Development of severity index in medium voltage underground cable using partial discharge mapping

Partial discharge is the main cause of cable failures. It is the responsibility of the utility company to ensure continuous supply of electricity to its customers. Hence, partial discharge needs to be detected and identified before it leads to supply interruptions due to cable insulation failure. In this work, PD diagnostic was carried out using the oscillating wave test system (OWTS). The measurement results together with the cable history data were then used to determine an index known as the severity index which can correctly characterise the cable health. Tests were carried out on 20 underground cables in the Temerloh region. Both crosslinked polyethylene (XLPE) and paper insulated lead cable (PILC) types of cable insulation were studied. By using the severity index classification of cable diagnosis, the electric utility can enhance the reliability of its distribution system by carrying out appropriate repair actions, and hence can save cost and reduce the number of forced outages.