Abstract: On February 20, 2007, Employee #1, who was also the supervisor, and two coworkers, all of whom worked for an electrical contractor, were providing service on high voltage electrical equipment. The site was a substation of a three-wire, three-phase, 600-amp, 15-kilovolt step-down transformer station, serial #82-9-016-1, that was located near Building 55 on the campus of California State Polytechnic University in Pomona. The substation feeds electric power to different buildings on campus. There were arcing problems on some of the insulators in the buss of the transformer, creating a fault on the transformer's circuit that caused power outages to some campus buildings. After a site assessment, it was determined that damaged insulators had to be replaced to solve the issue of power outages. At approximately 4:00 p.m., one of the University's electricians turned the tie to Feeder-3 switch in the electrical room of Building #35 to the "closed" position, but it was not locked out. This allowed the electric power to back feed to Feeder-3 and re-energize the circuit to the transformer where Employee #1 and his coworkers were trying to fix the problem. Employee #1 was changing insulators at the south side of the transformer when he was sustained a serious electric shock, suffering third- and fourth-degree burns over various parts of his body. He was transported to Pomona Valley Hospital for initial treatment, and then airlifted to the Grossman Burn Center for further medical treatment. Employee #1 was hospitalized for several months and underwent various surgical treatments, including amputation of his left shoulder and removal of part of his skull.