Abstract: An electrician with 11 years of experience was putting the cover on the center unit of a 1200-ampere, 480/277-volt Square D electrical cabinet in the DVD department of a CD and DVD manufacturer. He and another worker had installed two 400-ampere circuit breakers and wiring in the cabinet that morning and had tested the equipment after installing it. As the electrician was using a nut driver to tighten one of the bolts for the cover, a 500-mcm conductor that was hanging under tension sprung loose and hit his right hand. His right hand moved, and the nut driver contacted the center phase bus and center plate inside the cabinet and caused an electrical fault. The nut driver had gone through a 13-millimeter by 19-millimeter opening at the top of the cabinet near the very top of the bus assembly. The ensuing electric arc burned the employee's face, neck, hands, and arms. He was hospitalized for 20 days with second-degree burns to his face and third-degree burns to his neck, hands, and arms.