Experiences with commissioning testing of HV & EHV cable systems: The influence of voltage level and duration for identifying life limiting defects

Over the last decade and a half, thousands of kilometres of installed XLPE HV and EHV cable systems have been subjected to after-laying commissioning testing prior to energization. The commissioning test usually consists of a combination of AC HiPot & Partial Discharge (PD) testing. PD testing, in particular, has gained acceptance as a valid diagnostic tool for condition assessment of cable insulation. It is well known and understood that the results obtained from a partial discharge test depend not only on the conditions under which the test was performed but also on the test equipment itself including the type of sensor used and its location. Relying on experienced gained with AC Withstand and PD commissioning testing of more than 2,100 km of HV & EHV cable systems the paper examines the influence of voltage source and withstand duration of the withstand test for successfully identifying life limiting defects in newly laid HV & EHV Cable systems both in terms of breakdown and also in terms of detection of partial discharge sources from the same defects. The paper further provides statistical summary of tests performed on more than 2100 km of HV and EHV cable systems including failure rates of accessories and PD occurrence rates. The paper also provides several case studies of PD detected in cable accessories during AC HiPot commissioning testing.