Pulse waveform, phase-resolved and pulse sequence analysis of partial discharges during electrical tree growth in epoxy resin

Summary

Electrical trees are one of the main mechanisms of degradation and failure in high voltage polymeric insulation. Their growth is associated to partial discharge (PD) activity, and thus, the stage of progression of electrical trees could be inferred from the PD behaviour. Conventionally, