Patent GB-549756-A (GB)
Title: Improvements relating to gas-blast circuit breakers combined with isolating switches
IPC: H01H33/32
Filed: 1941-11-27
Abstract: 549,756. Fluid-pressure servomotor-control systems. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 27, 1941, No. 15263. Convention date, Nov. 29, 1940. [Class 135] [Also in Group XXXVII] A circuit-breaker arrangement comprises, for each phase a pair of interrupter units at which the circuit is initially broken and, if desired, also finally made, in series with an isolating switch the phases of which are gang-operated. Separate pressuregas sources for the phases are provided for purposes of arc-extinguishing and operation and means 'are provided to ensure that operation of the isolators is prevented unless adequate pressure is available for operating the interrupters and arcquenching thereat. The isolators comprise centrally pivoted arms 24a ... c bridging contacts 19a ... c in series with two interrupter units 12 Fig. 2, each of which comprises a mpvable contact 13 operable by a spring-plunger 15, and fixed contact 14, and gas-pipe 23, in which connection Specifications 483,996 and 554,936, [both in Group XXXVII], are referred to. The isolators are linked together and jointly operated by a crank 30 and rod 29, which has a lost-motion connection 33 and cams 34, 35 for removing locking levers 31, 32. Rod 29 is attached to piston 50 of a pneumatic motor, the supply to which is taken from a reservoir 36b and controlled by open and close valves 53, 54 the former being pneumatically operable by lever 56, and the latter either by electromagnet 59 or by handle 86. Reservoirs 36a ... c are adapted to supply the gas pipes 23 over valves 38a ... c controlled by a pilot valve 39, opening of which admits air below piston 42c (referring to valve 38c) to open the,valve 41c. After a brief space, a further valve 61c is opened and supplies air above spring-piston 67 which operates lever 56. Valves similar to 61c are provided in the other phases and operate further spring-pistons 68, 69 to remove stops' 74, 75 and so allow access of the air to piston 67, thus ensuring that the isolator is not opened unless adequate pressure for the interrupter is provided. Pilot valve 39 can be opened by a circuit-breaker opening solenoid 108, a manual circuit opening lever 87, or by a rod 94 and lever 93 which are actuated by cam 91 towards the end of the closing movement of rod 29 the timing in the latter case being such that the interrupters open and are airblown just prior to engagement of the isolating arms with contacts 19a ... c. Since in this case the operation of valves 38a ... c would also result in operation of valves 61c and hence of lever 56 it is necessary to block one of the pistons 74, 75, which is effected by contacts 118 energizing a solenoid 84 which projects a stop 83 into the path of piston 74. This stop 83 is also operable by the manual handle 86, and when automatic reclosing of the interrupters without opening of the isolators is required. When the manual closing switch 100 is operated a circuit for the closing solenoid 59 is made over contacts 98 of gas-pressure switch 99, cut off switch 101 and' contacts 102 which are closed by cam 103 on rod 29, the hold-in contacts 106 being closed when the solenoid 59 lifts. When the manual opening switch 107 is closed, a circuit for the trip solenoid 108 is made over pressure-switch contacts 110 and contacts 111 which are closed when the isolators are closed the hold-in circuit being closed when the solenoid 108 closed contacts 112 and including limit contacts 113 which are opened by solenoid 84 when the breaker is being used as an automatically-reclosing breaker. Automatic opening is effected by a relay 115 energized from the line and having its contacts paralleling those of switch 107. For automatic reclosing purposes, a manual selector switch 122 is closed and with a further switch 121 closed operation of relay 115 makes, over contacts 119, the circuit of the solenoid 84 in addition to closing the circuit of solenoid 108 so that the contacts 13, 14 open, but the isolators are locked. When the overload is removed; contacts of relay 115 reopen and the air-supply is cut off so that contacts 13, 14 reclose. If the switch 100 is moved to closed position when 121, 122 are closed, the circuit of 84 is broken at contacts 119 by energization of solenoid 123 which only restores with a time lag, thus preventing immediate reclosure of the circuit-breaker when it is tripped after being manually closed on to a short-circuit. The switch 121 is arranged so that it can only be closed and opened by closure of switches 100 and 107 respectively. In order to provide trip-free operation, a dumping valve may be provided between manifold 52 and cylinder 49, as described in Specification 548,520.