GB212039A - Improvements in or relating to high tension electrical switch gear - Google Patents

Abstract

212,039. Davies, D. R., and Metropolitan-Vickers Electrical Co., Ltd. Jan. 19, 1923. Oil-switches; earthing; switchboards.-In hightension heavy-current switchgear of the type in which duplicate sets of bus-bars are used, instead of employing a main oil-break circuit-breaker interlocked with alternatively-operable selector switches for each set of bus-bars, the selector switches not being capable of breaking the circuit as they are only opened after the circuit has been broken by the main switch, the main oil circuit-breaker is omitted and selector switches for each set of bus-bars are employed which are capable of breaking heavy currents under abnormal conditions. As shown in Fig. 1, the incoming feeder 3 is divided into two branches 6. 7 connected by alternatively-operable circuit breakers 4, 5 to duplicate sets of bus-bars 1. 2. In the constructioual form shown in Fig. 2. cir cuit-breakers 9. 10 forming the selector switches are arranged back to back, their adjacent terminals 11, 12 being connected through a T-connection 14 to the feeder 15. Two sets of bus-bars 1, 2 are located in their casings 17, 18 adjacent to the tops of the circuit-breakers 9, 10 and to their operating mechanisms 23, 24. The earthing switch comprises a contact 26 operated by a screwed rod 27 which passes through a fixed nut 29, the contact 26 co-operating with a fixed contact mounted on the cable T-piece 14. Interlocks of known form are provided between the operating mechanisms of the circuit-breaker oil-tank lowering gear so that earthing may be effected after the circuit-breakers 4, 5 are opened, their contacts being effectively earthed before the tanks are lowered. In the modification shown in Fig. 3 the feeder 15 is brought from the trifurcating box to an oil filled chamber 33 containing isolating switches 34, 35, the remote contacts of which are connected through leads 36, 37 to the terminals 11, 12 of the circuit breakers 9, 10 which act as selector switches. The switches 34, 35 are interlocked with the alternatively-operable circuit-breakers 9, 10 so that they may be opened only after the circuit has been broken.