GB234510A - Improvements in and relating to automatic reclosing circuit breaker systems - Google Patents

Abstract

234,510. British Thomson-Houston Co., Ltd., (Assignees of Anderson, A. E.). May 24, 1924, [Convention date]. Cut-out systems.-In an automatically-reclosing circuit-breaker system of the kind in which successive reclosure is held up if a very heavy overload or short-circuit occurs, additional relays are provided which automatically re-introduce the automatic reclosing features when the short-circuit current is reduced. As shown, one overload relay 7 operates with delay action when an ordinary overload arises and a second relay 14 operates, instantaneously only in the event of a very heavy overload. The first relay 7 acts to close the tripping circuit 5 of the circuit-breaker 3 which, in assuming the off position, opens the actuating circuit of an auxiliary relay 11 which in assuming its off position closes contacts 26, 27, 28. This completes the circuit of the reclosing relay 8 through the closed contacts 32, 39 of a lock-out relay 12 in series with the contacts 35 of a notching relay 10. The relay 8 closes and completes the actuating circuit of a hesitating relay 9 which, in closing, completes the reclosing circuit of the reclosing coil 4. The relay 9 has a slow release to ensure that the reclosing circuit shall remain completed long enough to enable the circuit-breaker to close. The notching relay provides for reclosure a predetermined number of times after which further reclosure is precluded until the contacts 35 have been reclosed by hand. To deal, according to the invention, with very heavy overloads the instantaneous overload relay 14, an additional relay 16 with its operating winding connected across the voltage of the load, and the lock-out relay 12 are provided. In the event of such overload, the relay 14 closes as well as the relay 7, thereby connecting the operating winding of the lock-out relay 12 to the supply through the back contacts 24 of the circuitbreaker. The relay 12 is raised to the off position where it is automatically retained by the latch 13. In this position, the circuit of the reclosing relay 8 is open-circuited at contacts 39, 32 and the circuit-breaker cannot automatically reclose until the lock-out relay is released. This is effected when the voltage across the load is restored, that is when the short-circuit has disappeared, and is adequate to close the relay 29 thereby energizing the tripping magnet 17 through the resistance 30.