NFPA 70E-2009

ARC FLASH PROTECTION

What is an Electric Arc?

• Electric Arc –The passage of a substantial electric current through a gas, such as air or vaporized metal.– An electric arc...

• Typically lasts less than one second

• Has an extremely high percentage of radiant energy

• Is explosive in nature• Can ignite and/or melt most

things in its path.

The Arc1

2

Electrical Hazards• ARC FLASH – A dangerous condition associated

with the release of energy caused by an electric arc due to either a phase to ground or phase to phase fault.– Note that this explosive condition includes a broad

spectrum of electromagnetic energy, vaporized metal (plasma), heat, pressure wave, fragments and a spray of molten metal projectiles.

• PLASMA - Superheated gas that is created by the arc flash and expands rapidly from the Arc location.

C

Arc Flash • This phase to ground or

phase to phase fault can result from many factors, including dropped tools, accidental contact with electrical systems, build up of conductive dust, corrosion, and improper work procedures.

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Example of an arc flash

Electrical Hazards

• Arc Blast –Pressure wave caused by the expansion of gases and conducting materials with flying molten materials. (Arc temperature can reach 35,000°F - this is four times hotter than the surface of the sun. Fatal burns can occur at distances over 10 ft.).

Serious injuries and damage can resultan arc flash/blast.

What Determines the Intensity of an Electric

Arc Exposure? • The electric arc itself • Its fault current • Its duration • Its configuration or

enclosure – Also known as “Arc-in-a-

Box” C

What Determines the Intensity of an Electric Arc Exposure?

• The number of phases involved.

• The system you’re working on– Its electrode gap– Its available voltage

• Your location– How close or far you are from

the electric arc when it occurs

What Risks are Possible with Electric

Arc Exposures? • Electrocution. • Physical injury resulting from

explosive forces. • Burn injuries (without

electrical contact) resulting from: – Intense radiant energy – Molten metal splatter – Secondary fires (e.g., from

transformer oils) • The ignition or melting of

clothing.

Why Are Burn Injuries a Major Concern?

• The most severe burns are caused by ignited clothing, not by the original flash fire or electric arc exposure.

C

Electric Arc Flash81 Cal Incident

Outer Layer

Inner Layer

Survival Chances from Burn Injuries (recap)

0102030405060708090

100

20-29 30-39 40-49 50-59

25%50%75%

% of body burn

American Burn Association Study

Are You in Compliance?• Industry standards and

regulations:– OSHA 29 CFR 1910 Subpart S– NEC – NFPA 70E-2009 Edition– Various ASTM Requirements

OSHA Regulations

• OSHA 29CFR 1910, Sub-part S-Electrical. – Design safety standards for electrical

systems. These regulations are contained in 1910.301 through 1910.399.

Hazardous Locations

OSHA Regulations • 29CFR 1910.335(a)(1)(i)

– “Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed”.

What is the NFPA 70E-2009?

• NFPA 70E is:– National consensus standard and a

“Standard for Electrical Safety in the Workplace”.

– and is a part of the National Electrical Code and has been adopted by OSHA as an enforcement standard.

NFPA 70E – 2009 Edition Standard

– Addresses hazards: • Shock • Arc Flash

– Requirements for shock and arc flash boundaries.

– Requirements for personal protective equipment.

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Content of NFPA 70E, Standard for Electrical Safety in the Workplace

NFPA 70E 2009 • Chapter 1 addresses safe installations,

procedures for avoiding injury during electrical work, proper tools, and PPE.

• Chapter 2 addresses maintenance requirements. • Chapter 3 addresses special equipment, i.e.

battery rooms, electrolytic cells, lasers, and electronics.

• Chapter 4 addresses installation requirements similar to OSHA Subpart S.

Electrical Installations NFPA vs. OSHA

OSHA NFPA Reference 1910.301 -

.308 70E, Chap.

