

8. Bond to Vent Pipe~. Bond to Steel

Door/Frame10. Test Clamp

11. Indicating Plate

12. Main EarthingOTenninalof Electrical Installaoon:

13. EarthTe~tion Point

65

....rrr.­...................................

7" '.................­...­....IIII...­.­......

66

Drum pump bond.

Temporary bonding jumper to pail.

Bus to facility ground and pipe grounding.

---

Attachments to ground bus.

MISCELLANEOUS BONDING EXAMPLES(MBE) 1

, .._--

.~

Jumper to ground bus.

Drum or pail bonding to ground bus.

-

-Ji •--==-.--_---=::..~....c.;.1-- 1D

Drum and pall bonding.

Pipe and drum.

MBE2

Drum and pail bonding.

Mixer bonding.

67

MBE3

I

""'."".,...,..,.........til'......................... ,

i

.1

68

TraCk. Door OperatorAnd Shttt MellI HoodTo Stell Column•.

le Bart CopperGround, CAOWELDConnection io Door

~.CAOWEu)Connection io0vef!1ud OoOt

Sliding Do'or Bonding

Swinging Door Bonding

Coiling Overhead Door Bonding

Shut Metal Hood.--

Door1iB~·

(Typ. For 2)

Colltng--.Overhead

Doclr

National LIghtning. safelY InatitUte

891 N. Hoover A.veLoulavWe CO 80027

MBE4

Tank car bondin9 at siding.

Rail SidingTypIcal Parts NeededFor Static Grounding

69

/rll~.-.....'\i· .l • ,! r:AO.WELD\.. ~. "J •.>.......--~•.

~, .f.,,/,"r Ii~ .\, : .'. • Drum SIOIIllle ~.\' • • • TYJlICaI Part. Needed .

" .' For Sialic GlOUnlllng..........---_./

Drum storage rack bonding.

National ~htning. 8afety tnitltute .891 N. ffoover Ave .louisville CO 80027

MBE5

,70 •,

.­.---.-.---.-.­.....­............---.-"---"t)~t)

~

ttlf/}

~

fI}

eJI.fJ'.fI}f1}

HIERARCHY OF BONDING JUMPERS

71

Long wire:OK for LF,poor for HF

Minimumwire length isimprovement

Short, widebraid strapbetter

, Short widemet.al platewith multiplebonds isbest

@):: c:(§)

lo~ 0]o ". 'f galvanised, ti~ned . 0

. 0 .' ~l or stainless steel 0, '

BONDING JUMPER CABLE INDUCTAN~

Calculated Inductance (l1H) of Standard Size Cable

Length

AWGNO. 6 in. 12 in.

4/0 0.098 0.238

110 0.108 0.259

2 0.115 0.273

4 0.122 0.287

6 0.129 0.301

10 . 0.144 0.329

14 0.158 0.358

National lightning. safety InStilUte891 N. Hoover Avelouisville CO 80027

36 in.

0.914

0.977

1.020

1.063

1.105

1.189

1.274

•72 .-.,.,

II..•..••••".•••••••­......-­...............fJIfI1~

tIPe­li

--­""e---e-e­t)

N . '81 LIghtning

, "'~'891 N. rAy.'Loulavile CO ~0027

BONDING TECHNIQUES RATEDON 1:10 SCALE OF EFFECTIVENESS

(10 is best)

TherMlal <':hemi<".aI Mechanical

Exo- Con- ScrewsGas or thermic Spot duct;ve Twisted Wire

~ ~ ~rc \fIeld ~ ~ Adhesive ~ Crimp !l!!!! Clamps !2!:! Terminal ~ ~

\ Low Resistance '9 10 10 10 10 . ) 9 9 9 8 9 9 9 9

Electrical ResistanceStability 10 10 10 10 10 7 8 9 , , 7 9 S 8

Properties ~ Volt.1ge Drop 9 10 10 10 10 , , 9 10 a 8 9 S 8Current

Capacity ., H~ 10 10 , , 9 9 a , 9 8 9

Mechanical{PuIlOff Force ., 10 10 10 10 1 9 , 9 , 3 10 2 S

Properties . low Creep , 10 10 10 10 , , 9 , 8 :3 8 2 S. Strength ., 10 to 10 7 "

, 9 10 8 , 9 " 8

Conductor c.ioJid Wire 10 . 10 10 10 10 10 10 to , 9 10 9 10t,randed Wire , , 8 , 0 , 9 10 2 , 2 , IIJ

Applicability A.luminum Wire , 2 1 8 0 2 9 8 ", If I I;

8us 8ars andStructures '8 I' S 9 9 , , 7 10 7 10

High Tempera-

~ lure, ,. 10 10 10 1 I ,

", 7 8 S ?

Low Temperature , 10' 10 10 10 , 8 9 , , 8 8 7 7

Environmental Thermal ~hock .8 ,. 10 10 10 7 9 8 If , 2 8 2 8f Vibration ·6 7, 10 10 9 J 7 9 ,'* 2 , 1 7

CorrosiveAtmosphere 9 ·10 10 10 JO , 6 9 8 3 7 9 " 8

Aging 9 10 10 10 10 , 8 8 8 1 7 8 7 8

Cost fTooling 7 If ) " If 9 8 8 7 10 , 10 10 11)Economy' .Process , , , , , 8 , , a 10 JO 10 10 JO

Accessibility iMe-thod Nee-ds8 ,

", 8 8 B 9 8 9 9 9 10 8In Assembly I Litt Ie Space

Ea~ of Repair I 6. , , 9 9 9 9 7 9 JO 10 10 9

••••••••••••••••••••••••••••••••••'...........•..•

74

ex6th e rm ic'junction

com pression C-taps

mechanical type connector

exotherm ic to 'ground rod

conduit/ground rod clam p conduit bonding hU,b, .

TYPICAL CONNECTOR TERMINATIONS

exotherm icto bus ,bar

2-hole crim p type connector

com pression H-taps

heavy duty pipe clam p

BONDING INSPECTION CHECKLIST(NLSI recommendation 1 milliohm or less)

A. General Overall Condition (check):

75

Excellent

B. Resistance Measurements:

Good _ Poor

Location of Bond

c. Deficiencies:

Location

. .NatiOnal~IngSBfety Institute

881 N. Hoover AveLouIavlIIe CO 80027

Condition or. "

Deficiency

Resistance in milliohms

. Comedve Action Taken

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Four

EXTERIOR LIGHTNINGPROTECTION FOR STRUCTURES

Air IcnalDab Db CWIly 1IIop"" roof.

A: so-a(l$-<llI_tP0Cin9B: 2O-a (.....'01 2$ooft (7.....,-..,..,"V

...................... ""

77

la) Singl, MoolZont01 IlIOltcIlon ".1_by~ lints

\1110.._ GloullOWiftslent 01~OtIVlto or 9'0IlIIQ ""'lll'r< _ ''''f'

Chapter Four Overview

Air terminals (in the air) are intended to intercept lightning and conduct italong a preferred route to earth/ground. Lightning Rods are mounted directlyon the structure to be protected. Masts, Poles and Overhead Shield Wires areplaced next to or above the protected structure. All these types of airterminals are validated universally by the codes and standards. Otherdesigns, promoted by vendors seeking commercial advantage, have beenrejected by the scientific community. Caveat Emptor!

Air terminals usually are an important sub-system in the hazard mitigationtoolkit. However, if lightning strikes next to the structure to be protected,and not on it, then no air terminal design has contributed anything to thelightning protection design.

78

(

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4

•••444444

•••••••••••..

APPROVED AIR TERMINAL DESIGNS(per USA Codes & Standards)

1. FARJ\DAY CAGE OR FARAnAY-LIKE CAGE.

Fully enclosed metal box (impractical) Of,

1.1 Steel rebar reinforced concrete per Codes.1.2 Interior shielding of exterior walls per EMC.

2. INTEGRAL (DIRECT) DESIGN.

2.1 Franklin Rods per Codes.

3. INDIRECT DESIGN

3.1 Free Standing Mast(s) per Codes.3.2 ,Ov~rhead (catenary) shield wires per Codes.

Codes = NFPA-780, NASA E0012E, MIL 419A, AFI 32-1065,NAVSEA OP 5 and others. Also include international code IEe 62305.

National LightningSafety Institute

891 N. Hoover AveLouisville CO 80027

79

81

-.82

FLORIDA ROCKET LAUNCH SITES

Examples of Overhead Shield Wires (OSW) at Launch Sites SLC 40 (topphoto) and SLC 41 (lower photo). The asset is the launch vehicle. Thenetwork or grid of grounded shield wires serve to capture both vertical andangled incoming lightnings before they can reach the high value equipment.

FRANKLIN AIR TERMINAL ARRANGEMENTON FLAT-ROOFED STRUCTURE, PER NFPA-780.

(PERIMETER RODS WITH 8m SEPARATION.ACROSS-ROOF RODS WITH 15m SEPARATION.

DOWNCONDUCTORS TO GROUND WITH33m SEPARATION.)

83

National LightningSafety InstJtute

891 N. Hoover AveLouisville CO 80027

•84

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LOCATION OF FRANKLIN AIR TERMINALSFOR VARIOUS ROOF CONFIGURATIONS,

PER NFPA-780.

t AlR TERMINALS ..:: GROUNDS

National LightningSafety Institute

891 N. Hoover Avelouisville CO 80027

FUll. GABLE

t-- - ~IIIII

~IIIII

--- -~

GREATER THAN A·,O­NOT TO ExceeD

85

TYPICAL FRANKLIN RODCONFIGURATIONS AND DETAILS

PER NFPA-780

Air terminal and bondingplacement must attend toall details for effectiveness.

J«)l1:AU.tUV.. I'(lIl ......,SIolAl,L n to<ll6 ro 1lofsu:e~"ANooo(""ll-J(fg.~iIO'neu

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FUNCTIONALITY OF OVERHEAD SHIELD WIRE (OHW)AIR TERMINAL DESIGN - TWO MASTS SUPPORTING

A SUSPENDED AND GROUNDED WIRE.

OVERHEAD SHIELD WIRE - VIEW I

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POLES, BONDING AND GROUNDING

AIR TERMIN-Al

National LightningSafety Institute

891' N; ffoover.Avelouisville CO 80027

AIR TERMINAl.

..90 .-.­....

•.,••.,.,.,•••••••••••••••••••••••••••I••II

•

PREFERENCE FOR MAST AND ,OVERHEAD SHIELD WIREAIR TERMINAL DESIGNS, AS CITED BY CODES

1. Per NFPA-780 (2000), Standard for the Installation ofLightning Protection Systems, Appendix K Protection ofStructuresHousing Explosive Materials, K.2, p. 38 Design Consideration:

UWhere the effects of electromagnetic coupling are of concern, amast of overhead wire (catenary) systems might be preferred overintegral systems unless a Faraday Cage or shield is required. Theremoval (isolation) of the down conductors will reduce the magneticfield strength in the structure and reduce the probability of a sideflashfrom a down conductor."

2. Per NASA E-0012E (2001), Standard for Facility Groundingand Lightning Protection, section 5.2.17, p. 31 Ordinance FacilityGrounding and Bonding:

"It is recommended that ordinance facilities with a perimeter ofover 300 feet that require lightning protection have either a mast oroverhead wire system as specified in KSC..STD..E0013 and AFR 91-43."

3. Per US Air Force AFI32-1065 (1998), Grounding Systems,section 14.5, p. 11 Explosives Facilities with Large Perimeters: .

"New explosives facilities (including igloos) with a perimeter over91.4 meters (300 feet) that require lightning protection and do not usethe structural steel as the air terminals must nse either a mast system oran over~ead wire system. See Attachment 4 for requirements. Sincethese' systems provide better protection, and maintenance is easier,consider using this type of protection for other kinds of facilities."

91

CONE OF PROTECTION INTERPRETATIONOF ELECTROGEOMETRIC MODEL

92 4

•••tt,,,••••••••••••••••.,•••••'""••.,"•""f',...

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Important Notes:1. This is a Theoretical Assumption. Lightning may ignore it.2. This protection concept does not include safety for people.

Touch and Step Voltage issues still apply to persons.3. Protection angle is a function of height of structure. For

example, recommendations by USA NFPA -780 are:3.1 Structures not exceeding 25 ft. (7.6m) are

considered protected with a one-to·two angle.3.2 Structures not exceeding 50 ft. (15m) are

considered protected with a one-to-one angle.

h

93

ROLLING SPHERE INTERPRETATIONOF ELECTROGEOMETRIC MODEL

Important Notes:1. This is a Theoretical Assumption. Lightning may ignore it.2. This protection concept does not include safety for people.

Touch and Step Voltage issues still apply to persons.3. Rolling Ball Radii varies according to Codes, for example:

3.1 USANFPA-780, R=46m3.2 USA Dept Energy and Dept Defense, R = 33m3.3 International Code IEC 62305

kA R % ProtectionLevel I 3 20m 99Level II 5 30m 75Level III 10 45m 50Level IV 15 60m 50

4. British BS 66551, R:; 20m for buildings with explosives,flammables or sensitive electronic equipment contents.

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94

CONE OF PROTECTION (DOTTED LINES)AND ROLLING BALL (SOLID LINE)

PROTECTION AREA THEORIES.AREAS INSIDE THEORETICAL PROTECTIONAREAS DO NOT REQUIRE AIR TERMINALS.(THESE AREAS ARE NOT SAFE FOR PEOPLE.)

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PROTECTED BV TERMINALON HIGHER ROOF

('1) ptil~e~"",,£'

~,p..O ~~ #'!i"'~TE: 0" 45 DEGREES~ (1;1 CONE OF PROTECTION)

Natlonal LightningSafety Institute

891 N. Hoover Avelouisville CO 80027

FALLS OUTSIDECONE OF PROTECTIONADDITIONAL TERMINALSNEEDED

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Five

INTERIOR LIGHTNING PROTECTIONFOR THE ELECTRICAL SYSTEM OF A

COMPLEX FACILITY

95

Chapter Five Overview

NFPA-780 v. 2004 now uses the "shall" descriptive for installing surgeprotection devices (SPD) at power and communications circuits. NLSI'streatment of the subject describes: SPD locations; how SPDs functiontowards transient waveforms; what's inside the SPD boxes; and installationrecommendations.

There are many poor-performing SPDs on the market, so Caveat Emptoragain! Suggested due diligence will include separating reputable vendorsfrom fly-by-nights and asking for Certified Test Results. Also, looking forconformity to the more stringent European lEe codes which award the CElabel is a good idea. lEe requires a 10 X 350 us (vs IEEE 8 X 20 us) testingprocedure.

A first class detailed treatment of the SPD subject is contained in IEEE Std1100, Recommended Practice for Powering and Grounding ElectronicEquipment. This text should be in the librmy of every lightning protectionengmeer.

97

HOW SIDE FLASHCAN OCCUR

CAPACITIVE ANDINDUCTIVE COUPLING

TO BUILDINGINTERNAL WIRING,

Power sockers

Tolf building

Internal wiring system

lightningInlpuIsecurrentRowing down

conductor Wlf-n.-f.;::::;L::::;:::7.::i.J-------

Magnetic Fieldftnefuctive)coupling.

LiShtni~Olf terminations ----I

~

_Main powercoble

\:J'\I'llf-+-t-t- Side· Rosh due 10 verylarge voltage between/lglitnil\9 cOndulor andInternal;earthed cable•

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3m.

lightningconduclors

lightningimpulsecurrent-+-~t

50kA!J.lsec

National lightningSafety Institute

891 N. Hoover AvelOUisville CO 80027

•

­..till'­.................

98

I

/ Category A/6kVISOOA

I

III 8ronc;h feeder

>20m fromI IrOM'Ormet

II

I .I Category B16kV/3kA

SPD LOCATIONS PER IEEE

CategoryC10kV/l01cA

National LightningSafety Institute

891 N. Hoover AveLouisville co·80027

AREAS NEEDING SPDs IN TYPICALCOMMERCIAL BUILDING

99

AREAS NEEDING SPDs IN TYPICALPROCESS CONTROL PLANT

100

p......mon fo.- tra,"mttt.n •.......t ~..."". flow.hmpef"'G'tunl. f\,. OM go•..n......

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~ for itKoming POW*f".uppiy In 00l0pMn. 'Y.......

!1"XI 1"1........c_comm•• (av. M.cMm1 .ftdoux.lUory ckrtoc..-nm. 4ioorocc." 'Y'Nm' etc..

PROBABLE WORST CASES OF TRANSIENT INSULTS FORLOW, MEDIUM, AND HIGH EXPOSURE LEVELS

AT VARIOUS LOCATIONS

101

- Mains power supply - Category C

Systemexposure Peak voltage Peak current

level

High 20kV 10kA

Medium 10 kV 5kA

Low 6kV 3kA

Derived Irom OrigInal work In IEEE C62.41-1991 and reproduced fromas 6651:1992

- Mains power supply - Category A

Systemexposure Peak voltage Peak current

level

High 6kV SOOA

Medium' 4kV 333 A

Low 2kV 167 A', '

, .

DerIVed Irom onginal work In UL 1449 and reptoduced from

as 6651:1992

• Mains power supply - Category B

Systemexposure Peak voltage Peak current

level

High 6kV 3kA

Medium 4kV 2kA

Low 2 kV 1kA

Derived from origInal work In IEEE C62.4 ,- 1991 and UL 1449 andreproduced from as 6651: 1992

- Data lines - Category C

Systemexposure Peak voltage Peak current

level

High 5 kV 125A

Medium 3kV 75A

Low 1.5kV 37.5 A. ,

Derived from origInal work in CCln IX K I 7 ond reprodllceet Iromas 6651:1992

VOLTAGE (1.2 x 50) AND CURRENT (8 x 20)TRANSIENT SPECIFICATIONS, BASED UPON

ANSI/IEEE TYPICAL WAVEFORMS

Voltage

102 ~

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~

C

C

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•••••••••••••••••.<•••,,,,,,,,,,

Time

Time

lpeak (3kA)

1.2J..l.s

20J-ls

Current transient

50/U

Voltage transient

Current

10%

I90%1---.........

90% \o----e~-Vpeak (6kV)

103

OVERVIEW OF SPD FUNCTIONS

Varistor SIliconavalanche

diode

Gas tube P·lype N·type

Thyristor SPOs

1. Graphic Symbols used todesignate SPD components.

Generic Voltage-Limiting Type("Clamp")

Voltage-Switching Type("Crowbar")

2. Typical Volt-Time characteristicfor a voltage switching SPD.

.'.'

•••••••, Prospective voltage....

0'

L-.- Sperkover or tum-on

Crowbars

oI

1I

2I

3I

4

Microseconds

Normal System Voltage

3. Typical I-V characteristicof a.clamping SPD.. "...............................................................................

..•......• '~I~~~'I~~'~~~~~l' . ..j . .~

0.001 0.01 0.1 1 10 100 1000Amperes

4. Basic two-step (hybrid) defenseagainst surge impingement.

Restrict

Protectedcircuit

( First stage) (second stage)

Time Current

a) GDT waveform and circuit b) MOV waveform and circuitsymbol symbol'

•104 4

••••••••••••••••••••••••••.'•.,•••••••..........­..

> .' ' •

Volts ...

TRANSIENT LIMITING CHARACTERISTICSOF GENERIC SPD COMPONENTS,

ASSUMING 8 X 20 VOLTAGE WAVEFORM.

Volts

Current'

,c) 'S':'ppression diode waveform, and circuit symbol" '

. Volts

RELATIVE ADVANTAGES AND DISADVANTAGESOF PRINCIPAL TYPES OF SPD PROTECTIVE ELEMENTS

Protective EnergySpeed of level handling

Component response (sensitivity) capability Stability Comments

Gas-filled Fast fair High Fair High-energy handling when $0 constructed.discharge (micro- low-voltage ionization levels, versatile,

tube seconds) selF-restoring, long-life, maintenance-freeInitial high voltage resistance let through

Air gap Fast Poor High Poor Highly unstable and vulnerable to changes in environmentalconditioM, will not divert transients under 600V whichwill destroy $OlicJ..stote equipment, requires maintenance

Surge relay Slow Good High Good Good in olmost ell areas except speed of response -(millisecond) the millisecond response cannot prevent the microsecond

death of transistors requires maintenance, bulky

Corban gop fast Poor High Poor Fairly fast response, but nol completely self-restoring (in caseof high-energy transients), ionization level too high toprotect semiconductors, noisy in operation,requires maintenance

Zener diodes Very fast Very good low Very good fast respoM8, but seriously limited in energy·(picoseconds) handling capability - will not protect equipment from

external transients $uch as lightning or induction from powerlines, easily damaged

Circuit breakers Slow fair High fair Very slow, require maintenance, bulky

fuses Very slow Good High Fair Require replacement. Responce time determined by fuse CUffent

Meta\.oxide Very fast . Fair High Poor 'Soft' voltage clamping characteristic is not sufficiendyvaristor accurate for modern Iow-power semiconductor devices ,

characteristics change over lifetime/and number ofpulses absorbed

National LightningsafelY Institute

891 N. Hoover Avelouisville CO 80027

105

DESIRABLE SPD OPERATING CHARACTERISTICS(Adapted from G. Celli, ICLP 2003

Voltage protection level (Up): parameter thatcharacterizes the perfonnance of the SPD in limitingthe voltage across its tenninals;Residual voltage (UreJ.· peak value of .voltage thatappears between the terminals of an SPD due to theleakage of a discharge current; .Maximum continuous operating voltage (UJ:maximum rms or de voltage which may becontinuously applied to an SPD;Nominal discharge current (l,J: crest value of thecurrent having a wave shape 8/20;Maximum discharge current (l~ .• crest value of acurrent through an SPD with 8/20 wave shape and 'magnitude according to the operating duty ,t~st

(lmax:>ln); . . . . ... . . .. ... . .Impulse current (limp):, defined 'by 'a curr~nt value(Ipeak), 'a 'charge' (Q) and a specific'energy (W/R).

National Lightningsafety Institute

891 N. Hoover Ave.Louisville CO 80027

106 '

THREE STAGE SPD COMBINES GOOD PROPERTIES OFDIFFERENT PROTECTION DEVICES TO MANAGE AN INPUT

TRANSIENT OPTIMALLY.

107

VOLTIOE>---e--t DROP

ELEMENT2

LIGHlNITRANSVOL11GEICURRENTSOURCE

STIOE2MOVDSlI~

---

L\V1= R.i

orAV1 =l.diJdt

SWE1mlUlNCHEDIODE (SAD)

PRO'1"B:TEDINPUT

Problem: A lightning surge strikes a signal input in electronic equipment. This surge canbe represented by a voltage/current source with the open-circuit voltage/short-circuitcurrent characteristics of the combination wave of page 43.

The surge energy is diverted to ground as folloWS:

0) Current will not flow until the input voltage reaches the SAD's clamping voltage.The open circuit 1,2150 f.lS voltage curve applies.

1) The SAD fires in about 1 ns and clamps the voltage at about 18V thus protectingthe exposed input effectively. Short circuit 8120 Os current curve appliesapproximately. Since the SAD can dissipate only 1500 Watts (80 Amps). the risingcurrent must be redirected to a second stage.

2) As a second stage a MOV is usually chosen to keep the clamping characteristic,preventing short circuit of the signal source at low energy transients. The current orthe rate of rise of the current, which now is entirely circulating through the SAD.creates a voltage AV1 across the Voltage drop element 1. When the total voltageAV1+VSAD reaches the MOVs clamping voltage (about 27V) the current flowsthrough the MOV, protecting thus the SAD.

3) The still rising surge current develops a voltage drop AV2 across element 2. WhenAV2+VMOV reaches the gas tube firing voltage the gas tube turns on and directsmost of the extremely high lightning energy to earth ground.

A 90V gas tube will fire at its rated voltage in about 1 s. But its firing voltagedepends on the rate of rise of the 'applied voltage. During the very fast lightningtransient it will fire at about 650V.

Solution: The three-stage SPD combines the time response, clamping characteristics andenergy handling capabilities of different devices ensuring effective input protection andavoiding protection device failure.

Courtesy Profs. C. Brio:to tprd M.. Simon, Univ. de 111 Republica, Montevideo Uruguay

SURGE REFERENCE EQUALIZER (SRE)

C108 C

CC««««««4

C

C

C

C

•(

(

...

/Telephoneprotectors

Surgereferenceequalizer

Branch circuit

Service.. panel

SREs eliminate the threat of potential differences where data andAC power lines are remotely grounded. Power and data lines areconnected to the SRE. The SRE is installed at the point of use ofthe equipment. SREs are available at most electronics stores.

Fuse 100 PowerTIp Sup pression

L

TELEPHONE NGas .LINE tube

G

Ring100

Metal water pi pe

SURGE PROTECTION CHECKLIST

1.0 The following factors justify the suitability of SPDs:

1.1 Surge damage has been suffered or issuspected.

1.2 Surge damage has been suffered by othernearby facilities or organizations.

1.3 A Risk Analysis indicates significantprobabilities.

1.4 The consequences of surge damage are serious,despite a low probability.

1.5 Surge protection is specified by an insurancecompany -or parent organization.

1.6 Experience with surge protection elsewhere hasvalidated their application.

2.0 What should SPDs protect?

2.1 Main Entry Panel

2.2 Selected Branch Panels according to criticality.

2.3 Telephone Lines and Telephone Switch.

2.4 Cables for Telemetry, Instrumentation, andControl

2.5 Antenna Cables

2.6 Security and Fire Alarm Systems

2.7 Outdoor Lighting.

109

RECOMMENDED SPD SPECIFICATIONS

NLSI applies the below criteria in assessing merits of surgeprotection devices:

1. UL 1449 Listed under TVSS for load side installation AND UL1449 Listed for Surge Arrestor for line side installation.

2. Replaceable MOV modules. No spark gaps with impulsebreakdown voltages. No use of potting'compounds to encapsulateMOVs.

3. Environmentally-neutral materials with no off-gassing.4. All mode protection L-N, L-G, N-G, L-L.5. Internally-fused disconnects on each phase for means of circuit

protection from failed components.6. SPD passes tests per IEEE Std C6234 sub 7.5 and 7.5.4 for loss of

neutral protection.7. Cable connection between bus and SPD minimum # 8 AWG.8. Enclosure all steel with UL-approved fasteners.9. No power consumption. No follow-on current.10. Response time less than one nanosecond. Self-restoring response..11. Bipolar operation. Clamping operation is the same· for external or

internal transients. '12. Continuous self-monitoring with indicator lamps for each mode, and remote alarm relays in each phase. Audible'alarm .with push~

to-test and push-to-silence abilities.13. Independent, certified test results furnished.14. Manufacturer compliance with ISO 9000 QC procedures.15. Meets all requirements ofFAA. Accepted by FAA for high

threat environments..

National Ughtningsafety Institute

891 N. Hoover AveLoulsvUleCO 80627

4110 4

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RECOMMENDED SPD INSTALLATION PRACTICES

1. SPDS should be installed as close as possible to their respectivepanels. Inches instead of feet is the Rule. Lead length is critical forthe SPD to operate efficiently. For example, a #6 AWG cablelength of five feet causes a voltage drop of 275V. Where possible,mount the SPD directly against the panel to be protected.

2. Avoid tight bends. Follow the NFPA-780 eight inch Rule tominimize inductance.

3. Leads should be twisted to reduce magnetic coupling. Refer toFAA-OI9d, Table V, page 35 for details.

4. SPD remote monitoring alarms should be placed in a fully­operational area, not in a closet or in an infrequently-visitedequipment room.

5. SPDs should be inspected regularly. During the lightning seasonlook them over daily. Smell smoke? Many SPDs work via failure.A burned SPD module should be replaced promptly.

National Lightningsafety Institute

891 N, Hoover Avolouisville CO 80021

111

SPD EVALUATION FORMThe following tables can be used to compare different TVSS products or todocument the different lVSS device specifications for the correct application.

Note: the numbers provided are example specifications, typical for TVSS

devices intended for a staged application.

Specifications/features desired

~-

Application voltage

MCOV

Peak surge current

Filter freq. range

Energy rating

Response time

Protection modes

UL approved

Let through voltage

Operational indicators

Diagnostic indicators

Overcurrent protection

Alarms

Warranty

Pricing

Manufacturer name

Application voltage

MCQV.

