State of the Art in GIS PD Diagnostics

This paper presents the state of the art in GIS PD diagnostics. The guidelines for a risk assessment procedure on defects in GIS based on PD measurements are described. The procedure starts with sensitive PD measurements to detect critical defects and follows with an identification of the type of the defect and its location inside the GIS. This information, combined with other essential data from the manufacturer's experience and a trend analysis of the PD activity, is the base for the estimation of the criticality of the defects. Finally, the risk assessment is performed based on the estimated dielectric failure probability and failure consequences. To detect and eliminate critical insulation defects, PD monitoring systems are applied. The ultra-high frequency measurement method is used worldwide by GIS manufacturers during routine testing in the factory, during on-site commissioning and by utilities for continuous in-service monitoring.