Electricity: electrical systems and devices – Safety and protection of systems and devices – Ground fault protection
Patent
1980-03-21
1982-03-16
Moose, Jr., HarryE.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Ground fault protection
324117R, H02H 328
Patent
active
043204333
ABSTRACT:
For use in D-C power transmission systems there is provided a circuit breaker system which is responsive to leakage currents to ground to break the circuit from the power source to the D-C transmission lines. A toroidal saturable core surrounds the D-C transmission line feed conductors and carries on such core a primary and a secondary transformer winding. An A-C source is connected to the primary winding in series with one of two field coils in the electromagnetic circuit of an electromagnetically actuated circuit breaker. The other field coil in the electromagnetic circuit of the breaker is connected to the secondary winding on the saturable core.
The two field coils are wound to produce at any instant and with the same current therethrough opposite magnetic effects of the same magnitude, that is, with the core unsaturated, the magnetic effects of the currents flowing through the two field coils cancel each other and the transmission line remains activated by reason of the closure of the breaker which is normally held closed by a permanent magnet included therein. If leakage current rises in either side of the D-C transmission line, saturation of the transformer's toroidal core occurs, the current through the secondary winding and second field coil is reduced, the magnetic effects of the two field coils no longer cancel each other, the net magnetic flux exceeds that of the permanent magnet holding the breaker shut in the absence of leakage current and the breaker opens, de-activating the defective transmission line.
REFERENCES:
patent: 3708723 (1973-01-01), Shand et al.
patent: 4021729 (1977-05-01), Hudson, Jr.
patent: 4118597 (1978-10-01), Proctor et al.
patent: 4280162 (1981-07-01), Tanka et al.
Birchard Bruce L.
Fuji Electric & Co., Ltd.
Moose, Jr. HarryE.
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