P.eak surge current'

Filter freq. range

Energy rating

Response time

Protection modes

UL approved

Let through voltage

O'perational indicators

Diagnostic indic,ators

Overcurrent protection

Alarms

Warranty

Pricing

" Manufacturer name

Hardwired TVSSSample Model 1 Model 2 Model 3

240V

300V

5

x750 V

5 Yr.

$250

Communications TVSSSample Model 1 Model 2 Model 3

240V300V

5

x750 V

1 Yr.

$250

Receptacle TVSSSample Model 1 Model 2 Model 3

120V--150V

3

x--330 V--

1 Yr.

$65

112

USEFUL SPD FOLLOW-UP REFERENCES

1. IEEE Std 1100-2005 Powering and Grounding ElectronicEquipment, Institute ofElectrical and Electronic Engineers,NY NY 2005

2.. Internet Web Sites:2.1. www.polyphaser.com2.2 www.phoenixcontact.com2.3 www.mtlsurgetechnologies.com

3. EMCfor Systems and Installations, Tim Williams andKeith Armstrong, Newnes·Publishers, London 2000

4. Noise Reduction Techniques in Electronic Systems,HenryW. Ott, John Wiley, NY NY 1988.

5. Protection ofElectronic Circuits from Overvoltage,Ronald B. Standler, John Wiley, NY NY 1989.

6. Recommended Practice for Protecting ResidentialStructures andAppliances Against Surges, EPRI PEACCorporation, EPRI~ 1999

National Lightningsafety Institute

891 N. Hoover AveLouisville CO 80027

113

Ode to the Missing Surge ProtectorAuthor Unknown,

Supplied by National Lightning Safety Institutewww.Iightningsafety.com

Ifa transient hits a pocket on a socket on a portAnd the bus is interrupted at a very last resort

And the access ofthe memory makes your floppy disc abortThen the shocked packet pocket has an error to report.

Ifyour cursor finds a menu item followed by a dashAnd the double-clicking icon puts your window in the trash

And your data is corrupted 'cause the index doesn't hashThen your situations' hopeless and your system's gonna crash.

Ifthe label on the cable on the table at your houseSays the network is connected to the button on your mouse

But your packets want to tunnel to another protocolThat's repeatedly rejected by the pririter down the hall

And your screen is all distorted by the side effects ofgaussSo your icons in the window are as fickle as a grouseThen you may as well reboot and go out with a bang

'euz sure as I'm a poet, the sucker's gonna hang.

National LightningSafety Institute

891 N. Hoover Avelouisville CO 80027 .

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Six

COMMUNICATIONS FACILITIES,EXTERIOR LIGHTNING

PROTECTION

115

Chapter Six Overview~etY applicati?D,

Communications facilities often have a critical life..$ lie broadcastingespeci~ly wit? E911, air traffic control and some pll::S on some .levelsoperations. This Chapter and the following Chapter 7 fo~ " for Engmee!s.of detail not contained elsewhere in Lightning ProtectiIJ can be appliedHowever, many of the principles in these two ctmpte.t6generally to other facilities.

. ... . COnsider vari~usExtenor lightnlng protection of communications SItes muStOiDg and bondmg~esigns oftowers, adjacent equipment buildings and grouJJ~ce cannot beISsues at both locations. Regular inspection and maintcignored without peril. ent InstallationsMotorola R56 Quality Standardsfor FixedNetwork EquiP'"is a recommended follow-up to information herein.

"116 •

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TOWER BONDING - SELF SUPPORTING TOWER

-

117

Grounding KM

ClAOUHDIlOD_

I-~ Grounding Kit ..To Central Office

J, 2 1001 (0.6 me'.r) minimum below graoe..

To Central Ground Field

116 Bare Copper

National LightningSafety Institute

891 N. Hoover Avelouisville CO 80027

."

118 •

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BONO GUYSTOGETHERAND TO AGROUND ROD

TO CO GROUtJO FIB.O

BOND TO SHI8.0

IfSBARECOPPER

TOWER BONDING - GUYED TOWER

National lightningSafety lnatftute

891 N. Hoover Avelouisville CO 80027

•••__0. _ ..... _ ._-_•••• '"

TOWER BONDING - BUILDING MOUNTED

'--- Grounding Kits

119

National lightningsafety InStitute

891 N. Hoover AveLoulaville CO 80027

DODDOD

.....-- '2 Copper

....To Central OfficeGroUnd Field

120

GUYED TOWER WITH EQUIPMENT BUILDING,GROUNDING CONFIGURATION

llnnBd AWG #2 solid or-.rancl811.nol>-InSutalllcl ___copperwue

TInned AWG #2 lOUd or ~rIUandad. non·inlulaled 8c:opperwite ~--1~ __

ExltmII bUM bar 1II f1l\Iy point ClQIlIMC:Ied 10lI>Cltmal ground ring UIlng lIMed AWG "2,olill or nandad, non-lnlutaled c:opPt' wira.

Grounding Guy Wiresat anchors:

MONOPOLE TOWER WITH EQUIPMENT BUILDING,GROUNDING CONFIGURATION

llnnacl AWG ;n IOIld orllranded, non-insulatedc:opper wlr1I

building

OPTIMUM GROUNDING DESIGNSHOWING PERFORMANCE WITH LIGHTNING ATTACK

(Source: Polypbaser Corp.)

121

Recommended site grounding system about to be hitby lightning.

On a well designed ground system, the strike energyspreads out initially from the building.

Neglecting the coax currents, the strike energy movesoutward from the tower base along the radial line.

As It spreads, " loses energy due to the spreading andI·R losses.

+--f--G""""OAOOS

""LINENTR'f

As it reaches and saturates the radial system, It willtraverse the building perimeter.

By the time It surrounds the building, the radials havespread out much of the energy.

122

TYPICAL COMMUNICATIONS SITE,EXTERIOR GROUNDING PLAN

.---_ EOUIPOTENTIAL Pt.ANE MESH Sl7f.lSPACINGS~IOULO BE MINIMAL SIZE PHACTICAL

·STnUCTUUE

,'-, .-'

~ /f,~ /"

K. J~r., '. ", ,/ ,

METAL PIPES ENTERING I ...... '- . \)THE fACILITY-SHOULDB~' ".,. /" ~/EA/R"T'tf ,.~"GROUNDED AT TilE I ,JJ, ,. ....FACILITY ENTRY POINT '~.., ...... ,, f, El.ECTRODE SUOSYSl EM ' ./"

,,\ I""" I ROUNDING Fon fOlJlPOTENT~" Y LANE I "·--·GHOUN[)ING FOH STRucn JHf\L "

STEEL ''' ..."" ) / /

National Lightningsafety Institute .

891 N. Hoover AveLouisville CO 80027

123

EXAMPLE OF EXTERIOR GROUNDING RING(ALSO CALLED COUNTERPOISE)

nNNED AWG 11'2 SOUD ORSTRANDED NON-INSULAlED COPPeR----------

)KI

)KI

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GENERATOR

~ X X X X X X X X X X X X~ X X X X X 2<~t..,j... " AlR .,'l' " " CONOlnONER /.,.... _ ./

t---I-------·-----/--~---.__ Tj ~ .E"=~

BUILDING

laCOANO : I :" / ~I 1-;l;;.~~I~--------------- ~ './ !

..I... I GROUNDf /.---------~-..--------..-?'~~w* / GROUND RODS ' , ,./ -....,~\X X X *7* x x X

FENCE ~CORNER POST FENCE EXTERNAl GROUND DOUBI.£

RING A MINIMUM OF DOOR GATETWO FEET FROM

BUllOlNG

Nons: IN WHEREGATE MATERIAl. IS iM­PROPER FOR ~WELD.

CUlMP WITH APPROVEDMATERIALS.

~ ORCl.AMPEACH

GATE TO

SUPPORT'~OC>o<lW'~NNEDAWG #6 MINIMUM

STRANDED COPPER ORWELDING CABLE

ALTERNATIVE COAXIAL CABLE ROUTINGFROM TOWER TO EQUIPMENT BUILDING

124

BEST

InoUneP,olllClo'

ADVANTAGES

Low l dlldt voltage

DISADVANTAGES

'} Coax must maketight bends.

21 Coax enters at floorlevel.

GOOD

l..-LlneProt.cIor low L dVdt at tower 1) large L di/dt for in

line protector unlesslarge groundingsurface areaconductor is used forbuilding CGK andprotector.

21 Sloped line willintercept tower magfields.

OK

Low l dildt at bUilding 11 Coax must enter atfloor level.

'2) Slop~d line willintercept tower magfields.

ACCEPTABLE

BulkhMclPanel

InoUneProtector

1) Enters building high. Large straps cost morebut are needed to reduce

21 Does not intercept L di/dt voltagetower mag field.

Na' nal Lightningsafety Institute ,

891N. Hoover Avelouisville CO $0021

BOND OUTER SHIELD OFCOAXIAL CABLE AND

ELLIPITCAL WAVEGUIDETO TOWER LEG

125

Tower Leg

#6AWG

Transmission Line

IC==::::=l.-- Bonding Clampand Weather Seal

Elliptical Waveguide

Entry Plane

National LightningSafety Institute

69' N. Hoover AveLouisville CO 60027

To Cenlral OttlceGround Flekl

+

Grounding klls should connect totile entry p,lite at a ,common poln,and run In a downward dlrecllontOWllld grOUnd,

Connecllon 10 grouno flelo5houIQ be eXlernal tothe Central Offica I)uilolng

TYPICAL TREATMENT OF INCOMING COAXIAL CABLES

Bond the cable sheath to the exterior building ground reference at the bulkhead.Install SPDs immediately at coaxial cables at the bulkhead.

Assure that bulkhead is well-grounded.Bond cable trays to bulkhead.

llc••

-GFIOUNOlHQ KIT~NSIOEBOOTl

. 1ofJl.11Pti1.ltlCNCOPPER stAAPs

TO AAOIALSySTEM

The Idelll grounding 50lutlon 15 to. develop II single point ground 5Y51em III the bulkhead ell/TII/l(t

panel. ProtectOT5 elln be mounted to this pllnel to prevent sUlgreu';'enl from going Into the tqllipmf/l'-

126

GROUNDING CHECKLIST FOR COMM. SITESTABLE I, EXTERIOR ITEMS

127

KEY: EGBEGR1GB

External Ground BarExternal Ground RingIsolated Ground Bar

IGRIGZMGB

Isolated Ground RingIsolated Ground ZoneMaster Ground Bar

GENERAL: All bends in ground wires are to have a minimal 8-inch bending radius.AC surge protector to be installed on the load side of the main ac disconnect.AC to tower lighting to be surge protected.IGZ cable tray to be isolated from all other cable trays.IGZ cable tray to be isolated from all casual contacts with ground.No ground wires in metal conduit unless conduit is bonded to ground at both ends.

Table 1. ExtemalSite Grounding Checklist

ITEM v DESCRIPTION CONDUCTOR CONNECTION

All Siles (MTSO And CeU) Require:

Connections to the EGR (External Ground Ring):

I EGB Note 2 CADWELD

2 IGR (each comer and every 16 feet between) #2 solid CAD WELD

3 ground rods (every 16 feet) and under EGB #2 solid CADWELD

4 MGB #2 solid CADWELD

All Cell Siles Require:

Connections to the EGR (External Ground Ring):

I tower ground ring (2 connections recommended) #2 solid mechanical

2 lightning arrestor bracket #2 solid CADWELD

Connections to the tower:

I from tower ground ring #2 solid CADWELD

2 lOp of rf lines ground kit mechanical

3 rf lines at exit from tower ground kit mechanical

4 guy wire to ground rods (guyed towers only) #2 stranded mechanical

Connections to the tower ring:

I from tower leges) #2 solid I CADWELD

2 from EGR (2 connections recommended) #2 solid " CADWELD

Miscellaneous external grounding connections(connect to nearest pointo! external system):

I metal fencing within 7 feet #2 solid 'Note 1..

"

2 metal building parts #2 solid Note I

3 fuel storage tanks #2 solid Note I

4 utility grounding electrode systems #2 solid Note I

5 metal objects more than 2 ft. sq. and within 7 ft. #2 solid Note 1

6 reinforcing bar in concrete floor (if accessible) #2 solid Note I

7 building skids or anchors (if accessible) #2 solid Note I

8 exterior cable tray, ice bridge #2 solid Note I

9 generator grounding system (if applicable) #2 solid Note I

10 generator chassis (if not otherwise grounded) #2 solid Note 1

Connections to the EGB (External Ground Bar):

I waveguide entry window #2 stranded mechanical

2 rf line ground kits at building entry #2 stranded mechanical

3 EGR #2 solid CAD WELD

NOTES: I. All below ground connections muSl be exothermic. Above ground connections may be mechanical.2. Either two #2 AWG solid wires or one 2-inch xI/I6-inch coooer strao must be used.

-

128

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INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Seven

COMMUNICATIONS FACILITIES,INTERIOR LIGHTNING

PROTECTION

. - Transient protectors should always be .installed between the source of the threat and theequipment we are trying to protect

129

Chapter Seven Overview

Several classifications of SPDs, signal reference grids, computer grounds,AC grounds, single-point grounds, multi-point grounds, lightning grounds,Halo Grounds, equipotential bonding, shielding, cable tray treatment, LANs,isolated equipment protectors ... this is a busy subject. Attention to detail isrequired to avoid calamity.

For further reading and much more depth on the subject, we suggest FAA~STD-019d Lightning and Surge Protection, Grounding, Bonding andShielding for Facilities and Electronic Equipment. Critical operations atairport control towers - with safety from lightning's effects - are descnoedhere.

. ,',

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TYPICAL COMMUNICATIONS SITE,INTERIOR GROUNDING PLAN

CARRIER/PAIR GAIN ANDOTHER MISCaLANEOUS

EOUIPMENT

RADIO EOUIPMENT MASTERGAOU~ (1.1GB)

MAIN CABINETS fTfP A r----DISTRIBUTING ReM G N B L W N N~ I r GROUNOWiNDOWBARIGWB)---lFRAME & " • ..., " I. I 0.0050 I~QRI.ARGEIIJ 1PROTECTORS o.om ,0.GOllO ,JUNCTION 80XfEP T· IGZ 1

~D--- - -----. ELECTRONIC

ABLE ENT E TO GMI'S I § SWITCHING IG~NDB~~B) INOTHERlGZ"S I I "001111" eaUIPMENT

(, , " t, ~ I I ----- ,.;;. 1

~~1TTl I I TOOTHERNON·IQZ I II ~~ I Il CABLE SHIELD EQUIPMENT GROUNDS. I I I;;)t"~ IGAOUNDS(I6GAUGE) 0.00&11 DiG'iTA'LCARRleR'1- - --J

OR BONDING RIBBON 0.010 I & ELECTRONIC

l..010 T PAIR GAIN

~METAU.ICWATeRSYSTEMGR~. I EOUIPMENT

I OPTIONAL

MDrGtiiil(MrB

) MlC:ve} I ~e~~«;:~~1IGB)TOweRQROU~ I &ASSOC14TEO

Al6 GAUGE ~ ~ • • • •• .-+0:0111 !! 0.010 I 1 I ,.. 1/!I!!i~ ~PROTECTION & TIP CABLE & I I t-'J rcr--, ~

SHIELDGAOUND(I6QAUGE) 0 L~~~~ n I ..- il' o.oo~n I "STANDBYII RODG!'lND. I l.--:;=:"--HH+--~

GENE~~~ I J. 0.0111 O.OUl I II11I ! o,oo~n0.00&11 (a"lOl\\.AAGEIll " ,. H., c.°F~~ I

I ,.' ~ ",;"";;J 0.00&0 111111 I

COMMERCIAL I ~STANOARDAC 0.0111 IACPOWER .. I RECEPTACLES 8UIl.D1NG ..------------1

r-- GREEN IN NON-!GZ STRUC1U\ALI= ~I= I WIRE AREAS __ GROUND I_ I-~ 1 .J...::: """'"ir I ELECT~MECHANICAL

~ '1-1- I .......- . I / SWITCHING

~ I _t..t=: ----crREeNWJReTOiGz-·- '" ~EQ~·PROTSEURCTOR~ I r lLL. IGROUND 8~~=== I~ ~MAlNE II "a':! ..~

HEm NEUTRAL. BArm:~~':i8HOWN I~=11~1TIRES lell l,r<.;>n~t ISERvICE ENTRANCE B~RCUIT' L __~·GREEN::::!::.!W~IA~E:..__...;... ;...__..;.,........_.===~~==·=!"':'-.,;..==':;"'~"'~t-/JI

PANEL BOARD PANELBOARO REMOVESTRAPS

National UghtningSafety Institute

891 N. Hoover AveLouisville CO 80027

"HALO GROUND" PROVIDES SHORTEST-DISTANCEBONDING BETWEEN EQUIPMENT CABINETS

AND EARTH REFERENCE.

" \I I1\1\1\1\I'1\\ \\ ,I I

\ \(5)I ,

\ \ /I I ~\, //, ~ .......

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,,'" "",/ , \I.... \ \I ........ , \ \IIIII

: (6)III

t..""

. A - Exterior Ring Ground8 - Peripheral ConductorC :- Supplementary Conductoro-Interior-E:xterior BondE ~ Interior Unit BondF - Exterior Unit Bond~ - Ground Rod

.(1) - Equipment Lineup(2) - Power Plant(3) - Miscellaneous Unit(4) - Waveguide Hatchplate(5) - Antenna Tower Leg .(6) - E:ngine-AltematorEnclosure

4132 4

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EXAMPLES OF INTERIOR GROUNDING & BONDING

Ground Grid

TO EXTeIlNAl.GllOUNDRING

TO ElCTeRIOIIGROUND RING.TYPICAl.. CORNERS.

BUILDINGEXTERIOIIWAU.~ WID1 SURGEPROTEcnON~,

/"1 STAm4,~rn,~ ~KS ~CONNEcnoN I__ ~t

U I I Ill. J I \

;ZCAlUTAAY

~

TRANS", SSiON~.UNE ENTRY

E

a£cmJ --iPANEL

"'\

TYPE~~ fJ.--ilI.

PAOTECTr

( 1Nlm01lHN.O~ 10 EXTERIOR GROUND RING IF BUILDING CoIlNERS ARE ....GlIOU'OHG RING MORE '!MAN IS' APART. TYPICAL OPPOSITE SIDES OF BUIl.DlNG.

Power ProtectionLayout

ACB_IIPAHEL

\~o!

I

CAIU TAAY SYSTCM GROUND RING #2 AWQ IROUND(MUST BE BONDeD TO AU. COANEFlS NKJ BENDSI

GRCUNDWI;NDOWI;!!:::=i~~~~F:::::~@

~ll,..~\ BONDING STIW'

TYPEMll8'TEI..EPHONC SURGE

PAO-mrr~

,TYPE 1AC SUllGE

Q PAOTl'CTOR

~P\IC CONDUITINF1.OOR"""--.... EOUIPMENT RACK OR CAIIlNET OUT10GIIOUND 1.001\

NOTE: EACH INDMDUAl. RACK lYPlCI\L, AU. CORNERSOR CABINET MUST BE BONDED OF EOUIPMENT ROOM.TO '!liE GROUND WINDOW.

ANOTE: EACH INOIVIOUALRACK 011 CAIIlNET MUSTBE PLUGGeD INTO ASINGl.E SURGE SUPPReS­SION RECEPTACLE.

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EXample .Only .Equipotential Plane

BuildingSteel

Ground. Ring··

BONDING RAISED FLOOR INCOMMUNICATIONS OR COMPUTER ROOM

TO ACHIEVE EQUIPOTENTIAL GROUNDING

Walls

..';'

Hdonal UghtningSafety Institute .

881 N. Hoover A.veLoulavilte CO 80027

Steel

Plumbins ana;)ioewcrk

.. - .

BONDING INTERIOR :METALLIC COrvtPONENTSTO OBTAlN EQUIPOTENTIAL GROUNDING

Structural steelwork (and re-oars)• use weided sl'.JcIS

135

NatiaftaJUghlnillgsate=- .II1N. AveLouisviIe CO 80027

CABINET OR RACK BONDING DETAILFOR ·COMMUNICATIONS EQUIPMENT

IsolatedElectronicGround Bus(SPG)

To Single­Point'GroundingSystem

. National LightningSafely Institute

891 N. ffoover AveloUisville CO 80027

:\AC p.ower line

IndividualElectronicEquipmentUnlt8

Equipment Gtollldlng Conductorconnected to

~ronlc EquIpment Rack .. and

ElectronicEqu~ Enclosures

~~...

To Multipoint.Ground System .

•136 •

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138

DETAILS OF CABLE TRAYS & DUCTS

I--=:::: !*,p; bL: II b:\

"c;S;

Continuity between sections

Wires OK for 50J60Hz. but poorfor higher frequencies· ShOlt, wiceStraps (one eacn side) ~reterred

U-brackets wlttl multiple fixingsare good at I'Ilgh frequencies·seam welclea JOInts are oest

Bonding cable traysand ducts to cabinets

* MAINTAIN MINIMUM 2-INCHSEPARATION BETWEENCONDUCTOR BUNDLES.

CONTAOlllNTERCONNECT UNES

baSe of OlJctor tray bentdown and fixedevery 100mm

U·braCket • seemwelded. or fixedevery 100mm

Nationai Lightningsafety Institute·

. 891 N.. Hoover AveLouiSviUe CO 80027

GROUNDING CHECKLIST FOR COMM. SITESTABLE 2, INTERIOR ITEMS

Table 2. Internal Site Grounding Checklist

ITEM yo' DESCRIPTION CONDUCTOR CONNECfION

Connections to the MGB (Master Ground Bar):

I racks containing rf equipment #6 stranded mechanical

2 waveguide entry window #6 stranded mechanical

3 RMC (receiver multicoupler) #6 stranded mechanical

4 telephone protector grounding tenninal #6 stranded mechanical

5 generator chassis (if not otherwise grounded) #6 stranded mechanical

6 channel bank racks #6 stranded mechanical

7 EGR #2 solid mechanical

8 metal water utility pipe #6 stranded mechanical

9 multi-grounded neutral #6 stranded mechanical

10 building steel (if accessible) #6 stranded mechanical

11 IGR #2 stranded mechanical

12 1GB #2 stranded mechanical

13 ground bar of +24 Ydc power system #6 stranded mechanical

14 ground bar of -48 Ydc power system #6 stranded mechanical

Connections to the IGR (Internal Ground Ring):

I all racks not grounded to MGB or 1GB #6 stranded mechanical

2 ventilation louvers and ducts #6 stranded mechanical

3 cell site cable tray (multiple points) #6 stranded mechanical

4 metal door and window frames #6 stranded mechanical

5 metal battery racks #6 stranded mechanical

6 Halon system..'

#6 stranded . mechanical

7 transfer switch enclosure #6 stranded mechanical

8· miscel1ane~ussignificant metal Objects #6 stranded mechanical

9 EGR (every 16 ft.) #2 solid mechanical

10 MGB #2 stranded mechanical

Connections to the 1GB (Internal Ground Bar):

1 MGB #2 stranded mechanical

2 cellular switch frame #6 stranded mechanical

3· grounds from a~ o.ut.lets i~. the I~Z #6 stranded mechanical

IGZ cable tray (one point only)..

#6 stranded mechanical-4

5 JOZ distribution frame #6 st~ded mechanical

6 modem frame #6 stranded mechanical

7 other EMX associated frames' #6 stranded . mechanical

139

SPD & UPS LAYOUT FOR COMM. BUILDING

Surge Suppressor (loadof transfer. switch)

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SURGE PROTECTION ADDED FORSUSCEPTffiLE EQUIPMENT

Panel boardand SPD(typical)

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Surge/impulse

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Surge/impulse

Branch circuittypical)

Central officefeeder (COF) cubleor interbuilding cable

r;:=~=:::J -+

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Surge/impulse

Serviceground

Metal cold-water pipingsystem and telecommunicationsground connection

Undergroundmetal cold­water pipingmain service

Service g.rollnd~

SURGE PROTECTION CHECKLIST

1.0 The following factors justify the suitability of SPDs:

1.1 Surge damage has been suffered or issuspected.

1.2 Surge damage has been suffered by othernearby facilities or organizations.

1.3 A Risk Analysis indicates significantprobabilities.

1.4 The consequences of surge damage are serious,despite a low probability.

1.5 Surge protection is specified by an insurancecompany or parent organization.

1.6 Experience with surge protection elsewhere hasvalidated their application.

2.0 What should SPDs protect?

2.1 Main Entry Panel

2.2 Selected Branch Panels according to criticality.

2.3 Telephone Lines and Telephone Switch.

2.4 Cables for Telemetry, Instrumentation, andControl

2.5 Antenna Cables

2.6 Security and Fire Alarm Systems

2.7 Outdoor Lighting.

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CABLES

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891 N. Hqover Avelouisville CO 80027

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RECOMMENDED SURGE PROTECTION FOR THE LAN

Office

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Bridge

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National Lightningsafety Institute

891 N. Hoover AveLouisville CO 80027

ALTERNATIVE METHODS OF SHIELDINGFOR SURGE PROTECTION & REDUCTION

146

Shield Against

Below average shielding characteristics againstinductive and capacitive c~upling.

Above average shielding characteristics againstcapacitive coupling.

Average shielding characteristics against inductiveand capacitive coupling.

Best shielding characteristics against inductive,capacitive and electrostatic coupling.

Good shielding characteristics against inductive andcapa~itive coupling, Best shielding against electrostaticdischarge.

Foil Braid

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National Lightning. Safety Institute891 N. Hoover AveLouisville CO 80027

147

BONDING OF ALL CABLE SHIELDS TO TERMINAL STRIP

INSULATION

National LIghtningS8f8ty Institute

891 N. Hoover Avelouisville CO 80021

SIGNAL LIKE

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NOISE OR "HUM" REDUCTION TECHNIQUES

• Grounding• Twisted Pair Wire• Shielding• Transient Protection• Cast Iron Pipe

Drain Ground

148

National LightningSafety Institute

891 N. Hoover AveLouisville CO 80027

149

NOISE OR "HUM" REDUCTION TECHNIQUEUSING "ISOLATED EQUIPMENT PROTECTOR"

GROUND LOOP - HUM

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PROTECTOR

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National LightningSafety Institute

891 N. Hoover AveLouisvll!e CO 80027

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150

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Eight

LIGHTNING PROTECTION FORHIGH RISK INSTALLATIONS

SUCH ASELECTRIC POWER FACILITIES,EXPLOSIVES, MUNITIONS, &

VOLATILE FUELS

151

Chapter Eight Overview

Previous chapters in the book have examined subsystems or tools formitigation ofthe lightning hazard. Chapter Nine integrates all of them into ahomologuous approach. Got your Topological Shielding correctlyorganized? Have you completed your Decision Tree Checklist?

A NLSI six page summary document "21st Century Lightning Safety forEnvironments Containing Sensitive Electronics, Explosives and VolatileSubstances" is included.

153

DECISION TREE FOyACIl:ITY LIGHlNING SAFETYby National Lightning Safety InstitUte, www.ligh1Dingsafetv·com

1.0 Is lightning protection beneficial? ·1.1 Risk Analysis and ProbabIlIty Study

1.2 Cost vs Benefit?1.3 Assessment of Risk.

2.0 If Facility already haS been insulted by lightning, omit #1.2.1 Examine damaged components.2.2 Determine vulnerabilities.2.3 Perform Lessons Learned

3.0 Lightning protection is re.quir~.3.1 See guidance contamed m IEC 61024, IEEE 142, IEEE

1100, FAA 019d, FAA 6950, MIL 4l9A, NASA

E0012E NFPA-7804.0 Examine Facility and speciJ)' sub-category protection

requirements in accord~ce with: .4.1 Air Terminal optiOns: F~anklm Rod, Overhead, Mast or

Quasi-Faraday Cage deSIgns.4.2 Bonding: Achieve equi-potential of all adjacent

metallics.4.3 Shielding: EmploY where bene:ij.cial.4.4 Surge Suppression: Protect all AC power, data, etc

IIOs.4.5 Grounding: Achieve volumetric efficiencies. . .

. 4.6 Lightning Detector: For st~stop of auxiliary ACpower & for early~at wammg;

4.7 Testing: Verify loW tmpedance paths.4.8 Maintenance>periodic inspections, record-keeping

5.0 Develop Procedures and Policy for STOP/START ofactivities during lightning threat conditions.5.1 Recognize impending threat situation5.2 Notify affected areas to CEASE OPERATIONS5.3 Personnel to safety locations .

