Ageing of polymers studied by spectral analysis of UWB partial discharge signals

Abstract

UWB measurements of partial discharges can be used for an assessment of the deterioration process of dielectrics. It has been shown that the degradation process in voids due to partial discharges (PD) proceeds in three consecutive stages. Test results on samples with artificially introduced voids, as well as tests on complete high voltage components like post insulators are presented to show the applicability of this method. A comparison is made between results obtained by analysis of the time signal and results obtained by analysis of the frequency content of the PD pulses, In real high voltage components the pulse shape of the discharge is distorted due to the bad UWB properties of most components. It is shown that spectral analysis of the PD signal is to be preferred when it comes to the analysis of the progression of ageing of complete high voltage components.