4 Markings & Identification X X

Work Space 3’ X X

Impedance Requirements X

Polarity & Grounding X X

GFCI for Restrooms & Rooftops

X

Hazardous Locations Class I “Divisions”

Class I “Zones”

Safety Related Work Practices NFPA vs. OSHA

OSHA NFPA

Reference 1910.331-.360 NFPA 70E

Working on Live Parts X X

Qualified Employees Training

X X

Approach Boundaries X

PPE Some X

Electrical Safety Program X

Scope of Standard • Covers electrical safety requirements for

employee workplaces that are necessary for the protection of employees in their pursuit of gainful employment. – Includes:

• Public & Private premises • Mobile Homes, Recreational vehicles • Floating Buildings • Yards, Lots, Parking Lots • Carnivals • Industrial Substations • Electrical Utility Installations

What Job Tasks are Covered Under NFPA 70E*?

• Installing conductors and other electrical equipment on industrial substations or buildings, residential or commercial.

• Connecting the installations to a supply of electricity.

• Installing other outside conductors.

*Examples Only

What Job Tasks are NOT Covered under NFPA 70E?

Installations...• In ships, watercraft, railway rolling stock,

aircraft, or automotive vehicles other thanmobile homes and RVs.

• In underground mines.• Of railways for operation of rolling stock.• Communication equip. under control of

communication utilities.• Under the control of electric utilities.

Electrical Safety Program Principles

• Inspect/evaluate electrical equipment.• Maintain equipment insulation and

enclosures.• Plan every job.• Document first time procedures.• Deenergize, if possible.

Electrical Safety Program Principles

• Anticipate unexpected events. • Identify and minimize the hazard. • Protect from shock, burn, blast, and

other hazards. • Use the right tools for the job. • Assess employee’s ability. • Audit these principles.

Electrical Safety Program

• Components – Employee Training – Procedures

• Working on or near live parts at 50V or greater – Hazard Evaluation and Assessment – Job Briefing – Energized Electrical Work Permit System – Inspection of Portable Cord & Plug

Equipment and Flexible Cord Sets

Electrical Safety Program Controls

• Every conductor or circuit is considered live until proven otherwise.

• No bare-hand contact with exposed energized parts above 50V, unless using the “bare handed method” properly.

• Deenergizing electrical to make it safe is considered a potentially hazardous task.

Electrical Safety Program Controls

• Employer develops the programs and the employees apply them.

• Train employees to make them qualified.

• Identify & categorize tasks to be performed on or near exposed electrical.

• Identify & use precautions appropriate to the working environment.

Lockout/Tagout

• Individual LOTO– Used when only one person is working and

circuit is under that persons control and observation and only on one shift.

• Simple LOTO– Used when only one person is working and

it involves deenergizing one set of conductors or circuit part.

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Lockout/Tagout• Complex LOTO

– Used when there is:• Multiple energy sources Multiple crews• Multiple crafts Multiple employers• Multiple shifts Particular Sequences• Different disconnecting means

– One person in charge• Can install locks on behalf of other employees

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Lockout/Tagout

– Requires written procedures

– Requires written plan

– Testing requirement

– Personnel accountability system

– Formal lock removal process

– Installation of temporary grounds

Temporary Grounding

• Prevent employees from being exposed to hazardous differences of electrical potential.

• Capable of conducting the maximum fault current that could flow.

• Must meet requirements of ASTM on Temporary Grounds.

• Impedance low enough to cause immediate operation of protective devices.

Definitions

• Flash Protection Boundary – An approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur.

Definitions• Limited Approach Boundary – An

approach limit at a distance from an exposed live part within which a shock hazard exists.

• Restricted Approach Boundary – An approach limit at a distance from an exposed live part where there is an increased risk of shock due to electrical arc for employees working in close proximity to the live part.

Definitions

• Prohibited Approach Boundary – An approach limit at a distance from an exposed live part which work is considered to be the same as making contact with the live part.

Definitions• Working near (live parts) – Any activity

inside of a Limited Approach Boundary.

• Working on (live parts) – Coming into contact with live parts with the hands, feet, or other body parts with tools, probes, or test equipment regardless of the PPE a person is wearing.

Definitions Qualified Person: • One who has skills and knowledge

related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.

•If your not a qualified person, what is your role around electricity?

