Ground fault responsive protective system for electric power distribution apparatus

Claim 1

A GROUND FAULT PROTECTIVE SYSTEM FOR A.-C. ELECTRIC POWER APPARATUS COMPRISING: (A) A FIRST MULTIPOLE CIRCUIT INTERRUPTER ADAPTED TO BE CONNECTED TO A POLYPHASE SOURCE OF ELECTRIC POWER, SAID SOURCE HAVING A NEUTRAL TERMINAL; (B) A PLURALITY OF ADDITIONAL MULTIPOLE CIRCUIT INTERRUPTERS CONNECTED TO SAID FIRST CIRCUIT INTERRUPTER; (C) A GROUNDED METAL STRUCTURE FOR HOUSING ALL OF SAID CIRCUIT INTERRUPTERS AND THEIR INTERCONNECTIONS; (D) A PLURALITY OF MULTIWIRE FEEDER CIRCUITS EMANATING FROM SAID STRUCTURE AND CONNECTED THEREIN TO SAID ADDITIONAL CIRCUIT INTERRUPTERS, RESPECTIVELY; (E) GROUNDED METAL CONDUIT MEANS RESPECTIVELY EMBRACING SAID FEEDER CIRCUITS OUTSIDE SAID STRUCTURE; (F) FIRST CONDUCTING MEANS ADAPTED TO BE CONNECTED BETWEEN SAID CONDUIT MEANS AND THE NEUTRAL TERMINAL OF SAID SOURCE, SAID FIRST CONDUCTING MEANS BEING ELECTRICALLY INSULATED FROM SAID STRUCTURE; (G) SECOND CONDUCTING MEANS CONNECTED BETWEEN SAID STRUCTURE AND SAID FIRST CONDUCTING MEANS, AND (H) ELECTRORESPONSIVE MEANS COUPLED TO SAID SECOND CONDUCTING MEANS FOR INITIATING CIRCUIT INTERRUPTING OPERATION OF SAID FIRST CIRCUIT INTERRUPTER IN SUBSTANTIALLY INSTANTANEOUS RESPONSE TO CURRENT IN THE SECOND CONDUCTING MEANS ATTAINING AT LEAST A PREDETERMINED MAGNITUDE.