Online condition monitoring of partial discharge in HV underground cables

Partial discharges are symptomatic of many degradation phenomena in power cables and can cause further deterioration of the insulation in many cases. The partial discharges may be detected by using online and offline techniques. However, offline techniques have a significant disadvantage in that they require the cables to be taken out of circuit. Hence, electricity supply companies prefer the use of online techniques. The downside is that online techniques have their own disadvantages e.g. interference, ambiguity of partial discharge location, and sensor optimisation difficulties. The paper provides an overview of the current state of the art in partial discharge detection and location and also suggests how some of the disadvantages of online detection and location might be overcome.