Method and apparatus for detecting a reduction in the degree of vacuum of a vacuum valve while in operation

A device for detecting a reduction in the degree of vacuum of a vacuum valve, comprising:

• an insulating container which is evacuated;
• contact means made up of a movable electrode and a stationary electrode;
• an arc shield electrically connected to one of said electrodes and having a protrusion formed on the outer surface thereof and surrounding said contact means, said contact means and said arc shield being set in said insulating container;
• a detecting electrode confronted with the outer surface of said insulating container so as to provide an air gap therebetween;
• and
• a current sensor for detecting a discharge current which is induced through said protrusion when the degree of vacuum of said vacuum valve is reduced and outputting detection signal, said detecting electrode being grounded through said current sensor.

A device for detecting a reduction in the degree of vacuum of a vacuum valve, comprising:

• an insulating container which is evacuated and having a protrusion on the inner surface thereof;
• contact means made up of a movable electrode and a stationary electrode;
• an arc shield which surrounds said contact means and is electrically connected to one of said electrodes, said contact means and arc shield being set in said insulating container;
• a detecting electrode confronted with the outer surface of said insulating container so as to provide an air gap therebetween;
• a current sensor for detecting a discharge current which is induced through said protrusion when the degree of vacuum of said vacuum valve is reduced and outputting a detection signal, said detecting electrode being grounded through said current sensor;
• and
• a signal processing unit which, in response to said output of said current sensor, outputs an alarm signal to indicate the reduction in the degree of vacuum of said vacuum valve.