Detecting degree of water treeing in XLPE power cable systemsusing polarisation and depolarisation current method

摘要

Insulation degradation is a major concernfor aged power cable systems. Water tree is the maincause of insulation degradation of polymer insulatedcable and is the main cause of its failure in longservice. In addition to the magnitude and voltagedependence of the dielectric response (also calleddegree of non-linearity) used to evaluate the conditionof the insulation, another method of assessing thecondition of XLPE power cable is presented in thispaper. The proposed method utilises the dischargecharacteristics of the cable. In order to convert thevalue of the proposed method into figure of merit thatgives a figure for the insulation condition, tan valuesare calculated using Fourier transformation. Amongseveral other methods for interpretation, the proposedmethod is shown to be temperature independent thatcan be used for on-site diagnosis of cable. However itsapplicability to cable diagnosis requires furtherjustification through additional research work.