The relationship research between the internal pressure and shield potential in vacuum interrupters

Potential on middle shield of vacuum interrupter is one of techniques to determine the degradation of pressure in vacuum interrupters. Extensive research on the component of the shield potential and the cause of its conformation was done, certain results were obtained in theory and experiments. However, among multiple interpretations in causes of interrupter shield potential, there are still no accepted standards, and it is difficult to dealing with different types of circuit breakers according to the same standards in practical application. Seek out the mechanism relationship between the shield potential and internal pressure. This paper starting with the relevant electromagnetic theory and Gas discharge theory, the degradation of the internal pressure process was divided into three phases as discussed, and the theoretical basis of each stages based on was described. In particular the pressure in vacuum interrupters is lower than 0.1 Pa when potential value of the shield is more difficult to determine, 3D finite element method was used to calculate the shield potential in it, variation of shielding potential in this vacuum range was analyzed, result of the research provides a method to determine the feasibility and assessment of internal pressure, with good application reference value.