Effect of Residual Charges on Impulse Withstand Voltage Characteristics of Air-Insulated Gap with a Barrier Inserted

The effect of residual charges on the impulse withstand voltage characteristics of air-insulated gap with a barrier inserted are investigated. Lightning impulse tests were carried out to study the impulse withstand voltage characteristics in the presence of residual charges under different gap distances by the up-and-down method. The potential distribution on barrier surfaces were measured under different conditions of streamer discharges and breakdown. The results show that the 50% impulse breakdown voltage $U_{50}$ is slightly increased and the difference between the maximum and minimum applied voltages is significant in the presence of residual charges at the gap distance of 30 cm. The resting time between shots has little effect on the $U_{50}$ There are more residual charges accumulated on the barrier surface with the shot time increased and still residual charges on the barrier surface after breakdown. The results can provide a reference for improving the insulation performance of air-insulated gap.