Fuji Electric Co., Ltd.

Noboru Usui

Toshio Kobayashi

Mamoru Yamada

Tadao Kitamura

Yukio Osawa

An improved vacuum valve including an insulating container and an arc shield held in the insulating container, wherein a protrusion is formed on either the outer cylindrical surface of the arc shield or on the inner surface of the container. A detecting electrode is set confronted with the outer surface of the insulating container with an air gap therebetween, and is grounded through a current sensor. The current sensor detects a discharge current which is induced through the protrusion when the degree of vacuum of the vacuum valve is reduced, to output a detection signal. In response to the detection signal, a signal processing unit outputs an alarm signal indicating the reduction in the degree of vacuum of the vacuum valve. Thus, while the vacuum valve is in operation, its vacuum reduction can be positively detected with the vacuum valve maintained unchanged in reliability.

Growing community of inventors

Kawasaki, Japan

Noboru Usui