. 5.4 Reassess threat55- Notify ALL CLEAR - RESUME OPERATIONS

------------

PRlNCIPLES OF TOPOLOGICAL SHIELDING(Adapted from Rakov, 2003)

Ground wire

Zone 0

Earth

Zone 1 is located at the building exterior, where bonding and SPDsare applied to all incoming (penetrating) conductors. Example:the treatment of coaxial cables from an adjacent tower as theyenter the facility. The shield wires are bonded to ground and thesignal lines of the cables are treated with SPDs. This is the firstshielded line ofdefense.

Zone 2 is' located at the 'entry to the communications room inside abuilding. Further bondiIig and SPDs are applied to this secondary'shield location for all 'conductors inCluding AC power and signal'circuits.

~~ne 3 is located at the ind.iyi~1.!~1 ,~quipment cabinets and(of theeq:uipment itself. Telephone punch blocks also are to be included.Here, additional bonding and SPDs provid'ea third shielded layer. '

NatIonal Lightningsafety InStitute ,

891 N. Hoover AveLouisviHe,C080027

154

Field deviceField cobles

Telecommunication cables

At interfaces between zones,the lightning currents encounterequipotential bonding, SPDs,and screening to reducetransients to manageable levels.(adapted from P. Hasse, 1992)

I Lightning protectionequipotential bonding

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FORTRESS OR ZONE PROTECTION CONCEPT

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National Ughtningsafety Institute

891 N. Hoover Avelouisville CO 80027

PREFERENCE FOR MAST AND OVERHEAD SHIELD WIREAIR TERMINAL DESIGNS, AS CITED BY CODES

1. Per NFPA-780 (2000), Standard for the Installation ofLightning Protection Systems, Appendix K Protection ofStructuresHousing Explosive Materials, K.2, p. 38 Design Consideration:

"Where the effects of electromagnetic coupling are of concern, amast of overhead wire (catenary) systems might be preferred overintegral systems unless a Faraday Cage or shield is required. Theremoval (isolation) of the down conductors will reduce the magneticfield strength in the structure and reduce the probability of a sideflashfrom a down conductor."

2. Per NASA E-0012E (2001), Standard for Facility Groundingand Lightning Protection, section 5.2.17, p. 31 Ordinance FacilityGrounding and Bonding:

"It is recommended that ordinance facilities with a perimeter ofover 300 feet that require lightning protection have either a mast oroverhead wire system as specified in KSC-STD-E0013 and AFR91-43."

3. Per US Air Force AFI 32-1065 (1998), Grounding Systems, "section14.5, p. 11 ExPlosives Facilities with Large Perimeters:

"New explosives facilities (including igloos) with a perimeter over91.4 meters (3~0 feet) that require lightning protection and do not usethe structural steel as the air terminals must use either a mast system oran overhead wire system~" See Attachment 4" for requirements. Sincethese systems provide better protectbm, and maintenance is easier,consider using this type of protection for other" kinds of facilities."

157

volatile hydroc.arbonwalls is c.ritic.aL

refineryfaulty

Installation ofdouble ,'Vall seals and

Photo: 1 and other emergency COlnrrrUlllcatl0JrlS

antenna/tower sites as ~'en as at communications can centers. NEe250, R56~ FAA-091e and lEe 62305 needed develop robust lightningdefenses.

~ -~ - - - - - -- -- - - - - ----

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ERRORS AT CRITICAl.! FACILTIES, PARTS 3 & 4

shown atop the RHS pole cannot and willradius" far exceeds USA and

stdJ3.dards. Reslu]t';r TIus 1250 MW gas-fired power plant

158

GOING BEYOND THE CODESAn Expanding List ofThings You Learn On-The-Job

By Richard Kithil Jr.National Lightning Safety Institute (NLSI)

www.lightningsafetv.com

General Safety.- Don't work on any lightning protection issues where thunderstorms are forecast.-When working around RF, wear a personal Electromagnetic Energy (EME)monitoring device.- Always have some form oftwo way communications while working alone.

Safe Shelters.- Large substantial buildings are safe places. However, do not contact with

anything that could become energized by lightning. This ineludes water fromcopper water pipes, metal doors/windows, appliances and other electricalequipment, telephones, etc. etc. Sit on a chair and read a book. Get the idea?- Small wooden or fibreglas shelters are fine for sun or rain shelter: for lightningthey wont work. Flashover, step voltage and touch voltage issues make themdangerous places. Avoid them- Faraday-like metal shielded refuges work well. They include fully-enclosedmetal vehicles such as cars, vans, trucks, buses, heavy equipment (with enclosedROPS canopies). Plastic cars wont work. Neither will riding mowers, ATVs, golfcars, etc.- The best safe shelter for commercial/industrial applications sis a metal shippingcontainer. Cheap. Portable. Double-duty as a storage area. Watch the details:OSHA requires two doors. Think about ventilation (cut some windows/doors andcover them with expanded metal shielding). Think about benches or chairs(people may be inside for -some time). Think about, keeping out critters like 'snakes, bugs, wasps, birds. Think about a water Supply. InStall battery-powered'lights and fans,'but' do 'not 'install anything working off AC line power.;...-do thjs

': and you have compromised the C~e.' ,

Electromagnetic Energy Safety- In environments where explosion hazards may exist, non-incendive

intrinsically- safe electrical components must be used where acceptable. Notethat some areas may be entirely unacceptable for housing electronic equipment.

Communications Sites.- Aluminum ladders designed for climbing should not be used as cable trays or ',runways."" '"

- Cable separation should consider 'AC power, DC power, RF, groun~ and data"ground cables to avoid induced interference.~"Leave all battery issues to a battery "expert.

159

- Fixed or portable fire suppression systems must not be used in communicationssites.- If a building has a sprinkler system, make sure the cable runways do not block

the sprinklers.- Generators installed outside buildings, within 1.8 m (6 ft.) of the buildings, mustbe bonded to the nearest practical earth electrode system. Longer distances shouldhave an additional ground rod.- Generators inside buildings should have fresh air intake sized at 1.5 times theradiator dimensions to assure adequate ventilation. Vibration isolation betweenthe generator and frame is recommended.- For tower-top pre-amps which require DC voltage for operation, use a lightningarrestor that can pass DC current.- To pass a safety inspection, must-have items include: ABC and C02 fireextinguishers; fITst aid kit; interior and exterior lighting.- Incoming coaxials must be run through weather ports (boots) which also arerodent/insect proof.- Tower lighting cables carrying AC power should not be bundled along withtransmission lines or other conductors anywhere within cable ladders or thebuilding interior.

External Grounding.- Before excavating or digging, do the "locates." Call before you dig !

- Exothemic welding should not be done unless another person (experienced infITst aid) is present. A suitable fire extinguisher should be present during theprocess.- Wear safety glasses, hard hat, steel-toed boots when working with high­compression fittings.- Braided bonding straps shall not be used because they corrode too quickly andcan be a point for RF interference.- Avoid differences in potential. Do not install· separate . grounding .electrodesystems. Follow'NEC 250lIEEE 142/FAA 019d requirements here. '- Before disconnecting a grounding electrode conductor, check for 'current. Neverdisconnect the gro~dofa live' circuit. ~,.-death or severe injury could result.- For non..critical sites, an electrode system resistance of 25 ohms is OK. Forcritical sites, where disruption of service could cause system-wide outages, anelectrode system resistance of 5 ohms is suggested. "Outside the box" solutions toimproving grounds include: chemical ground rods; prefabricated/buried wire grid;Ufer ground; magnesium sulphate; other backfills. (The best costlbenefit artificial.ground, enhancement "electrode is Coke ~ree:z;e.. Avoid Bentonite due .to·shrink/expand properties.)

, -..Check soils for pH (hydrogen ion concentration) for acidic soils· where pH isb~low --In highly.acidic soilsJarger diameter..conductors should be considered~

- Optimum spacing apart for ground rods is 2 X length.- A bare copper buried ring electr04e proyides mor~ conductor surface area thanmany rods. Consider a ring electrode 'Where practical. .' . .. .

160

I'

Power Sources.- Aluminum conductors should not be used. Never mix aluminum and copperwires, connectors, panels, or receptacles. The two metals have differentcoefficients of expansion, so loose connections or joints can result.- Consumer grade power receptacle strips should not be used for permanentinstallations. Do not mount receptacle power strips on the floor. Damage canresult from foot traffic, water, water seepage or fire sprinkler activation withelectrocution ofpersonnel a major hazard.

Surge Protection Devices (SPD or TVSS).- Gas discharge tubes (GDT) should not be used as AC power line SPDs. OK touse them on signal and data lines. When the GDT "crowbars" the transient iteffectively short circuits the line causing a momentary power outage for at least ~cycle. This normally will trip the breaker.- MOVs are suitable only for secondary protection in a redundant scheme. Theyact as high impedance open circuits until breakdown voltage is impressed. Thenthey begin to clamp. Specified breakdown voltage is maintained at low current,but at (lightning's) high currents the clamping voltage might rise higher thanspecified. MOVs degrade with use and their life is a function of numbers andsizes of surges.- SADs' voltage clamping is constant with use, however individual SADs are

unable to absorb very much current. For this reason they are staged in aseries/parallel configuration to increase total power handling capabilities. SADsprovide the tightest clamping characteristics. SPDs using silicon avalanche diode(SAD) technology may develop an artificial diode bias when subjected to strongRF fields that may be present at AM, FM, or TV broadcast sites. This bias maycause data circuit errors.- Common Mode AC power SPDs should not be used. These devices may fail in a

. short· 'circuit' conditlon~' Should ..this occur,. the.'AC power neutral conductor .:..becomes bonded to.. ~e. ground or equipment grounding conductor:' causingundesired currents in the gro~d or grounding. condu~tor(s).This is a personalsafety hazard and a violation ofNEC. Note: Common mode circUits may be usedon signal/data lines... SPDs come in packaged assemblies, typically the above devices are staged

inside.- Redundant SPD philosophy is: Protect the Main Panel; Protect Relevant BranchPanels; Protect the .Relevant Plug-ins; Protect SignalJData.- All AC 'power SPDs should have the Inte111atiorial CE ·certification. This' is 'amore rigorous test standard than the IEEE certification. UL certification bringseven lesser testing requirements. . .- Maintenance of SPDs enclosed within a panel requires panelboard' coverremoval. This work should be performed only by licensed electrician.

.- SPD.· cabinets. containing MOVs shall. not be encapsulaUXl. Omy removable·module MOVs are acceptable.

161

- Never look into a fibre optic cable. Invisible laser light is dangerous and cancause damage to the eyes.

Air Terminals.- A little bitty lightning rod & downconductor cannot carry all that current andvoltage. Where they gonna go? They will attach to all pathways, and flowaccording to impedances.- Alternatives to rods: Overhead grounded shield wires and free-standing nearbyconductive masts/poles. These indirect designs often are better than rods...so saysNASA E-0013 and USAF AFI 32-1065. In some cases (ex. steel radio tower) - norods may be the answer. A rod design is very high maintenance.- Air terminals are one of several lightning protection defenses or sub-systems.Others include: Bonding; Grounding; Shielding; Surge Protection. Select a facilityor structure of concern and rank 1-2-3 etc. the above defenses in order ofimportance.

Bonding.- Ifyou don't bond everything, your lightning protection system won't work.

More to come, no doubt. ..

(dated Aug. 2006)

162 4

•44444444444«4

4

~

~

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21 st CENTURY LIGHTNING SAFETY FOR ENVIRONMENTSCONTAINING SENSITIVE ELECTRONICS, EXPLOSIVES AND

VOLATILE SUBSTANCES.by Richard Kithi~ Founder & CEO

National Lightning Safety Institute (NLSI)www.1ightningsafety.com

1. ABSTRACT.In the USA civilian sector lightning causes $4-5 billion losses per year (NLSI, 1999). In thegovernment sector, the military (DDESB - Department of Defense Explosive Safety Board) hasreported 88 identifiable lightning induced munitions explosions with costs and deaths notcalculated. DDESB was formed as a result of the July 1926 Picatinny Arsenal incident whichkilled 14 people and cost $70 million. The US Department of Energy (DOE) has reported 346known -lightning events to its facilities during the 1990-2000 period. Recent Russian lightningincidents to arsenals include: June 1998 near Losiniy (Yekaterinburg); and June 2001 nearNerchinsk (Siberia). In Beira Mozambique (October 2002) lightning exploded a militaryammunition storage depot with considerable loss of lives and collatem.l damage. The most recentexamples of lightning-caused munitions explosions are: 13 Feb 2005, Hezbollah's Lebanese two­story ammunition storage complex near Majadel; and 29 Nov 2005 a government arms depotnear Walikale, Democratic Republic of Congo. With such examples, it is difficult to support aposition that catastrophic lightning incidents are rare. How to mitigate the lightning hazard atsensitive facilities? This paper suggests adoption of a homologuous lightning safety planningprocess which can be applied to most contemporary environments.

2. LIGHlNING BEHAVIOR & CHARACTERISTICS.2.1. Physics of Lightning. Lightning's characteristics include current levels approaching 400 leAwith the 50% average being about25kA, temperatures to 15,000 C, and voltages in the hundredsof millions. There are some ten cloud-to-cloud lightnings for each cloud-to-ground lightningflash. Globally, some 2000 on-going thunderstorms generate about 50-100 lightning strikes toearth per second. Lightning is the agency which maintains the earth's electrical balance. Thephenomenology of lightning flashes to earth, as presently understood, follows an approximatebehavior: the downward Leader (gas plasma channel) from a thundercloud pulses toward earth.Ground-based air terminators such as fences, trees, blades ofgrass, comers ofbuildings, people,lightning rods, power poles etc., etc. emit varying degrees of induced electric activity. They mayrespond at breakdown voltage by forming upward Streamers. In this intensified local field someLeader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the currentflows. Lightning flashes to ground are the result A series ofreturn strokes follow.2.2 Lightning Effects . Thermal stress ofmaterials around the attachment point is determined by:a) heat conduction from arc root; b) heat radiation from arc channel; an~ c) Joule heating. Theradial acoustic shock wave can cause mechanical damage. Magnetic pressures - up to 6000atmospheres for ,a 200 kA flash - are proportional to the square of the current and inverselyproportional to the square of the diameter of struck objects. Voltage sparking is a result ofdielectric breakdown. Thermal sparking is caused is caused when melted materials are thrownout from hot spots. Exploding high current arcs, due to the rapid heating of air in enclosedspaces, have been observed to fracture massive objects (i.e. concrete and rocks). Voltagetransfers from an intended lightning conductor into electrical circuits can occur due to capacitivecoupling, inductive coupling, and/or resistance (i.e. insulation breakdown) coupling. Transfer

1

163

impedance, due to loss of skin effect attenuation or shielding, can radiate interference and noiseinto power and signal lines. Transfer inductance (mutual coupling) can induce voltages into aloop which can cause current flows in other coupled circuits.2.3 Behavior of Lightning. Absolute protection from lightning may exist in a thick-walled andfully enclosed Faraday Cage, however this is impractical in most cases. Lightning "prevention"exists only as a vendor-inspired marketing tool. Important new information about lightning mayaffect sensitive facilities. First, the average distance between successive cloud-to-ground flashesis greater than previously thought. The old recommended safe distance from the previous flashwas 1..3 miles. New information suggests that a safe distance should be 6-8 miles (Lopez &Holle, National Severe Storm Center, 1998). Second, some 40% of cloud-to-ground lightningsare forked, with two or more attachment points to the earth. This means there is more lightningto earth than previously measured (Krider, IntI. Com. Atmospheric Electricity,1998). Third,radial horizontal arcing in excess of 20 m from the base of the lightning flash extends thehazardous environment (Sandia Labs, 1997). Lightning is a capricious, random, stochastic andunpredictable event. At the macro-level, much about lightning is understood. At the micro-level,much has yet to be learned.When lightning strikes an asset, facility or structure (AFS) return-stroke current will divide upamong all parallel conductive paths between attachment point and earth. Division of current willbe inversely proportional to the AFS path impedance, Z (Z = R + XL, resistance plus inductivereactance). The resistance term_ will be low assuming effectively bonded metallic conductors.The inductance, and related inductive reactance, presented to the total return stroke current willbe determined by the combination of all the individual inductive paths in parallel. Essentiallylightning is a current source. A given stroke will contain a given amount of charge (coulombs =amp/seconds) that must be neutralized during the discharge process. If the return stroke current is50kA - that is the magnitude of the current that will flow, whether it flows through one ohm or1000 ohms. Therefore, achieving the lowest possible impedance serves to minimize the transientvoltage developed across the AFS path through which the current is flowing [e(t) = I (t)R + Ldi/dt)]..

3. LIGHlNING PROTECTION DESIGNS.. . Mitigation 9f lightning consequences can be achieved by the use ofa de~ed systems approach,

de'scribed below' in general teims. '., .. '" .3.1 Air Terminals. Since Franklin's day lightning rods have been installed upon ordinarystructures as sacrificial attachment points, intending to conduct direct flashes to earth. Thisintegral air terminal design does not provide protection for electronics, explosives, or peopleinside modem structures. Inductive and capacitive coupling (transfer impedance) from lightning­energized conductors can result in significant voltages and currents on interior power, signal anpother conductors. Overhead shield wUesand mast systems located above or next to the structureare suggested alternatives in many circumstances. These are termed indirect air terminaldesigns. Such methods presume to collect lightning above or away from the sensitive structure,thus avoiding or reducing flashover attachment of unwanted currents and voltages to the facilityand equipments. These designs have been in use by the electric power industry for over 100years. Investigation into applicability of dielectric shielding may provide additional protection

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where upward leader suppression may influence breakdown voltages (Sandia Laboratories,1997). Faraday-like interior shielding, either via rebar or inner-wall screening, is underinvestigation for critical applications (US Army Tacom-Ardec).Unconventional air terminal designs which claim the elimination or redirecting of lightning(DAS/CTS - charge dissipators) or lightning preferential capture (early streamer emitters - ESE)deserve a very skeptical reception. Their uselessness has been well-described in publicationssuch as: NASAlNavy Tall Tower Study; 1975, R.H. Golde "Lightning" 1977; FAA AirportStudy 1989; T. Horvath "Computation of Lightning Protection" 1991; D. MacKerras et ai, IEEProc-Sci Meas. Technol, V. 144, No.1 1997; National Lightning Safety Institute "Royal ThaiAir Force Study" 1997; A. Mousa "IEEE Trans. Power Delivery, V. 13, No. 4 1998;International Conference on Lightning Protection - Technical Committee personalcorrespondence 2000; Uman & Rakov "Critical Review of Nonconventional Approaches toLightning Protection", AMS Dec. 2002; etc. Merits of radioactive air terminals have beeninvestigated and dismissed by reputable scientists (RH. Golde op cit and C.B. Moore personalcorrespondence, 2000).3.2 Downconductors. Downconductor pathways should be installed outside of the structure.Rigid strap is preferred to flexible cable due to inductance advantages. Conductors should not bepainted, since this will increase impedance. Gradual bends always should be employed to avoidflashover problems. Building structural steel also may be used in place ofdownconductors wherepractical as a beneficial subsystem emulating the Faraday Cage concept.3.3 Bonding assures that unrelated conductive objects are at the same electrical potential.Without proper bonding, lightning protection systems will not work. All metallic conductorsentering structures (ex. AC power lines, gas and water pipes, data and signal lines, HVACducting, conduits and piping, railroad tracks, overhead bridge cranes, roll up doors, personnelmetal door frames, hand railings, etc.) should be electrically referenced to the same groundpotential. Connector bonding should be exothermal and not mechanical wherever possible,especially in below-grade locations. Mechanical bonds are subject to corrosion and physicaldamage. HVAC vents that penetrate one structure from another should not be ignored as theymay become troublesome electrical pathways. Frequent inspection and resistance measuring(maximum 10 milliohms) of connectors to assure continuity is recommended.3.4 Grounding. The grounding system must address low earth impedance as well as lowresistance. A spectral study of lightning's typical impulse reveals both a high and a lowfrequency content. The grounding system appears to .the lightning impulse as a transmission linewhere wave propagation theory applies. A considerable part of lightning's current respondshorizontally when striking the ground: it is estimated that less than 15% ofit penetrates the earth.As a result, low resistance values (25 ohms per NEC) are less important that volumetricefficiencies.Equipotential grounding is achieved when all equipments within the structure(s) are referencedto a master bus bar which in tum is bonded to the external grounding system. Earth loops andconsequential differential rise times must be avoided. The grounding system should be designedto reduce AC impedance and DC resistance. The use of buried linear or radial techniques canlower impedance as they allow lightning energy to diverge as each buried conductor sharesvoltage gradients. Ground rings connected around structures are useful. Proper use of concrete

3

footing and foundations (Ufer grounds) increases volume. Where high resistance soils or poormoisture content or absence of salts or freezing temperatures are present, treatment of soils withcarbon, Coke Breeze, concrete, natural salts or other low resistance additives may be useful.These should be deployed on a case-by-case basis where lowering grounding impedances aredifficult an/or expensive by traditional means.3.5 Corrosion and cathodic reactance issues should be considered during the site analysis phase.Where incompatible materials are joined, suitable bi-metallic connectors should be adopted.Joining of aluminum down conductors together with copper ground wires is a typical situationpromising future troubles.3.6 Transients and Surges. Electronic and electrical protection approaches are well-described inIEEEI100. Ordinary fuses and circuit breakers are not capable of dealing with lightning-inducedtransients.. Surge protection devices (SPD aka transient limiters) may shunt current, block energyfrom traveling down the wire, filter certain frequencies, clamp voltage levels, or perform acombination of these tasks. Voltage clamping devices capable of handling extremely highamperages of the surge, as well as reducing the extremely fast rising edge (dv/dt and di/dt) of thetransient are recommended.Protecting the AC power main panel; protecting all relevant secondary distribution panels; andprotecting all valuable plug-in devices. such as process control instrumentation, computers,printers, fire alarms, data recording & SCADA equipment, etc. are suggested. Protectingincoming and outgoing data and signal lines (modem, LAN, etc.) is essential. All electricaldevices which serve the primary asset such as well heads, remote security alarms, CCTVcameras, high mast lighting, etc. should be included.Transient limiters should be installed with short lead lengths to their respective panels. Underfast rise time conditions, cable inductance becomes important and high transient voltages can bedeveloPed across long leads. SPDs with replacable internal modules are suggested.In all instances the use high quality, high speed, self-diagnosing SPD components is suggested.Transient limiting devices may use spark gap, diverters, metal oxide varistors, gas tube arrestors,silicon avalanche diodes, or other technologies. Hybrid devices, using a combination of thesetechniques, are preferred. SPDs conforming to the European CE mark are tested to a 10 X 350 uswaveform, while those tested to IEEE and UL standards only meet a 8 X 20 us waveform. It issuggested that user SPD requirements and specifications conform to the CE mark, as well as ISO9000-9001 series quality control standards.Uninterupted Power Supplies (UPSs) provide battery backup in cases of power qualityanomalies...brownouts, capacitor bank switching, outages, lightning, etc. UPSs are employed asback-up or temporary power supplies. They sholl1d not be used in place of dedicated SPDdevices. Correct Category A installation configuration is: AC wall outlet to SPD to UPS toequipment.3.7 Detection. Lightning detectors, available at differing costs and technologies, are useful toprovide early warning. Their sensors acquire lightning signals such as RF, EF, or light fromCloud-to-Cloud or Cloud-to-Ground or atmospheric gradients. Users should beware of over­confidence in detection equipment. It is not perfect and it does not always acquire all lightningall the tiem. Detectors cannot ''predicf' lightning. Detectors cannot help with "Bolt From TheBlue" events. An interesting application is their use to disconnect from AC line power and to

4

166 4t

•••444

•••••••••••t•t•••••••••••••f••f••••

engage standby power before the arrival of lightning. A notification system of radios, sirens,loudspeakers or other communication means should be coupled with the detector. See the NLSIWWW site for a more detailed treatment ofdetectors.3.8 Testing & Maintenance. Modem diagnostic testing is available to "verify" the performanceof lightning conducting devices as well as to indicate the general route of lightning throughstructures. With such techniques, lightning pathways can be inferred reliably. Sensors whichregister lightning current attachments can be fastened to downconductors. Regular physicalinspections and testing should be a part of an established preventive maintenance program.Failure to maintain any lightning protection system may render it ineffective.

4. PERSONNEL SAFETY ISSUES.Lightning safety should be practiced by all people during thunderstorms. Measuring lightning'sdistance is useful. Using the "FlashIBang" (FIB) technique, for every five seconds - from thetime of seeing the lightning flash to hearing the associated thunder - lightning is one mile away.A FIB of 10 = 2 miles; a FIB of 20 = 4 miles, etc. The distance from Strike A to Strike B toStrike C can be as much as 5-8 miles. The National Lightning Safety Institute recommends the30/30 Rule: suspend activities at a FIB of 30 (6 miles), or when first hearing thunder. Outdooractivities should not be resumed until 30 minutes has expired from the last observed thunder orlightning. This is a conservative approach: perhaps it is not practical in all circumstances.Ifone is suddenly exposed to nearby lightning, adopting the so-called Lightning Safety Position(LSP) is suggested. LSP means staying away from other people, removing metal objects,crouching with feet together, head bowed, and placing hands on ears to reduce acoustic shockfrom nearby thunder. When lightning threatens, standard safety measures should include: avoidwater and all metal objects; get off the higher elevations including rooftops; avoid solitary trees;stay offthe telephone. A fully enclosed metal vehicle - van, car or truck - is a safe place becauseof the (partial) Faraday Cage effect. Used metal shipping containers, properly ventilated andshielded, are high recommended for outdoor workers. A large permanent building can beconsidered a safe place. In all situations, people should avoid becoming a part of the electricalcircuit. [Benjamin Franklin's advice was to lie in a silk hammock, supported by two woodenposts, located inside a house.]Every organization should consider adopting and promulgating a Lightning Safety Plan specificto its operations. An all-encompassing General Rule should be: "If you can hear it (thunder),clear it (evacuate); ifyou can see it (lightning), flee it."

5. CODES AND STANDARDS.In the USA there is no single lightning safety code or standard providing comprehensiveassistance. US Government lightning protection documents should be consulted. The FederalAviation Administration FAA-SID-019d is valuable. The IEEE 142 and IEEE 1100 aresuggested. Other recommended federal codes include military documents MIL HDBK 419A,Army PAM 385-64, NAVSEA OP 5, AFI 32-1065, NASA SID E0012E, MIL SID 188-124B,MIL SID 1542B, MIL SID 5087B, and UFC 3-570-01. The DOE M440.1-1 and the BritishCode BS 6551 are helpful. The German lightning protection standard for nuclear power plantsKTA 2206 places special emphasis on the coupling of overvoltages at instrument and control

5

167

cables. The International Electrotechnical Commission IEC 62305 series for lightning protectionis the single best reference document for the lightning protection engineer. Adopted by manycountries, IEC 62305 is a science-based document applicable to many design situations. Toooften ignored in most Codes is the very essential electromagnetic compatibility (EMC) subject,especially important for explosives safety and facilities containing electronics, VSDs, PLCs, andmonitoring equipment.

6. CONCLUSION.Lightning has its own agenda and may cause damage despite application of best efforts. Anycomprehensive approach for protection should be site-specific to attain maximum efficiencies. Inorder to mitigate the hazard, systematic attention to details of grounding, bonding, shielding, airtenninals, surge protection devices, detection & notification, personnel education, maintenance,and employment ofrisk management principles is recommended.

7. REFERENCES.7.1 International Conference on Lightning Protection (lCLP) Proceedings, Avignon (2004),Cracow (2002), Athens (2000), Birmingham (1998), Florence (1996).7.2 IEEE SID 142-1991 Grounding of Industrial and Commercial Power Systems.7.3 IEEE SID 1100-1999 Powering and Grounding Electronic Equipment7.3 IEEE Transactions on Electromagnetic Compatibility, Nov. 19987.4 National Research Council, Transportation Research Board, NCHRP Report 317, June 19897.5 International Electrotechnical Commission (lEC), International Standard for LightningProtection. See: http://www.iec.ch7.6 Gardner RL, Lightning Electromagnetics, Hemisphere Publishing, NY NY 19917.7 EMC for Systems and Installations, T. Williams and K. Armstrong, Newnes, Oxford UK,

2000.7.8 NATO STANAG 4236, Lightning Environmental Conditions, 1995.

Note: Rev. 2005. Permission to copy and to re-print this paper is freely given. Please credit NLSIas the original author. The National Lightning Safety Institute is a non-profit, non-productindependent organization providing objective infonnation about lightning safety issues. See theNLSI Website at: www.lightningsafety.com

6

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169

ATTENTION TO DETAIL

For aviation, communications, explosives, military, nuclear,process control and other critical facilities, attention to verydetailed lightning protection cannot be overstated. Conformity toEMC - electromagnetic compatibility - issues is very important.

