Abstract: Two test technicians were conducting electrical tests and design value confirmations on a large power delivery system (equipment used to control and distribute electric power from a high-voltage transformer for electric utility customers). The front section of the unit contained circuit breakers, reclosers, switchgear, metering devices, and associated wiring. The rear section was a high-voltage compartment, containing busbars for attachment to the source and a transformer to convert the 7200-volt input to the 120/240-volt control voltage. The senior test technician attached a temporary 120/240-volt power supply to the transformer terminals in the front enclosure but failed to disconnect the existing conductors leading back to the transformer. Disconnecting these conductors was specified in the test procedure and known to be necessary by all involved. Additionally, a jumper, which would eventually have been connected to one of the outside transformer terminals to provide reduced voltage to the control section, might have contacted the rear section busbar because of vibration from repeated operation of the reclosers during testing. At some point, the test technician went around to the rear of the unit and entered the cramped high-voltage enclosure through one of two 0.6-meter by 1.1-meter hatches. As he was moving around inside the enclosure, he repeatedly contacted the energized busbar and grounded surfaces, eventually causing two 30-ampere circuit breakers to open. The technician was electrocuted. There were no direct witnesses to the incident, and his coworker became aware of a problem only after he heard arcing and noticed the lights dim. There was no apparent reason for the technician to have entered the compartment. However, there are occasions in which the technicians do make partial entries to verify that values or ratings coincide with design specifications. These entries are only performed with the equipment deenergized.