Abstract: Two journeyman high-voltage electricians were dispatched to a substation to troubleshoot a regulator that was not responding to automatic control. They had completed a low-voltage relay examination and replaced a loose Porter Brumfield relay in its socket. They then placed the controls on manual, adjusted voltage, and returned the regulator to automatic control to determine whether it was functioning correctly. The stepping device moved one step, and then the regulator failed, spewing burning insulating oil out of the overpressure vent. The hot oil burned both employees. One of them died of his injuries.