Abstract: A three-person power line crew was replacing one of a set of three voltage regulators at a substation. The crew consisted of a substation supervisor and two substation electricians. The crew's maintenance supervisor stopped by to observe the operation. The crew obtained switching orders to deenergize the three regulators, which were located on the east side of the substation. The bad regulator was located on the south end of the regulator bank. The crew bypassed the load on the regulators and deenergized them. The crew then replaced the malfunctioning regulator with an Allis-Chalmers regulator (Serial No. 3-3740-00228-9). After the crew visually determined that the controls were in the neutral position as required by the manufacturer, the two electricians took a break. One of them was at the back of the maintenance truck, which was located about 4.3 meters south-southwest of the new regulator. The other electrician was further forward. While these two employees were on break, the substation supervisor closed the bus-side contacts on the three regulators, energizing them. He then closed the load-side contacts. About 5 minutes passed since the supervisor energized the south regulator, but none of the regulators was under full load, as the bypasses were shunting load around the regulators. When the supervisor opened the bypass switch for the new regulator and placed it under load, the regulator failed. The internal pressure in the regulator forced open its lid directly in line with the first electrician, who was sitting on the back of the truck. A large quantity of burning oil from the regulator struck him. The oil also struck the other electrician and the maintenance supervisor, but they were apparently not injured. The second electrician and the substation supervisor extinguished the flames on the injured employee, while the maintenance supervisor summoned emergency medical services with his radio. The injured employee was transported to a local hospital and transferred to a burn center, where he died of complications resulting from second- and third-degree burns over 80 percent of his body.