Characterization of GIS Spacers Exposed to SF6 Decomposition Products

SF6 gas-insulated switchgear is a sealed system, but low- level contamination can accumulate and affect spacer performance. The degradation of a number of spacer materials exposed to either direct arcing conditions or arc by-products was investigated to correlate their surface molecular features with changes in electrical performance. Electron Spectroscopy for Chemical Analysis, Scanning Electron Microscopy, Infrared and Thermal Analysis were used to probe the surface of the dielectrics. In the immediate vicinity of the spark, spacer surfaces undergo irreversible chemical, morphological, and physical changes with extensive pyrolysis and surface erosion. There is clear evidence of chemical reactions with high concentrations of fluorine bonded to the organic resin. Exposure of spacer materials to SF6 arcing by-products results in significant reduction in electrical properties with profound changes in the chemical structure of both epoxy moieties and/ or filler particles. This paper will describe the surface characterization techniques as applied to degraded spacer surfaces and discuss the possible degradation mechanisms.