Investigation of the VFTO Related Repeated Breakdown Processes in UHV GIS

1100 kV GIS tests were performed to experimentally investigate the circuit on the repeated breakdown process and the VFTO generated when using a disconnector to switch an unload busbar.Since the random feature of the repeated breakdown process,about 500 rounds of opening and closing operations were performed.The breakdown characteristic of the contact gap during operations,the statistic distribution of the residual voltages at the unload busbar after each opening operation and the statistic distribution of the p.f.phase of first breakdown in each closing operation were obtained.Based on the test results,the repeated breakdown process and its influence on the VFTO were analyzed,and the conditions for the repeated breakdown process to be terminated were presented.