DANIEL E CORDRAY
Engineers in Delaware

4295175, Oct 13, 1981

Apr 21, 1980

6/142512

Daniel E. Cordray - Media PA

General Electric Company - Philadelphia PA

H02H 726

361 69

A pilot wire relay protection system for detecting and responding to phase-to-phase, three-phase, phase-to-phase to ground, and ground current faults including relatively low level ground current faults occurring within an electrical power network is disclosed. The pilot wire relay protection system includes current transformers coupled to transmission lines of the electrical power network for developing coupled currents representative of the transmission-line currents. The current transformers are positioned at the ends of a section of the electrical power network for which protection is desired. The coupled currents from the current transformers are inputted to pilot relays having an analog device for producing a composite signal indicative of the condition of the protected section of the network. The pilot wire relay also includes an electronic device to detect if preset fault limits have been exceeded. Upon detecting a condition indicative of a fault within the protected section, the pilot relay transmits an electrical signal to a power circuit breaker which in turn disconnects the protected section of the electrical power network from the remainder of the network.