•Who would be a qualified person?

•Are you a qualified person?

Approach Limits

• Principles– Increase the distance between the person

and decrease the potential for an accident.– Unqualified employees should not cross the

Flash Protection Boundary.– Qualified personnel shall not cross the Flash

Protection Boundary unless appropriate PPE is used.

Approach Limits

• Qualified personnel shall not approach or take any conductive objects closer than the Restricted Approach Boundary unless they or the electrical equipment is protected AND – They have a plan – Are using the appropriate PPE for the energy

level involved

Approach Limits

Exposed EnergizedPart

Flash Protection Boundary

Limited Approach Boundary

Restricted Approach Boundary Prohibited

Approach Boundary

Prohibited Space

Restricted Space

Limited Space

Approach Limits Nominal Voltage Range

Flash Protection Boundary 50-300KA

Limited A. B. Exposed Movable C.

Limited A. B. Exposed Fixed C.

Restricted Approach Boundary

Prohibited Boundary

50 – 300V

4 ft. 10 ft. 3.5 ft. Avoid Contact

Avoid Contact

301 – 600V

4 ft. 10 ft. 3.5 ft. 1 ft. 1 in.

600 – 750V

Based on Cal’s.

10 ft. 3.5 ft. 1 ft. 1 in.

751 – 15 KV

Based on Cal’s.

10 ft. 5 ft. 2 ft. 2 in. 7 in.

Exposed Energized Parts

• Only qualified persons are allowed to work on live exposed parts.

• Spaces and areas with live parts must be well lighted.

• Don’t reach into blind areas.• When working in confined spaces with

live parts, protective shields, barriers, or insulating materials shall be used on the live circuits, etc.

Exposed Energized Parts

• Ladders must be of nonconductive materials.

• Conductive clothing and jewelry should not be worn.

• Nonconductive cleaning materials and or precautions should be used around live parts.

• Control hazards to prevent ignition of flammable & combustible materials.

Overhead Lines• Should be deenergized and grounded

when working around.• Employees should be aware of the

approach distances.• Mechanical and vehicular equipment

should be kept at least 10’ away, in transit 4’.

• Blanketing may also be used as an added precaution.

• Watch overhead when working with long, conductive objects.

Electrical Power and Lighting Circuits

• Circuit breakers must be used to open circuits under load conditions.

• Safety of the circuits must be checked before reenergization.

• Over-current protection cannot be modified.

• Only qualified employees can test electrical parts or circuits operating at 50V or more.

Use of Equipment70 E & 1910.334

• Cords must have proper grounding.• Check the cord for defects.• Do not lift or lower equipment by the

cord.• Do not unplug equipment by pulling on

the cord.• Do not tack or staple cords in place.• Cords must be approved for the

location.

Flexible Cords

• Visually check for defects such as: – Loose Parts – Deformed or missing prongs – Damaged jackets or insulation – Conduct on a daily basis

Safeguards for Personal Protection - 1910.335

• Employers must provide personal protective equipment.

• Employees must wear it.• Must be maintained in a safe condition

and inspected.• Non-conductive head protection must

be worn.• Appropriate tools should be used.

Who’s Required To Do What?

• NFPA 70E 130.6 (C) General: employees working in areas

where there are electrical hazards shall be provided with, and shall use, protective equipment that is designed and constructed for the specific part of the body to be protected and for the work to be performed.

PPE Clothing Not Permitted

– Clothing made from Synthetic materials such as acetate, nylon, polyester, rayon, either alone or in blends with cotton, shall not be worn.• The most severe burns are caused by

ignited clothing, not by the original Flash Fire or Electrical Arc Exposure.

• Clothed areas can be burned more severely than exposed skin.

Personal Protective Equipment

• 70E 2009, Table 130.7(C)(9)(a)Hazard Risk Category Classifications,pages 29 thru 31.– Based on task, voltage, type of equipment and

notes (fault current and clearing time) the table shows:• hazard / risk category• if V-rated gloves are required• if V-rated tools are required

– For any task, voltage, fault current or clearing times not listed in the table, do the calculation outlined in 70E, 130.3(A),page 25.

