A fully coordinated approach for phase and ground fault protection of 480 volt systems utilizing fuses

The results of a research project to determine if a fully coordinated phase and ground fault system could be created are reported. A fused system was pursued with the following goals: (1) minimize damage from faults (NEC 110-10, 110-9); (2) isolate the fault in the smallest possible section of the power system; (3) include the requirements for ground fault protection on the service entrance and coordination with downstream devices; (4) make the system simple, safe, and flexible; and (5) make the system reliable and reasonable in cost. The ways in which these goals were attained are described.<>