Transient Recovery Voltage Distribution Ratio and Voltage Sharing Measure of Double- and Triple-Break Vacuum Circuit Breakers

Transient recovery voltage (TRV) distribution ratio and voltage sharing measure of series arrangement double- and triple-break vacuum circuit breakers (VCBs) were studied in this paper. The mathematical analysis of the TRV distribution ratio in a double-break VCB shows that the uneven TRV distribution ratio is caused by the stray capacitances and the imbalanced postarc current as a result of the difference of the postarc plasma characteristics in each vacuum interrupter. This has been proven by the synthetic breaking tests and simulation results based on a modified vacuum arc interruption model of a double-break VCB. On this basis, voltage sharing measure for a 126-kV triple-break VCB designed for the 110-kV power network has been discussed. The synthetic breaking test results indicated that the 126-kV triple-break VCB with 1000-pF grading capacitors has a substantially uniform TRV distribution, and can successfully break the rated short-circuit interrupting current (40 kA
_rms
).