The flash is instantaneous, almost too fast for the eye to comprehend. But the end result of this incident could be more than $15 million in direct and indirect costs to a company.
What is arc flash?
An arc flash is a short circuit through the air. When insulation or isolation between electrified conductors is breached or can no longer withstand the applied voltage, an arc flash occurs. As employees work on or near energized conductors or circuits, movement near or contact with the equipment, or a failure of the equipment, may cause a phase-to-ground and/or a phase-to-phase fault.
The temperature of an arc can reach more than 5000 F as it creates a brilliant flash of light and a loud noise. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment, spreading hot gases, melting metal, causing death or severe radiation burns, and creating pressure waves that can damage hearing or brain function and a flash that can damage eyesight. The fast-moving pressure wave also can send loose material such as pieces of equipment, metal tools, and other objects flying, injuring anyone standing nearby.
via The Dangers of Arc Flash Incidents – MAINTENANCE TECHNOLOGY.