Protective electrical system for remotely powered mobile machines

Claim 1

A PROTECTIVE ELECTRICAL SYSTEM PROVIDING CONTINUOUS MONITORING OF THE INTEGRITY OF THE GROUND CONNECTION TO A MOBILE MACHINE SUPPLIED WITH POWER THROUGH A POWER CABLE FROM A STATIONARY POWER SUBSTATION PROVIDED WITH A POWER SOURCE, A MOBILE MACHINE HAVING AN ELECTRICALLY OPERABLE LOAD, A TRAILING POWER CABLE HAVING POWER CONDUCTORS AND A GROUND WIRE ALL EXTENDING BETWEEN SAID SUBSTATION AND SAID MACHINE WITH SAID CONDUCTORS CONNECTED TO SAID ELECTRICALLY OPERABLE LOAD, SAID GROUND WIRE BEING GROUNDED TO SAID MACHINE AND CONNECTED TO GROUND AT SAID SUBSTATION, RELAY MEANS AT SAID SUBSTATION CONNECTED TO OPERATE CONTACTS DISPOSED TO COUPLE SAID CONDUCTORS TO SAID POWER SOURCE DEPENDENT ON THE CONDITION OF OPERATION OF SAID RELAY MEANS, A GROUND MONITORING WIRE IN SAID CABLE EXTENDING BETWEEN SAID SUBSTATION AND SAID MACHINE AND FORMING WITH SAID GROUND WIRE A TWO WIRE CONTROL CITCUIT FOR SAID RELAY MEANS, A DIRECT CURRENT POWER SUPPLY ON SAID MACHINE HAVING CONNECTIONS GROUNDING ONE SIDE THEREOF TO SAID MACHINE AND CONNECTING THE OTHER SIDE THEREOF TO SAID GROUND MONITORING WIRE, AND SELECTIVELY OPERABLE CIRCUIT CLOSING MEANS ON SAID MACHINE INTERPOSED IN ONE OF SAID CONNECTIONS TO SELECTIVELY CONNECT SAID DIRECT CURRENT POWER SUPPLY TO SAID CONTROL CIRCUIT WHEREBY SAID POWER SUPPLY ENERGIZES SAID RELAY MEANS TO EFFECT CLOSURE OF SAID CONTACTS SAID THEREBY APPLY POWER TO SAID ELECTRICALLY OPERABLE LOAD.