Dielectric Testing of GIS

Currently the main use of GIS technology for power distribution systems is for compact substation equipment. In addition, in terms of performance the GIS shall have an expected service life up to more than 40 years and target failure rates for insulation coordination less than 0.1 failures per 100 bay years.

To maintain such a high quality standard as well as long lifecycles, intensive development tests, routine tests and on-site commissioning tests are required. Moreover, the monitoring of the insulation in service may help to avoid unforeseen major dielectric failures. Therefore, different HV dielectric test procedures like power frequency (50/60 Hz) tests or tests with variable frequency (10…300 Hz) are available. Common practice is to combine the HV dielectric test with complementary PD measurement techniques like conventional (30 kHz … 1 MHz), UHF (0.1 … 2 GHz) or acoustic (10 kHz … 100 kHz) ones. This paper will discuss the HV AC dielectric tests to verify the insulation co-ordination as per the design criteria as well as to verify the insulation condition during the life cycle of GIS as per the latest IEC standards including physical, technical and economical aspects.