Ground Fault by Restriking Surge of SF6 Gas-Insulated Disconnecting Switching and its Synthetic Tests

During a breaking operation of charging current with a disconnecting switch (DS) in SF6 gas-insulated switchgear (GIS), the occurrence of a fault to ground from the DS contact by a restriking surge was reported to be observed. The flashover voltage in this case, is appreciably lower than the normal withstand voltage to the ground. It has been clarified through high-speed photography with an image converter camera that the flashover is caused by a streamer generated during restriking between the DS contacts. In this respect, with the objective of confirming these phenomena in a simulated power system, two synthetic test circuits were constructed by using 550kV DS´s. Verification tests were carried out to confirm the equivalence between these two test circuits. The DS´s subjected to test withstood a surge voltage of 2.3pu-the maximum voltage obtained by simulating calculations of various GIS configurations.