Voltage Distribution Characteristics of Multiple-break Vacuum Circuit Breakers

The static voltage distributions and capacitance matrixes of two triple-break vacuum circuit breakers with different structure arrangements were calculated with the finite element method(FEM). Then the voltage distributions of two arrangements under ac voltages were measured. Experiment results verify the accuracy of the numerical calculations. The results show that the vertical arrangement has a better voltage distribution than the U-shaped arrangement. And the capacitance matrixes are useful to choose suitable grading capacitors. The voltage distribution characteristics after high current interruption was preliminary analyzed. The ohmic impedance of the gap during post-arc current period was calculated using the "Continuous Transition Model" to evaluate its influences on the voltage distribution. The results indicate that the voltage distribution may be determined by the ohmic impedances in the first few microseconds after current zero, especially after arcing conditions followed by large post-arc currents.