Arc Flash Definition
An electrical arc is an electrical breakdown of a gas (e.g. air) which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge.
An arc flash is the consequence of an electric arc which can occur where there is sufficient voltage in an electrical system and a path to ground or lower voltage. It is usually caused by a short circuit of energized conductors.
An arc flash caused by an electric arc with 1,000 amperes or more can cause substantial damage, fire or injury. The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extreme force. A typical arc flash incident can be inconsequential but could conceivably easily produce a more severe explosion. 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. (Forces may exceed 100kPa (KiloPascal), and debris is spread up to 300meters/second with temperatures of up to 20,000°C).
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. The thermal incident energy onto the worker can cause severe skin burns or have lethal consequences.