PD scaling relationships in GIS insulators: theory and experimental verification

Partial discharge (PD) testing is commonly used as a quality control measure for epoxy insulators in gas-insulated switchgear (GIS). Occasional inservice failures have indicated that improvements to the technology should be considered. Recent theoretical developments have provided a means of assessing the detectability of partial discharges in such insulators. The theory also provides a model which can be used to relate the characteristics of voids within insulators with the measured signal and the inception/extinction voltages. The authors describe measurements which provide the experimental evidence in support of the theory. Application of the theory results in more stringent PD acceptance criteria for higher voltage class insulators