Protective Clothing• For most low-energy work (240 volts or below),

natural-fiber, non-melting clothing is adequate; some higher risk tasks require FR clothing.

• Most work on or near systems rated 480 volts and above requires at least one layer of flame-resistant (FR) clothing worn over natural-fiber clothing.

• High-energy tasks require FR flash suits and flash hoods worn over FR clothing.

Underlayers • Meltable synthetic fibers

shall be avoided in fabric underlayers (underwear) next to the skin. – When the FR clothing

system has been appropriately assessed to the hazard, then a cotton undergarment will provide additional protection.

Personal Protective Equipment (PPE) Requirements

Required PPE includes: • Flame-resistant clothing

• Flash suits (for high-energy arc exposure) • Flash suit or Balaclava hoods • Natural Fiber Clothing • Fire Retardant Coveralls

• Insulating gloves • Insulated tools

• This is in addition to normally used hard hat,

safety shoes, safety glasses, and hearing protection.

NFPA 70E Provides Two Choices for Selecting the Appropriate

PPE:

• Conduct an arc flash hazard analysis, and document the incident energy exposure.– Duke Flux Software (Freeware)– ArcPro II Software– IEEE 1584 Standard

• As an alternate, use the “Hazard Risk Category Classifications” table to choose the PPE level required for the task.

Hazard Risk Category Tables

ASTM F-1959 Electric Arc Panel Test Results

ATPV - Arc Thermal Performance Value Total incident energy (cal/cm2) on the surface of a

fabric that would be expected to just cause a second degree burn on skin behind and in contact with the fabric.

HAF - Heat Attenuation Factor

Percent of the Incident Energy Blocked By the Fabric.

Ebt - BreakOpen Threshold Energy Average of the five highest incident energy values

(cal/cm2) which did not cause breakopen of the fabric (and are below the Stoll Curve).

Simulated Electric Arc Blast – Untreated Cotton Shirt ( 5.7 oz/yd2

)

Before Electric Arc Blast During Electric Arc Blast After Electric Arc Blast

Simulated Electric Arc Blast: NOMEX® Workwear (4.5 oz/yd2 )

Before Electric Arc Blast During Electric Arc Blast After Electric Arc Blast

Personal Protective EquipmentHazard/Risk category Protective Clothing ATPV/ Cal/cm2

0 Untreated Cotton ATPV n/a1 FR shirt and FR pants ATPV 4 cal/cm2

2 Cotton underwear plus FR shirt and FR pants

ATPV 8 cal/cm2

3 Cotton underwear plus FR shirt and FR pants plus FR coverall

ATPV 25 cal/cm2

4 Cotton underwear plus FR shirt and FR pants plus double layer switching coat and pants

ATPV 40 cal/cm2.

Protective Clothing (non-melting)

70E, page 34 ATPV=arc thermalperformance value Cal/cm2 (Calories per Sq. Centimeter)

NFPA 70E – Hazard Risk 0 Hazard/Risk

category Protective Clothing ATPV/ Cal/cm2

0 Untreated Cotton ATPV n/a

This hazard risk category poses minimal risk. Some examples of tasks in this category are tasks that involve:

• Circuit breaker or fused switch operation with covers on when working with Panel boards rated 240 V and below. • Contactor operation with enclosure doors closed when working with NEMA E2 (fused contactor) Motor Starters, 2.3 kV through 7.2 kV.

NFPA 70E – Hazard Risk 1 Hazard/Risk

category Protective Clothing ATPV/ Cal/cm2

1 FR shirt and FR pants

ATPV 4 cal/cm2

This hazard risk category poses some risk. Some examples of tasks in this category are tasks that involve:

• Circuit breaker or fused switch operation with covers off when working with Panel boards rated 240 V and below. • Opening hinged covers (to expose bare, energized parts) when working with "Other 600 V Class (277 V through 600 V, nominal) Equipment.

