Patent ID: 8110770

Claim:
A vacuum circuit breaker comprising: a ground tank configured to be filled with an insulating gas at a pressure higher than the atmospheric pressure; a vacuum interrupter which includes: a vacuum vessel, electrodes which are supported, respectively, by a movable lead and a fixed lead in the vacuum vessel, and which are arranged so that the electrodes can be selectively contacted with each other and separated from each other, and a bellows to retain the vacuum between the movable lead and the vacuum vessel; a movable-side contact case and a fixed-side contact case which are supported through insulating members in the ground tank, and which are provided on both sides of the vacuum interrupter; a movable-side conductor and a fixed-side conductor which are connected, respectively, with the movable-side contact case and the fixed side contact case, and which extend through bushings in the ground tank; and an insulating operating rod extending through one of the insulating members and connecting the movable lead with an operating mechanism, wherein the movable-side conductor is tubular and comprises an inside cavity, wherein the movable-side contact case includes a chamber which communicates with a space on a non-vacuum side of the bellows, wherein the chamber is isolated from a space configured to be filled with the insulating gas in the ground tank by a sealing device, and wherein the chamber communicates with an outside atmosphere through the inside cavity of the movable-side conductor.