GB198683A - Improvements in and relating to automatic reclosing circuit breaker systems - Google Patents

Abstract

198,683. British Thomson - Houston Co., Ltd., (Assignees of Anderson, A. E.). June 5, 1922, [Convention date]. Cut-out systems.-An automatically-reclosing circuit-breaker system comprises relay arrangements whereby the circuit-breaker is reclosed in response to a predetermined voltage across the load circuit when the load circuit is not supplied with current at some other point, and in response to the current, which is proportional to the voltage difference supplied to the load circuit from the source of current to be connected by the closing of the circuit-breaker, when the load circuit is supplied at some other point. As shown in the Figure, two sources 8, 7 supply a load circuit 1, 2 through circuit-breakers 9, 10 oi which 10 is automatically reclosed by means of the coil 11 which acts also as a maintaining coil and is normally connected across 3, 4 through the overload relav 12, the back contacts 14 and the hand-operated switch 15. The reclosing action is under the control of a reclosing relay 24 consisting of a polar structure having a magnetizing winding 35 and a fixed high resistance winding 31 which surrounds the armature and is connected permanently across the load circuit. The relay closes its contacts when winding 35 is energized and the voltage across the winding 31, that is, across the load is adequate. The connections of the winding 35 are under the control of relays 19, 20 of which relay 19 opens when the applied potential is above a small predetermined value and relay 20 closes when the applied potential is above a predetermined high value. In the normal closed position of the circuit-breaker 10, a resistor 18 is short-circuited thereby. The voltage drop across this resistor is used for reclosing; it is very much greater when supply is from a single source than when from multiple sources. When an overload or short-circuit occurs on the load 1, 2 the overload relay 12 opens, opening the circuit of 11, whereupon the circuit-breaker opens, opening contacts 14 and, consequently, deenergizing 35 whereupon the reclosing relay opens its contacts 22, 23. A delay-action relay 26 in connection with the relays 19, 20 is now connected across 3, 4 through contacts 27 and, when conditions have been stabilized, relay 26 closes its contacts 25. Resistor 18 is now in shunt to the circuit-breaker, and a small current is supplied to the load through the resistor. The overload relay 12 recloses. In the case of a load supplied, from a single source, the circuitbreaker 10 is reclosed in the following manner. Practically the full potential of the source exists across 18 and, consequently, 19 opens and 20 closes; the latter connects 35 across 3, 4 through 25 and 15. When the load resistance increases, the potential across it and consequently across 31 increases until sufficient to operate the reclosing relay and close 22, 23. This completes the reclosing circuit 3, 11, 12, 22-23, 20, 25, 15, 4 and the circuit breaker recloses and the conditions existing before the overload &c. are reproduced. If the load is supplied from sources in addition to 3, 4, the potential difference across 18, which is the difference of the voltages across 3, 4 and 1, 2, is inadequate to close 20 but serves to close 19. When this potential difference decreases to a predetermined value, due to the increase of the load resistance, 19 closes, completing a circuit for reclosing the circuit breaker 11, as follows-3, 11, 12, 19, 25, 15, 4. If all load is disconnected from the load circuit in the case of supply from a single source only, the reclosing circuit of 11 is completed through the relay 19 as described above in connection with multiple sources.