Studies of epoxy spacers subjected to internal and external partial discharge and SF6 byproducts

The early phases of the internal and external spacer surface degradation process were characterized using electrical and chemical techniques in order to develop a better understanding of the long-term aging mechanisms. Reaction of nitrogen gas in a discharge cavity with the epoxy void wall was readily detected by ESCA (electron spectroscopy for chemical analysis), and the technique could find application in determining the void size below which no damage occurs. A similarly substantial modification of spacer surface properties could be brought about by exposure to localized corona discharges, associated with material transfer from the electrode and leading ultimately to the formation of tracklike paths on the epoxy surface. The results are of interest in connection with the electrical treeing of GIS (gas-insulated switchgear) spacers