Vacuum loss detection

A method of detecting a loss of vacuum in a vacuum interrupter, the method comprising:

• measuring an indication of impedance of a material that oxidizes in the presence of air and is enclosed in an evacuated space that is internal to a vacuum interrupter, wherein the material is initially non-oxidized and becomes oxidized in response to air entering the evacuated space;
• determining, based on the measured indication of impedance of the material, an indication of pressure of the evacuated space;
• and
• generating a signal that represents a condition of the evacuated space based on the determined indication of pressure.

A vacuum interrupter comprising:

• a stationary contact;
• a movable contact configured to move relative to the stationary contact between an open position and a closed position, the stationary contact and the movable contact being separated in the open position and being in contact in the closed position;
• a central shield configured to contain arcs that form between the stationary contact and the moveable contact when separated in the open position;
• a second shield positioned such that the central shield is between the second shield and either the movable contact or the stationary contact;
• a vessel that encloses the central shield, the movable contact, and the stationary contact in an evacuated space;
• and
• a sensor configured to produce an indication of impedance of a region in the evacuated space, the sensor being separate and distinct from the second shield and the central shield, and the second shield being between the sensor and the central shield, wherein
• the sensor comprises a material that oxidizes in the presence of air and is configured to produce an indication of impedance of the material, the material being initially non-oxidized and becoming oxidized in response to air entering the evacuated space, or
• the sensor comprises a thermal sensor in an insulator that at least partially surrounds the vessel.

A system comprising:

• a vacuum interrupter comprising:
• a stationary contact;
• a movable contact configured to move relative to the stationary contact between an open position and a closed position, the stationary contact and the movable contact being separated in the open position and being in contact in the closed position;
• and
• a vessel that encloses the movable contact and the stationary contact in an evacuated space;
• an insulator that at least partially surrounds the vessel;
• a thermal sensor configured to produce an indication of a temperature of a region that is in the evacuated space, the thermal sensor being positioned in the insulator and outside of the evacuated space;
• and
• a control system coupled to the sensor and configured to receive data from and to provide data to the sensor, the control system comprising an electronic processor and an electronic storage that stores instructions that, when executed, cause the electronic processor to:
• access the indication of the temperature of the region that is in the evacuated space, and
• determine a condition of the evacuated space based on the accessed indication of temperature.