Apparatus and method for automatic ground fault clearing

Claim 1

APPARATUS FOR CLEARING GROUND FAULTS OCCURRING IN A DELTA CONNECTED THREE-PHASE POWER DISTRIBUTION SYSTEM WHICH HAS A CENTRAL PANEL FEEDING A PLURALITY OF BRANCH CIRCUITS CONNECTED TO POWER UTILIZING APPARATUS THROUGH OVERCURRENT PROTECTIVE DEVICES, SAID APPARATUS BEING ADAPTED FOR CONNECTION BETWEEN GROUND AND FIRST AND SECOND PHASES OF SAID SYSTEM AT A POINT WHICH IS ELECTRICALLY ADJACENT SAID CENTRAL PANEL AND COMMON TO SAID BRANCH CIRCUITS, SAID APPARATUS COMPRISING: (A) FIRST AND SECOND OVERVOLTAGE DETECTORS RESPECTIVELY CONNECTED BETWEEN SAID FIRST AND SECOND PHASES AND GROUND, SAID DETECTORS RESPECTIVELY INCLUDING FIRST AND SECOND SWITCH MEANS ADAPTED FOR ACTUATION UPON THE OCCURRENCE OF OVERVOLTAGE BETWEEN THE FIRST AND SECOND PHASES AND GROUND, RESPECTIVELY, AND (B) A TRIPPING CURRENT DERIVING CIRCUIT ASSOCIATED WITH SAID SWITCH MEANS ADAPTED TO BE COMPLETED BETWEEN EITHER SAID FIRST PHASE AND GROUND OR SAID SECOND PHASE AND GROUND UPON ACTUATION OF SAID FIRST OR SECOND DETECTORS RESPECTIVELY FOR ESTABLISHING BETWEEN ONE OF SAID PHASES AND GROUND A CURRENT SUFFICIENT TO ACTUATE AN OVERCURRENT PROTECTIVE DEVICE, WHEREBY THERE IS ALOS ESTABLISHED THROUGH SAID GROUND FAULT BETWEEN GROUND AND ONE OF THE OTHER PHASES A CURRENT WHICH EFFECTS ACTUATION OF THE OVERCURRENT PROTECTIVE DEVICE ELECTRICALLY CLOSET TO SAID FAULT.