Hitachi, Ltd.

Kouichi Sadou

Hideo Kawamoto

Tadahiko Nogami

Yasuhide Takeda

Goro Daimon

Hiroshi Maeda

Hiroyoshi Sadamura

For the purpose of providing a gas circuit breaker with a structure of hydraulic pressure operation system capable of detecting the occurrence of an incomplete closed state of the valves therein to prevent their erroneous motion during the subsequent motion, and a liquid-pressure driving system to be used therefor, a check valve is arranged so as to suppress the flow into the space on the side of the downstream of a closed-circuit operation spool valve, wherein the space on the side of the downstream of the closed-circuit operation spool valve is connected through a second diaphragm to a low-pressure oil tank and the operation time or operation number of a liquid-pressure pump is measured.

Gas circuit breaker and liquid pressure-driving system to be used

Occurrence of erroneous operation in which circuit closing operation unexpectedly happens after circuit opening operation even though an abnormality such that a circuit closing system is left in a circuit closing condition even after completion of the circuit closing operation. Accordingly, a circuit closing control valve has such an arrangement that its pilot chamber becomes a low pressure so that the circuit closing control valve is opened, and a lock valve having two pilot chambers connected to a circuit closing pilot valve and a circuit opening pilot valve, which are both become a low pressure, is located in a passage connecting between the pilot chamber of the circuit opening control valve and a return port. With this arrangement, if the above-mentioned abnormality occurs, the circuit closing condition is maintained unless a circuit opening instruction is delivered, and once the circuit opening operation is effected, the lock valve is opened so as to connect the pilot chamber of the circuit opening control valve to the lower pressure side so that the circuit opening control valve is left to be opened in order to disable the circuit closing operation, thereby it is possible to prevent occurrence of erroneous operation.

Hydraulic drive device for circuit breaker and circuit breaker using the

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Hitachi, Japan

Kouichi Sadou