arc flash basics The International Facilities Management Association – Wichita Chapter Presented By: Dee Jones, P.E. Electrical Engineering Division of

arc flash basics

The International Facilities

Management Association – Wichita ChapterPresented By: Dee Jones, P.E.

Electrical Engineering Division of AVO Training Institute, Inc.

FACILITY MANAGERS AND ARC FLASH SAFETY

1. What is an arc flash?2. What are the hazards and consequences

of arc flash incidents?3. What do I need to do to provide a safe

work environment?

WHAT IS AN ARC FLASH?

• A rapid release of energy due to an arcing fault

- Phase-to-phase- Phase-to-neutral- Phase-to-ground

• Air is the conductor during an arc fault

ARC FLASH VIDEO

• We have just viewed an arc flash at 138,000 volts

• Now let us view one at 480 volts

• What differences do you observe?

WHAT IS AN ARC FLASH?

• Typically an arc flash could be over in less than 6 cycles which is 0.1 seconds (s)

• 0.1 s converted to milliseconds (ms) would be 100 ms The human eye blinks at 300 to 400 ms

• The blink of an eye is 3 to 4 times slower than an arc flash

WHAT IS AN ARC FLASH/BLAST?

• An arc blast is a multi-hazard event:– Arc flash (temperature rise, incident energy, UV)– Arc blast (explosion)

• Expansion produces explosion with:– Molten metal– Vaporized metal (plasma)– Fragmented metal– High temperatures– Pressure on the body– 165 db– Toxic fumes

50 cal/cm22000 psf

< 740 mph

1000 °C

Visible

UV

IR

165 db15000 °C

WHERE DO I BEGIN? Arc Flash Hazard

PROCESS

• Understand the laws and regulations• Evaluate the degree and nature of the hazard• Begin or modify a safe work program• Select appropriate personal protective equipment (PPE)• Determine PPE supply and maintenance policy• Install warning labels on electrical equipment• Training• Implement or improve electrical equipment maintenance program• Ongoing review of hazards analysis and safe work program

FUNDAMENTALS: Arc Flash Hazard

KEY ARC FLASH TERMS

Incident Energy: Amount of energy impressed on a surface, a certain distance from the source, generated during an electric arc event.

Based on:• Available fault current (amperage)• Distance from the equipment (feet and inches)• Fault clearing time (seconds or cycles)

KEY ARC FLASH TERMS

• Units of Measurement: • Calories per centimeter squared (cal/cm2) • FR clothing rated in arc thermal performance value (ATPV), given

in cal/cm2

• 1 cal/cm2 is equivalent to the energy produced from a lighter in one second• 1.2 cal/cm2 causes beginning of 2nd degree burn• 10.7 cal/cm2 causes beginning of 3rd degree burn

KEY ARC FLASH TERMS

Limited approach boundary• Shock hazard exists

Restricted approach boundary• Increased shock hazard due to electric arc over

combined with inadvertent movement

Prohibited approach boundary• Same as making contact

Arc Flash Protection boundary• An approach limit within which a person could receive a

2nd degree burn

NFPA 70E® pg 10

KEY ARC FLASH TERMS

Arc Flash Hazard: A dangerous condition associated with the possible release of energy caused by an electric arc.

FPN No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. Under normal operating conditions, enclosed energized equipment that has been properly installed and maintained is not likely to pose an arc flash hazard.

DE-ENERGIZED WORK

Working on de-energized equipment

Equipment is not considered de-energized until absence of voltage is verified. PPE MUST BE WORN.

Once absence of voltage is verified and equipment is grounded with lock out/tag out in place work can proceed without further arc flash clothing requirements.

ARC FLASH EFFECTS

• NIOSH studies show that 10-15 employees are hospitalized every day with electrical arc flash related burns

• NFPA 70E® states that over 2,000 people are admitted into burn centers each year with severe electrical burns (2-6 months average stay). NFPA 70E® Pg. 87

RULES AND REGULATIONS: Arc Flash Hazard

Rules and Regulations

NON-COMPLIANCE

U.S. Postal Service faces nationwide complaint for electrical safety violations… The Occupational Safety and Health Administration (OSHA) issued fines totaling more than $6.2 million …for willful and serious electrical safety violations at 30 U.S. Postal Service (USPS) … facilities across the country.

…untrained or unqualified workers performing tests…inadequate personal protective equipment (PPE) and warning signs…The postal Service exposed workers … to the serious and potentially fatal hazards of shock, electrocution, and arc flash..

