Current-Zero Characteristics of a Vacuum Circuit Breaker at Short-Circuit Current Interruption

High resolution measurements on the post-arc current in vacuum circuit breakers reveal a period, immediately following current-zero, in which the voltage remains practically zero. The most widely used model for simulating the interaction between the post-arc current with the electrical circuit lacks a proper explanation for this event, and hence it needs to be complemented. We demonstrate that the breaker's electrical behaviour during this zero-voltage period can be explained by using the theory of a Langmuir probe. Such probes are used to investigate plasma properties, such as the ion density and the electron temperature, and we extrapolate its theory to the vacuum circuit breaker. The simulation results obtained with this model are in good agreement with measured data.