GIS insulation co-ordination: on-site tests and dielectric diagnostic techniques. A utility point of view

This paper summarizes the Electricite de France experience with insulation co-ordination of GIs. After a review of the insulation co-ordination practice mainly dealing with fast front overvoltage and the one minute AC test, some results of the on-site test procedure applied since 30 years are presented and related to the insulation co-ordination practice. The in-service return of experience dealing with dielectric failures is analyzed then the dielectric diagnostic techniques now available are briefly presented with their possibilities and limitations. According to this survey, the expectations of EDF from these diagnostic techniques as well as the new on-site test and on-line monitoring tendencies at EDF are presented.