Abstract: A power line worker was assigned to replace a knife switch at a substation. He was to unbolt the switch after a coworker removed the energized leads to the switch to deenergize it. To perform this task, the power line worker had exchanged a hand ratchet wrench for a hydraulic impact wrench. This reduced the approach distance between the switch and the tower to less than 25 millimeters. The power line worker started to remove the switch before it was completely deenergized. As the power line worker was unbolting the switch, the impact wrench contacted the tower, and an electrical fault occurred. The ensuing electric arc burned the power line worker. He sustained first-, second-, and third-degree burns above his waist, including burns to his head and hands. He was hospitalized for his injuries.