1975-03-06
1977-01-11
Moose, Harry
317 20, H02H 320
Patent
active
040029506
ABSTRACT:
The ac transmission system is protected by circuit breaker apparatus capable of responding to fault current levels exceeding a predetermined critical fault level, but less than the maximum fault current. The fault current levels exceeding the critical level are detected by comparison of actual line current to a simulation of the critical level of fault current for one of a plurality of phases 01, 02, 03. Reference signals in quadrature with the three line voltages are continuously fed to differential amplifiers having both inputs connected in parallel until a potential fault is detected when one input is disconnected and clamped at the potential it had at the time of disconnect. The resulting output of the differential amplifiers accurately simulates the time-varying current of a system fault. The simulated signals are compared to actual line current to determine in less than one cycle if a fault is occurring and to order the appropriate breaker action.
REFERENCES:
patent: 3611040 (1971-10-01), Ainsworth
patent: 3873887 (1975-03-01), Barkan et al.
B488,634, published Jan. 20, 1976, filed July 15, 1974.
Dicke Allen A.
Hughes Aircraft Company
MacAllister William H.
Moose Harry
Rengel Richard J.
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