NFPA 70E – Hazard Risk 2 Hazard/Risk

category Protective Clothing ATPV/ Cal/cm2

2 Cotton underwear plus FR shirt and FR pants

ATPV 8 cal/cm2

This hazard risk category involves tasks that pose a moderate risk. Some examples of tasks in this category are tasks that involve:

• Circuit breaker or fused switch operation with enclosure doors closed when working with 600 V Class Motor Control Centers (MCCs). • Work on control circuits with energized parts 120 V or below, exposed when working on Metal Clad Switchgear, 1 kV and above.

NFPA 70E – Hazard Risk 3 Hazard/Risk

category Protective Clothing ATPV/ Cal/cm2

3 Cotton underwear plus FR shirt and FR pants plus FR coverall

ATPV 25 cal/cm2

This hazard risk category involves tasks that pose a high risk. Some examples of tasks in this category are tasks that involve:

• Insertion or removal of circuit breakers from cubicles, doors open, when working with 600 V Class Switchgear (with power circuit breakers or fused switches). • Opening hinged covers (to expose bare, energized parts) when working with "Metal Clad Switchgear, 1 kV and above.

NFPA 70 E – Hazard Risk 4 Hazard/Risk

category Protective Clothing ATPV/ Cal/cm2

4 Cotton underwear plus FR shirt and FR pants plus double layer switching coat and pants

ATPV 40 cal/cm2.

This hazard risk category represents tasks that pose the greatest risk. Some examples of tasks in this category are tasks that involve:

• Removal of bolted covers (to expose bare, energized parts) when working with NEMA E2 (fused contactor) Motor Starters, 2.3 kV through 7.2 kV. • Opening voltage transformer or control power transformer compartments when working with Metal Clad Switchgear, 1kV and above.

Care and Maintenance

• All personal protective equipment shall be maintained in a sanitary and reliable condition.

• Oil and other stains should be cleaned to eliminate a fuel source.

• FR clothing shall be inspected before each use.

What Products are Available to Accomplish these Requirements?

• Voltage rated gloves and protectors.

• Insulated/Insulating tools.• Insulating blankets.• Insulating protective

shielding.• Insulating sleeves.• Dielectric footwear.

Additional Equipment

Dielectric Footwear Arc & Flame Resistant Raingear

Insulating Blanket

Insulating Shielding

Insulating Gloves OSHA 1910.333(a)(1)

• Rubber insulating gloves are among the most important articles of personal protective equipment for electrical workers.

• They are the first line of defense for contact with any energized components or lines.

Leather Protector Gloves

Leather Protector Gloves should always be worn over TYPE I or II electrical insulating gloves to provide needed mechanical protection against abrasion or cuts.

Gloves & Shoes

• Gloves rated by voltage » Class 00 = 500 volts max » Class 0 = 1000 volts max » Class 1 = 10 kV max » Class 2 = 20 kV max

• Shoes - Heavy-duty leather work shoes shall be used for all tasks when ATPV is 5 cal/cm2 and above.

• insulating soles are recommended. • overshoes or dielectric boots are

recommended.

Portable Glove Inflation Tester

• All insulating gloves must be electrically tested every six months to be in accordance with OSHA 29 CFR 1910.137.

• In addition, gloves must be visually inspected to check for tears, rips and punctures. – Salisbury G-99 glove inflator

will simplify visual inspection.

Hard Hats

Classifications under old and new standards: Z89.1 – 1986 Z89.1 – 1997 Application Test Voltage (Old Standard) (New Standard) A G General 2,200 B E Electrical 20,000 C C Conductive Not Tested

Z89.1-1997, Type 1, Class C,E,G - This is the ANSI stamp of approval that specifies the hard hat meets all safety requirements.

Additional Protective Equipment

• Face shields are available that are listed with ATPV ratings from many manufacturers... Do not use general duty face shields.– Always wear safety glasses under face

shields (no metal frames).– Always wear a hard hat.– Hearing protection is recommended.– Protective hoods or parkas should be worn in

conjunction with shields and hard hats.

Insulated Tools • Insulated tools that

meet ASTM F1505 and OSHA 1910.333 (c)(2).

• The tools are rated 1000V to be used on working with energized equipment.