Investigation on restrikes of high-voltage vacuum interrupters (72.5 kV) switching capacitve load

Circuit breakers are used for safe switching in power supply networks under the most difficult circuit conditions. In the high-voltage level (Um > 52 kV) SF6 switchgear has been established because of its good arc extinguishing properties and dielectric strength. However, the high greenhouse gas potential of SF6 and the formation of toxic and corrosive decomposition products that must be disposed of during maintenance work at great expense are disadvantageous.

In the medium voltage level the vacuum technology has been established. Vacuum interrupters are characterized among other things by a high life expectancy and low maintenance requirements. Due to the above-mentioned advantages of this technology, a progression to establish vacuum switchgear in the higher voltage levels is desired.

When switching off capacitive loads particularly high demands are placed on the dielectric strength of the circuit breaker. After contact opening and arc interruption the recovery voltage can reach values ​​up to twice the rated voltage peak. During that time a restrike must not occur.

A central part of the research is to investigate the possible causes that lead to the failure of the circuit breaker during the recovery voltage phase. For this purpose, a synthetic test circuit has been developed and constructed in a former research project to simulate the capacitive switching event.