GB755016A - Improvements relating to electric switchgear - Google Patents

Abstract

755,016. Air-blast switches; oil-break switches. REYROLLE & CO., Ltd., A. July 8. 1954 [July 8, 1953], No. 18961/53. Class 38(5) In multi-pole distribution system employing a circuit-breaker having two seriesconnected breaks, the junction point between the breaks of each pole is connected, on operation of the breaker, to each other pole through an impedance and diverter gap which is arranged to be closed or to break down on operation of the circuit-breaker and to be subsequently restored to its initial condition. For A.C. circuits the impedance may be a resistance and/or a capacitance, but for D.C. circuits it is an inductance or inductance-capacity combination. For three-phase applications the resistance-gap combination may be star-connected and earthed so that on earth fault, one combination will shunt the fault and the break on the fault side of the breaker, whereas for phase faults, two impedances in series will shunt the fault and the two breaks on the fault side. In a conventional oil-tank type breaker, the bridging bar may be arranged in its open position to engage one terminal of an impedance the other terminal of which is earthed at the tank. In Fig. 2, operation of a trip valve 17 admits air from reservoir 16 via pipe 19 and apertures 20 to raise a piston 21 and operate a rack mechanism 27, 28 to separate the main contacts 24, 26. Air also passes through pipe 37 to raise a piston 35 against spring 38 and move a contact 34 to close a tubular fixed contact 33 leading to atmosphere and connected to the conducting body 15 common to the two breaks. A resistance 12 connected to the earthed base 13 at one end is thus connected either before or similtaneously with the breaker opening to the junction of the breaks and disconnected when the spring 38 restores the piston 35 after removal of the air-pressure. In Fig. 3, a gap 50 in a container 51 charged with gas via a port 52, is caused to break down by release of the pressure at a trip valve 55, so connecting a capacitance 49 between 15 and earth and diverting current from a fault. Before reclosure of the breaker the container is re-charged to normal insulation level of the system by way of valve 53.