EC&M magazine Jan. 24, 2011 by Beck Ireland

NON-COMPLIANCE - VIDEO BACKGROUND

Information from an article by Ken Mastrullo in Fall 2004 NETA World Magazine

“Electrical Safety Should Never Take a Holiday”

• Perform preventive maintenance on Memorial Day morning• Open 15 kV switch to start emergency generator• Run generator for 3 hours under load to test reliability of

system• All workers had minimum of 5 years of experience

NON-COMPLIANCE - 15KV ARC-FLASH VIDEO

NON-COMPLIANCE - EFFECT ON WORKERS

• Two workers had serious 2nd and 3rd degree burns• One of the workers was burned over 60% of his body• The third worker has suffered long term effects, including

neurological problems• Three families will never be the same again

NON-COMPLIANCE - POST EVALUATION

• No hazard analysis• Workers were not properly trained (qualified)• Workers were wearing poly-blend clothing• All three workers were within the flash protection

boundary

NON-COMPLIANCE - END RESULTS

• OSHA citations and fines- 5 serious

- 2 willful - >$100,000

• Medical expenses• Litigation• Negative publicity• They are required to do an OSHA mandated arc flash

analysis

RESULTS OF NON-COMPLIANCE



He did fully recover!He was LUCKY!!

EVALUATE THE DEGREE AND NATURE OF THE HAZARD

NFPA 70E

NFPA 70E TABLES

When the NFPA 70E® Table 130.7(C)(9) is used in lieu of an arc flash hazard analysis, the notes for available fault current and clearing time must be used

This table is limited in application because available fault current and clearing times may not correspond to the notes

Refer to NFPA 70E, Paragraph 130.7(C)(9):“The assumed maximum short-circuit current capacities and maximum fault clearing times for various tasks are listed in the notes…”“…for power systems with greater than the assumed maximum short circuit current capacity or with longer than the assumed maximum fault clearing times, an arc flash hazard analysis shall be required…”

NFPA 70E® Pg. 30-34

NFPA 70E® TABLE 130.7(C)(9)

600 V Class Motor Control Centers (MCCs) – Note 2 (except as indicated)

Perform infrared thermography and other non-contact inspections outside the restricted approach boundary

1 N N

CB or fused switch or starter operation with enclosure doors closed

0 N N

600 V Class Switchgear (with power circuit breakers or fused switches) – Note 4

Perform infrared thermography and other non-contact inspections outside the restricted approach boundary

2 N N

CB or fused switch or starter operation with enclosure doors closed

0 N N

NFPA 70E® TABLE 130.7(C)(9) NOTES

1. Maximum of 25 kA short circuit current available; maximum of 0.03 sec (2 cycle) fault clearing time.



4. Maximum of 35 kA short circuit current available; maximum of up to 0.5 sec (30 cycle) fault clearing time.

NFPA 70E TABLES

The Tables should be used primarily for contractors. Contractors are not responsible for arc flash hazard analysis. The owner of the property is responsible (NFPA 70E, 110.5 Relationships with Contractors (Outside Service Personnel, etc.).

Secondarily the Tables with notes should be used for interim use until owners complete their arc flash hazard analysis

NFPA 70E® Pg. 30-34Tables provide no guidance for locations exceeding 40 calories. These locations must be identified.

ARC FLASH HAZARD ANALYSIS NFPA 70E

WHAT IS ARC FLASH HAZARD ANALYSIS?

Mathematical methods used to determine and reduce, where possible, the risk of personal injury as result of exposure to incident energy from arc flash

Identifies:• Incident energy exposure of the worker• Flash protection boundary• Appropriate work distance • Required PPE

WHAT IS ARC FLASH HAZARD ANALYSIS?

• Arc flash hazard expressed in incident energy

• Arc flash protective clothing is rated in arc thermal performance value (ATPV)– ATPV is expressed in cal/cm2

ARC FLASH HAZARD ANALYSIS

For the best results on an arc flash hazard analysis:• Use a registered Professional Engineer (PE)• Calculation engineering software or equivalent qualified

staff to perform and review results • Dedicated time and resources• Have a clearly defined scope of work and deliverables

ENGINEERING:Arc Flash Hazard Analysis

ENGINEERING ANALYSIS PROCESS

USE CORRECT SIGNAGE

Using generic arc flash hazard warning labels:

National Electrical Code (NEC®) 110.16 •Requires flash protection field marks for equipment with live working condition•Refers to ANSI Z535.4-1998, Product Safety Signs and Labels, for the design of safety signs and labels

