Study on voltage distribution characteristic of a 363 kV fast multi-break vacuum circuit breaker

Vacuum circuit breaker (VCB) has a longer life and shorter opening time than SF6 circuit breaker, but current single-break VCB cannot be applied in high-voltage power system directly. Here, a fast 363kV multi-break VCB design is presented and its voltage distribution characteristic and stray capacitors are analysed. A three-dimensional finite-element model of modularised hexa-break VCB composed of 12 vacuum interrupter modules installed on three series connected platforms is developed to calculate the voltage distribution and distributed capacitances. The result shows that the voltage distribution is uneven, and the first break shares the 67.974% of the whole applied voltage. On account of distributed capacitances parameters, an equivalent capacitance model with PSCAD is built to discuss the voltage distribution characteristic at different grading capacitance values, and the optimal grading capacitance value is determined to 10nF.