Suppression of Very Fast Transient Overvoltages across Insulating Flange of 1000 kV GIS

Abstract

Field tests of 1000 kV (UHV) gas insulated switchgear (GIS) have been conducted at the UHV equipment test site and many beneficial results have been obtained. Suppression of very fast transient overvoltages (VFTOs) across an insulating flange of UHV GIS was tried for switching overvoltages by operating a disconnecting switch and its performance was observed at the test site. A Zinc Oxide element with a doughnut shape was fitted to the insulating washer around several bolts in the insulating flange and the potential of suppression of the VFTOs was confirmed. The VFTOs across the insulating flange and the VFTOs across the insulating joint of a gas pipe were analyzed with EMTP. Analytical calculations correlated with the results from the field testing.