Abstract: A reclosing relay in accordance with the disclosed invention comprises a reclose initiate (RI) input and a drive to last reclosure (DTLR) input, and an output at which a close signal is provided to effect the reclosure of a circuit breaker associated with the reclosing relay. The reclosing relay is operative when it receives a first RI signal at its RI input to provide the close signal to the associated circuit breaker substantially immediately or with time delay as programmed by settings. The reclosing relay is operative when it receives a signal from a second RI contact at its DTLR input to provide the close signal to the circuit breaker only after synchronism is identified between the line voltages on either side of the associated circuit breaker.

Abstract: A system and method for automatically testing the operation of a protective relay system is disclosed. The system and method provide for continuous testing to ensure proper operation of the protective relay system while the relay remains in service and without interrupting the normal operation of the relay. This testing is performed by storing reference data corresponding to test signals, generating test signals, sampling a specific test signal, processing that test signal through the relay and comparing the processed test signal with the corresponding reference data. Upon detection of an error in the relay, the system and method further provide for isolation of the relay from the electric power system and automatic testing of individual electrical components within the protective relay system to determine the identity of the malfunctioning component.

Abstract: A microcomputer based reclosing relay performs a number of sequences to generate a succession of reclosure signals for a circuit breaker at timed intervals. The digital processing unit of the relay maintains flags, counts and running times for generating the succession of timed reclosures in a volatile memory. Periodically, these flags, counts and running times are copied to a non-volatile memory such as an EEPROM. Upon restoration of power following an interruption of power which results in loss of the contents of the volatile memory, the digital processing unit recopies the flags, counts and running times saved in the non-volatile memory back into the volatile memory, so that the relay can resume generating the succession of reclosures from the point at which power was lost. The flags and counts are copied to the EEPROM only when they change state, while the running times are only saved once a second to prolong the service life of the EEPROM.

Abstract: A rotating disc electromagnetic relay has an operating element which applies a torque to the disc tending to close the main contacts and a restraint element generating a torque which together with a spring tends to open the relay contacts. The operating and restraint elements each have an E-shaped core defining two magnetic circuits with a common center leg. Two voltages to be compared are applied to two input coils on the center leg of each element in the same sense to generate a flux representative of the sum of the voltages in the operating element and in the opposite sense to produce a flux representative of the difference between the two voltages in the restraint element. The flux in the common leg of each element divides between the two magnetic circuits. The flux in one magnetic circuit of each element is shifted in phase by a first lag coil on an outer leg of the core to generate the opening and closing torque, respectively.