The Basics of Arc Flash Protection

2008

Rob Vajko

12/15/2008

The Basics Arc Flash Protection

“An arcing fault can be defined as the flow of current through a path where it is not intended to flow”

www.nationalsafetyinc.com

© National Safety, Inc.

What is an Arc‐Flash? An arc flash starts with an arcing fault. An arcing fault can be defined as the flow of current through a path where it is not intended to flow. The current creates an electric arc plasma and releases dangerous amounts of energy

An electric arc is the passage of substantial electrical current through ionized air and gases.

Bad things can happen.

An electric arc fault is a bad thing!



The above photo is a still shot of a video clip of a arc flash that you can view online at http://205.243.100.155/frames/mpg/345kV_SWITCH.MPG



The above photo is a still shot of a video clip of a arc flash that you can view online at: http://205.243.100.155/frames/mpg/500kV_Switch.mpg



Clothed areas can be more severely burned than exposed skin!

The Costs of Burn Injury

Personal • Burns are one of the most painful injuries a human can experience

• Burn victims often seek psychological care

• Rehabilitation is a slow and difficult process

Financial • Medical costs quickly accumulate due to years of treatment

• Rehabilitation costs can exceed 1 million US$ per person



Arc Blast Hazards Up to 80% of all electrical injuries are burns resulting from an arc flash and ignition of FLAMABLE clothing

Approximately 1 person dies daily in the U.S. from arc blasts, and 6‐7 people are admitted to hospitals for associated injuries

Pressure waves associated with Arc Blasts can:

Vaporize copper, expanding it 67,000 times its initial volume

Create a sonic boom condition



There is a known case where a utility cabinet door was blown off the hinges and embedded in a concrete wall 1.5 inches 10 feet away from the utility cabinet.



HOW TO PREVENT ARC FLASH

Regulations and Standards Several industry standards concern the prevention of arc flash incidents:

OSHA 29 ‐ Code of Federal Regulations (CFR) Part 1910 Subpart S.

NFPA 70‐2002 ‐ National Electrical Code.

NFPA 70E‐2000 ‐ Standard for Electrical Safety Requirements for Employee Workplaces.

IEEE Standard 1584‐2002 ‐ Guide for Performing Arc Flash Hazard Calculations.

Regulations for the State of Washington (Check with your own state agencies)

WAC 295‐155 – Washington State Electrical Standards for Construction

WAC 296‐44 – Washington State Electrical Construction Code

WAC 296‐45 – Washington State Electrical Work Safety Rules

WISHA 6 Point Plan Compliance with the latest OSHA standards involves adherence to a six‐point plan:

A facility must provide, and be able to demonstrate a safety program with defined responsibilities.

Calculations for the degree of arc flash hazard.

Correct personal protective equipment (PPE) for workers.

Training for workers on the hazards of arc flash.



Appropriate tools for safe working.

Warning labels on equipment.

Companies will be cited and fined for not complying with these standards.

NFPA 70E promotes establishing electrically safe work conditions by...

1. Identifying all power sources

2. Interrupting the load and disconnecting power

3. Visually verifying that a disconnect has opened the circuit

4. Locking out and tagging the circuit

5. Testing for voltage

6. Grounding all power conductors

How can we prevent arc flash when we have to work on or near energized parts?

Special situations:

Interruption of life support equipment

Deactivation of emergency alarm systems

Shutdown of hazardous location ventilation equipment

Removal of illumination for an area

A. Use written permit system for planning & conducting work in these situations

B. Use the appropriate tools for voltage and current levels when performing all electrical work

NFPA 70E ‐ Key PPE Steps



1. Determine Arc Flash Protection Boundary

2. Conduct Arc Flash Hazard Analysis

3. Select Required “FR Clothing” & “PPE” Based on Specific Hazard Present Within Flash Protection Boundary



Personal Protective Equipment Select Required “FR Clothing” & “PPE” Based on Specific Hazard Present Within Flash Protection Boundary

Wear the appropriate protection when working on or around energized equipment!



What Types Of Arc Protective Flame Resistant Garments Are Available?

Basic FR Clothing Options

Shirts

• Knit and Woven

• Short and Long Sleeve

Pants

• Uniform

• Dress

• Jeans

Coveralls

Cold and Inclement Weather FR Clothing Options

• Rain wear

• Lined and Unlined Jackets

• Fleece Sweatshirts and Sweatpants

• Insulated Overalls and Coveralls

• Insulated Parkas

• Long Underwear and Socks

• Hoods/Balaclavas

• Vests



FR Garment Examples Category 1 Category 2 Category 2

Category 3 and 4



FR Clothing Selection Criteria Protection

Wearer Comfort

Durability

• Flame Resistance Durability

• Garment Wear Life

Cost Effectiveness

• Initial Cost

• Life Cycle Cost

Ease of Care / Appearance

In Summary

• Burn Injuries From Electric Arc Exposures Can Be Fatal or Can Severely Injure the Worker

• Based on Known Electrical Parameters and Work Practices, Arc Exposure Intensity Can Be Estimated for the Hazard, hence job tasks listed and recommendations on PPE to wear.

• Based On Estimated Arc Exposure Intensity, Appropriate Protective Clothing Selections Can Be Made To Minimize Worker Burn Injury Levels In The Event Of An Electric Arc Accident

• In Many Situations, Layering of FR Clothing Is Required to Match Electric Arc Hazard Energy Levels



Photo courtesy of Hugh Hoagland www.arcwear.com

REMEMBER • The Outermost Garment Must Be Flame and Arc Resistant • Meltable Substrates Can Increase Worker Injury

Other Considerations • Face Shields Rated for Arc Hazard

• Hearing Protection Rated for Arc Hazard

• Hand and Foot Protection Rated for Arc Hazard

Rain wear with Non‐Meltable Substrate (ASTM F‐1891)

Rain wear with Meltable Substrate



Exposure Energy Basics • Exposure Energy is Expressed in cal/cm2

• Measured Using Thermal Sensors

• 1 cal/cm2 » the Exposure on the Tip of a Finger by a Cigarette Lighter in 1 Second

An Exposure Energy of 1 to 2 cal/cm2 Will Cause a 2nd Degree Burn on Human Skin

Definitions ARC RATING ‐ The maximum incident energy resistance demonstrated by a material PRIOR TO BREAKOPEN OR AT THE ONSET OF A SECOND DEGREE BURN. A 1st Degree Burn or less is the goal during an electrical arc flash.

HRC ‐ Hazard Risk Category. Current categories that apply to workers are Level 0‐4. Remember 4, 8, 25, 40!

FLAT PANEL TESTING ‐ This is how our fabrics are tested and how the calorie rating is found (breakthrough threshold).

CALORIE/CM² ‐ This is a measurement of ENERGY. A Cigarette lighter placed under your finger for 1 second equals roughly a 1 calorie burn.

What is a Calorie?

• A Calorie is a measurement of energy, similar to labels on food products

• A 100 cal/cm² blast can reach temperatures of up to 35,000 degrees Fahrenheit in the center, and 11,000 degrees on the perimeter

Arc Hazard Exposure Levels Category 0 – N/A

Category 1 – 4 cal/cm²*






Over 40 cal – Recommended to re‐engineer system to a lower rating.

* Req'd minimum Rating of PPE.

1.2 cal/cm² is the ONSET of a second degree burn

PPE Levels are the maximum at each exposure category

The Basics of Arc Flash Protection

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