Patent Document ID: 4757263
Application ID: 07044919
Patent Flag: 1

Claim One:
1. In an improved apparatus for simultaneously and continuously monitoring, in situ, the insulation characteristics of a plurality of separate pieces of high voltage alternating current electrical equipment including instrument transformers, high voltage bushings of power circuit breakers and transformers, and other like equipment, each of said pieces of electrical equipment being provided with a capacitance tap, said apparatus comprising: (A) separate capacitance tap adapter means for providing coupling between said apparatus and each of said capacitance taps; (B) separate impedor means operatively associated with each of said capacitance tap adapter means and having an electrical impedance so low that current in said impedor means is substantially determined by the impendance of the insulation of said equipment being monitored, and of such value that the voltage between said capacitance tap and ground is in the range of about 10 to about 140 volts ac RMS; (C) separate connector means permanently associated with each said impedor means for permitting coupling of an external circuit to said impedor means without interruption of current through said insulation; and (D) external circuit means adapted to be coupled to said impedor means and responsive to a signal applied to said impedor means from said electrical equipment, the insulation characteristics thereof being monitored, said connector means permitting said external circuit to be detachably coupled to said impedor means; the improved apparatus in combination therewith for providing for simultaneous, continuous monitoring, of more than one such piece of equipment, for providing voltage limiting characteristics and attendant protection for said external circuit upon the occurrence of a failed open event of said impedor means and/or leads operatively associated therewith, thereby substantially eliminating possible human safety hazards and damage to said external circuit, and for all said pieces of electrical equipment that are on the same voltage and phase, for eliminating the requirement for providing a plurality of connecting means for coupling a reference voltage source normally juxtaposed said external circuit, which external circuit is normally remotely located relative to said piece of electrical equipment and which improved apparatus comprises: (1) as each of said impedor means, at least two shunt capacitors of capacitance value selected such that added together they provide a shunt to ground that, with normal insulation current flowing therethrough, develops a voltage ranging between about 10 to about 140 volts ac RMS, and (2) a single voltage reference source operatively associated with each high voltage alternating current bus to which said pieces of equipment, being monitored, are coupled for providing a predetermined fraction of said bus voltage in substantial phase relationship therewith for coupling of same with said external circuit; said improved apparatus characterized by the fact that if one of said shunt capacitors fails open or a lead operatively associated therewith opens thereby causing the output voltage from a capacitance tap adapter means to be biased upward to normally constitute an apparatus and safety hazard, said improved apparatus limits said output voltage from said capacitor tap adapter means to said external circuit to about 20 to about 280 volts, and said improved apparatus further characterized by the fact that said connecting means for coupling said single voltage reference source with said external circuit is fixedly mounted in a manner so as to substantially eliminate impedments relative to human ingress or egress of the area between said pieces of equipment being monitored and said external circuit remotely located therefrom.