LABEL THE EQUIPMENT

Required by NEC 110.16

IMPLEMENTATIONAfter Completion of the Arc Flash

Hazard Analysis

IMPLEMENTATION

• Implement your results- It can only make your facility safer

• Allocate time and resources- PPE- Develop and implement an Electrical Safety Program- Training- Implement a preventive maintenance program

PERSONAL PROTECTIVE EQUIPMENT Selection

PROTECTIVE EQUIPMENT

If the arc flash hazard analysis is completed properly:• The PPE requirements will be specific• PPE purchases can be specific to the need• PPE will be adequate but not excessive• PPE will meet the requirements and intent of OSHA

1910.132 • Most importantly PPE will protect the workers from

recognized hazards

EXAMPLES OF ARC FLASH PPE

multi-layer flash hood

Balaclava (sock hood)Flash Suit

Various combinations

Balaclava w/face shield

PERSONAL AND OTHER PROTECTIVE EQUIPMENT

NFPA 70E, 130.7

Includes:• Arc-rated jacket, parka, or

rainwear• Hard hat• Safety glasses or safety

goggles• Hearing protection (ear canal

inserts)• Leather gloves• Leather work shoes

ELECTRICAL SAFETY PROGRAM:Develop and Implement

ARC FLASH PREVENTION

PPE is the last line of defense in the event of an arc flash incident

“The protection is not intended to prevent all injuries but to mitigate the impact of an arc flash upon the individual, should one occur. In many cases, the use of PPE has saved lives and prevented injury.” IEEE Std 1584-2002, page 4

Your first choice should be to reduce or eliminate the hazard!

TRAINING:Develop and Implement

PLAN FOR TRAINING OSHA AND 70E REQUIREMENTS

OSHA and NFPA 70E require training as part of the electrical safety program. You can now customize this training to include the results of your Arc Flash Hazard Analysis

MAINTENANCE:Develop and Implement an

Maintenance Program

INADEQUATE EQUIPMENT MAINTENANCE

Example:• A low-voltage power circuit breaker has not been

operated or maintained for several years• The lubrication has become sticky or hardened• The circuit breaker could take additional time to clear a

fault condition


Two flash hazard analyses will be performed using a 20,000-amp short-circuit with the worker 18 inches from the arc:• Based on what the system is supposed to do 0.083 seconds (s) (5 cycles) • Due to a sticky mechanism, the breaker now has an unintentional time delay of 0.5 s (30 cycles)


(1) DB = 18 in.(2) tA = 0.083 second (5 cycles)(3) F = 20kA

EMB = 1038.7DB-1.4738tA[0.0093F2-0.3453F+5.9675]

= 1038x0.0141x0.083[0.0093x400-0.3453x20+5.9675]= 1.4636x[2.7815]= 3.5 cal/cm2

NFPA 70E-2009, Section 130.3(B)(1) requires arc-rated FR clothing and other PPE to be selected based on this incident energy level exposure. Therefore the FR clothing and PPE must have an arc rating of at least 3.5 cal/cm2.

NFPA 70E® pg. 35-37


(1) DB = 18 in.(2) tA = 0.5 second (30 cycles)(3) F = 20kA

EMB = 1038.7DB-1.4738tA[0.0093F2-0.3453F+5.9675]

= 1038x0.0141x0.5[0.0093x400-0.3453x20+5.9675]= 7.3179x[2.7815]= 20.4 cal/cm2

NFPA 70E-2009, Section 130.3(B)(1) requires arc-rated FR clothing and other PPE to be selected based on this incident energy level exposure. Therefore the FR clothing and PPE must have an arc rating of at least 20.4 cal/cm2.

NFPA 70E® pg. 35-37

PLAN FOR ANALYSIS MAINTENANCE

• Analysis reviewed every 5 years, per NFPA 70E® 130.3

• An analysis maintenance plan will integrate changes to the system over time

• Maintenance of the database is more economical than starting from scratch

NFPA 70E® Pg. 25

CONCLUSION:Arc Flash Hazard Analysis

ARC FLASH CASE HISTORY VIDEO

• This video is produced by Dow Chemical and is a report of an actual arc flash incident where proper PPE was utilized and the employee was not injured.

CONCLUSIONS

Arc Flash Hazard Analysis is risk management. You have 3 choices.

AVO Electrical Engineering Division Dee Jones, P.E.Principal Engineer and Division Manager1.877.594.3156 x 7347Direct: [email protected] BusbeaCorporate Sales & Development1.877.594.3156 x 7318 Direct: [email protected]

mailto:[email protected]

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arc flash basics The International Facilities Management Association – Wichita Chapter Presented By: Dee Jones, P.E. Electrical Engineering Division of