GROUND FAULT PROTECTION CIRCUIT FOR A MULTIPLE SOURCE SYSTEM

摘要

An improved ground faultprotection system is provided forprotecting an electrical powerdistribution system having multiplesources and multiple grounds.In accordance with a preferredembodiment, an electrical powerdistribution circuit having a primaryelectrical circuit for distributingelectrical power from a pluralityof sources to a plurality of loadsis provided with a ground faultprotection circuit magneticallycoupled to the primary circuit. Theprimary electrical circuit includesconventional main and tie busesfor distributing power to the loadsand switches or circuit breakers forinterrupting power from flowingin the buses. The ground faultprotection circuit includes currentsensors, tripping functions orground fault relays associated witheach circuit breaker and a novel useof an auxiliary transformer. Whena ground fault occurs, the groundfault protection circuit is capable of sensing and determining the specificbus in which a ground fault condition exists. It then selectivelysends a trip current generated by the associated current sensor only to theproper tripping functions for tripping the appropriate circuitbreakers in the affected bus in order to isolate the ground fau this avoidsunnecessary tripping of circuit breakers in bus portions whichare not affected by the ground fault. The auxiliary transformer uniquely sendsthe trip current to portions of the ground fault protectioncircuits that would not have been connected, or accessible, in the groundfault protection circuits of the prior art.