Investigation of PD detection on XLPE cables

The insulation lifetime of XLPE power cables is determined by several factors. One of the most important of these is the occurrences of partial discharge (PD) in the dielectric. The ability to detect and locate the PD sources is limited by attenuation and distortion of the high frequency PD pulses as they propagate through the cable. This paper presents the results of measurements of PD pulses that are generated by an artificial PD defect with capacitance-coupled sensors used for the detection of PD, rather than a high frequency current transformer (HFCT). The results show that the external capacitance sensors have a number of advantages, such as better sensitivity, for the detection of PD pulses. PD pulse waveforms were evaluated by three different integral methods in order to estimate the best way to characterise the PD pulses. The PD pulse is severely attenuated and distorted with increasing length of the power cable and the frequency of the PD pulse and some means of characterising is necessary. Simulation results are compared with test measurement results and it has been found that the cable model developed and used was able to predict the measurement results accurately.