Negative-sequence time-overcurrent relay

Details Negative-sequence time-overcurrent relay Negative-sequence time-overcurrent relay

1994-06-30

1995-12-12

Pellinen, A. D.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With phase sequence network analyzer

361 31, H02H 3093

Patent

active

054755590

ABSTRACT:
Disclosed is a negative-sequence time-overcurrent relay for use in a polyphase synchronous rotary electric machine having a main-circuit breaker and an exciting circuit. The negative-sequence time-overcurrent relay has a first unit for extracting a fundamental-wave component and a harmonic component from a predetermined electric parameter for each phase given to the polyphase synchronous rotary electric machine, a second unit for extracting a fundamental-wave negative sequence current for each phase from a fundamental wave, a first calculating unit for squaring the fundamental-wave negative sequence current for each phase, a second calculating unit for squaring the harmonic component for each phase, a first adding unit for adding phase-by-phase operational outputs from the second calculating unit, a multiplying unit for multiplying an output from the first adding unit by a predetermined constant, a second adding unit for adding a phase-by-phase output from the first second calculating unit to an output from the multiplying unit, and a determining unit for determining that the polyphase synchronous rotary electric machine is protected when a sum of added values for individual phases obtained from the second adding unit exceeds a predetermined value.

REFERENCES:
patent: 4210948 (1980-07-01), Waltz
"Instruction For Negative-Sequence Time Overcurrent Relay"; Toshiba; (6E2S0819); pp. 1-10.
Sakai, Y., et al.; 1992 National Convention record of IEEE Japan, No. 1293; Mar., 1992.
Patent Abstracts of Japan, vol. 18, No. 47 (E-1496), Jan. 25, 1994, JP-A-5 268 718, Oct. 15, 1993.

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