What Causes An Arc Flash?

July 2017: A worker was troubleshooting an electrical system for a water pump at a client's site. As he tested the in-feed side of the power in the disconnect box, there was an arc flash that burned his left hand and arm.

September 2016: A worker was working in a panel box changing a contactor when the contactor failed, causing an arc flash that burned his left arm, face, and neck.

December 2015: A worker who was retrieving fish tape from a conduit line received burns on his face and the back of his hands from a fireball. The fish tape touched the back of the bus bar and instantly caused an explosion. The arc flash blew out two of the branch circuit boxes and burned the rest of the services. The system was energized and carrying an electrical load of approximately 480 volts nominal AC and 3,000 amps.

The work required a Level II hot work permit, which included a qualified buddy (journeyman electrician), hard hats, safety glasses, full-face shield (flash rated, nonconductive), rubber gloves (properly rated and tested at 1,000 volts per minute), double-insulated hand tools, flame retardant outer garments, a copy of the "hot work process," and a rescue system. But the victim did not have a Level II hot work permit and was wearing only safety glasses.