Ground leakage detection apparatus for ungrounded systems including toroidal core detector means

Claim 1

A GROUND-FAULT DETECTOR, COMPRISING MEANS FOR MONITORING GROUND-FAULT CURRENT INCLUDING A TRANSFORMER HAVING A SECONDARY WINDING, FAULT-RESPONSIVE MEANS CONNECTED TO SAID SECONDARY WINDING AND INCLUDING SWITCHING MEANS RESPONSIVE TO A PREDETERMINED LEVEL OF CURRENT IN SAID SECONDARY WINDING, A RELAY CONNECTED TO SAID SWITCHING MEANS, FAULT-SIGNALLING MEANS CONTROLLED BY SAID RELAY, AND AN ENERGIZING SOURCE OF CURRENT CONNECTED TO SAID RELAY AND SAID SWITCHING MEANS, SAID ENERGIZING SOURCE INCLUDING MEANS PROVIDING A HOLD-IN LEVEL OF VOLTAGE FOR SAID RELAY UNDER STEADY-STATE CONDITIONS AND PULLIN VOLTAGE INDER NO-LOAD CONDITIONS, AND A STORAGE CAPACITOR ACROSS SAID SUPPLY PROPORTIONED TO PROVIDE A PULL-IN CURRENT PULSE FOR SAID RELAY UPON OPERATION OF SAID SWITCHING MEANS.