Abstract: Two employees were installing new compression-type connectors on conductors on the load side of an electrical switchboard. The switchboard contained a three-phase circuit operating at 480 volts (277 volts to ground), 1200 amperes. The fuses for the circuit had been removed, deenergizing the load side of the circuit. Employee #2 was tightening one of the connectors when the supply side of the circuit faulted to ground or from one phase to another. (Employee #1 was standing beside employee #2, in front of the switchboard.) No defects that could have caused the fault were found in the switchboard. A pair of pliers and a screwdriver were lying in the bottom of the switchboard. It was theorized that employee #1 may have attempted to remove them while employee #2 was installing the connectors and, in the process, may have accidentally struck the uninsulated portion of the circuit on the energized side. Both employees received second- and third-degree burns from the ensuing electric arc and were hospitalized.