A very good source of EMC information, available at no cost viathe Internet, is available to readers at:

www.compliance-club.com/archivel/OOl018.html

This is Chapter 5 - Lightning and Surge Protectionfrom the book "EMC for Systems and Installations"by Eur Ing Keith Armstrong C.Eng MIEE MIEEE.

_II -1-- ••••--..------------

170

171

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Nine

INTERNATIONAL VIEW OFUNCONVENTIONAL AIR

TERMINALSSUCH AS "ESE" AND "CTSIDAS"

"This ,;sum; is on, ofIhr mosl baRS/lui, dtctptll'f Plt~ffoffmud 1'1'1 tl," lten. ttlu 'N! bfrttl. "

\ - - - - - - - - - - - - ----- - -

Chapter Nine Overview

Shortly after Franklin's 1752 lightning rod inventio~.competing vendorspromoted different designs. Some had three points. Some had. five points.Salespeople were known to have told lightning rod users that an annualreturn visit, at additional cost, was needed to file down the points to maintainsharpness Or the rods would not work.

Today there are vendors .calling their unconventional designs "EarlyStreamer" (ESE) air tenninals and "Dissipation Array Systems" (DAS) and"Charge Transfer 8yste1T1$" (CTS). Literature describing the merits of suchptoductsmake claims of perfection. Comparisons to accepted andconventional designs --- Franklin Rods and free-standing masts andoverhead shield wires --- make the ESEIDAS/CTS products attractiveatfrrstglance. But behind the P$ueo.o-scientific language lies simple advertisingexaggeration.

We. provide some background information for reader education.

~'The Farce can have astronginjluence on the weak-minded."Ob..f.,;.:Wan KeDobi, SI.AR. WARS

. '"

.,172 tJ

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PEER-REVIEWED TECHNICAL PAPERS ONCTSIDAS/ESE DESIGNS

Experimental study on lightning protection performance of air terminals

Lee, J.B, Myung, S.H. Cho, Y.G. Chang. S.H. Kim. J.S. KiI, G.5.Korea Eleclrotechnol. Res. lnst.. Changwon, South Korea

This paper appears In: Power System TtcbOQlogyl_~,Q,PZ,.PI9.Ce.•dlo.g••.P,QW,tJ:CO(l 2,002 ..lntematlooalConfere.flCQ 0.0Publication Date: 13·17 Ocl. 2002Volume: 4On pagels): 2222 • 2226 volANumber of Pages: 4 vol. 2691ISSN:Digilal Object Identifier: 10.1109/1CPST.2002.1047177Posted online: 2002·12·1017:23:34.0

AbstractThere are claims that ESE (early streamer emission) air terminals offer a vastly increased zone of protectionover that of tradilionallightning rods by causing the early emission of an upward streamer/leader and In contrasl10 ESE, multipOint OAS (dissipation array systems) eliminate Ilghlning stroke to utilities by generating the samepolarity charges to cloud charges. This paper deals with the results of • comparative tesl of a particular type ofESE al( terminals and DAS wilh a simple rod conducted in til, KERI HV laboralory, which include lightningImpulse voltage tesls, flashover direction testa and corona emission current mealur,menta. Results from Ihesetesls show a complelely random acattering of characteristics to the conventional and special air terminals underIdentical electrical and geometrical condllions. Allo the characteristics of special air terminals are not ,upenor toa SImple rod for lightning and switching Impulse vollagea.

Experimental validation of conventional and nonconventionallightningprotection systems

Rison. W.Electr. Eng. Dept, New Mexico lnst of Min. &Techno!., Socorro, NM. USA

This paper appears in: Pow9.rEngln.terlng So(;I9.N~:l~n_er.l Meeting, 2003, I.EEEPublication Date: 13·17 july 2003Volume: 4On pagels): 2200 Vol. 4Number of Pages: 4 vol. 2666ISSN:Digital Ob/eclldenlifier: 10.1109/PES.2003.1270959Posted online: 2004-03-08 14:01:20.0

AbstractThree types of lightning protectlonsystems are in common use today: conventional syslems, charge transfersystems, and systems based on early .Irumer emission air terminals. There is a wealth of empIrical dalavalidating the effectiveness of conventional lightning prottctlon systems installed in accordance withrecognized standards. Field .tudles of charge tran.fer system. show that they do not prevent lightning slrikes ashas been claimed. Studies of earty streamer emlllion air terminals show that their performance in the field ISsimilar to that of conventional sharp-poinled air terminals, and they do not have 8 greatly enhanced zone ofprotection as has been claimed.

The basis of conventional lightning protection systems

Tobias, J.M,U.S. Army Commun.-Electron. Command, Fort Monmouth, NJ. USA

This paper appears in: 1nQ.u.$tJYApp,lI.cl!tIQns.IE~e.Trl!n$ac:;tlons onPublication Date: July·Aug, 2004Volume: 40 , luue: "On page(s): 958 • 962ISSN: 0093-9994Digital Object Identifier: 10.110errlA.2004,831277Posted online: 2004-07·1911:11:01.0

AbstractThe study of lightning protection system design encompasses nearly 300 years, Yel, many of the onglOalsources for common design practices used today remain obscure, ThIS paper traces the significanidevelopmenl$ in lightning protection from the late 1700s to the modern day. EmphaSIS Is placed on significanievents in the history that have had direct consequences in the establishment of deSIgn practices for lightningprotection. It Is also demonstrated that many of the design practicas used today were subject 10 SIgnificantscrutiny and empirical qualification. Our lnlent IS to familiarize Ihe student ot lightning protection deSign withIhe originallilerature, testing. and other noteworthy contributions to the deSIgn of effective lightning protectionsystems.

173

Friday evening in a suburb ofKuala Lumpur.

In message 693 (June 8, 2001), I posted a picture ofa building with its

corner of the roof struck by lightning. A similar incident occurred last

The apartment building was installed with two French made ESE airterminals. The triangular gradient wall at the end ofone ofthe roofridges was struck by lightning and badly damaged, sending the concretedebris falling onto a sub-compaet car and a motorcycle on the groundbelow. Fortunately, no one was hurt since there was a thunderstorm withplenty of lightning and heavy rainfall at that time and no one wasoutside.

174

"Hartono" <hartono@pc.jaring.my>"LP/PQ" <UghtnlngProtectlon@yahoogroups.com>Tuesday, February 101 20045:11 AMKL strike 2.JPG; KL strike 3.JPG; KL strike 4.JPG;.KL strike 5.JPG; KL strike 1.JPG[LP/PQ] Safety around buildings during thunderstorms

From:To:Sent:Attach:Subject:

The damaged wall was made of light-weight concrete which probablyexplains the extensive damage done by the lightning strike. The concrete

can be easily broken with a small hammer.

The air tenninal is about 30m away from the damaged wall. Based on theINERIS report (pg 18/46) by P. Gruet, the ESE model is called SateHt.

From:To:Cc:Sent:Subject:

"BUlent Ozince" <ozince@yahoo.com><lightningprotection@yahoogroups.com><vlad.mazur@sauron.nsstnoaa.gov>Monday, February 16, 2004 4:42 AM[LP/PQj lightning protection of radar sites

175

Dear Friends,

Last week in IstanbuilTurkey, there was a severe winterstorm. At night we heard in the news that ligh~ng .struck one ofthe radar sites related to weatherforecasting. This radar site was constructed 1 month agoand was protected with ESE terminals. According to theofficial report, lightning struck 7 times thatnight and caused big holes in the radome and damage tothe electronic devices.

Once again, ESE terminals didn't work. The damageis too much and the people are getting angry.

I hope you could help me to find a document regardingcorrect protection of radar sites by Franklin rods.

Best Regards

BUlent OzinceElectrical Engineer

(THE SHORT VERSION)

I The National Lightning Protection Corp. sells the well-known ESE device named Prevectron tram theFrench manufacturer Indelee, whereas Heary Bros. produce and sell their own ESE model.

THE RESULT OF:A COURT CASE CONCERNING ESE DEVICES.

176

2004.01.21

Phone: +45 39 65 1710Fax: +45 39 68 33 38

Mobil: +45 22 127032E~mail: aa-e-p@get2neldk

Significantly, the verdict rejected the ESE vendor's claims that their ESE terminals' com­pliance with various ESE standards justified the advertised expanded zones of protec­tion for ESE devices. The Court found that the conformance with foreign ESE standardsfailed to prove claimed increased zones of protection for ESE rods. The Court found thatthe ESE vendor's claims are not supported by tests sufficiently reliable to support thoseclaims and are therefore in violation of American "truth-in-advertising" laws.

Information for whom it may concern.

AAGE E. PEDERSENAsc. Professor, DocentStaenget1AOK 2820 GentofteDenmark

In connection with the N.FPA's rejection of ESE draft standard 781, three ESE compa­nies (Heary Bros. Lightning Protection Co., Inc., lightning Preventor of America, Inc.,and the National lightning Protection Corp.,i of which the two first mentioned havemerged) sued a lightning protection trade association and two lightning protection com­panies (Lightning Protection Institute, Thompson Lightning Protection Inc., and EastCoast lightning Equipment, Inc.). The lawsuit, which was initiated in 1996, contained al­legations of conspiracy, false advertising and product defamation regarding the adver­tised improved efficiency of ESE terminals compared to conventional Franklin rods.

In October, 2003, the Federal District Court of Arizona summarily dismissed the lawsuit.The dismissal was largely based on the fact that the ESE vendors presented no admis-

sible evidence at all to support their claims. Additionally, the Court granted a favorableruling to a counterclaim against the ESE vendors. The ESE vendors were convicted offalsely advertising the claimed increase in efficiency of ESE rods in comparison to con­ventional Franldin rods.

THE FULL VERSION, cf. the homepage of the district court:http://www.azd.uscourts.gov/azdlcourtoDinions.nsflOpinlons%20bv%20date?OpenViewDate 2003.10.23 - CV 96-2796 PHX ROB, Heary Bros. Lightning Protection Co., Inc., et al. vs. LightningProtection Institute, et al.

(THE SHORT VERSION)

THE RESULT OF:A COURT CASE CONCERNING ESE DEVICES.

Significantly, the verdict rejected the ESE vendor's claims that their ESE terminals' com­pliance with various ESE standards justified the advertised expanded zones of protec­tion for ESE devices. The Court found that the conformance with foreign ESE standardsfailed to prove claimed increased zones of protection for ESE rods. The Court found thatthe ESE vendor's claims are not supported by tests SUfficiently reliable to support thoseclaiins·and are therefore in violation of American "truth-in-advertising" laws.

176

2004.01.21

Phone: +45 39 6517 10Fax: +45 39 68 33 38

Mobil: +4522127032E-mail: aa-e-p@get2netdk

AAGE E. PEDERSENAsc. Professor, DocentStaenget1AOK 2820 GentofteDenmark

Information for whom it may concern.

In connection with the NFPA's rejection of ESE draft standard 781, three ESE compa­nies (Heary Bros. Lightning Protection Co., Inc., Lightning Preventor of America, Inc.,and the National lightning Protection Corp.,1 of which the two first mentioned havemerged) sued a lightning protection trade association and two lightning protection com­panies (Lightning Protection Institute, Thompson lightning Protection Inc., and EastCoast Lightning Equipment, Inc.). The lawsuit, which was initiated in 1996, contained al­legations of conspiracy, false advertising and product defamation regarding the adver­tised improved efficiency of ESE terminals compared to conventional Franklin rods.

In October, 2003, the Federal District Court of Arizona summarily dismissed the lawsuit.The dismissal was largely based on the fact that the ESE vendors presented no admis-

sible evidence at all to support their claims. Additionally, the Court granted a favorableruling to a counterclaim against the ESE vendors. The ESE vendors were convicted offalsely advertising the claimed increase in efficiency of ESE rods in comparison to con­ventional Franklin rods.

THE FULL VERSION, ct. the homepage of the district court:http://mMt.azd.uscourts.gov/azdlcourtopinions.nsflOpfnlons%20by%20date?OpenViewDate 2003.10.23 - CV 96-2796 PHX ROS, Heary Bros. Lightning Protection Co., Inc., et al. vs. LightningProtection Institute, et al.

1The National Lightning Protection Corp. sells the well-known ESE device named Prevectron from theFrench manufacturer Indelee, whereas Heary Bros. produce and sell their own ESE model.

",.",.

",.

".....".,.",.",..."...

A CRITICAL REVIEWOF NONCONVENTIONAL

APPROACHES TO LIGHTNINGPROTECTION

BY M. A. UMAN AND V. A. RAKov

.' . -.: . . '., . ~".~': .. . .. ...., . " . ::.~:: "

Neither-data -nor theory.:'Supports..~dalms .that- hgt.rtitl~g-:ehmJnation,: :-and·;·:_.eariy-_~streamer· .

-" ..e~isSion" tethri"I~~~s:~~~":'.s~~~rior to C6~veiiti~f:lai·: lightning" prQ~e.2tib~:syStems

(

ONVENTIONAL SYSTEMS. Properly de­signed conventionallightning protection systemsfor ground-based structures serve to provide

lightning attachment points and paths for the light­ning current to follow from the attachment pointsinto the ground without harm to the protected struc­ture. Such systems are basically composed of threeelements: 1) "air terminals» at appropriate points onthe stmctu.re to intercept theligh~2) "down con­ductors" to carry the lightning current from the airterminals toward the ground, and 3) "grounding elec­trodes" to pass the lightning current into the earth.The three system components must be electricallywell connected Many national and internationalstan­dards descn'be conventional lightningprotection sys-

AMERICAN METEOROLOGICAL SOCIETY

terns (e.g.,NFPA 1997,hereafter NFPA 780), and theefficacy of the conventional approach has been welldemonstrated inpractice (e.g.) Harris 1843, 140-156;Symons 1882; Lodge 1892; Peters 1915; Covert 1930;Keller 1939; Szpor 1959). The classic text on the con­ventionallightning protection ofstructures is Golde(1973). The theoretical justification of the conven­tional approach is fairly crude, in part due to our in­complete understanding oflightnings attachment toground-based objects. Hence, the fact that conven­tional systems have a history ofsuccess in preventingor minimizing damage to structures is the primaryjustification for their use. It is nevertheless instruc­tive to review the current understanding ofthe light­ning processes, this understanding being consistentwith the experience gained from the use of conven­tional structural lightning protection systems.

The lightning stepped leader, the process that ini­tiates a cloud-to-ground flash, begins in the eloudcharge region (near 5-km height in temperate sum­mer for the typical flash that lowers negative charge)and propagates toward Earth at a typical averagespeed of 105 m S-I. The charge on the leader channel(effectively drained from the cloud charge source)produces an electric field near the earth·s surface thatis enhanced by objects projecting above the surfacesuch as trees and grounded air terminals on struc-

DECEMBER 2002 BAns- I 1809

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the leader i'S lims tQ hnndre~j!,

ihis electric fidd l)c,sQtne:, iatgt:pr'(}lhlCe dectriml breakdown f;i?'tW"et?l1

,mdthe ground or between the and oneof the elevated Such electrical hreakdown,which Qccurs in laboratorygap electric field ofa few 11llI1d!'ul

Chowdhurl20(0), involves nne or more up,w;lf(l>C![mljectingle~:lXj­

crs ent;;trmtmg from tht, ground or

One of these leadersmeets one of the branches of the downward,propa.

gating JearJt'f and establishes II path be­tween cloud and gmlWtt Figure I shows a slrnpiiliedpicture nflightniog attachment to tlstnlct'urt: that isprotected bjf ,I cwrWf'ntiloua! lightning pf()teclion sy·s.

tern cmpJnying air terminals in the limn (lfljghtningrmk

"Vve om,' the models iJrvo,!w::{jm till:' wnventiouai lightnillgprotectlolLThe attadltnent of tIll! leader ttl

Hften de.!>CI'ibl:"d

Ilgil1tning, prot¢'ctilli) ;'lI1UCln;., The <' ....,,.,, ..~

,,~.w,,"'"y" tJll;:,dis!:,m,;:e from thethe object to be struck at the instant that the

bre<lkdmVll reached acros~ the ..... ~. ",.""Of, alternatively, is det1m:d as the djst~mce from theIf'~,tl"rtl;n to the object to be strtlCk at the lime when<ln1,lpwatd'crH1nedingJ.ea~er is from the

to he Givcl1an as~iU.l'tred lltriJ;jngan imaginary sun.tee·· iH;lQ,re

gr\lundill1d tlhjects on the groltl1d ljY<,;Il' UJl~t,

when the downwa.td"propaga.tlng leaderthrough that at a spedficlocation, the leaderis bya specific point on the g:rou:rni tiT onit gnmnded (Jpjecl. The geometricalconSu'l1dio!l ·{ifthis surface can be ;>CCM111Jished simply hy roWttg animaginary .sphere Qfradius equal tDt}I(::'<lI,SUIl.led

ingdistance acro!:!> the and aCroSs ohjecison

fiG. I. The lightning attadtrneflt pr~c~$;!1~(~)i:he

stepped leader descends to witbin about I no m qf iIi

housl'! with (onventimml lightning protel:t1on (not t6scale), (b) upward leaders laundled from II.gh'tnlngrlXlsand neat'by tree, and (c) rormectiol1l11adc between t>l'l.ebranch of the downward.moving stepped IlClader .litH.!one upward-moving leader thepa-til forcurrent flow of the. re-tUrf1 stroke.

the ground. the so-called rolling sphere method (e.g.,Lee 1978;NFPA 780). The locus ofallpoints traversedby the center of the rolling sphere forms the imagi­nary capture surface referred to above. Those pointsthat the rolling sphere touches can be struck. accord­ing to this approach; andpointswhere the sphere doesnot touch cannot be. Figure 2 illustrates the rollingsphere approach. In this approach, any objects be­neath the surface shown by the dashed lines in Fig. 2cannot be struck (are protected), and any ground­based objects projecting through that surface can bestruck (are unprotected). In the commonlyused roll­ingsphere approach, the striking distance is assumedto be the same for any object projecting above theearth's surface or for the earth itself. There are varia­tions of this technique in which the assumption ofequal striking distances for different objects and forthe earth is replaced by the assumption of differentstriking distances for objects of different geometry(e.g., Eriksson 1987a,b). One can use the rollingsphere method with constant assumed sphere radiusto position air terminals on a structure so that one ofthe terminals, rather than a roofedge or otherpart ofthe structure, initiates the upward leaderthat connectsto the downward leader; that is, the striking distanceto an air terminal is reached by a downward-propa­gating leaderbefore the striking distance to a portionofthe protected stnlcture is reached.

Assuming a distribution ofcharge along the leaderchannel and a value ofbreakdown field, one can re­late the striking distance to the charge on the steppedleader channel and then using the observed correla­tion between the charge and peak current of the re­sultant return stroke (Berger et al. 1975) one can findthe relationship between the striking distance and thereturn strokepeak current. Given all the assumptionsinvolved, this.relationship is necessarily crude. Ac­cording to Illtemational Standard lEe 61024-1 (lEC

.1993) 99% ofs~g distances exceed 20 m. 20 m.being associated with a first stroke peak current ofabout3·kA; 91% eXceed 45 m. asSociated with about10 kA; and 84% exceed 60 m, associated with about16 kA. Clearly, these are very rough estimates. Thetypical first stroke peak current isnear 30kA (Bergeret al. 1975) fur which various calculated striking dis­tances, using different assumptions on breakdownparameters, are generally between 50 and 150 m(Golde 1977). consistent with the typical observedstriking distances reviewed byUman (1987, 99-109,205-230). For the placement ofair terminals in a con­ventionallightning protection system,NFPA 780 rec­ommends adopting a striking distance of 46 m.Smaller assumed striking distances result in a more

AMERICAN METEOROLOGICAL SOCIETY

FIG. 2.. Zone ofprotection for a single mast ofheight H,as detennined by the roBing sphere method. Adaptedfrom NFPA 780.

conservative approach to protection; that is, more airterminals are required, as can be inferred from Fig.2, and lightning discharges with lower peak currentsare intercepted by the air terminals. According tosome standards, a wire mesh covering the top ofthestructure mayplaythe role ofthe airterminals. (Notethat the rolling sphere method would predict thatlightning can attach to the structure between themetal mesh conductors unless the mesh is elevatedabove the top of the structure.) For example. lEe(1993) states thatameshsize of15m xIS mis equiva­lent to protection with lightning rod air terminalsdesigned for an assumed 45-m striking distance.Apparently, the specified relationship between meshsize and striking distance is a matter of experiencerather than theory.

NONCONVENTIONAL SYSTEMS. With thisbriefbackground in COI\ventionallightning.protec­tion. Wl: now. and in th,e follOwing sections, considernonconventional approaches to lightningprotection.Noncon'Ventionallightning protection sch~mes forground-based structures generallyfall into one oftwoclasses: 1) "lightning elimination" or 2) "earlystreamer emission." Nonconventional systems usingthese two techniques are commercially available un­der a variety of trade names and are claimed to besuperior to the conventional lightning protectiondescribed above. The primary intent of this paper isto review the literature on the two nonconventionalapproaches in conjunction with the pertinent light­ning literature so thatwe can examine the hypothesisthat systems employing these techniques function asadvertised. that is, are superior to the conventional

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lechnique described in the sedion "CmwentionjjSystems." We will show that the suggested advan tagesof the nonconventjonal methods over the woven­tional technique are not $'Upported by the availableexperimental data or by theory. This conclusion isconsistetlt with that ofGolde (1977) who reviewed thenonconventlonal approaches to lightning protectionbased on the information availahle at the time of hiswriting.

LIGHTNING ELIMINATION. General informationand theory. The primary claim of the proponents of

lightning elimination systems (which more recentlyhave been called "charge transft~r systems") is thatthose syi>1emS produce<::onditions underwhich light­ning either does not occur or cannot strike the pro·tected structure, as opposed to the conventional ap­proach ofintercepting the imminent lightning strikeand rendering it hltrmless by providing a nondestruc·tive path for the lightning Cllrrent to flow to ground.Lightning elimination systems include one or moredevated arrays ofsharp points, often simiiarto barbed.....'ire, that are installed on or near the structure to bepr rays are connected to groundingell' conductors as in the case ofcon··ventionallightningprotection systems. The principle

ation systems., accord-

using multiple-point corona discharget

hased on his sinall-scale lahor<ttory ex­

periments, had suggested that '"the

dous effect;; of lightning (Cohen 19(0). Hughes(1977) states that a patt>nl for a multiple.point s~'stemwas issued in 1930 to J. ~t Cage of L.os Angeles, Cali·fornia. The patent describes the use of point·bearingwires suspcnded from a sleel tower to protect petro­leum storage tanks (rom Hghtning< A similar system,commonly referred to as a dissipation array systt'm(D,'\8) or a charge transfer system (C1'5), has been

cmnmerciaHy avaihlble since 1971 although the pwt!·Het name and the name ofthe companytha! markctt'uit have changed over time (Carpenter 1977; Carpen­ter and Auer 1995). Most lightning elimination sys­

tems were originally designed for t.a11 cnmmunicatinntuwers, hut recently they have been applied to a widera nge ofsystems and facilities including electrical sub­stations, power lines, and airports.

Carpenter and Auer (I995) give their view oitheoperation of the (lissipatiol1 array marketed hy theleading manufacturcL This array, schelll<llicallyshown in Fig. 3, consists of]) an "ionizt'r'· with mallYhundreds of points, 2) a "ground current (or charge)collector," which is essentially a grounding system,and 3) conductors (labeled "service wire,!;" in Fig. 3)connecting the ionizer to the . Theground charge collector is said to "netl! " thepositive charge on the ground thatwould otherwiseaccompany the negative cloud charge overh<~dd. It isfurther stated that "millions ofionized air molecul.es"fr( are drawn away from the site (pre­

to the positive charge "neutralized"d) toward the thundercloud by the highfield, and, in the process. "a protective

'space charge' or ion cloud is formed betweenthe site

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I

and the storm." According to Carpenter and Auer ted from a dissipation array, there will be a reduc­(1995), "manyconsider the space charge the primary tion of the local electric field near the array and anprotective mode, saying its function is much like a enhancement of the field at a distance from the ar­Faraday shield providing a second mode of protec- ray of the order of the size of the array, the magni­tion." Carpenter and Auer (1995) do notsupport their tude of this effect depending on the magnitudes ofdescription of the principle of operation of dissipa- the corona current and the wind. The corona currenttion arrays with quantitative arguments. In a com- is self-limitingin the sense that the corona-producedment accompanying the paper ofCarpenter and Auer charge shields the array and therefore reduces the(1995), Zipse (see also Zipse 1994) points out that electric field that drives the corona discharge. Thetrees and blades of grass generate corona discharge, negative cloud charge that is the source of mostoften exceeding that of dissipation arrays, without cloud-to-ground lightning is located at 5 km or soapparently inhibiting lightning. This same point has in temperate regions and has a value ofsome tens ofbeen previouslymade byZeleny (1934) and by Golde coulombs. During the 10 s ofcloud-charge regenera­(1977). Zeleny (1934) observed that "during a stonn tion, charges emitted by the array may move a vern­in Switzerland the top of a whole forest was seen to cal distance of up to 150 m and, if there is, for ex­take on a vivid glow, repeatedly, which increased in ample, as m 5""1 horizontal wind, horizontally aboutbrilliance until a lightning bolt struck." Ette and Utah 50 m. A vertical wind would also have an effect(I973) reported that the average corona currents from (Chahners 1967,239-262). As the ions move awaya metal point and from palm trees of comparable from the array) their shielding effect is reduced, andheight were similar (see below). Interestingly, Zipse the electric field near the array may increase. The(2001) has referred to the conclusions ofZipse (1994) effect of corona on upward-lightning leader initia­as "erroneous," stating that corona on trees is inca- tion in a slowly varying thundercloud electric fieldpable of producing as much charge as the charge has been theoretically studied by Aleksandrov et al.transfer system. Zipse (2001) also states that the light- (2001). However, they did not consider the practi­Ding elimination system may fail to eliminate light- caDyimportant (from the lightning protection point ofning, and, in this case, it acts as a conventional light- view) case of the initiation of an upward-connectingning protection system. leader in response to the approaching downward

We now estimate the value of corona-produced leader. Ifthe rapidly varying electric field associatedcharge and the distance over which such charge can with the approaching stepped leaderaets to overcomemove during the typical cloud-charge regeneration the shielding effect of corona space charge near thetime, of the order of 10 s (e.g., Chauzyand Souia grounded object, the resultant upward-connecting1987), between lightning discharges. In the absence leader will escape the space charge cloud and inter­ofa downward-propagating leader:» both the charged cept the descending leader:» as discussed in the sec­light ions and the heavier aerosol ions formed byion- tion "Conventional systems."particle attachment in the humid air near the points According to the'Draft Standard regarding chargeofa dissipation arraymove in response to 1) the e1ec- transfer systems submitted to the IEEE (IEEE P1576/tric field ofthe cloud charge, other space charg~and D2.012001) bytheirproponents, a 12-poin~ arraywillthe chargeon theground arid on grounded objects; and ' , produce a coronacuttentof700 pA:undera thunder­

,2) the' Wind. Typical electric fields near the ground storm.: Zipse (2001) ~rted on a corona current of" under thunde~stormsse1domexceed 10 kV m-1, 500 pA from four sets of three points ,installed on'a,

while 100mor so above the groUnd the fields can be 2o-m pole, apparently measured in the absence ofnear50 kV m-1 (Chauzyetal. 1991; Soula and Chauzy lightning in the immediate vicinity of the pole. It is1991). The mobilities of atmospheric light ions in not clearwho performed thesemeasurements or how.electric fields oII0 to 50 kV m-1 are in the range of1 More important) it is not clear if the reported valueto 3 X 10-4 m2 V-I 5-1 (Chauzy and Renneia 1985; is average or peak current. The actual corona currentChauzy and Soula 1999). Heavier ions move two or- from a large number ofpoints depends on the spac­den ofmagnitude more slowly. Thus, above the field ing between the, pq~ts since the corona from eacheiUiancement region of the dissipation array, up- point reduces the electric field at adjacent points andward-directed drift velocities of light ions mayap- hence their individual current output (e.g., Chahnersproach 15 mS-I. Horizontal wind speeds of several 1967,239-262). Thus, manycl~selyspacedpoints dometers per second are common under thunderclouds not necessarily emit more corona current than sev­so that the light ions funned by corona discharge will eral wen-separated points. Ette and Utah (1973), inalso move horizontally. If sufficient charge is emit- perhaps the best studyto date ofcorona current from

181

AMERICAN METEOROLOGICAL SOOETY DECEMBER 2002 BAm- / /81l

grounded objects under thunderstorms, found theaverage corona current from a 10-m metal point tobe about 0.5 pA, while palm trees of 13- and 18-mheight produced between 1 and 2 pA. IEEE P15761D2.01 (2001) states that the appropriate array designshould consist ofa sufficient number ofcorona pointsso that the arraywill emit a charge equal to that on astepped leader:. apparently taken as 5 C, in a time of10 S, the cloud-charge regeneration time noted in theprevious paragraph. If, for example, a current ofroughly 1rnA were emitted from a 10-point array, asstated in IEEE P15761D2.0 (2001) without adequateexperimental evidence, then a charge of10-2 C wouldflowinto the air in the 10-s charge regeneration time.To emit 5 C to the air in 10 S, the arraywould require5000 well-separated points. According to Zipse(2001), a typical arraycontains 4000 points, althoughusuallylocated in close proximityto each other. Thereare no well-documented data in the literature on co­rona current that could be extrapolated to a large ar­ray and certainly no evidence that several coulombsof corona charge can be released in 10 s or so froman array ofany practical dimensions.

