Interruption behaviours with 84/72-kV VCB and GCB

The interruption behaviours of a high voltage vacuum circuit breaker (VCB) have been investigated in detail [1]-[3]. A VCB has several specific interruption behaviours compared to an SF₆ gas circuit breaker (GCB). In particular, a higher thermal interruption capability and a high frequency (HF) re-ignition and HF interruption phenomena might cause switching overvoltage. Interruption behaviours such as the chopping characteristic and HF re-ignition and HF interruption behaviours were measured in this study under the same testing conditions as for several current interruption testing duties using a model VCB and GCB with the same rated voltage of 84/72 kV. The results show that the current chopping level of the VCB is relatively low, so any overvoltage due to current chopping when using a HV-VCB does not significantly influence transmission networks. However, HV-VCB iterates the HF re-ignitions and HF interruptions during the half cycle of inductive current (180-700 A) switching tests and additional large current switching tests. Therefore, HV-VCB may generate steep overvoltages, which may affect the protection relay and secondary equipment operations.