Arc Flash

Arc Flash Hazard Analysis Training
Practical course teaches the regulations, standards, techniques and calculations used to determine PPE for arc flash protection.
www.electricaltrainingservices.com

Free Arc Flash Label Information Guide
Guide used to inform & recognize info provided on Arc Flash labels.
www.DuraLabel.com

Fire Resistant Coveralls
Shop Nomex, Cotton, Indura. All Colors & Weights. Buy Now & Save.
SafetySupplyAmerica.com

Arc Flash Labels
Create custom arc flash and other safety labels from your desktop. Indoor/outdoor vinyl material won't fade in sunlight. The perfect choice for the harshest environments. Saves you money.
arcflashsolution.com

Arc Flash Analysis
Arc Flash training, analysis, mitigation, system studies, upgrades.
www.magnaelectric.com

Arc Flash Protective Clothing
Oberon is the Pioneer & Leader in the Electrical Arc Flash protection market. Products comply with NFPA 70E, Astm F1506, Astm F2178, OSHA 1910.269 & Ansi Z87.1.
www.arcflash.com

Welding & Arc Flash - Signs and Labels
OSHA Standards for worker safety. Easy to search 100s of signs today.
www.ComplianceSigns.com/welding

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An arc flash (or arc blast) event is a type of electricity explosion that results from a low impedance connection to ground or another voltage phase also called a "short" in an electrical system. A short circuit can occur anywhere in an electrical system, usually during maintenance work when the unexpected occurs. For instance a tool dropping, a wire slipping out of your hand a mechanical accessory falling loose and so on. A dangerous arc flash can only occur if the fault current is very high - in the range 1000 Ampere or more. The massive energy released in the fault instantly vaporizes the metal conductors involved, blasting molten metal and expanding Plasma (physics) outward with extreme force. A typical arc flash incident can be inconsequential but could conceivably easily produce a more severe explosion (see calculation below). The result of the violent event can cause destruction of equipment involved, fire, and injury not only to the worker but also to nearby people.

In addition to the explosive blast of such a fault, destruction also arises from the intense radiant heat produced by the arc. The metal plasma arc produces tremendous amounts of light energy from far infrared to ultraviolet. Surfaces of nearby people and objects absorb this energy and are instantly heated to vaporizing temperatures. The effects of this can be seen on adjacent walls and equipment - they are often ablated and eroded from the radiant effects.

In general, arc flash incidents are highly improbable on systems operating at less than 240 volts phase to phase (120volt to ground) when fed by less than a 125 Volt-ampere transformer. 120 volts does not provide sufficient energy to cause an arc flash hazard. Most 480V electrical services have sufficient capacity to cause an arc flash hazard. Medium-voltage equipment (above 600V) is higher energy and therefore a higher arc flash hazard.

As an example of the energy released in an arc flash incident, consider a single phase-to-phase fault on a 480V system with 20,000 amps of fault current. The resulting power is 9.6MW. If the fault lasts for 10 cycles at 60Hz, the resulting energy would be 1.6 megajoules. For comparison, TNT releases 2175J/g when detonated. Thus, this fault energy is equivalent to 736 grams of TNT, or approximately 1.5 pounds. The character of an arc flash blast is quite different from a chemical explosion (more heat and light, less mechanical shock), but the resulting devastation is comparable. The rapidly expanding superheated vapor produced by the arc can cause serious injury or damage, and the intense Ultraviolet light and Infrared light produced by the arc can temporarily and sometimes even permanently blind or cause eye damage to people.

Research Both the Institute of Electrical and Electronics Engineers (IEEE) and the National Fire Protection Association (NFPA) have joined forces on an initiative to fund and support research and testing to increase the understanding of Arc Flash IEEE/NFPA Collaborative Research Project. The results of this collaborative project will provide information that will be used to improve electrical safety standards, predict the hazards associated with arching faults and accompanying arc blasts, and provide practical safeguards for employees in the workplace.

Standards Four principal standards govern safe work practice when arc flash hazards are present:

Occupational Safety and Health Administration Standards 29-CFR, Part 1910. Occupational Safety and Health Standards. 1910 sub part S (electrical) Standard number 1910.333 specifically addresses Standards for Work Practices and references NFPA 70E.
The National Fire Protection Association (NFPA) Standard 70 - 2002 “The National Electrical Code” (NEC) contains requirements for warning labels.
NFPA 70E 2000 provides guidance on implementing appropriate work practices that are required to safeguard workers from injury while working on or near exposed electrical conductors or circuit parts that could become energized.

The Canadian_Standards_Association upcoming CSA Z462 Arc Flash Standard is under development and will become Canada's version of NFPA70E when it is released in 2008 CSA Electrical Safety Conference

The Institute of Electronics and Electrical Engineers IEEE 1584 – 2002 Guide to Performing Arc-Flash Hazard Calculations. IEEE 1584 Working Group website

Arc flash hazard software exists that allow businesses to comply with the myriad of government regulations while providing their workforce with an optimally safe environment. Many software companies now offer arc flash hazard solutions. Few power services companies calculate safe flash boundaries.

References External links

Security camera footage of an arc flash incident.
Controlled arc flash experiment.