Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Patent
1983-06-22
1985-02-26
Salce, Patrick R.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
361 36, 361 67, 361 86, H02H 328, H02H 7045
Patent
active
045020868
ABSTRACT:
A differential protective relay for protecting devices on an ac electrical power system. The protected devices can include a transformer, a generator, or a station bus. The differential protective relay evaluates the current flowing into and out of the protected device only during the period when the current transformers are not saturated. The differential protective relay also detects internal faults accompanying external faults by evaluating the ratio between the current flowing into and out of the protective device. When this ratio exceeds a predetermined limit the protective relay evaluates the difference between the current flowing into and out of the device to determine if this difference is sufficiently large to trip the relay. When a current transformer associated with the differential protective relay is saturated, the differential protective relay produces a restraint signal to restrain tripping.
REFERENCES:
patent: 3974423 (1976-08-01), Ulyanitsky et al.
patent: 4204237 (1980-05-01), Zocholl
patent: 4237512 (1980-12-01), Forford
Mitsubishi "Bus-Protection Relay System" Pamphlet, pub. date unknown.
"Busbar Differential Protection Type RYDSS" by Forford, Internal ASEA Publication, pub. date unknown.
"Basic Theory of Bus Differential Protection Type RADSS" ASEA Phamphlet RK63-200E, Edition 1, 1978.
"A Half Cycle Bus Differential Relay and its Application", by Forford, Internal ASEA, Publication; 11-13-73.
"Applied Protective Relaying" Westinghouse Electic Corp., Relay Instr. Div. 1979, pp. 9-1 through 9-10.
Mitsubishi Denki & Kabushiki Kaisha
Salce Patrick R.
Zitelli W. E.
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