An arc flash (or arc blast) event is a type of electrical explosion that results from a fault in a high-current low- or medium-voltage electrical system. Typically, the explosion is triggered when a short circuit occurs in electrical switchgear, often during maintenance work. An arc flash can only occur if the fault current is very high - several tens of thousands of amps. The massive energy released in the fault instantly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extreme force. A typical arc flash incident can easily produce more explosive energy than a pound of TNT detonating (see calculation below). The result of this violent event is usually destruction of the equipment involved, fire, and severe injury to any nearby people. Arc flash is an especially hazardous problem because it tends to occur when workers manipulating live equipment for testing or repair accidentally cause a fault. In these cases, permanent disability or death of the proximate worker is the common result.
ESFI and National Institute
for Occupational Safety and Health Office of Mine Safety and Health
(NIOSH) have joined together to promote NIOSH's video,
Arc Flash Awareness and the companion booklet, Information and
Discussion Topics for Electrical Workers. The 25-minute video
contains information on what is an arc flash, causes of an arc
flash and electrical safety regulations. It also provides important
safety recommendations: NFPA 70E.
