Patent ID: 9646785
Date: 2017-05-09
CPC Classifications: H01H,H02B

Claim:
1. A vacuum monitoring device, which monitors a vacuum deterioration of a vacuum valve, of a metal tank type vacuum circuit breaker which includes the vacuum valve inside a metal tank and has a connecting line of the vacuum valve led out to the external of the metal tank through a bushing, the bushing having an internal shield having a low-pass function, comprising: a first antenna installed inside the metal tank; a second antenna installed outside the metal tank; a first detection portion which measures the intensity of an electromagnetic wave, resulting from a partial discharge of the vacuum valve, which is detected by the first antenna; a second detection portion which measures the intensity of an electromagnetic wave, resulting from a noise out of the metal tank, which is detected by the second antenna; and a determination portion which determines a vacuum deterioration of the vacuum valve by comparing the intensity of the electromagnetic wave detected by the first detection portion and the intensity of the electromagnetic wave detected by the second detection portion, the device being characterized in that the first and second detection portions include frequency filters which pass a frequency band, of electromagnetic waves resulting from discharges occurring when the vacuum valve deteriorates in vacuum, which is attenuated by the internal shield.