Simulation of the Asynchronous Breakdowns of Serial Connected Vacuum Interrupters

The objective of this paper is to study simulation of the asynchronous breakdown phenomenon of serial connected vacuum interrupters. Lightning impulse breakdown experiments was carried out on two serial connected vacuum interrupters to obtain a reference breakdown waveform. An equivalent circuit of the experimental structure was established. Stray capacitance and inductance of the circuit diagram was obtained by simulation with the finite element method. Breakdown process of the vacuum gap was represented by a variable resistor. The resistance was calculated by the particle tracing method. Simulation of the proposed model was carried out by setting the same breakdown moment as the experimental breakdown moment. Results showed that the simulated voltage waveform was similar to the experimental voltage waveform, with a maximum error less than 5%. It was also found by the simulated results that the measured voltage waveform by the voltage divider could be quite different from the voltage across the vacuum gaps, and the vacuum breakdown event itself could be influenced by the parameters of the voltage divider. Detailed discussion on breakdown development process of serial connected vacuum gaps was carried out based on the simulation results.