Golde (1977) has suggested that dissipation arraysinstalled on tall structures, typically towers, will in­hibit upward lightning flashes (initiated by leadersthatpropagate upward from the tall structure into thecloud) bymodifying the needlelike shape ofthe struc­ture tops to a shape that has a less pronounced field­enhancing effect. While this suggestion is not unrea­sonable, there are no measurements to support itUpward lightning discharges occur from objectsgreater than 100 m or so in height (above flat terrain)and most lightning associated with objects ofheightabove 300 m or so is upward (Eriksson 1978; Rakovand Lutz 1988). In thisview, dissipation arrays wouldinadvertentlyreduce the probabilityofoccurrence ofthese upwardflashes; which repreSent the majorityofflashes to very tall towers.- The upward flashes con­tain initial conttDuoUs Currentand often contain'sub­sequent strokes similar to those in nonnal cloud-to­ground lightning (e.g., Uman 1987; Rakov2001), thushaving the potential for damage to electronics. It isimportant to note that damage to electronics can beprevented or minimized bythe use ofso-called surgeprotection, as opposed to the structural protectionthat1s the subject ofibis p~per.The -reduction oftheelectric field at the tower top due to the increase ofits effective radius ofcurvature, disOlssedabove; doesnot require either the release ofspace charge to pro­vide shielding or the dissipation ofcloud charge. Theview ofGolde (1977) has been expanded on byMousa(1998), who- argues that the suppression of upward

18141 BAnS- DECEMBER 2002'

flashes will be particularly effective for towers of300-mheight or more and that dissipation arrays willhave no effect whatsoever on the frequency ofstrikesto smaller structures such as power substations andtransmission line towers.

Mousa (1998) has reviewed lightning eliminationdevices that are claimed to employ corona dischargefrom multiple points. Monsa (1998) shows drawings ofsix so-called dissipaters produced by five differentmanufacturers. One of these, the umbrella dissipater,has been described by Bent and Llewellyn (1977) asabout 300 m ofbarbed wire wrapped spirallyaroundthe frame of a 6-m-diameter umbrella. The barbedwire has 2-cm barbs with four barbs separated by 90°placed every 7 em along the wire. The umbrella dis­sipater described by Bent and Llewellyn (1977) wasmounted ona 30.5-mtower in Merritt Island, Florida.Mousa (1998) also describes aballdissipater, a barbedpower line shield wire, a conical barbed wire array, acylindrical dissipater, a panel dissipater (fakir's bed ofnails), and a doughnut dissipater. Mousa (1998) alsodiscusses theextensive groundingprocedures used bythe manufacturers and installers oflightning elimina­tion devices (see also Zipse 2001). The leadingmanu­facturer (see Carpenter and Auer 1995) typical1yusesa buried ground ring (the ground current collectorin Fig. 3) that encircles the structure with I-m-longground rods located at100mintervals around the ring.In poorlyconduetingsoil, the samemanufactureruseschemical ground rods ofits own design, hollow cop­per tubes filled with a chemical that leaches into thesoil in order to reduce the soil conductivitysurround­ing the groundingsystem. In additionto the structurallightning protection, this same manufacturer highlyrecommends the installation of surge protective de­vices on sensitive electronicsat the sametime that thedissipation arraysyste.mis iilstalled.-Carpenter (1971)­lists manycustomerswho report acessation ofJight-,ning..caused damage after installation of the systemhe manufactures (presumably including'both stroc- ­tura1 and surge protection components). However, asMonsa (1998) points out, most lightning eliminationsystems can, in principle, provide conventional light­ningprotection (see also Zipse 2001); thatis, they canintercept a lightning strike and direct its current intothe ground without damage to themselves or to theprotected structure if there is sufficient coverage'ofthe stiueture byarrays (air terminals). Further, dam­age to electronics within the structure can be elimi­nated orminimized bywayofthe installation ofsurgeprotective devices and good groundin~ this protec­tive effect having nothing to do with the structuralprotection (lightning elimination) component

182

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Observations; We summarize now the records of ob­seIVed lightning strikes to dissipation arrays. In 1988and 1989 the FederalAviation Administration (FAA)conducted studies ofthe performance of dissipationarrays relative to conventional lightning protectionsystems at three Florida airports (FAA 1990). Anumbrella dissipation array installed on the centraltower ofthe Tampa International Airport was struckby lightning on 27 August 1989, as shown by videoand current records (FAA 1990, see appendix E).Carpenter and Auer (1995) have disputed the find­ings ofFAA (1990), and Mousa (1998) has reviewedthe attempts ofthe dissipation arraymanufacturer tosuppress FAA (1990). Additional lightning strikes todissipation arrays are described by Durrett (1977),Bent and Llewellyn (1977)~ and Rourke (1994). Theformer two references describe strikes to towers pro­tected by dissipation arrays at the Kennedy SpaceCenter, Florida, and at Eglin Air Force Base, Florida,respectively. Rourke (1994) considers lightningstrikes to a nuclear power plant The plant was struckby lightning three times in two years, 1988 and 1989,before having dissipation arrays installed. After dis­sipation array installation, the plant was also struckthree times in two years, 1991 and 1992. Rourke (1994)notes that "there has been no evidence that lightningdissipation arrays can protect a structure bydissipat­ing electric charge priorto the creation ofthe lightning."

Kuwabara et al (1998) reported on a study ofdis­sipation array systems that were installed in summer1994 atop two communication towers on the roofofa building in Japan. Kuwabara et al (1998) state thatthe dissipation array "was not installed per themanufacturer's recommendations as a result of thebuilding construction conditions in Japan.»Measurements of lightning current waveforms dur­ing strikes to the towers were made prior to the in-

. stallatiO,D of dissipation arrayS, from winter '1991 ~winter 1994, and after the installation, from winter1995 to winter 1996. Additionally, six direct Strikesto the towers with the arrays "installed Were photo­graphed between December 1997 and January 1998.Twenty-six lightning current waveforms were re­corded in the three years before installation of thedissipation arrays and 16 in the year or so after instal­lation. The statistical distribution ofpeak currentswasessentially the same before and after installation. Es­timated pe~ currents vaded from 1 to·lOO kA.Kuwahara et al. (1998) state that after installing thedissipation ar!ays, improving the grounding,. andimproving the surge protection in summer 1994"mal­functions of the telecommunications system causedbylightning direct strike have not occurred," whereas

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they were common before. Apparently, the presenceof the dissipation arrays neither prevented the light­ning strikes nor changed the characteristics of thelightning stroke current, while the equipment dam­age was eliminated by means ofimproved surge pro­tection and grounding.

EARLY STREAMER EMISSION. General informa­tion and theory. The attractive effect of an air teoni­nalwould be enhanced by a longer upward-connect­ing leader (e.g., Rakov and Lutz 1990); the longer theleader, the greater the enhancement. Early streameremission (ESE) systems are similar to conventionalstructural lightning protection systems except thatthey employ air terminals that, according to theirproponents, launch an upward-connecting leader tomeet the descending-stepped leader at an earlier timethan would a conventional air terminal having simi­lar geometry and installed at the same height. Thisearlier initiated upward-connecting leader is claimedto be capable ofextending to significantly longer dis­tances and, as aresult, to provide a significantly largerzone ofprotection than theupward-connecting leaderfrom a conventional air terminal ofthe same height Ifthis be true, itwould followthat a single earlystreameremission air terminal could replace many conven­tional air terminals,which is the primaryclaim ofESEproponents. Without this claim, ESE systems wouldbe indistinguishable from conventional systems.

There are several types ofearly streamer emissionsystems. All employ specially designed air terminalsthat are claimed to create enhanced ionization nearthe air terminal, either by employing radioactivesources, bya specialarrangement ofpassive electron­ics and electrodes that facilitate the electrical break­down ofsmall sparkgaps in a high electric field oftheapproaching stepped leader, or by the applicatio~ofan externa1,voltage,~ the ~r.tenn,inalfr:om~ m~­

madesource. The firstearlystreamer emission deviceswere sO-caned mmoactive rods, rodswith radioactive'

.'material placed on them, although when these wereinitially marketed the term early streamer emissionhad not been coined. According to Baatz (1972), in1914 the Hungarian physicist L Szillard first raisedthe question ofwhether the attractive effect ofa light­ning rod could be increased by the addition of a ra­dioactive source., Various tests in·the field and, the laboratory have

shown that~ under thunderstorm conditions, there islittle or no difference between the action ofa radio-

, ,

active rod and that of a similarly installed conven-tional rod ofthe same height (e.g., Miiller-Hillebrand1962b; Baatz 1972). Heary et al. (1989) published

DECEMBER 2002 BAf'IS- 11815

------ - . ~ _. --- - ~--

laboratory tests purporting to showthe superiority of stepped leader that initiates the usual cloud-ta-groundradioactive rods over conventional rods, but, in dis- lightning flash) at an earlier time, by a time intervalcussions accompanying that paper, five researchers ~t, than do conventional air terminals. They claim(G. Carraca, I. S. Grant, A. C. Liew, C. Menemenlis, that this earlier initiated leader occurs in a smallerand A. M. Monsa) use the paper's results to argue oth- electric field than is required for the initiation of aerwise. Mackerras et alA (1987) have given examples leader by a conventional rod. Further, they translateof the failure of radioactive lightning protective sys- the claimed time advantage iit into a length arlvan­terns in Singapore where, at the time of their study, tage, l1L, for the earlier initiated leader via tiL =vAt,over 100 such systems were installed. Golde (1977) where v is the speed ofthe upward-connecting leader.cites the failure ofa radioactive lightning rod to pre- ESE proponents assume that the speed ofthe upward­vent lightning from knocking the papal crest off connecting leader is of the order of 106 m S-1 (e.g.,Bernini Colonnade at the Vatican on 6 March 1976. French Standard 1995). This value ofleader speed isThe crestwas located about 150 m from a 22-m-high arbitrary, since it is not supported by experimentalradioactive rod that was supposed to protect it. data, as discussed next. The only existing measure-

Surveys of the ESE literature by van Brunt et al. ments of upward positive leader speeds in natural(1995; see also van Brunt et alA 2000) and Bryan et aI. lightning are due to McEachron (1939), Berger and(1999), commissioned bythe U.S. National Fire Pro- Vogelsanger (1966,1969), and YokOYama et al.tection Association, were part ofan independent in- (1990). McEachron (1939) reported that upward posi­vestigation to determine if there should be a U.S. tive leaders initiated from the Empire State Buildingnational standard for earlystreamer emission systems propagated at speeds ranging from 5.2 x 10· to 6.4 xsuch as the NFPA 780 for conventional systems. lOS m S-I, with the lengths of individual leader stepsBased on these surveys, NFPA concluded that there ranging from 6.2 to 23 m. Berger and Vogelsangerwas "no basis for the claims ofenhanced protection" (1966, 1969) measured speeds between 4 X 1()4 andofESE systems relative to conventional systems and, about 106m S-1 for seven upward positive leaders, withhence, no basis for issuing a standard for ESEsystems. the individual leader step lengths ranging from 4 toNevertheless, there are presentlyboth a French Stan- 40 m. Further, for four ofthe seven leaders Berger anddard (1995) and a Spanish Standard (1996) for the Vogelsanger (1966) measured speeds ranging from 4laboratory qualification of early streamer emission to 7.5 x 104 m S-1 and step lengths from 4 to 8 m atsystems for lightning protection ofstructures. Strong altitudes rangingfrom 40 to 110 m fromthe tower top,arguments can be made that no laboratoryspark test where a connection between a downward leader andcan be extrapolated to describe the case of natural an upward-connecting leader would be expected.lightning. For example, the length ofmdividualsteps Yokoyama et alA (1990) measured, for three cases,in the lightning stepped leader is ofthe order oftens upward leader speeds between 0.8 to 2.7 x lOS m S-I.

of meters, a distance considerably larger than the They show figures in which the stepping ofboth thelength of labor~t~ryspark ga.ps, of ~e,order, of a , upward and d~wnwardleader: if) ,apparent. Yokoyamameter. specified, to test and certifyESa systems [e.g., ,et at (i990) report that the lengths' of.theu~d­Fr~nch Standard (1995) that requires a gap no connectingleaderswhose speeds theymeasuredwetesmaller than 2 m with the airt~rminalbeing between from some tens ofmeters to over 100 m at the time0.25 and 6.5 times the gap size]. It is not likely that that a connectionwas madewiththe downward-mov­one can adequately simulate the natural-lightning ing stepped leader. Their measurements are appar­attachment process in a 2-m laboratory gap. As an- entlythe onlyones ofthe speeds ofupward-connect­other example, in natural lightning the downward ing leaders that actuallyconnect to downward leadersnegative leader from the cloud has a length ofmany below the cloud base, as opposed to upward positivekilometers while the positive upward-connecting leaders in upward flashes that enter the cloud. Inter­discharge from the ground or from elevated objects estingly, positive upward-connecting leaders in labo­is generally much shorter~ some tens to hundreds of ratory spark experiments typically have speeds of 'meters long. On the other hand, in laboratory spark' 1()4 m S-I, an order of magmtude lower than typicalstudies intended to simulate lightning strikes to values in natpra}lightning and two orders ofmagni­grounded objects, positive leaders are always much tude lower than the 1()6 m S-1 assumedby ESE propO­longer than negative leaders.' nents (e.g., Berger 1992). Yokoyama et al. (1990) also

ESE proponents argue that ESE air terminals emit reported on the speed of individual optical step for­, ·a positive upward-moving ,connecting leader (in- mation,thisirrelevantm~mentbeingsometimes·

tended to meet the downward-moving negative, referenced by ESE proponents in support of the ar-

18161 BAns- DECEMBER2002

184

bitrarily assumed value v = 106 m S-I for average up­ward-connecting leader speed, cited above.

Mackerras et al (1997) and Chalmers et al. (1999)critically review the proposed ESE techniques. Bothpapers raise the important question of whether anupward-connecting leader, ifindeed launched by anESE rod earlier than for aconventional rod, andhencelaunched in a lower electric field, is able to propagatein the required manner in this lower field. Accord­ing to Mackerras et al (1997), once the upward-con­necting leaderpropagates into the space remote fromthe air terminal, its further progression depends uponthe supplyofenergyfrom the electric field in the spacenearthe tip ofthe leader and upon the dielectric prop­erties of the air undergoing breakdown, neither ofthese factors being influenced by the air terminalUsing this and geometrical arguments, Mackerraset al. (1997) conclude that "it is not possible to gain asignificant improvement in lightning interceptionperformance by causing the early emission of astreamer from an air terminal."

It is necessary for proponents of ESE devices toassume the arbitrary value ofl'=1()6 m S-I for a valueof At of about 100 JlS in order to claim a significantlength advantage AL of 100 m for the upward-con­necting leader from an ESE rod over that from a con­ventional rod. Ifthe value of v = 105 m S-I, which isconsistent with the available experimental data wereused instead, even allowing a 100-JlS time advantageand even assuming that the leader could propagate inthe lower field in which its initiation is claimed to oc­cur, the length advantage would be only AL = 10 m,which is not likely to be significant in most practicalsituations.

Observations. Two triggered-lightning tests ofa com­mercial ESE system described by Eybert-Berardet al.(1998) are sometinies cited in support ofthe efficacyofthe ESE i:echDique.. That particularESE systemhadseven! spark gaps at the tip·of the air teimhial thatwere intended to be activated in a sufficiently highelectric field. The first triggered-lightning test, con­ducted in Florida, showed a current pulse of about0.8-A peak and 2-ps duration from an ESE rod 85 psprior to a triggered-lightningreturn stroke to groundat a distance not given byEybert-Berard et al. (1998).The ESE rod was not struck. No appreciable currentfollowed the initial pul.$e in the. ESE rod. which.sug­gests that the observed current pulse was not associ­atedwith the initiation ofan upward leader. Thus,this.experiment proves nothing relative to ESE systemvalidation. The second triggered-lightning experi­ment, conducted in France and described in the same

AMERICAN METEOROLOGICAL SOOETY

paper, involved lightning that was triggered near anESErodwith a conventional rod located farther away.The ESE rod was the attachment point of a leaderlreturn strokesequence, possiblybecause it was placedcloser to the rocket launcher than the conventionalrod. Unfortunately, the positions ofthe ESE and con­ventional rods were not interchanged to see if onlythe rod (whether ESE or conventional) that is closerto the rocket launcher is always struck or if a moredistant ESE rod could compete with a conventionalrod placed closer to the launcher.

Thus, there is, in fact, no support for the proposedESEtechnique in the results ofanyexperimental studyinvolving eithertriggered ornatural lightning. On thecontrary, natural-lightning studies have shown thatESE systems do not work as their proponents claim.Moore et al (2000a,b) report no advantage ofESErods over conventional rods from their studies on amountain top in NewMexico. In fact, theyfuund thatin 7 yr of observations neither ESE rods nor sharpconventional rods were struck,while U conventionalrods with blunt tips (diameters ranging from 12.7 to25.4 rom) were struck. Case studies in Malaysia byHartono and Robiah (1995, 1999,manuscript submit­ted to the NFPA, hereafter HR99; Hartono andRobiah 2000) show that there was lightning damageto buildings within the advertised protection zone ofthe ESE systems. These papers include before and af­ter photographs fur over two dozen cases, providingdirect evidence of the failure of such systems. Inter­estingly, the studies by Hartono and Robiah (1995) onbuildingsprotected usingconventional systems showsimilar lightning damage. Hartono and Robiah (1995,2000; HR99) conclude that there is no advantage inusingan ESE systemrelative to conventional systems.

We do not discuss here the results of laboratorystudies ofthe ESE te.chnique since we do DQt believethat laboratory sparks c;m adequatelysimul.ate thenatural-lightningattachmentprocess. as discussed inthe section '"General information and theory."

SUMMARY. The conventional lightning protectiontechnique has proven its effectiveness as evidencedby the compara~ve statistics oflightning damage toprotected and unprotected structures. The rollingspheremethod commonlyused in the design ofsuchsystems is relatively crude, in part, because of our

. -insufficient understanding of the lightning attach­mentprocess,but itdoes represent a useful engineer­Plg tool fur determining the number and positionsofair terminals.

Lightningelimination systems cannot prevent theinitiation of lightning in the thundercloud and are

DECEMBER 2002 BAllS-I 1811 .

185

2

unlikely to be able to avert an imminent lightningstrike. Further, these systems are indeed struck bylightnin~in which case theyactas conventional light­ning protection systems. The overall lightning elimi­nation system often includes both structural and surgeprotection componen~the latter being likelyrespon­sible for the reported improved lightning perfor­mance ofthe protected object.

There is no experimental evidence that an ESE airterminal can protect a larger volume ofspace (ie., canattract a lightning to itselffrom farther away) than cana similarly placed and grounded conventional rod ofthe same height. An upward-connectingleader speedof106 m 8-1 is required to produce the "length advan­tage" of100 m claimed bythe proponents ofESE sys­tems in order to demonstrate the superiority of theESE technique over the conventionalmethod oflight­ning protection. The typical measured upward posi­tive leader speed is an order of magnitude lower,lOS m S-I, inconsistent with this claim. Given the lackofevidence ofthe superiority ofESE systems over con­ventional systems, adequate lightning protectionwould require that each ofthem have a similar num­ber ofair terminals.

ACKNOWLEDGMENTS.This research was supported

in part by NSF Grant ATM-0003994. The authors wish to

thank E. P. Krider and an anonymous reviewer for many

valuable comments that helped improve the manuscript.

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IEEE P15761D2.01, 2001: Draft standard for lightningprotection system using the charge transfer system

AMERICAN METEOROLOGICAL SOGETY

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188

News

Title: WARNING! of the ICLP Scientific Committee

Date: 14-09-2005

Text:

The Cautionary Message hasn't stopped the sale and promotion of the different types of.Early .Streamer Emission (ESE) systems. Thus the problem of non-conventional airtermination still exists.

Not only Early Streamer Emission (ESE) systems and Ion Plasma Generators (IPG)systems, claimed drastically to enhance lightning reception, but also Charge TransferSystem (CTS) and Dissipation Array System (DAS), claimed to prevent lightning toproteCted structures, are still produced and installed.

These systems are installed in conflict with the requirements of IEC's lightning protectionstandards and as they are not efficient according to the claims, such systems should beabandoned because they will be dangerous to use.

In this situation the invited paper presented by Prof. Aa. E. Pedersen during theiCL,P'2004 is of central importance and therefore presented below.

ESE AND OTHER NON-CONVENTIONAL LP SYSTEMS

by

AAGE E PEDERSEN

Honorary Member of the Scientific Committee of ICLP

Home office: Staenget 1 A, OK 2820 Gentofte, Denmark

Phone: +45 39 65 17 10

E-mail: aa-e-p@get2net.dk&aa-e-p@vip.cybercity.dk

THE TECHNICAL ASPECTS:

. Great efforts have been devoted to improve the efficiency of lightning protection and~any possibilities have been suggested over the years.

Radioactive rods have been used for many years but have shown no advantage relativeto 'ordinary lightning rods, and the use of radioactive material for this purpose has nowbeen abandoned in most countries.

Laser-triggered lightning involves an electrically powered, sophisticated and sensitivesetup that might prevent its practical use as lightning protection except at very specialsituations. In addition the method has until now shown difficulties with certainty to ensuresubsequent flashes.

Early Streamer Emission System (ESE), attempts to utilize an emission of earlydischarges (streamers) on special lightning rods, to provoke and trigger an early lightningflash and thus protect the surrounding over a greater area than in the case of ordinarylightning rods. Even though the name Early Streamer Emission indicates, that it is theearly onset of streamers on ESE rods relative to the ones on ordinary lightning rods, thatis a measure for the advantage, it appears that the advantage actually is determined bythe time difference between the instances of the first appearance of any type ofdischarges on the two types of lightning rods, an interpretation that will favour the rodwith the smallest curvature radius on the tip.

Even though the hypothesis seems logical, actual experience in the field has shown thatthe triggering of a flash is extremely complex and much more complicated thananticipated in the hypothesis.

An indication of this complexity is apparent in the experience with rocket-triggeredlightning. In spite of great effort to trigger the lightning stroke at a suitable instance, aflash often fails to follow regardless of the extreme influence caused in the electric fieldby the trailing wire from the rocket, and the resulting generation of very long streamersand leaders.

.Another experience with formation of long streamers is found under EHV (Extra HighVoltages) and UHV (Ultra High Voltages) switching impulse tests where extremely longstreamers are experienced often with termination in the blue sky and sometimesterminating on the ground far away from the test object often without causing SUbsequentflashover.

Therefore, the concept of early streamers is not sufficient and inadequate as a parameterfor the determination of any advantage of ESE rods versus ordinary lightning rods.

Moreover, several investigations (for inst. by Z.A. Hartono and by Charles B. More et al)have shown numbers of missinterceptions, and lightning stokes terminating in the closevicinity of ESE rods, and that competition race between ordinary Franklin rods and ESErods arranged in parallel setups and exposed to natural lightning did not favour the ESErods as it should be expected according to the claimed properties.

Creditability of the claimed properties for non-conventional LP devices:

In' the opera "The Elixir of Love" (L'Elisir d'amore) by Gaetano Donizetti, the quackDulcamara sells medicine at a high prize against all sorts of sufferings including loveproblems. To make the story short, the medicine appears to work in a peculiar way,mainly because people believe in it.

To avoid that sort of business in real life, laws have been issued against dishonest or

fraudulent advertisements requiring that the manufacturers or vendors must be able toprove the advertised properties.

Thus the arguments "I am convinced it worksHor HI believe it work" just isn't enough.

In most countries laws concerning Product Responsibility and laws concerning ProductReliability have been issued, but the laws are not always followed.

An advertisement for a known beauty cream promises the user to get 10 years youngerskin. If this was true, a warning should be given not to be used by children less than 10!

Because this advertisement is not dangerous, nobody seems to object even though theadvertisement violates the laws.

. On the other hand, if safety problems are involved there exist tough requirements for theacceptance of products.

As an example, this is the case for the acceptance of new drugs where strictrequirements have to be fulfilled and numerous tests conducted before such drugs canbe marketed.

As another example, the knowledge of the actual tensile strength for straps and slingsare necessary in order to evaluate the load such straps and slings can be used for with asufficient high safety margin. I think that everyone will agree that it is indispensable toperform actual tensile strength tests, and that it will not be sufficient indirectly to evaluatethe. tensile strength by means of measurements of other parameters, for inst. theelasticity coefficient.

Therefore, relevant standards are important for components, apparatuses or systemsWhere safety is the issue, or where safety is involved, and moreover, that the standards

, contain tests' specifications relevant to the circumstances under which the items aregoing to be used.

, Consequently standards, norms and code of practice should comply with at least one ofthe following requirements:

- Founded on recognized and verified physical theory and models.

- Founded on recognized and verified empirical models and experiences.

- Founded on recognized tradition and practice and experiments from the fieldcollected over sufficient number of years.

,Question 1: Do the non-conventional lightning protection systems, as safety. providing systems, obey the abovementioned requirements for safety?

'Answer 1: No, none direct measurement of the protection offered has beensuccessfully conducted or sufficient empirical data collected from field tests toconvince the international technical and scientific community within this field, nor

are the systems founded on any recognized or verified physical theory.

Question 2: Does the French ESE standard NF C 17-102 (1995) rest on any of thestated preconditions for safety standards?

Answer 2: No, the French ESE standard does not require or specify any directmethod to evaluate the efficiency of the protection offered by the non-conventionallightning protection system, leaving the evaluation of the performance alone onthe basis of an indirect method, a method that is partly inadequate partly incorrect.The same seems to apply for the other national ESE standards.

The French ESE standard and its major deficiencies:

- The hypothesis for the function of the ESE rod is insufficient and inadequate, andthe hypothesis seems to be limited alone to discharges over smaller distances.

- The French standard does neither require nor specify verification tests undernatural lightning conditions.

- Only laboratory tests for the verification of the function is specified and required.However, laboratory tests are insufficient and inadequate because it is impossiblein any laboratory to simulate natural lightning conditions not least due to thelimited space and the vast nonlinear characteristics of the lightning processes.

- Only negative lightning is considered.

- The standard misinterprets the use of the rolling sphere concept.

- The standard seems to cover a wide range of lightning rods with auxiliarystimulation of predischarges on the tip of the rods. However, the standard does notdistinguish between the different types, for which reason the standard is lackingnecessary specifications versus the different form and principles for the individualdevice.

- Tests of the electronic components and auxiliary systems for the ESE rods,including the power supply for the ones which need it, to withstand lightninginfluences and aging are missing. Similarly are tests for evaluating the effect of theexternal environment missing, for example the effect of contamination for floatingelectrode systems.

- Requirements and specifications for the recurrent inspections and possibilities fortesting of the individual ESE rods, including any necessary auxiliary systems, toverify their original and unchanged properties, are neither required nor specified inthe French ESE standard or in its copies in other countries.

