Time-varying partial discharge spectral characteristics in solid polymer insulation

Partial discharges (PDs) in polymer insulation are characterised by features that change as the insulation defect ages and progresses to total failure. This study presents results of an experimental investigation into evolution of PD spectral features. Typical insulation defects in polyethylene insulation were exposed to accelerated PD-induced ageing until failure. The PD frequency spectra were measured at appropriate time intervals. The manner in which the various frequency spectra features evolved depended on the type of PD source. Applications of this knowledge include an emphasis on more diligence in the interpretation of online PD logged data. Furthermore, a PD defect recognition criterion is suggested that is based on continuous monitoring and evaluation of PD frequency spectral features.