Control circuit for a circuit interrupter

Related U.S. Application Data

[63] Continuation of Ser. No. 791,195, Oct. 25, 1985, abandoned.

[51] Int. Q." H02H 3/093

[52] U.S. CI 361/93; 361/96;

361/110

[58] Field of Search 361/93-98,

361/110,42-50,111

[56] References Cited

U.S. PATENT DOCUMENTS

3,634,729 1/1972 Hendry et al 361/96

3,831,061 8/1974 Boyd 317/36

4,002,950 1/1977 Dickerson '. 361/94

4,017,766 4/1977 Vercellotti et al 361/94 X

4,060,844 11/1977 Davis et al 361/98 X

4,104,691 8/1978 Slump et al /. 361/98 X

4,114,089 9/1978 Ahmed 361/110 X

4,152,744 5/1979 Pang 361/98 X

4,193,104 3/1980 Nercessian 361/110 X

•4,200,897 4/1980 Dawley 361/110 X

4,219,858 8/1980 DePuy et al 361/93

4,258,403 3/1981 Shimp 361/42

4,297,741 10/1981 Howell 361/93

4,347,541 8/1982 Chen et al 361/50

4,442,472 4/1984 Pang et al 361/97 X

4,464,709 8/1984 Barter 361/98 X

4,544,981 10/1985 Hakoopian 361/95

4,567,540 • 1/1986 Ruta 361/98 X

4.571.658 2/1986 Ruta 361/96

4.571.659 2/1986 Demeyer et al 361/97 X

4,587,590 4/1986 Bala et al 361/94

4,589,073 5/1986 Kidd 361/93 X

4,597,025 • 6/1986 Rutchiz et al 361/94

- 4,605,982 8/1986 Harner et al 361/94

OTHER PUBLICATIONS Keders et al., "A Current—Limiting Device for Service

A control circuit is provided for a circuit interrupter that achieves an inverse-time characteristic for overcurrents that include instantaneous current levels higher than the interrupting capability of the circuit interrupter by synchronizing the operation of the circuit interrupter to ensure that circuit interruption takes place when the instantaneous current is within the interrupting capability of the circuit interrupter. This interrupting capability is similar to let-through current and is defined by the instantaneous magnitude of the current at the time of interruption or at a particular stage thereof. The control circuit is responsive to a time-current characteristic signal generator that provides a time-current signal in response to overcurrent after the passage of a time delay that is inversely related to the overcurrent. The control circuit utilizes the time-current signal to permit asynchronous operation of the circuit interrupter when the peak of the overcurrent is expected to be within the interrupting capabilities of the circuit interrupter and to control operation of the circuit interrupter in a manner synchronized with the overcurrent when the peak of the overcurrent is expected to exceed the interrupting capabilities of the circuit interrupter; the interruption in the synchronized manner being arranged to occur when the instantaneous current is within the interrupting capabilities of the circuit interrupter. If such overcurrents are predicted, the rate of change of the current and the instantaneous current being within a predetermined current range are utilized to synchronize operation of the circuit interrupter.

18 Claims, 5 Drawing Sheets

OTHER PUBLICATIONS Bottger, "The Application of Is—Limiters in Three Phase Systems", pp. 1-7, 1967, Calor—Emag Company, Germany.

Calor—Emag Company, Leaflet No. 1197/6E, "Fault Levels Too High?", 2 pages, date unknown. Blythe, M. C, "Limiting Fault Currents Between Private and Public Networks", 4 pages, Oct. 5, 1973, reprinted from Electrical Review, Calor—Emag.

Kroon, P. J., "The Development and Application of a 69 kV Fault Current Limiter", pp. 237-244, Apr. 1, 1971, 7th IEEE/PES Transmission and Distribution Conference and Exposition.

"Pyristor Pyrotechnic Systems", Carbone Ferraz, Inc. brochure, date unknown.

"Prototype Fault Current Limiter", EPRI Report, EL—1396, May 1980, title page through p. 2—3, and pp. 7—1 to 7—19, and 8—1.