PD-pattern of defects in XLPE cable insulation at different test voltage shapes

There is a growing interest in onsite PD measurement of XLPE-insulated medium voltage cable systems. Due to the high capacitive load, these cable systems are voltage tested using either resonant circuits or very low frequency (VLF) generators with sine or cosine-rectangular voltage shape. The aspect of PD behaviour at such voltages is investigated, PD measurements on XLPE test samples are presented at test voltages with variable voltage shape and frequency. The main focus is on voids in XLPE as a typical defect, PD fingerprint as well as PD pulse rates are considered.