To conclude:

Even though the hypothesis behind the ESE concept at a first glance might seem rationaland likely, it has shown to be partly wrong and in any case insufficient. Moreover, the .,

CDN

working group has selected a laboratory test in the standard for the determination of theadvantage over ordinary lightning rods, a non-representative test in a non-representativeenvironment, and thus a test that cannot take into account the nonlinearity of thedischarge phenomena between laboratory conditions with stroke lengths quoted inmeters while lightning discharges are quoted in kilometres.

As done by the working group behind the standard, it is fully legitimate to extrapolate thetheories and models for discharges over moderate distances to lightning conditions inspite of the vast nonlinearities of the discharge phenomena. However it is indispensablesubsequently to demonstrate and verify that the extrapolation with sufficient accuracydoes work in practice. Unfortunately this has not been done, and it seems to reveal thatthe working group has suffered the lack of support by scientists with sufficient knowledgeconcerning physics of lightning.

In addition to the missing requirement in the standard for verification tests under naturallightning condition, the manufacturers have never succeeded in verifying the claimedefficiencies for any of the different I;:SE types (in a way that satisfies the internationaltechnical and scientific community within this field) in spite of the repeated promises overmore than 15 years.

Similarly, it has neither been possible for independent scientists nor organizations toconfirm the claimed advantages. On the other hand several investigations have indicatedthat the ESE devices offer no advantages relative to ordinary lightning rods.

To avoid similar problems and unfortunate errors and mistakes in the future, anystandard ought to be exposed to international criticisms, especially when thestandard concerns safety matters and devices used for safety purposes.

THE MORAL ASPECTS:

In spite of the lack of verification of the claimed properties, and in spite of the repeatedcriticisms from the scientific community, the ESE manufacturers have continued for morethan 15 years to sell and promote ESE systems with promises of the non-provenefficiencies compared to ord,inary lightning rods.

Instead of providing the repeatedly promised proofs for their claims, they have intimidatedpersons, organizations, companies and standard-organizations with threats of legalaQtions when they have pointed out, that the claimed advantages are un-proven andwhen they have warned against the use according to the claims until proven. Somemanufacturers and vendors have even got so far as actually suing some of them.

. Even the French Engineering Society (SEE) has been threatened with legal action by theFrench manufacturer. '

THE LEGAL ASPECT:

- In the light of the current laws, what sort of responsibility does the manufacturersof ESE devices carry for their products?

Last update: 28-06-04

- Is it possible for the manufacturers and the vendors to liberate themselves forany responsibility by referring to the French ESE standard or its copies in othercountries, and leave the responsibility to the national standard organizations?

- Do the working groups behind the standards (and its single members) carry anylegal responsibility?

- Who is in the last end responsible for the standard in France (and in othernations for the copies of the French ESE standard)?

- What sort of responsibility does scientists and scientific organizations like ICLPcarry to enlighten similar problems like the ones in the ESE standards withprotection systems that might be dangerous to use?

WHAT TO DO ABOUT THE SITUATION?

- How can the relevant authorities in France (and other nations) be approached toinform them about the problem with the ESE devices, and what can we do to helpthem solve the problems with the ESE standards?

- Do we need some sort of Codex for standardization, production, verification andcommerce of safety devices like lightning protection devices, or should we merelyleave it up to the market?

INTENSIVE WORKSHOP,LIGHTNING PROTECTION

FOR ENGINEERS

Chapter Ten

LIGHTNING SAFETY FOROUTDOOR ACTIVITIES

195

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The circumstances for a side flash.

Chapter Ten Overview

People safety. Here's one short summary sentence. When you hearthunder, go to safety immediately. Thunder is the acoustic companion ofthe electrical event. Our hearing range is about 5-8 miles (8-12 km) and ifyou hear thunder that is how close the lightning is to you. See lightning butdon't hear thunder? The lightning is more distant than your hearing range.

Learn and teach others The 30130 Rule in this Chapter. It is a lightning safetyrecommendation ofNLSI, the Boy Scouts, the NCAA, the National WeatherService, and many other outdoor organizations. See also IEEE 80,Guide forSafety in AC Substation Grounding as a useful technical document.

In this Chapter you will find many safety documents which you can copyand employ for your own needs. Help advocate lightning safety awareness!

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DECISION TREE FOR PEOPLE LIGHTNING SAFETYby National Lightning Safety Institute, www.ligbtningsafety.com

1. Is lightning safety appropriate? Ifthere is any likelihoodoflightning occurrence, go to #2, below.

2. For individuals and for groups, develop a Lightning SafetyPlan. Emphasize Safety ahead ofcontinuation ofactivities.

3. A general Plan for all circumstances "Ifyou see lightningor hear thunder, go to a safe location immediately." See safelocations defined in 4.3 below.

4. More specific Plans should be tailored to specific locations andsituations. Some examples:4.1 For people outdoors where lightning detection technology is

available: Suspend activities and seek shelter when lightningenters a 6 mile radius or when radar indicates 40 dBZ echoswithin a 6 mile radius; resume activities 30 minutes after the "6 .miles rule" changes. Same applies indoors.

4.2 For people outdoors where there is no lightning detectiontechnology: Apply the 30/30 Rule, ~'At a flash-to-bang count of30 (6 miles) suspend activities and seek shelter; resumeactivities only after lightning or thunder has not been observedfor 30 minutes." Same applies indoors.

4.3 In all cases, safe shelter is defined as inside a large permanentstructure while avoiding contact with inte;rior metal/electricaland other conductors.4.3.1 Less safe, but "probably safe" locations include fully­

enclosed all-metal vehicles with windows closed.4.3.2 Unsafe outside locations include the high ground, near

water, near trees, near metal objects, open ground, nearconductors.

National LightningSafety Institute

891 N. Hoover AveLouisville CO 80027

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3. Person Yis subject to touch potential.

4. Person Z is subject to transferred potential.

5. The potential depends on the current magnitude andthe impedence of the path of the lightning discharge.

e

6. Step potential increases with the size of the step a-b inthe radial direction from the conductor and decreaseswith the increase in the distance between person Xandthe conductor.

7. The transferred potential increases with increase inthe radial distance between the down conductor and thegroundg.

Extracts/rom the Australian Standard on LightningProtection A.S.1768-1983.

NUMBER OF LIGHTNING DEATHSBY STATE FROM 1995 TO 2004

State Deaths Rank of1996·2004 Deaths

Alabama 18 6Alaska 0 47Arizona 7 21Arkansas 8 20California 5 31

Colorado 31 3Connecticut 2 40Delaware 0 48D.C. 0 49Florida 85 1

Georgia 19 5Hawaii 0 50Idaho 6 26Illinois 12 11Indiana 12 12

Iowa 5 32Kansas 5 33Kentucky 5 34Louisiana 17 7Maine 1 43

Maryland 7 22Massachusetts 2 41Michigan 11 15Minnesota 6 27Mississippi 9 18

Missouri 7 23Montana 6 28Nebraska 3 36Nevada 0 51New Hampshire 0 52

The lightning fatality data were collected by NOAA(National Oceanic and Atmospheric Administration).They come from monthly and annual summariescompiled by the National Weather Service andpublished in monthly issues of Storm Data. Data forreoent years are available at:http://www.nws.noaa.gov/omlhazstats.shtml.

This table for the period from 1959 to 1994 is includedin the following artlole:

Curran, E.B., RL. Holle, and R.E. L6pez,2000: Ughtning casualties and damages in

State Deaths Rank of1995·2004 Deaths

New Jersey 6 29New Mexico 7 24New York 7 25North Carolina 17 8North Dakota 1 44

Ohio 22 4Oklahoma 10 16Oregon 1 45Pennsylvania 12 13Puerto Rico 3 37

Rhode Island 1 46South Carolina 14 9South Dakota 3 38Tennessee 10 17Texas 34 2

Utah 13 10Vermont 3 39Virginia 12 14Washington 2 42West Virginia 5 35

Wisconsin 9 19Wyoming 6 30

United States 489

One death each occurred in Guam and the U. S.Virgin Islands in 2003.

the United States from 1959 to 1994. Journalof Climate, 13, 3448-3453.

The 1959-1994 Information is also available at theNational Severe Storms Laboratory web site:

http://www.nsst.noaa.gov/papersltechmemosINWS-SR-193/techmemo-sr193.html

Ronald L. HolleHolle Meteorology & Photography

Oro Valley, AZ 6573718 June 2005

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LIGHTNING DEATHS BY STATE, 1995 TO 2004Source R Hol/e, 2005

Bi!Jk• 1·10.11-200 21..30031-62

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Source; Storm pataAlaska - 0 HawaII - 0D.C. - 0 Puerto Rico - 3Quam - 1 V1l'l1ln Islands ·1

LOCATIONS AND PERCENTAGES OF LIGHTNINGCASUALTIES

Source Storm Data 1959-1994

Code Location of United West N 5 N S Mjd· North· South-casualty States coast Roc:kies Rockies plains plains west east us:

13.7% 10.4- 8.6.

1 Under trees 13.4 9.7 14.5 14.8 13.5 13.6

2 Water related, fishing, 8.1 6.1 12.5 5.5 4.0 9.6 5.3 i.4 10.';boating, swimming. etc.

3 Golfing 3.9 1.2 4.3 4.6 4.2 2.2 6.2 3.1 3.6. Golfing and under trees 1.0 0.6 0 0.3 1.8 0.4 2.1 1.1 0.8~

5 Driving tractors, farm 3.0 1.2 7.1 2.1 9.0 4.1 2.6 2.0 2.iequipment, heavy roadequipment, etc.

6 Open field, ballparks, 26.8 19.0 36.5 40.5 20.6 30.4 27.1 20.6 26.2playgrounds, etc:.

I Telephone-related 2.4 1.8 1.6 1.5 3.9 2.8 ., - \.6 ., -.. / _.:>

8 Radios, transmitters. 0.7 0 2.0 0.3 0.2 0.9 0.6 0.5 1.0antennas, etc:.

0,9 Not reported, at 40.4 59.5 27.5 31.7 46.7 35.2 38.6 50.2 39.2various other andunknown locations

from "Psychological & Neurologic Sequelae to Lightning Strike& Electric Shock Injuries. II

G H EngJestatter. PhD.,Carolina Psychological Health Services, Dec.• 1994

* Denotes Psychological Symptoms** Denotes Physical Symptoms

Absense of Symbol Denotes Organic Damage

AFTER-EFFECTS TO LIGHTNING SURVIVORS,EXPERIENCED BY 25 PERCENT OR GREATER OF

VICTIMS.

•• MEMORY DEFICITS/LOSS 52°k • DEPRESSION 32%

.. ATTENTION DEFICITS 41°/0 INABILITY TO SIT LONG 32%

• SLEEP DISTUR.BANCE 44% eXTERNAL BURNS '32:l,'c

•• NUMBNESS/PARATHESIAS 36°k •• SEVERE HEADACHES 30%

•• DIZZINESS 38°k • AGORAPHOBIA/FEAR tN 29%

CROWDS

EASY FATIGUEA81L1TY 37%, .. STORM PHOBIA 29Ck

STIFFNESS IN JOINTS 35% 1ft INABILITY TO 2ge~

COPE/OVERWHELMED

.. lRRITA81LlTY/TEMPER LOSS 34°k •• GENERALIZED WEAKNESS 29°t'o

PHOTOPHOBIA 34°k •• UNABLE TO WORK 29°k

•• LOSS OF STRENGTHIWEAKNESS 34% • REDUCED LIBtDO 26%

MUSCLE SPASMS 34°fc, *. CONFUSION 25°.10

.. CHRONIC FATIGUE 32°k •• COORDINATION PROBLEMS 28°,'0

HEARING LOSS 25°k

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POLICY STATEMENT FOR LIGHTNING SAFETY

1.0 Purpose. Lightning Safety is an organizational priority. It is placed ahead ofcontinuity ofoperations although cessation of activities must be conducted ina safe manner.

2.0 Authority. Lightning safety is a shared responsibility. Management,supervisors and workers all must participate. Ifyou believe you are threatenedby lightning immediately take protective precautions. Our safety practice isdescribed below.

3.0 Procedures. The following decision hierarchy, while not perfect, is designedto provide maximum safety for people from lightning's effects:

3.1 Obtain advanced warning ofthe lightning hazard from sources such as:3.1.1 Hearing thunder and/or seeing lightning3.1.2 Indications from reliable detectors where available.3.1.3 TV Weather ChanneL Weather Radio, weather subscription

service or other sources ofinformation where available.3.2 Make decisions to suspend activities and to notify people.

3.2.1 Flash-To-Bang (Lightning to Thunder Ratio) of fiveseconds = one mile. At a count of thirty = six milessuspend activities. (Note: change this +/- to suit localcondition.)

3.2.2 Notify people via radio, siren or other means.3.3 Move to safe shelter. (Note: No shelter is 100% immune from

lightning.)3.3.1 Large permanent buildings. In or on all-metal vehicles such

as cars, vans, trucks, or construction machinery. These are"best" locations.

3.3.2 "Semi-safe" locations are: a dense forest; bushes; lowground; inside any type ofstructure.

3.3.3 UNSAFE PLACES. Stay away from: any metal objectsincluding electrical equipment and machinery; water; trees;hilltops; open spaces; caves; exposed areas.

3.4 Re-assess the hazard. Wait a (recommended) thirty minutes after thelast observed thunder or lightning. Lighting may strike from the backside ofa passing thundercloud. Be conservative.

3.5 Inform people to resume activities via radio, siren or other means.

4.0 Effective Date. This Policy is effective immediately.

5.0 Endorsement. This Policy is endorsed by the National Lightning SafetyInstitute (wwwJightningsafety.com). It is consistent with recommendationsfrom the National Weather Service, the American Meteorological Association,the National Collegiate AtWetic Association and others.

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LIGHTNING SAFETY FOR OUTDOOR WORKERS

Safety and productivity are not mutually compatible, so one must be chosen overthe other. Easy Choice: SafetY First! Lightning has visited most all outdoor workenvironments. Anticipate a high risk situation and move to a low risk location.

Lightning safety awareness is a priority at every one of our facilities. Education isthe single most important means to achieving lightning safety. The following steps aresuggested:

1. Monitor weather conditions in the early moming houlS. Local weatherforecasts - from The Weather Channel, or NOAA Weather Radio - should be noted 24 hoursprior to scheduled activities. An inexpensive portable weather radio is recommended forobtaining timely stonn data.

2. Suspension and resumption of work activities should be planned inadvance. Understanding of SAFE shelters is essential. SAFE evacuation sites include:

a. Fully enclosed metal vehicles with windows up.b. Substantial bUildings.c. The low ground. Seek cover in clumps of bushes.d. Trees of unifonn height, such as a forest.

3. UNSAFE SHELTER AREAS include all outdoor metal objects like powerpoles, fences and gates, high mast light poles, metal bleachelS, electrical equipment,mowing and road machinery, etc. AVOID solitary trees. AVOID water. AVOID open fields.AVOID the high ground and caves.

4. Lightning's distance from you is easy to calculate: if you hear thunder, itand the associated lightning are within audible range•••about 6..e miles away. The distancefrom Strike A to StrIke B also can be 6-8 miles. Ask yourself why you should NOT go toshelter immediately. Of course, different distances to shelter will detennlne different timesto suspend activities. A good lightning safety motto is:

[(you can see it flightningJ Dee it,· iryou can hear it (thunder), clear it.

5. If you feel your hair standing on end, andlor hear "crackling noises" - youare in lightning's electric field. If caught outside dUring close-In lightning, immediatelyremove metal objects (including baseball cap), place your feet together, duck your head,and crouch down low In baseball catcher's stance with hands on knees.

6. Walt a minimum of 20-30 minutes from the last observed lightning orthunder before resuming activities.

7. People who have been struck by lightning do not carry an electricalcharge and are safe to handle. Apply first aid immediately if you are qualified to do so. Getemergency help promptly.

Prepared by the National Lightning Safety Institute, 303-666-8817(www.lightningsafety.com)

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LIGHTNING SAFETY AT SWIMMING POOLS,EMERGENCY ACTION PLAN FOR THUNDERSTORMS.

1. General Information.

Lightning's behavior is random and unpredictable.Preparedness and quick response are the best defensestowards the lightning hazard.

Our pools are connected to a much larger surfacearea via underground water pipes, gas lines, electricand telephone wiring, fences, etc. A 'lightning strike atone place on this metallic network may inducedangerous shocks elsewhere. Indoor and outdoor poolsare to be treated the same for lightning and lightningsafety issues. .

2. Lightning Safety Program for SWimming Pools.

At the first signs of lightning or thunder, the poolswill be evacuated. ("If you can hear it (thunder), Clear It(suspend activities)." They will remain cleared for 30minutes after thE) last observed lightning or thunder.

Patrons should leave the pool and the shower area.Seek shelter inside the main building, or in a fullyenclosed metal vehicle with the windows up.

AVOID waiting under tall trees, umbrellas, or nearelectric power lines. AVOID use of showers or othercontact with water. AVOID use of the telephone. AVOIDcontact with metal objects.

Prepared by tile National Lightning safety Institute, 3030688-8817.

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LIGHTNING SAFETY FOR ATHLETIC FIELDS,EMERGENCY ACTION PLAN FOR THUNDERSTORMS.

- City of [.•.your name here...] -

1. General Information.

Lightning's behavior is random and unpredictable.Preparedness and quick response are the best defensesfor the lightning hazard.

Il'f you can see it, flee it;ifyou can hear it, clear it. "

2. Lightning Safety for Athletic Fields.

Hear thunder? You may be threatened by lightning.Leave the athletic fields. No permanent bUilding nearby?Your car, truck or van is the next safest place to bewhen lightning threatens.

AVOID the rain and sun shelters and the dugoutareas. These places are not safe from lightning. AVOIDgoing underneath trees...they can become lightningrods. AVOID metal fences, metal gates, tall metal lightpoles and power poles.

Wait 30 minutes after the last observed lightningand thunder before you leave safety. (Lightning oftencomes out of the back end of the T'storm.) Gameofficials will signal a resumption of activities.

Prepared by the National Lightning safety Institute, www.lightningsafety.com

------------------_..'...22:_.m

--------------------- ---LIGHTNING SAFETY ~ WHERE TO GO &WHAT TO DO.

210

---------------------

AVOID - Trees. Hilltops. Open fields. Fences. Power lines.Electrical equipment. Wet areas. All metal objects.

SEEK· Safety in a vehicle. Safety in a large building.

TWO PROPOSEDLIGHTNING SAFETY MESSAGES

YOU CAN USE

If lightning is striking nearby, as a last resort you should:1. Get away from metal objects and trees. 2. Squat down with feettogether. 3. Place hands over ears to protect against thunder.

4. Get to safer place as soon as possible.----------

BE ALERT FOR LIGHTNING. BE READY TO SEEK SAFETY.Prepared in the public interest by NlSI. See us at: www.lIghtnlngsafety.com

LIGHTNING SAFETY MOTTO:"If you can see it (lightning), flee it; If you can hear it (thunder), clear it!'

THIS IS NOTA LIGHTNING-SAFESTRUCTURE.

AVOID THIS LOCATIONDURINGTHUNDERSTORMS.

SAFESHELSTEELS

S USINGNTAINERS

211

High frequency current flowing through a conductor generates an electromagnetic field,one effect of which is to confine the current towards the outside of the conductor. This isknown as "skin effect" while the thickness of the layer to which most of the current isrestricted is known as "skin depth." The higher the frequency, the smaller the depth ofcurrent penetration.

OVERVIEW OF LIGHTNING DETECTION EQUIPMENT

Lightning hazards can be mitigated by advanced planning. One part of thissafety program should include an eariy detection and warning alarm package. Lightningdetectors can give notice to shut down dangerous operations before the arrival oflightning. They also may signal "all clear" conditions after the lightning threat haspassed. Some tyPe of detection package may help you with Duty-To-Warn issues.

Lightning detectors vary in complexity and cost from large dedicated equipmentpackages costing in excess of $150,000 to inexpensive $20-$30 Radio Shack portableweather radios. The Flash-ta-Bang (F-B) Method requires no dedicated detector: onlycounting the time in seconds from seeing lightning's flash, to hearing the associatedthunder or bang. For each five seconds, lightning is one mile away. Thus, a F-B of 10 =2 miles; 15 = 3 miles; 20 = 4 miles; etc.

The distances from lightning Strike A to Strike B to Strike C easily can exceedmore than 5 miles. How much time is needed to get to shelter? Three to four minutes issuggested. SusPension of activities is very site-specific. For general situations, werecommend activating your lightning defense at a F-B of 30 (lightning is six miles away).We also recommend waiting to resume activities 30 minutes after the last observedlightning or thunder. This protocol may seem excessively conservative in manysituations... (''we'li never get anything done under such strict guidelines... "). It is a case­by-case risk management decision. And yes, safety and productivity sometimes areincompatible. Safety, however, always should be the prevailing directive.

Available technologies of the present day lightning detectors include:

a. Radio Frequency (RFl Detectors. These measure energy discharges fromlightning. They can determine the approximate distance and direction of thethreat. See www.boltek.comb. Inferometers. These are multi-station devices, much more costly than RFdetectors. They measure lightning strike data more precisely. Usually theyrequire a skilled operator. See www.vaisala.comc. Network Systems. The National Lightning Detection Network and the USPLNsystems cover all the USA and reports lightning strikes to a central station.

- Local storm data is available by subscription. Past strike information is archivedand accessible upon request. See www.lightningstorin.com and wwW.uspln.comd. Electric Field Mills. These pre-lightning equipments measure the potentialgradient (voltage) changes of the earth's electric field and report changes asthresholds build to lightning breakdown values. For more on EFMs, seewww.missioninstruments.com and www.campbellscLcome. Optical Monitors. These can provide earlier warning as they detect cloud-to­cloud lightning that typically precedes cloud-to-ground lightning.f. Hybrid Designs. These monitors use a combination of the other single­technology designs. -Two or more sources of information (example: e-C, C-G,optical recognition, EFMs) may be better than just one. See www.wxline.comg. Subscription Services. NLSI Recommendation - Rent a Meteorologist. Herehired professionals make the critical decisions and advise you. This method mayblunt claims of Negligence if something goes wrong. And some of thesecompanies can provide windspeed, rain, hail, tornados and other data sets. Off­site lightning detection by subscription is available from several vendors,including: Accuweather.com; Meteorlogix.com ("Weather Sentry") andWeatherdata.com ("Sky Guard").

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Lightning Detection Options - Accuracy vs Cost vs Complexity

Source of Info. Accuracy Cost Complexity

Hearing Thunder Danger is Near No Cost SimpleTV Weather Channel General Info. No Cost SimpleWeather Radios General Info. Up to $40 SimpleHandheld Detectors 50-60ok Accurate Up to $500 SomewhatBoltek System 70-80% Accurate Up to $1500 SomewhatWXLine System 90-95% Accurate Up to $7000 SomewhatSubscription Service 95%+ Accurate Monthly Fee Simple

Beware of a false sense of confidence from detectors: none of them will detectall of the lightning all of the time. None of them will provide "first strike/Bolt Out of theBlue" information or forecast in advance the positions of lightning strikes on earth.Various detector detection receiver algorythms operate at different frequencies andwavelengths: Boltek Stormtracker in the Low Frequency Range 100-700 KHZ?; VaisalaGAl NLDN at 1Q0-400 KHZ; NMT Lightning Array at VHF 60-78 MHZ; NASA LIS andOTD optical at 777.4 m; Vaisala SAFIR VHF 109-119 MHZ; Vaisala GAl LDAR·II at 50­120 MHZ; GAl VLF at 20-50 KHZ; the UK Meteorological Office RDI at 9.8 KHZ; etc. Anexcellent summary of families of lightning detectors and future research is at:

http://thunder.msfc.nasa.gov/validation/instruments.html

Detectors can display early warning of lightning conditions to hazardousoperations. Some detectors can start/stop standby power generators. A signaling oralarm notification method is essential to alert field personnel of developing dangerouscircumstances. Two-way radios, remote-activation siren packages, strobe lights andother methods are available.

Essential companions to any type lightning detector include: 1) A writtenLightning Safety Policy; 2) Designation of Primary Safety Person; 3) Determination ofWhen to Suspend Activities; 4) Determination of Safe/Not Safe Shelters; 5) Notificationto Persons at Risk; 6) Education: at a minimum consider posting information aboutlightning and your organization's safety program; 7) Determination of When to ResumeActivities.

For many situations, if you hear thunder, your (brain) detector is working fine.Since ·lightning and thunder always· occur paired, the lightning associated with thethunder you just heard is within your hearing distance - some 7-9 miles. Immediately goto safe shelter. No place outside is safe!

Select the detector and/or signaling device that is site-specific to yourrequirements, easiest to use, and which offers the most favorable costlbenefrt to youroperation's budget. No detector is 100% perfect.

Summary: Detectors give advanced notice of the lightning hazard. Now considerother defenses to mitigate the hazard. Where is safe refuge? How long to get there?How long to stay there? What about computers and servers and telecommunications? Isfacility bonding and grounding and surge protection OK? Lightning rods required?Contact NLSI for assistance.

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INTENSIVE WORKSHOP,LIGHTNING PROTECTION"

FOR ENGINEERS

Chapter Eleven

REFERENCES, RESOURCESAND CODES

215

Chapter Eleven Overview

There is much available information about lightning safety: Google has1,230,000 hits and Yahoo delivers 2,180,000 hits. Whew!

New information about lightning behavior necessitates regular revision ofCodes and Standards. Note to the lightning protection engineer - thosedocuments typically contain minimum requirements not always sufficientfor achieving high levels ofprotection.

International conferences provide opportunities for introduction of newconcepts and debates about long-held assumptions. The InternationalConference on Lightning Protection (ICLP) is a world class resource. It isconducted every two years. See the high quality of submitted papers atwww.iclp2006.net

Thank you for your interest in lightning safety.

R. Kitbil, Editor

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GLOSSARY OF LIGHTNING TERMS-NATIONAL LIGHTNING SAFETY INSTITUTE·

ABSORPTION LOSS: The attenuation of an electromagnetic wave as it passes through a shield. Thisloss is due primarily to induced currents and the associated 12'R loss.

ACCESS WELL: A small covered opening in the earth using concrete, day pipe or other wall materialto provide access to an earth electrode system connection.

ACTION INTEGRAL: Defines the energy in any portion of the current path per ohm resistance. ~i2dt ismeasured in A2s or joules per ohm.

AIR TERMINAL: The lightning rod or intended attachment conductor placed on or above a building.structure, tower. for the purpose of intercepting lightning.

AIR-TERMINATION SYSTEM: Part of the external LPS which is intended to intercept lightning flashes.

AMBIENT FIELD: The electric field strength of the atmosphere at rest, In clear air and under static-freeconditions. Generally thought to be some 150·300v/rn at standard temperature and pressure.

ARRESTER: Components. devices or circuits used to attenuate, suppress or divert excess electrical(surge and transient) energy to ground. The terms arrester, suppressor and protector are usedinterchangeably except that the term arrester is used herein for components, devices and circuits atthe service disconnecting means.

BOND: The electrical connection between two metallic surfaces established to provide a lowresistance path between them. See also CORROSION.

BOND1NG: The joining of metallic parts to form an electrically conductive path to assure electricalcontinuity and the capacity to conduct current imposed between the metallic parts.

BONDING JUMPER: A conductor to assure electrical conductivity between metal parts required to beelectrically connected.

CADWELD®: Process of molecular bonding patented by ERiCa. Also welded connection.

CAPACITANCE: The capacity of an electric nonconductor that .permits the storage of energy whenoppos"e surfaces are maintained at a difference of potential..Measured at 1.0 Hz. unless other wisestated. . . .

CATERNARY SYSTEM: Suspended overhead wires as a part of the LPS: Sometimes called shieldwires.

CIRCUIT: An electronic closed-loop path between two or more points used for signal transfer.

CIRCULAR MIL: A unit of area equal to the area of a circle whose diameter is one mil (1 mil = 0.001inch).

CLAMPING VOLTAGE: The voltage that appears across surge suppressor tenninals when thesuppressor is conducting transient current.

CLOUD-TO-CLOUD (Ce) LIGHTNING: A lightning stroke between thunderclouds. Typically, CClightning precedes CG lightning.

217

COLUMB: Current Umes Time. A measurement of charge in amp-seconds.

CONDUCTOR SHJELDING: An envelope that encloses the conductor of a cable and provides anequipotentional surface in contact with the cable insulation.

