GB203131A - Improvements in and relating to automatic reclosing circuit breaker systems - Google Patents

Abstract

203,131. British Thomson - Houston Co., Ltd., (General Electric Co.). July 13, 1922. Cut-out arrangements.-In an automaticallyreclosing circuit-breaker system for a load circuit supplied from a number of points, the circuitbreakers are reclosed only when the overload is removed and the polarity thereof is the same as that of the source to be reconnected. As shown in the Figure, the sources 7, 8 supply the load circuit through circuit-breakers 9, 10. The automatic reclosing arrangements are shown applied to the circuit-breaker 10 which is closed and maintained closed by the winding 11 energized from the load circuit through a circuit including the contacts of an overload relay 12 in the supply circuit, the reclosing contacts 15, 14 of a reclosing relay 16, the closed contacts of a relay 17 and the contacts of the contactor 20. The reclosing relay has three cores; the outers are polarized by a winding 32 connected across the supply 7, and the inner carries an operating winding 34 normally' strengthening the pole 27 and weakening the pole 25. The winding 34 is connected across the load with a portion of a limiting resistance 36 in the connection. The resistance 36 is connected in parallel with the circuit-breaker 10 only when the contacts 14, 31 of the reclosing relay are closed. With normal conditions, the various relays take up the positions shown. In the event of an overload or short-circuit the overload relay 12 opens and slowly closes again under the influence of a dashpot 22. Thus the maintaining circuit of the circuit-breaker 11 is opened and the supply 7 cut off. If the overload brings out also the circuit-breaker 9, the following is the action for automatic resetting. Current in the actuating coil 34 having fallen off, the reclosing relay makes contact between 31, 14 under the action of spring 30. This completes a circuit for the winding 37 of the contactor 20 from the far side of the feeder 4 and through the reclosed overload relay 12. The contactor 20, thus closed, connects the limiting resistance 36 across the open circuit-breaker and closes a circuit through the winding 38 of the relay 18 which in closing completes an alternative circuit for the coil 37 through 36 independent of the reclosing relay. A small current is thus furnished to the load circuit and, when the resistance of the load circuit increases sufficiently, the winding 34 causes the return of the reclosing relay to bring the contacts 14, 15 together and complete the reclosing circuit of the circuit-breaker. If the circuitbreaker 9 remains closed when the circuit-breaker 10 opens on overload &c., the reclosing relay will remain in its reclosing position, without effect, however, owing to the opening of the contactor 20. A potential still remains upon the load circuit and this supplies the winding 38 of the relay 18 and, when the load resistance and consequently the potential across the load is adequate, the relay 18 closes and completes a circuit through the resistance 36 and the relay 12 for the contactor 20 whereupon the reolosing circuit is complete. If the polarities of the source and the load should become reversed. the reclosing relay will assume and maintain its ' open ' position.