Abstract: A ground-fault circuit-interrupter (GFCI) system is provided that provides reliable and timely tripping of faulted circuits while minimizing so-called “nuisance” tripping. The GFCI includes a voltage unbalance detection device coupled to the main bus circuit for detecting a voltage unbalance during a fault condition. A computer processor in communication with the voltage unbalance detection device is programmed to determine when an actual fault condition exists based on a state of the voltage unbalance and certain predetermined among the fault signal generated by a GFCI unit in the main bus circuit and the fault signals generated by GFCI units in individual feeder circuits.

Abstract: A ground-fault circuit-interrupter (GFCI) system is provided that provides reliable and timely tripping of faulted circuits while minimizing so-called “nuisance” tripping. The GFCI includes a voltage unbalance detection device coupled to the main bus circuit for detecting a voltage unbalance during a fault condition. A computer processor in communication with the voltage unbalance detection device is programmed to determine when an actual fault condition exists based on a state of the voltage unbalance and certain predetermined among the fault signal generated by a GFCI unit in the main bus circuit and the fault signals generated by GFCI units in individual feeder circuits.

Abstract: A ground-fault circuit-interrupter method and system for three-phase electrical power systems including a plurality of GFCI units and a processor forming a ground-fault circuit interrupting system for use in a three-phase power distribution network including a three-phase source of electrical power, a three- or four-wire main circuit, and a plurality of three- or four-wire feeder circuits connected across the main circuit. A GFCI unit is provided in the main circuit and in each of the feeder circuits. The processor is programmed to continuously monitor the main GFCI unit and each feeder GFCI unit to determine when and where a fault has occurred and, in response thereto, to interrupt the faulted circuit and to inhibit tripping of the non-faulted circuits. The novel GFCI system is applicable for solidly-grounded, resistance-grounded, or ungrounded as well as other three-phase systems.