CONE OF PROTECTION: A conic space around a vertical lightning rod used to define a region ofprotection. The cone whose height equals the height of the rod and whose base radius is equal to therod height. Regarded as an obsolete term. See ZONE OF PROTECTION.

COPPER CLAD STEEL: Steel with a coating of copper bonded on it.

CORONA DISCHARGE: A localized cold discharge in air which forms around grounded objectsproducing an enhancement in electric field strength to allow ionization growth. Calted St. Elmos's Fireby ancient mariners. Precedes an arc or spark.

COULOMB. A unit of energy. One coulomb =one amp second.

COUPLING: Energy transfer between circuits, equipments, or systems.

CORROSION: The degradation of metals overtime, usually due to OXidation.

CROWBAR: Crowbar is a method of shorting a surge current to ground in surge protection devices.This method provides protection against more massive surges than other types, but lowers theclamping voltage below the operational voltage of the electronic equipment causing noise andoperational problems. It also permits a follow current which can cause damage.

COUNTERPOISE: See RING ELECTRODE.

DATA LtNE: A cable canying information as distinct from power. Examples of data lines are telephoneJines, telemetry control and signal lines.

DOWN-CONDUCTOR SYSTEM: Part of the external LPS which is intended to conduct the lightningcurrent from the air-termination system to the earth-tennination system.

DOWNWARD FLASH: Lightning flash initiated by a downward leader from cloud to earth. A downwardflash consists of a first short stroke, which can be followed by SUbsequent short strokes and may

.. include· a long stroke. .'

EARTH: That portion of the earth's crust sufficiently below' the surface to act as an infinite sink orsource.for electric charge. Earth Is considered the universal ground or.reference zero potential level.· ,

EARTH ELECTRODE SYSTEM (GROUNDING ELECTRODE SYSTEM): A network of electricallyinterconnected rods. plates, mats, piping, incidental electrodes (metallic tanks. etc.) or grids installedbelow grade to establish a low resistance contact with earth.

EARTH-TERMINATION SYSTEM: Part of an external LPS which is intended to conduct and dispersethe lightning current to the earth.

ELECTROMAGNETIC C'ONI'PATIBILIlY (EMC): The capability of equipments or systems to beoperated in' their intended environment, within designated levels of efficiency. without causing orreceiving degradation due to unintentional·etectromagnetic interference. EMC Is the result of anengineering planning process applied during the life cycle of the equipment. The process involvescareful considerations of frequency allocation, design, procurement, production, site selection,installation, operation. and maintenance.

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ELECTROMAGNETIC INTERFERENCE (EMI): Any electrical or electromagnetic phenomenon,manmade or natural, either radiated or conducted. that results in unintentional and undesirableresponses from, or perfonnance degradation or malfunction of electronic equipment.

ELECTRON AVALANCHE: An electron multiplication process due to electron-impact ionization of gasmolecules. This is the initial stage in the development of an electrical discharge in air, e.g. a corona orstreamer.

ELECTRONIC MULTIPOINT GROUND SYSTEM: An electrically continuous network consisting ofinterconnected ground plates, equipment racks, cabinets, conduit, junction boxes, raceways, ductwork, pipes and other normally non-current-carrying metal elements for electronic signals. It includesconductors, jumpers and straps that connect individual electronic equipment components to theelectronic multipoint ground system.

ELECTRONIC SINGLE POINT GROUND SYSTEM: A single point ground system provides a singlepoint reference in the facility for electronic signals. The single point ground system shall be installed ina trunk and branch arrangement to prevent conductive loops in the system. It shall be isolated from allother ground systems except for an interconnection. where applicable, to the mUltipoint ground systemat the main ground plate. The single point ground system consists of Insulated conductors, copperground plates mounted on insulated stands, and insulated ground plates, buses, and/or signal groundterminals In the electronic equipment which are isolated from the frame of the equipment. See IEEE1100 and FAA 019d.

EQUIPMENT GROUND: A connection between a unit of electlical equipment and the facility groundnetwork.

EQUIPMENT GROUNDING CONDUCTOR: The conductor used to connect non-current-carryingmetal parts of equipment, raceways, or other enclosures to the system grounded conductor and/orgrounding electrode conductor at the service entrance or at the source of a separately derived system.

EQUIPOTENTIAL SIGNAL REFERENCE PLANE: An equipotential conducting plane designed tomaintain a number of electrical/electronic units having a common signal reference at the samepotential.

EXTERNAL LIGHTNING PROTECTION SYSTEM: It consists of an alr-tennlnatlon system, a downconduction system and an earth termination system.

FACILITY: A building or other structure, either fixed or transportable in nature, with its utilities, ground·networks, and electrical supporting structures. All wlring,cabling ·as well as· electrical· and electroniceq\ilpments are also part of the facility.

FACILITY GROUND NETWORK: The electrically conductive network, .Including·' all structures andgrounding cables bonded to the earth grounding counterpoise but excluding the instrumentationground network and electrical enclosures, conduit, and raceway systems. In steel frame structures, thestructural members may be bonded together and connected to the earth grounding counterpoise tofonn the basic network. In buildings using nonconductive structural methods and materials such asmasonry and In outside facility areas such as gas, propellant, or oxidizer service facililies, the facilityground network consists of condUctors, sized according to criteria inclUded in this standard, bonded toan earth grounding counterpoise and extending to all areas containing equipment to be grounded.

. '.. .

FACILITY GROUND SYSTEM: The electrically interconnected system of conductors and conductiveelements that provides multiple current paths to earth. The facility ground system includes the earthelectrode SUbsystem, lightning protection SUbsystem. signal reference subsystem, fault protectionSUbsystem, electronic mUltipoint ground system, electronic single point ground system, as well as thebuilding structure. equipment racks, cabinets, conduit, junction boxes, raceways, duct work, pipes, andother normally noncurrent-carrying metal elements.

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FARADAY CAGE OR SHIELD: An electrostatic (E field) shield made up of a conductive or partiallyconductive material or grid. Faraday cage or screen room is effective for protecting inside equipmentfrom outside radiated RF energies. Lightning flows around the exterior. not inside, the structure.

FIRST RETURN STROKE: That current flow along the previously ionized path occurring when thatpath is complete from cloud to ground.

FLASH: The total lightning discharge.

FLASHOVER: Arcing or sparking between two or more (isolated) conductors. See thermal sparking.

FOUNDATION EARTH ELECTRODE: Reinforcement steel of foundation or additional conductorembedded in the concrete foundation of a structure and used as an earth electrode. Also called"UFERll ground.

GROUND: tf not otherwise qualified. ground means any electricat connection to earth. either directlythrough a facility ground network or through some intennediary grounding system such as aninstrumentation ground network.

GROUND FLASH DENSITY (Ng): The average annual ground flash density is the number of lightningftashes per square kitometer per year. Replaces tess accurate ISOCERAUNIC DAYS.

GROUND IMPEDANCE: The ground resistance and the inductance/capacitance value of thegrounding system. Also called dynamic surge ground impedance.

GROUND LOOP: An undesired potential EMI condition formed when two or more pieces of equipmentare interconnected and earthed for shock safety hazard prevention purposes.

GROUND RESISTANCE: The resistance value of a given ground rod or grounding system asmeasured, usually by a fall of potential (3 stake) method. using a 100Hz signal source.

GROUNDED, EFFECTIVELY: Pennanently connected to earth through a ground connection ofsufficiently low impedance and having sufficient current carrying capacity that ground fautt currentwhich may occur cannot cause a voltage build up dangerous to personnel.

GROUNDING: ,Grounding is the act ,of effecting optimum, electrical continuity between conductingobjects and earth. '

HIGH FREQUENCY: All electrical signals at frequencies greater than 100 kiiohertz (kHz). Pulse and'digitalsigrials with ,rise and fall times of less than 10 microseconds are classified as high frequencysignals.

IMPEDANCE: The overall resistance to an electrical current. consisting of both inductance andresistance.

IMPROVED GROUNDING: Inadequate, not-connected, or toose grounding is a major cause of powerquality problems as well a$ personnel safety issues. Well-known techniques, verified by many Codes'and Standards, offer remediation and upgrade' 'apPrQaches. Minimum standards are in NEe (NFPA­70), section 250.

INDUCTANCE: 1. Property of aconduetor which 'makes it resist and oppose any current changethrough it. 2. A process where one charged object can transfer similar properties to a nearby objectwithout direct contact.

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INTERNAL LIGHTNING PROTECTION SYSTEM: All measures additional to those mentioned underextemal lightning protection system including the equipotential bonding. the compliance of the safetydistance and the reduction of the electromagnetic effects of lightning current Within the structure to beprotected, including. shielding and surge protection devices.

ISOKERAUNIC (OR ISOCERAUNIC): Value (number) of thunderstonns measured daily expressed asTd/yr. Examples: Cerromatoso, Colombia with 325 Td/yr.; Florida with 110 Td/yr; Alaska with 3 Td/yr..

JOULES: A unit of energy. One joule =one watt second.

LANOLINE: Any conductor, line or cable installed externally above or below grade to interconnectelectronic equipment in different facility structures or to connect externally. mounted electronicequipment.

LEADER: A preliminary breakdown that fonns an ionized path. See STREAMER.

LIGHTNING ELECTROMAGNETIC PULSE (LEMP): Voltages or currents induced into cables andother conductors by the radiated field from a lightning flash some distance away.

LIGHTNING FLASH TO EARTH: Electric discharge of atmospheric origin between cloud and earthconsisting of one or more strokes.

LIGHTNING GROUND: A connection between a lightning protection system and a facility groundnetwork or counterpoise.

LIGHTNING PROTECTION SUBSYSTEM: A complete subsystem of

LIGHTNING PROTECTION SYSTEM (LPS): The complete system used to protect a structure and itscontents against the effects of lightning. Commonly it consists of both external and internal lightningprotection systems. Includes air tenninals, interconnecting conductors. ground terminals, surgeprotection for data and power lines, shielding and bonding. and other equipment and techniques toassure that the lightning discharge will be directed safely to earth.

LIGHTNING STROKE: Single discharge in a lightning flash to earth.

LOW FREQUENCY: Indudes all voltages and currents, whether signals. contrOl, or power, from DCthrough 100 kHz. Pulse and digital signals with rise times of 10 s or greater are considered lowfrequency signals.

MAGNETIC FIELD: A vector field produced by a continuous flow of charge.

MULTIPLE STROKES: Lightning flash ·consisting In .average of 3--4 strokes. with typical time intervalbetween them of about 50 ms.

MUTUAL INDUCTANCE: The property of a circuit Whereby a voltage is induced in a loop by achanging current in a separate conductor.

NATIONAL ELECTRICAL CODE (NEe): A standard governing the use of electrical wire. cable. andfixtures installed in buildings. The National Fire Protection Association (NFPA-70) .sponsors it under.the auspices of the American NationalStandards InStitute (ANsi-CI)... .

NEUTRAL: The ac power system conductor which is intentionally grounded on the supply side of thefirst service disconnect (ing) means. It is the low potential (white) side of a single-phase ac circuit orthe low potential fourth wire of a three-phase wye distribution system. The neutral (groundedconductor) provides a current return path for ac power currents whereas the grounding (or green)conductor does not, except during fault conditions.

. -- ~--- -- -- ------

-----------222 4iI

ONSET FIELD: The electric field strength above which ionization occurs. generally thought to be2.6kV/m in dry air at standard temperature and pressure.

OVERSHOOT VOLTAGE: The fast rising voltage that appears across surge suppressor tenninalsbefore the suppressor turns on (conducts current) and clamps the input voltage to a specified level.

PENETRATION: The passage through a structure by a cable. wire. or other conductive object.

POWER: Power is (voltage x current) or a (COUlomb/second).

POWER GROUND: A designed connection between a power circuit conductor and a groundingcounterpoise.

POWER LINE: A cable canying AC or DC power.

PRESSURE CONNECTOR: A high-pressure method which uses hydraulic crimpers to createconnectivity.

PRIMARY CLOUD·TO-GROUND (CG) LIGHTNING STROKE: The initial discharge between thethundercloud and ground which generally is associated with a stepped leader propagation. Sometimesreferred to as the initial stroke or simply the lightning flash.

RADIO FREQUENCY INTERFERENCE (RFl): RFI is manmade or natural. Intentional or unintentionalelectromagnetic propagation which results in unintentional and undesirable responses from orperformance degradation or malfunction of. electronic equipment.

RESISTANCE: The property of a conductor to oppose the flow of an electric current and changeelectric energy into heat. For lightning safety purposes, low resistances are desired. They areexpressed in ohms.

REVERSE STANDOFF VOLTAGE: The maximum voltage that can be applied across surgesuppressor terminals with the surge suppressor remaining in a non-conducting state.

RF: Radio frequencies - any and all frequencies that can be radiated .as an· electroffi.agnetic wave(plane wave). . . .

. .

RING EARTH ELECTRODE: An earth electrode forming a closed loop around the structure below oron the surface ofthe earth·. Also called COUNTERPOISE. .

SAFETY DISTANCE: Minimum distance between two conductive parts within the structure to beprotected between which no dangerous sparking can occur. See "flashover".

SAFETY GROUND: The local earth ground. The earth ground which grounds the neutral return. Thewire may be green or bare and can be through a metal conduit. It may be earth grounded as manytimes as needed. (Neutral must only be grounded once at the entry location).

.SELF..INDUCTANCE: ·The property Of a Wire ·or circuit which causes a back e.mJ. to be generatedwhen a changing current flows through it.

SEPARATELY DERIVED SYSTEM: A premises wiring system whose power is derived from a battery.a solar photovoltaic system or from a generator. transfonner, or converter windings. and that has nodirect electrical connection, including a solidly connected grounded circuit conductor, to supplyconductors originating in another system. .

SHIELD: A housing, screen. or cover which substantially reduces the coupling of electric and magneticfields into or out of circuits or prevents accidental contact of objects or persons with parts orcomponents operating at hazardous vottage levels. Also Faraday Cage.

SHIELDING: The process of applying a conducting barrier between a potentially disturbing noisesource and electronic circuitry. Shielding may be accomplished by the use of metal barriers.enclosures, or wrappings around source circuits and receiving circuits.

SIGNAL GROUND: A connection between a signal circuit and its zero signal reference plane.

SIDEFLASH: Ughtning arcing from one conductor to another across a dielectric.

SKIN EFFECT: The gradient conduction and propagation of RF or RF components of a surge on theouter surfaces of conductors.

STATIC GROUND: A functional tenn describing a connection between conductive objects and afacility ground network or counterpoise for the purpose of dissipating static electncity.

STRIKE TERMINATION DEVICE: A broad classification of devices intended to intecept lightning.

STREAMER: See LEADER. An ionized channel launched from ground-based objects. LEADERScome from the cloud. STREAMERS come from the ground

STRIKING DISTANCE: The distance covered by the final leader step of a downward propagatingprimar)' lightning stroke in making contact with a grounded object. This distance vanes with the typeand intensity of the lightning stroke.

STROKE: A component discharge of a lightning flash, which follows a leader.

SUBSEQUENT RETURN STROKES-RESTRIKES: Those strokes occuning after the first return strokein a mutti-stroke flash.

SURGE: A type of electrical overstress. In the absence of protedive devices, the magnitUde of thepeak voltage of a surge is usually understood as at least twice the normal system voltage, and theduration of the overvoltage is less than a few milliseconds. (The word ·surge" is also used by someengineers and technicians to indicate what should properly be caned a swell.)

SURGE PROTECTION DEVICE (SPD): A d.evice designed to protect electrical apparatus from hightransient voltage and to timit the duration and the amplitude'of follow-cunent. Device that is· intended'to limit transient overvoltages and divert or absorb surge currents. Replaces TVSS tenninology

. . . .' .

SURGE REFERENCE EQUAUZER: A surge protective device used for connecting .equipment toexternal systems whereby aU conductors connected to the protected load are routed, physically andelectrically. through a single enclosure with a shared reference point between the input and outputports of each system.

SURGE SUPPRESSOR: Component (s). device (s) or circuit (s) designed to attenuate. suppress ordivert conducted transient(s) and surge energy to ground to protect electronic equipment.

SURGES AND SURGE SUPPRESSION: Surges are direct and induced excess energies in a surgingwavefonn. The toad is SUbject to .damage by voltages. which exceed specifications. Surge protectorscanctip off ordispe~ excess energy using a variety of techniques. . .

THERMAL SPARKING: Occurs when a very high current is forced to cross a joint between twoconducting materials which have an impertecl bonding or mating between their surfaces.

223

THUNDERCLOUD: A cloud containing a charge density sufficient to allow formation of a lightningstroke.

THUNDERSTORM DAY: A local calendar day on which thunder is heard.

THUNDERSTORM DAYS (Td): The number of thunderstorm days per year obtained fromISOCERAUNIC maps.

TOTAL SURGE ENERGY: Total sum of surge energy for all lines of a protector unit. Measured injoules. The minimum total energy which results in the failure of the unit.

TRANSFER IMPEDANCE: Referring to coax, is the impedance to transfer into or outside the coax atvarious frequencies usually below 1MHz. Due to loss of skin effect. attenuation or shielding at theselow frequencies, coax can be susceptible to interference and noise as well as the radiation of suchsignals.

TRANSFER INDUCTANCE: The property of a circuit whereby a voltage is induced in a loop by achanging current in another circuit, some part of which is included in the loop.

TRANSIENT: 1. A brief event, usually lasting less than a few milliseconds. In many situationstransmission line theory, rather than circuit analysis, must be used to describe the propagation of atransient voltage or current. 2. In mathematical analysis the transient is the part of the system'sbehavior before the steady state Is reached. 3. The work "transient" is often used to indicate a"transient overvoltage-. 4. TRANSIENT Voltage Surge Suppressor (TVSS) is being replaced with themore definitive tenn SURGE PROTECTION DEVICE (SPD).

TURNON VOLTAGE: The voltage required across a transient suppressor terminal to cause thesuppressor to conduct current.

UFER GROUND. Grounding electrodes encased in concrete. To mitigate concrete cracking,explosions and/or spalling under lightning threat, UFER grounds should also adopt additional buriedelectrodes, such as a ring electrode.

UPWARD FLASH: Lightning flash initiated by an upward leader from an earthed structure to a cloud.An upward flash consists of a first long stroke with or without multiple superimposed short strokes,which can be followed by subsequent short strokes possibly induding further long strokes.

UNINTERRUPTIBLE POWER 'SUPPLY (UPS): An apparatus that supplies continuous power to aload, despite. disturbances and outages in the .mains. A UPS contains a bank of rechargeable batteriesthat suppty power in the abse~ce of acceptable supply.voltage. .

WAVE IMPEDANCE: The ratio of the electric field strength to the magnetic field strength at the point ofobservation.

ZONE OF PROTECTION: The presumed volume of space adjacent to a lightning protection systemthat is substantially immune to lightning strikes. (fhis is stili subject to debate. The random nature oflightning and its behavior is such that Zone of Protection remains a general and theoretical model.

.Protectio~ from its effects therefor~, i~ an Absolute Sense, .is impl?5Sib.I~.~

224

225

ANNUAL USA LIGHTNING COSTS AND LOSSES,ComplIed by the NatIonal UghtnJng Saf&ty InstItUte (wwwJlghtnlngsafety.com)

Accurate information about Ughtnlng-caused damage is elusive, however intensive remlrch suggests realisticlightning costs and losses may reach S4-5 biIJwn per year. Available and verifiable reporting includes:

1. FIRES.1.1 Forest Fires.

1.1.1 Half the wildfires in the western USA are llghtning-caused. In total there are about 10,000 suchfires costing BLM about 5100 million annually. -Dale VllnCe, BLM, US Dept. Interior

1.2 Fires To structures.1. L2 From 1994-1999 aDDual average Ilgbtning-caused fires to structureJ and vehicles totaled 18,890incidents at a cost of 5209,000,000. - NFPA Research Report 5/112005.1.2.2 18-/_ ofall lumberyard ftret and JO·At ofaU church fires are lightning-related. -01do IMlU'tlllCeInstitIde, Columbus OB

2. INSURANCE INDUSTRY REPORTS.2.1 During the 5 year period 1992..1996, we paid out 51.7 billion In lightning-related claims. This was8.7°/. of total claims and J.B·At of dollar losses. - St. Ptlllllll& Co.2.2 Each year we have about 307,000 claims from lightning, amounting to 1051 relmbunements ofsome 5332 miIIwn.- Stttte FtII7tIIIISIU'tIIICe Co.2.3 Five percent of aU Insurance deims are lightning-related, amounting to over $1 billion per year. ­11U",1IIICe InfontUltion Institute, NY, PNu Rele4fe 19'9.2.4 On 8nnual average, we payout about 3-4./. ofour claims as a result of lightning. FtICtDry MutuillCmnpa1rJa.

3.STORAGE AND PROCESSING ACTIVITIES.3.1~ specifically at .torage and prousling actiVities lightning accounts for 61-/_ of theacddents initiated by natural events•••in North American 16 out of20 accidents involving petroleumprodum storage tanks were due to lightntng strikes. -J0IU'IUIl ofHIIZIIt'tkHIs MtIINiaLt 40 (199S) 43·$43.2 The most expensive civilian lightning loss on record in the USA wu a Denver warehouse hit onJuly 23, 1997. Damage to building and contents exceeded 550 million. - NISI, 19983.3 A lightning-eaused explosion at tbe Naval Air Rocket Test Station (Lake Denmark NJ, 1926) cost570 million with 13 people killed. - Po VJemeister, "TIle Lightning Book"

4. AIRCRAFT MISHAPS & UPSETS.4.1 More than SO-/_ of military aircraft weather-related in-flight mishap' are caused by UghtDiDg. •Major P.B. Qlm, Air Force Flight Dyntunics Lob.4.2 During 1988-1996, the US Air Force had direct repair costs of $1,577,%0 due to lightning damageto aircraft. - US Air Force SII/ety Center, AlbIUJl'el''lueNM.4.3 LIghtning costs about $2 bOOon aDBually ill airline operating costs and passenger delays. -NOAAReport No. 16, MIT, 13 Feb. 1996.

5. ELECTRICAL INFRASTRUCTURE.5.1 Some thirty percent of all power outages are 'lightning-related on annualaver&ge, Withtotal eost8 approaehing one bil6ondoDan. -Ralph Bernstein, EPRJ : Diels, etal (1997j. .5.2 Our City of Virginia Beach VA has 321 fully automatic tramc signals. From May. 1999 to )by

. 2000 we experienced 359 lightning CaUsed· maifundfoDJ at '. direct equipment eost of 536,425.Adding up aU USA cities, the total costs must be very high. -6. Von Eiken, Traffic SupenU01, City ofVJ1'gini4 Betu:h VA5.3 Utility company nuclear power plant digital and I&C equipment safety feature activations wereinitiated by lightning In 19-/0 of the cases... US NIIde.,. Regll/Btoty CoItUlliDion, NUREGlCR-6579.5.4 Our database shows 145 lightning events to privately-owned nuclear power plants in the period1985--2000. - U.S. Nuclear Regulatory Commilsion, ReportMorch 2001.

6. ELECTRONIC COMPO.NENT&6.1 Lightning 8c~ted tor 101,000 laptop .ad de.ktop computer losses amounting to 5125,417,000in damage in 1m. -Co11IpIIIet' Security News (www.secure-it.co~Iettm.Sttltistics96.1Itm)

7. DEPARTMENT OF ENERGY.7.1 From 1990 to 2000 our records show 346 lightning Incidents to USA 81 nuclear sites. - DOEOccIIrtmee Reporting mulProcessing System Dtlt4btzse.

_.1 , I!I!!!I!!!!!!I!I!!!!!!I!I--

HELPFUL LIGHTNING URLSby NiItiolUll LightningSafety Institute

Dept Defense Standards Library - Joint Spectrum Centerwww.jsc.mil

go to '1>ocmnents - EMC Standards Library"for Handbooks. Instructions and MilitmyStandards. Look esp. for: MIL 419A; MIL 188;MIL 5087B; MIL 1542; MILI757A

Atmospheric Electricity Newsletter - Global News X 2/Yr.www.ae.atmos.uah.edu

New Mexico Tech Lightning Researchwww.ee.nmtedul.....langmuir

IEEE Power Engineering Society - Lightningwww.ieee.orglpes-ligbtning

USA Weather Site with detailed USA Lightning Strike Datawww.weathennatrix.comlligJrtning

Off Site (Remote) Weather Subscription Serviceswww.Lightningstorm.comwww.Accuweather.comwwwJntellicastcom

Air Force LightningProtection API 32-1065 and other Pubs32-1065 andAFMAN 91-201

bttp://afpubs.hg.afmil

NCAA Lightning Safety Recommendation for Recreationwww.ncaaorgllibrarylmNrts science/§POrts moo handbook/2002-Q3/1d.pdf

National"Severe Stor.tit Lab. Ligb1Ding"www.nSsl.noaagov

goto"Jigh1niug"

~e LightnitigDetector with softWarewww.boltekcom

NASA on Lightning Detectionhttp://tbunder.msfc.nasa.gov

High speed lightning flash sequence photoshttp://wsx.lanl.goylligbtnin g .bolt.html "

226

P.2URLs

35 mm camera lightning triggerwww.ligh1ningtrigger.com

EMC Tutorial inclligbtningwww.compliance-<:lnb.comlarchivell001018.htm

Navy Lightning Code NAVSEA OPS and otherPubswww.navy.mil/noJJcathtml

USA Five Year LightningMapwww.crh.noaagov!pnblltglnsa 1m fmd.grf

Lightning Maps ofSelected CountriesSee www.lightningsafety.com section 6.17

Walt Lyons Sprites & Jets Upper Atmosphere Infowww.:fma-research.com

also from Alaska: http://elf.gi.alaskaedn

Ligbtning Protection Tutorial (vendor)www.polyphaser.com

Surge ProtectionDevices Tutorial (vendor)www.telematic.com

Lightning Photoswww.weatherimages.com

Federal Aviation Admin FAA 6950.19Ahttp://anslfaa-gov!ans600!orders-specificationsl695019 1of4.pdfalso see•..2of4.pdfand 30f4.pdfand 4of4.pdf

Web BnUetin Board.on Global LfgldningProtection Issueswww.groups.yahoo.comlgrouplLightingProtection

227

IUiI!!!!!!I! -------- ~--------~--

REVIEW OF COUNTRY LIGHTNING CODESAND THE INTERNATIONAL me 62305

1.0 Background and Present-Day Situation.1.1 More than 100 published lightning protection (LP) Codes and Standards are in

use by various countries and by agencies within countries. The USA NFPA-78Q-Z004 hasundergone significant upgrading with new infonnation about surge protection. The USDepartment of Energy recently released M440.1-1, Electrical Storms and LightningProtection for application to explosives facilities. The US Air Force modified AFI 32­1065 to provide better guidance for critical operations. Yet many USA codes andstandards represent only generalized and minimum levels of safety application: NFPA­780 and UL 96a by example are not required and have no force of law behind them. Onthe other hand, some USA documents provide exacting information for specific problemsconfronting the LP engineer: IEEE 1100, IEEE 142 and FAA SID 019d/e are examples.Motorola R56 contains specific guidance for radio engineers.

1.2 Looking outside of the USAt s -isolated boxes of information, a review ofothernations' LP documents is educational and interesting. There is considerable helpfulguidance in (by example) Singapore's CP 33, AustralialNew Zealand's AS/ANZ-1786(2003), South Africa's SABS-03, the German VDE 0185 and the British BS-6651. Thereis agreement and harmony among most national codes as the readers of the Chinese GB50057, the Russian RD 34.21.122-87, the Indian IS 2309, and the Polish PN;.86!E­05003/01 will discover. Only with "renegade" ESE standards promoted by powerfulcommercial lobbying groups such as the French NF C 17-102 and the Spanish UNE­21186 are government endorsements extant for unapproved, non-scientific LP systems.

2.0 The Future.2.1 Change is coming. The European TC ·81 Technical Committee of the

International Eleetrotechnical Commission (!BC, see www.iec.ch) is finalizing the five­part authoritative and comprehensive LP standard IEC 62305.

2.2 mc 62035 will address in d~~i1 th.e below. subject matters: . ' .2.2.1 Part 1 Prot"OOtiop of StrucroresAgainstLightning: General Principles..2.2~2 Part 2 Risk Managet:nent. .2.2.3 Part 3 Physical Damage and Life Hazard.2.2A Part 4 Electrical arid Electronic Systems within Structures.2.2.5 Part 5 Services (telecom, powerlines, etc.)

