Gas-blast circuit breaker

Abstract

The gas-blast circuit breaker has passages in the pump piston which connect the pump space to the arcing space surrounding the quenching tube and to the surrounding space located within the circuit breaker housing. These passages are held closed during switching-off and open during switching-on by valve devices. For this purpose, in one embodiment the pump piston is used as a valve seat and an annular disk is used as a valve body which is common to the first valve and to the second valve, the first valve controlling the passage between the pump space and the surrounding space, and the second valve controlling the passage between the pump space and the arcing space. When switching-off large currents, the piston is subjected to an overpressure in the switching-off direction, which overpressure is produced by switching gas flowing into the arcing space, in order to support the drive. The valves are prevented from opening due to the pressure in the pump space. During switching-on, the pump space is enlarged and the arcing space is reduced in size, causing the annular disk to be raised off the pump piston against the spring prestressing it by means of the reduced pressure in the pump space and the overpressure in the arcing space. Thus, the pump and arcing spaces are able to communicate with the surrounding space and to ensure pressure equalization without the drive having to apply more energy during switching-on than in the case of a circuit breaker without an arcing space.