To discontinue the power supply to equipment using gas, when a gas leakage occurs by a device which is small in size and economical as a whole, and with which a wiring work in a narrow space can be avoided as much as possible.
When a gas leakage is detected, the output of a gas leakage alarm device control unit 4 is amplified by an amplifier circuit 5 and outputted as an alarm by a buzzer 6, and at the same time, the excitation of the coil 7 of a relay is released. With the release of the excitation of the coil 7 of the relay, a relay contact 8 is closed, and the output is inputted to a leakage detection unit 9. Normally, the leakage detection unit 9 compares the output of a ZCT 11 with a set value, and if the former exceeds the latter, it decides that a leakage has occurred and turns on a thyristor 10. With this process, a breaker coil 12 is excited, a breaker contact 13 is opened resulting in a power supply being cut off. When the relay contact 8 is closed, the leakage detection unit 9 also turns on the thyristor 10 as in the case of leakage detection. Accordingly, the power supply is cut off with the same process in this manner.
NAKAE HIROSHI
KOBANAWA AKIHIKO
FUJI ELECTRIC CO LTD