Partial Discharge Characteristics of a Defective MV XLPE Cable

This paper presents the partial discharge (PD) test on a 22 kV underground cable having a simulated defect within the XLPE insulation. The defects were simulated using the nail, as the drill bits with a different drill diameter. The defect was created into the XLPE insulation layers of the underground cable. Besides, both end sides of the cable were electric field controlled. To simulate the defects for the experiment, the jacket in the middle of the cable was partially trimmed out, and the drill bits was driven through the insulation screen to the insulation layer. The diameter of the drill bits was controlled for each experiment. The PD experiment was conducted using high frequency current transformer (HFCT) sensor as an unconventional PD detection instrument. From analyzing the PD test results, a defect in the XLPE insulation causes vividly the PD inside the XLPE insulation. Consequently, the insulation gradually deteriorates undergoing the PD events. Moreover, the PD test results indicate that the larger diameter of the nail tip radius results in a higher PD magnitude than that generated by a smaller diameter.