2.3 All LP Codes and Standards are living documents subject to change. As newand veDfiable information about lightning defenses becomes understood, guidancedocuments will provide additional assistance and direction for safety.

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lEG 62305-1 Ed. 1.0: Protection against lightning - Part 1: General principles

81/262/FDIS

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Voting terminates on I Vote clos Ie

2005-10-21

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COMMISSION ELECTROTECHNIQUE INTERNATIONALE

EnvironmentEnvironnement

FINAL DRAFT INTERNATIONAL STANDARDPROJET FINAL DE NORME INTERNATIONAlE

ATTENTIONIEC - CENELEC

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Supersedes documentRemplace Ie document

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Distributed on I Diffuse Ie

2005-08-19

IECITC or SC CEI/CE ou sc81

Project number IEC 62305·1 Ed. 1.0Numero de projet

EMCCEM

oSafetySecurite

ATTENTIONVOTE PARALLELE

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Copyright© 2005 International Electrotechnical Commission, IEC. All rights reserved. It ispermitted to download this electronic file, to make a, copy and to print out the content for the salepurpose of preparing National Committee positions. You may not copy or "mirror" the file orprinted version of the docum.ent, or any part of it, for any other purpose without permission inwriting from lEG,

FORM FDIS (lEC)/FORMULAIRE FDIS (CEI) 2002·08·08

Titre

GEl 62305·1 Ed. 1.0: Protection contre la foudre - Partie 1: Principes generaux

Submitted for parallel voting In CENELECSoumis au vote parallele au CENELEC

CE DOCUMENT EST UN PROJET DIFFUSE POUR APPROBATION. IL HE PEUT ETRE CITE COMME NORME INTERNATIONALE AVANT SA PUBLICATIONEN TANT aUE TElLE.

OUTRE lE FAIT D'ORE EXAMINES POUR ETABLIR S'llS SONT ACCEPTABlES A DES FINS INDUSTRIEllES, TECHNOlOGlaUES ET COMMERCIALES,AINSI aUE DU POINT DE VUE DES UTiLISATEURS, LES PROJETS FINAUX DE NORMES INTERNATIONALES DOIVENT PARFOIS ETRE EXAMINES ENVUE DE LEUR POSSIBILITE DE DEVENIR DES NORMES POUVANT SERVIR DE REFERENCE DANS lES REGlEMENTATIONS NATIONAlES.

Functions concernedFonclions concernees

oINTERNATIONAL ELECTROTECHNICAL COMMISSION

THIS DOCUMENT IS A DRAFT DISTRIBUTED FOR APPROVAL. IT MAY NOT BE REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHEDAS SUCH.

IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, FINALDRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDSTO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.

Also of Interest to the following committeesInteresse egalement les comites suivants

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DESIGN CODEFOR LIGHTNING PROTECTION OF STRUCTURES

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PROTECTION OF BUILDINGS AND ALLIEDSTRUCTURES AGAINST LIGHTNING­

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RUSSIAN LIGHTNING PROTECTION DESIGN CODEFOR BUILDINGS AND STRUCTURES RD 34.21.122-87

ThiS Code is mandatory for all government ministries and agencies.The Code defines a mandatory set ofprocedures and devices to provide safety ofhuman beings (farmammals), buildings, structures, equipment, and materials against potential lightning-induced explosions,fires, and other types ofdamage.This Code serves as a mandatory reference source for designing buildings and structures.The Code does not cover design and construction 0/lightning protection lor power lines, electricalmodules ofelectric power plants and substations, contact lines, radio and TV antennas, cable, telephone,and radio transmission lines, or buildings and structures the operation o/which involves production, use,or storage ofordnance and explosives.This Code regulates lightning protection procedures performed during construction, and also includes theuse ofadditional lightning protection measures inside a building or structure during reconstruction orinsra/lation ofadditional process or electrical equipment.In addition to the Code requirements, building and structural design should also meet the lightningprotection requirements ofother existing standards, regulations, instructions, and state standards.

1. General Information

1.1. In accordance with the purpose of buildings and structures) a need in lightning protection andits category, as well as types of coverage areas provided by lightning rods and lightningconductors, are defined in Table I as a function of average annual lightning storm activity at thelocation of buildings or structures, and of the expected number of lightning strikes per year at thatlocation. Lightning protection must be arranged as per conditions specified in lines 3 and 4 ofTable l.

The assessment of the average annual lightning storm activity and expected number oflightning strikes for buildings and structures is made per Attachment 2~ various types of coverageareas are mapped per Attaclunent 3.

1.2. Buildings and structures that have lightning protection arrangement as per Categories I and IImust be protected against direct lightning strikes) secondary effects) and transfer of high-voltagepotential through ground surface, above- and undergroWld metal utility lines.

Buildings and structures with Category III lightning protection arrangement must beprotected against direct lightning strikes and transfer of high-voltage potential though groundsurface (above-ground) metal utility lines.

Outdoor facilities· with Category II lightning protection arrangemen~~l:lst be protectedagainst ·direci st~es and secondary lightning effec~. .... .. Outdoor facilities with.Category III lightning protection arrangement must be protectedagainst direct lightning strikes. .. . .

.Indoor arrangements for buildings with a large area (over 100 m ·wide) must includemeasures for equalizing the potential.

1.3. For buildings and structure~ that require Category I and II or Category I and III lightningprotection arrangement) lightning protection of the entire building or structure must be providedper Category 1.

') This Code ·has been developed by the: S~t~ S·cientific Ene~gy R~earch In~titute named after G.M.Krzhizhanovskyt the USSR Ministry ofEnergy~ coordinated with the USSR GosStroy (Letter#ACH-:-3945·8 of July30,1987) and approved by the Main Technical Directorate of the USSR Ministry of Energy.This Code voids the Instruction for Design and Arrangement ofLightning Protection ofBuildings, SN 305\t\\t\C}77. Q~ \..\gt\ "8

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SINGAPORE STANDARD

CP 33 : 1996(Ies 91.120.40)

CODE OF PRACTICE FOR

Lightning protection(Incorporating Amendment No.1, February 1999)

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Publi!?hed by. Singapore Productivity and Standards Board .'

1 Science Park DriveSingapore 118221

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UDC 621.316.93ISBN 0·626·07358·8 SASS 03·1985

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Code of Practice for

~ The protection of structures against~ lightningow

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. First RevisionPublished byTHE COUNCIL OF THE SOUTH AFRICAN BUREAU OF STANDARDS

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standard isfirst Slated

Chapter 3 Defmitions

ls.2 NFPA Official Definitions.

3.2.1* Approved. Acceptable to the authority havingjurisdic­tion.

3.2.2* Authority Having Jurisdiction (AHJ). An organization,office, or individual responsible for enforcing the require­ments of a code or standard, or for approving equipment.materials, an installation, or a procedure.

3.2.3 Labeled. Equipment or materials to which has been at·tached a label, symbol, or other identifYing mark of an organiza­tion that is acceptable to the authority having jurisdiction andconcerned with product evaluation, that maintains periodic in­spection of production of labeled eqUipment or materials, andby whose labeling the manufacturer indicates compliance withappropriate standards or perfonnance in a specified manner.

3.2.4* Usted. Equipment, materials, or services included in alist published by an organization that is acceptable to the au·thority having jurisdiction and concerned with evaluation ofprodUCts or services, that maintains periodic inspection ofproduction oflisted equipment or materials or periodic evalu­ation of services, and whose listing states that either the equip­ment, material, or service meets appropriate designated stan·dards or has been tested and found suitable for a specifiedpurpose.

3.1 General. The definitions contained in this chapter shallapply to the terms used in this standard. Where terms are notincluded, common usage of the terms shall apply.

1.4 Mechanical Execution of Work. Lightning protection sys­tems shall be installed in a neat and workmanlike"manner.

1.5* Maintenance. Recommended .,.", . for the mainte-nance of the lightning pr""~ be provided tothe owner at the ,.~

1.3 Listed. Labeled, or Approved Components. Where fit·tings, devices, or other components required by this standardare available as listed or labeled, such components shan beused,

INSTALLATION OF UGHTNlNG PROTECTION SYSTEMS

NFPA780

2004 Edition

Standard for the

Installation of lightning Protection Systems

IMPORTANT NOTE: This NFPA document is made available foruse wbjeet wimportant notices and legal disclai#let'$. These noticesand disclaimers appear in allpublicationl containingthis document 1.6~"'''

and~ be found under the heading "Important Noncu and~~.. O~claimers Concerning NFPA Documentl. It They can also h# .' O~ 11.' C

on~ii;t;:m::~:e:s~;df:~'~;C l\. srt ~~ ~~rt~ ~1C~£1'Nv,~:£f~~;'~"''''". 4 ~s't'C't\O~ S~ "rule b~s ~OR' \.}..J. :0 O~"B {\chan~e,.c }.' -0....10 Yl....... ~ ,1'r,v~~~: ~~ ~~ "f1~}.}."' .,..~y p-' Chapter 2 Referenced Publicationsletlon IS In, "'("1 G~).. ~)....remain. )..Jl: 2.1 General. The documents or portions thereof listed ill this

A r 0 ra h chapter are referenced within this standard and shall be con·re.eren, on r pa grap 'd d f . .

indicates mat cted from another NFPA Sl ere part 0 the requIrements of thiS document.document, As ...e user, the complete title and edition 2.2 NFPA Publication. National Fire Protection Association,of the source ulJcuments for mandatory extracts are given in 1 Batterymarch Park, Quincy, MA 02169·747l.

Chapter 2 an? ~ose for nonmandatory extracts. are giv~n in NFPA 70 National Electrical Cork~ 2002 edition, .Annex N. Edltonal changes to extracted materIal consIst of ' ,revising references to an appropriate division in this docu- 2.3 Other Publications. (Reserved)ment or the inclusion of the document number with the divi-sion number when the reference is to the original document.Reques~for interpretations or revisions ofextracted text shallbe senUo the technical committee responsible for the sOUl"cedocument.

Information 011 referenced publications can be found inChapter 2 and Annex N.

780-4

2004 Edl~on

Chapter 1 Administration

1.1 Scope.

1.1.1 This document shall cover traditional lightning protec­tion system installation requirement5 for the following:

(1) Ordinary structures(2) Miscellaneous structures and special occupancies(3) Heavy-duty SlaCks(4) Watercraft(5) Structures containing flammable vapors, flammable

gas~s, or liquids that give off flammable vapors

... 1.1.2* This document shall not cover lightning protection sys­tem ins~lIation requirements for the following:

(1) Explosives manufacturing buildings and magazines(2) Ele~tric generating, transmission, and distribution systems

... 1.1.3 This document shall not cover lightning protection sys­tem installation requirements for early streamer emission sys­tems or charge dissipation systems.

1.2 Pwipose. The purpose of this standard shall be to providefor the;safeguarding of persons and property trom hazardsarising from exposure to lightning.

239

NCM®GUIDELINE 1dLightning SafetyJuly 1997· Re~sed June 2006~~~~~~~~~~~~~~~~_

;

12

The NCM Committee on Com­petitive Safeguards and MedicalAspects of Sports acknowledgesthe significant input of Brian L.Bennett, formerly an athletic train­er with the· College of William andMary Division of Sports Medicine,Ronald L. Holle, a meteorologist,formerly of the National SevereStorms Laboratory (NSSL), andMary Ann Cooper, MD, Professorof Emergency Medicine of theUniversity of Illinois at Chicago, in .the development of this guideline.

Lightning is the most consistentand significant weather hazard thatmay affect interc01{egiate athletics.Within the United States, NationalOceanographic and AtmosphericAdministration (NOAA) estimatesthat 60-70 fatalities and about 10times as many injuries occur fromlightning strikes every year. Whilethe probability of being struck bylightning is low, the odds are sig­nificantly greater when a storm isin the area and proper safety pre­cautions are not followed.

Education and prevention are thekeys to lightning safety. The refer­ences associated with this guide­line are an excellent educationalresource. Prevention should beginlong before any intercollegiate ath­letics event or practice by beingproactive and having a lightningsafety plan in place. The followingsteps are recommended by theNCAA and NOAA to mitigate thelightning hazard:

1. Designate a person to moni­tor threatening weather and tomake the decision to remove ateam or individuals from an athlet­ics site or event. Alightning safe­ty plan should include plannedinstructions for participants andspectators, designation of warningand all clear signals, proper sig­nage, and designation of saferplaces for shelter from the light­ning.

2. Monitor local weather re­ports each day before any practiceor event. Be diligently aware ofpotential thunderstorms that mayform during scheduled intercolle­giate athletics events or practices.Weather information can be foundthrough various means via local

. television news coverage, theInternet, cable and satellite weath­er programming, or the NationalWeather Service (NWS) home­page at http://www.weather.gov.

3. Be informed of NationalWeather Service (NWS) issuedthunderstorm "watches" or Ilwarn­ings," as well as the warning signsof developing thunderstorms inthe area, such as high winds ordarkening skies. AIlwatch" meansconditions are favorable for severeweather to develop in an area; a"warning" means that severeweather has been reported in anarea and for everyone to take theproper precautions. A NOAAweather radio is particularly help­ful in providing this information.

4. Know where the closestII safer structure or location" is tothe field or playing area, and knowhow long it takes to get to thatlocation. Asafer structure or loca­tion is defined as:

a. Any bUilding normally occu­pied or frequently used by peo­ple, Le., a building with plumb­ing and/or electrical wiring thatacts to electrically ground thestructure. Avoid using theshower or plumbing facilitiesand contact with electrical appli­ances during athunderstorm.

b. Small covered shelters arenot safe from lightning. Dug­outs, rain shelters, golf shelters,and picnic shelters, even jf theyare properly grounded forstructural safety, are usually notproperly grounded from theeffects of lightning and sideflashes to people. They areusually very unsafe and mayactually increase the risk oflightning injury. Other danger­ous locations include areasconnected to, or near lightpoles, towers and fences thatcan carry anearby strike to peo­ple. Also dangerous is anylocation that makes the personthe highest point in the area.

c.ln the absence of a sturdy,frequently inhabited building,any vehicle with a hard metalroof (neither aconvertible, nor agolf cart) with the windows shut

Lightning Safety _

provides a measure of safety.The hard metal frame and roof,not the rubber tires is what pro~

tects occupants by dissipatinglightning current around thevehicle and not through theoccupants. It is important notto touch the metal framework ofthe vehicle. Some athleticsevents rent school buses assafer shelters to place aroundopen courses or fields.

5. Lightning awareness shouldbe heightened at the first flash oflightning, clap of thunder, and/orother criteria such as increasingwinds or darkening skies, no mat­ter how far away. These types ofactivities must be treated as awarning or l(wake~up call" to inter~

collegiate athletics personnel.

Specific lightning safety guidelineshave been developed with the assis­tance of lightning safety experts:

a. As aminimum, lightning safe­ty experts strongly recommendthat by the time the monitorobserves 30 seconds betweenseeing the lightning flash andhearing its associated thunder, allindividuals should have left theathletics site and reached asaferstructure or location.

b. Please note that thunder maybe hard to hear if there is an ath­letics event going on, particular­ly in stadia with large crowds.Implement your lightning safetyplan accordingly.

C. The existence of blue sky andthe absence of rain are not guar­antees that lightning will notstrike. At least 10 percent of light­ning occurs when there is norainfall and when blue sky is oftenvisible somewhere in the sky,especially with summer thunder­storms. Lightning can, and does,strike as far as 10 (or more) milesaway from the rain shaft.

d.Avoid using landline tele­phones, except in emergencysituations. People have beenkilled while using alandline tele­phone during a thunderstorm.Cellular or cordless phones aresafe alternatives to a landlinephone, particularly if the personand the antenna are locatedwithin asafer structure or loca­tion, and if all other-precautionsare followed.

e. To resume athletics activi­ties, lightning safety expertsrecommend waiting 30 minutesafter both the last sound ofthunder and last flash of light­ning. If lightning is seen with­out hearing thunder, lightningmay be out of range and there­fore less likely to be asignificantthreat. At night. be aware thatlightning can be visible at amuch greater distance than dur~

ing the day as clouds are beinglit from the inside by lightning.This greater distance may meanthat the lightning is no longer asignificant threat. At night, use

both the sound of thunder andseeing the lightning channelitself to decide on re-setting the30~minute "return-to-play"clock before resuming outdoorathletics activities.

f. People who have been struckby lightning do not carry anelectrical charge. Therefore,cardiopulmonary resuscitation(CPR) is safe for the responder.If possible, an injured personshould be moved to a saferlocation before starting CPR.Lightning-strike victims whoshow signs of cardiac or respi­ratory arrest need promptemergency help. If you are in a911 community, call for help.Prompt, aggressive CPR hasbeen highly effective for the sur­vival of victims of lightningstrikes.

Automatic external defibrillators(AED's) have become a com­mon, safe and effective meansof reviving persons in cardiacarrest. An AED should be con­sidered as part of your sidelineequipment. However, CPRshould never be delayed whilesearching for an AED.

Note: Weather watchers, real­time weather forecasts andcommercial weather~warning

devices are all tools that can beused to aid in decision-makingregarding stoppage of play,evacuation and return to play.

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DESIGN LIGHTNING SAFETY FOR THESE SITUATIONS:

1. Self-supporting 150 ft. cellular radio tower. Equipment building 6X6XI0 is 15 ft.away. Radio equipment in building. Cable tray. Overhead incoming AC power.Gated fence. Perimeter light masts.

2. Guard shack 12X12X12, manned 24 X 7. Peaked roof. Drive through gates. Highmast lighting. Radio antennas on building. AC power and telecomm inside. Airconditioning box on roof.

3. Row ofsix Earth Covered Explosive Storage Magazines each 20X40X15. Roll-updoors. Interior crane. Ventilation Stacks. High mast lighting. Perimeter fence.

4. Wastewater treatment plant. Three adjacent 100 ft. diameter uncovered steeltanks. Incoming AC power and telecom. Pumps, valves, relays, switches.Steel catwalks to all structures. Guyed radio tower 20 ft. high. Fenced.

5. Three story computer center building with flat roof. Many metal boxes on roof forwater chilling, HVAC, pumps, fans, motors. 175 employees. Lighted parking lot.Trees. Picnic and recreation area outside. Secondary building 1OXIOXl0 sharingAC power & telecomm 30 ft. away.

6. Metal shelter used as bus stop 10XIOXlO open on one side. No power. Telephonepole carrying AC power, cable and telephone services adjacent to shelter.

7. Wooden shelter on golf course 1OXlOXI0 with four posts supporting peaked roof.Interior lights. Pop machine. Water fountain. Picnic table.

8. Industrial cement plant on five acres. Fenced. Some permanent buildings. 125outdoor and indoor workers, 2 shifts. You are the Safety Manager. Develop aprogram for lightning safety for people and for electrical/electronic equipment.

Ml'11OtW. UGH1'NNGSAFETYNmIU1'E

8t1 North·fio«w8r 1we.1OI••co 80021-2214

Anonymous Critique for Workshop

1. The information presented to me was:a. Useful and applies to my work _

b. Not relevant. Needs revision ~~_-------c. Too technical_. Incomplete__' OK, except for _d.Other _

2. The best part of the course was:

3. The worst part of the course was:

4. Some information I need which was missing was: _

5. The top three things I'll remember about the course are:a. _b. _c. ,.-;...' _

6. I rate the instructor as follows on a 1-10 scale: Good Presenter of Information (GPI);Knew Subject (KS); Give any constructive comments,too.

a. GPI = _KS=---------------------Other= _

7. The meeeting room arrangement, choice of location,' and general logistics wereOK _; need improvement: _

8. Cost of the seminar was:a. about right _b. too high_c.other _

9. Workbooks, handout materials and visual aids were:a. Good. . Just Fair_. OK__b. Improvements Suggested ____.----------

10. Others in my organization or in my industry williwill not find the Workshopbeneficial.

11. There is a one day class on Inspection, Maintenance and Testing of the LPS.Would other people in your organization be Interested? (See instructor here.)

11. Other comments and opinions:

242

243

technical bookfrom ...NATIONAL LIGHTNING SAFETY INSTITUTE (NLSI)

www.lightningsafety.com

ItLIGHTNING PROTECTION FOR ENGINEERS

An Illustrated Guide in Accord with Recognized Codes & Standards

TABLE OF CONTENTS, Revision 3. August 2006

Part J

Part 2

Part 3

Part 4

PartS

Part 6

Part 7

Part 8

Part 9

Part 10

Part JJ

Lightning Physics, Lightning Behavior and Lightning Safety Overview

Risk Assessment

The Grounding and Bonding Imperative

Exterior Lightning Protection for Structures

Interior Lightning Protection for the Electrical SystemOf a Complex Facility

Communications Facilities, Exterior Lightning Protection

Communications Facilities, Interior Lightning Protection

Lightning Protection for High Risk Installations ContainingSensitive Electronics, Explosives, Munitions, or Volatile Fuels

International Views of Unconventional Air TerminalDesigns Such As ESE and CTSIDAS

Lightning Safety for Outdoor Workers

References, Resources and Codes

COST IS $79.95 + $5.00 S&H anywhere in the USA.International (overseas) express carrier delivery is available.

Contact us at Tel. 303-666-8817; Fax 303-666-8786; Email: Media@lightningsafety.com ,or you can mail this Order Form to: NLSI, 891 N. Hoover Ave., Louisville CO 80027-2294

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LIGHTNING PROTECTION FOR ENGINEERS

- Page Index -

1. Lightning Physics, Behavior and Safety Overview 1Chapter Overview 2The Convection Process 3Typical Waveform 4"Cold" vs "Hot" Lightning 5Log Normal Distribution 6Sequence of Steps in Typical Flash 7Streamer/Leader 8Lightning Behavior - Part 1 9Lightning Behavior - Part 2 10ACR 11Resistive, Magnetic & Electric Fields 12The Attachment Process 13TD/YR Worldwide 14Map TD/YR USA 15Map FDNRlSQIKM USA 16Little-Known Information 17Per NASA - The Protection Process 18Per NLSI - How to Get to Lightning Safety 19Matrix ofProtection Sub-Systems 20Lightning Mitigation Guideline 21

244 •

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2. Risk AssessmentChapter OverviewDetermining the Probabilities...Analysis ofNeed for ProtectionNLSI Version ofRisk Assessment

3. The Grounding & Bonding ImperativeChapter OverviewDefinition ofTermsFactors Affecting Soil Resistivity

232425-2829-3940

414243-4546

Types ofEarth Electrode SystemsVarious Grounding LayoutsGrounding Buildings with BasementsGrounding Buildings without BasementsGround Rod BondingGrounding Additives and BackfillsBonding Drive & Walk GatesBonding to Fence Post"Ufer" Ground DetailSeparation Distance, Grounds-to-Other ConductorsService Entry GroundingProblem with Poor BondingFacility Bonding Detail 1Facility Bonding Detail 2Bonding Building Steel to GroundGround Potential EqualizationBonding Separate Ground RodsBonding ConduitsBonding to Prevent Side FlashingMiscellaneous Bonding Examples (MBE) 1MBE2MBE3MBE4MBE5Hierarchy ofBonding JumpersBonding Jumper InductanceBonding Technique EffectivenessTypical Connector TenninationsBonding Inspection Checklist

4. Exterior Lightning Protection for StructuresChapter OverviewApproved Air Tenninal DesignsPersonal Shelter, Faraday Cage ConceptFree-Standing Steel MastsOverhead Wire (OHW) or Catenary DesignFranklin Rods 1

4748495051525354555657585960616263646566676869707172737475

77787980818283

245

-------------_....'

­246 \l1li~.

Franklin Rods 2 84Franklin Rods 3 85Function ofOverhead Shield Wire (OHW) 86Design OHW - View 1 87Design OHW - View 2 88Design OHW - View 3 89OHW Support Poles Details 90Preference for Mast & OHW per Codes 91Cone ofProtection (CP) Model 92Rolling Sphere (RS) Model 93Comparison ofCP and RS 94

5. Interior Lightning Protection for the Electrical SystemOfa Complex Facility 95

Chapter Overview 96Side Flash and Coupling to Building Wiring 97SPD Locations per IEEE 98SPDs Typical for Commercial Building 99SPDs Typical for Process Control Plant 100Worst Cases ofTransient Insults 101Voltage and Current Waveforms 102Overview ofSPD Functions 103Transient Limiting ofGeneric SPD Components 104Advantages & Disadvantages ofSPD Components 105Desirable SPD Operating Characteristics 106Three Stage SPD Example 107Surge Reference Equalizer 108Surge Protection Checklist 109Recommended SPD Specifications 110SPD Installation Practices 111SPD Evaluation Form 112SPD Follow-Up References 113The Missing Surge Protector 114

6. Communications Facilities, Exterior Lightning Protection 115Chapter Overview 116Tower Bonding - SelfSupporting Tower 117

Tower Bonding - Guyed Tower 118Tower Bonding - Building Mounted 119Tower Grounding Configurations 120Optimum Grounding Under Lightning Attack 121Exterior Ground Plan 122Exterior Ground Ring 123Coaxial Cable Routing 124Bonding Coaxial Cable Shield 125Coaxial Cables Entering Building 126Grounding Checklist, Exterior 127

7. Communications Facilities, Interior Lightning Protection 129Chapter Overview 130Typical Interior Grounding Plan 131"Halo" Ground 132Examples of Interior Grounding & Bonding 133Bonding Raised Floor 134Bonding Interior Metallic Components 135Cabinet & Rack Bonding 136Cable Tray Bonding 137Details of Cable & Duct Bonding 138Grounding Checklist, Interior 139SPD & UPS Layout 140Typical SPD Applications 141SPD Checklist 142SPDs - Satellite Systems 143SPDs for Computers & CCTV Systems 144SPDs for LAN Systems 145Alternative Methods of Shielding 146Bonding Cable Shields 147Noise Reduction 1 148Noise Reduction 2 149

8. Lightning Protection for High Risk Installations such asElectric Power Facilities, Explosives, Munitions &Volatile Fuels 151

Chapter Overview 152

~4{

Decision Tree for Facility Lightning SafetyPrinciples of Topological ShieldingFortress or Zone Protection ConceptPreference for Mast or OSW Air Terminal DesignsErrors at Critical Facilities, Parts 1 & 2Errors at Critical Facilities, Parts 3 & 4Going Beyond The Codes

21 st Century Lightning Safety for EnvironmentsContaining Sensitive Electronics, Explosives,And Volatile Substances

Attention to Detail

9. International View ofUnconventional Air TerminalsSuch as "ESE" and "CTS/DAS."

Chapter OverviewPeer-Reviewed Technical Papers (3 Abstracts)Email from MalaysiaEmail from TurkeyUSA Court Case Concerning ESEProfs. Uman & Rakov Paper on "CTS/DASIESE"

Warning ofthe ICLP Scientific Committee

10. Lightning Safety for Outdoor ActivitiesChapter Overview .Decision Tree for People Lightning SafetyLightning As It Originates From CloudsPour Mechanisms ofLightning AttachmentTouch and Step PotentialsInstantaneous Potential Differences

.. Lightning Deaths by State (1)Lightning Deaths by State (2)After Effects to Lightning SurvivorsSample Policy Statement for Lightning Safety

153154155156157158159-162

163­168

169

171172173174175176177-

188189­

194

195196197198199200201202203204205

248

Sample Poster for Outdoor WorkersSample Poster for Outdoor RecreationSample Poster for Swimming PoolsSample Poster for Athletic FieldsSample Lightning Safety MessagesSafe Shelters - Faraday Like CageOverview ofLightning Detection Equipment

11. References, Resources and CodesChapter OverviewGlossary ofLightning Terms

Annual USA Lightning Costs & LossesHelpful Lightning URLs

Review of Country Codes and the IEC 62305Examples of Selected Codes (Cover Pages Only)

IEC 62305 (www.iec.ch)AustralialNew Zealand AS/NZ 1768British BS6651China GB 50057-94India IS 2309Russia RD 34.21.122-87Singapore CP 33South Africa SABS 03USA NFPA-780USA NCAA Guideline ld

Quiz - DesignLPSs for Various SituationsNLSI 2 Day Class CritiqueLP ENG Book Order FormPage Index

206207208209210211212-

213

215216217-

224225226-

227228229230231232233234235236237238239­240241242243244-

249

SIX STAGES OF A PROJECT

1. ENTHUSIASM

2. DISENCHANTMENT

3. PANIC

4. SEARCH FOR THE GUILTY

5. PUNISHMENT OF THE INNOCENT

6. PROMOTION FOR THOSE NOT INVOLVED

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