GB271502A - Improvements in and relating to automatic reclosing circuit breaker systems - Google Patents

Abstract

271,502. British Thomson-Houston Co., Ltd., (Assignees of Traver, O. C.). May 22, 1926, [Convention date]. Protective arrangements. - Two circuits 2, 3 are interconnected by an automatic reclosing circuit-breaker 1 opened upon overload as determined by a relay 8, either or both the circuits 2, 3 being supplied by associated sources 4, 5. The circuit-breaker 1 is normally held closed by a coil 6 energized from circuit 2 through resistor 31, contacts 26, coil 6, contacts 7 and 22 to earth. Assuming a fault occurs on circuit 3 and source 4 is the only one operative, the coil 6 is de-energized by the opening of contacts 7, which remain open for a while owing to the dash-pot 23. On the opening of the circuit-breaker 1, the circuit 3 is supplied through a load indicating resistor 10, across which there is a large voltage drop owing to the fault, therefore both relays 12, 13 pick-up. The relay 13 completes a circuit for the coils 16, 18 and 17, 19 of relay 11 from the circuits 2 and 3 to ground respectively. Coils 16, 17 are additive and coils 18, 19 are subtractive. As the fault disappears, the voltage on the circuit 3 increases until coils 16, 17 overpower coils 18, 19 and relay 11 closes its contacts to complete circuit of coil 6 through contacts 21 to ground and thus to reclose the circuit-breaker 1, whereupon the relays 12, 13 drop and the circuit of coil 6 is maintained through contacts 22. If the source 5 is also operative when the fault occurs on the circuit 3, then although the relay 12 picks-up, there is not sufficient voltage across the resistor 10 for the relay 13 to pick-up, so the relay 11 remains inactive. As this fault disappears, the energization of the relay 12 weakens until it drops and completes the normal circuit for the coil 6, whereupon the circuit-breaker 1 recloses. If the fault occurs on the circuit 2 instead of on the circuit 3, the action of the relays 11, 12, 13 is the same, but another relay 14 is energized through back contacts 24 on the circuit-breaker 1 from the sound circuit 3 sufficiently to pick-up, opening its contacts 26 and closing its contacts 25 so that the circuit for the coil 6 is from the circuit 3 through resistor 30 instead of from circuit 2 through resistor 31. When the fault on the circuit 2 is removed, the circuit breaker 1 closes and the relay 14 is deenergized. The relay 14 closes its contacts 26 before opening its contacts 25 so that energizarion of coil 6 is maintained. While both contacts 25, 26 are closed, the circuits 2, 3 are interconnected through these contacts, therefore the resistors 30, 31 are provided to prevent excess currents flowing through these contacts.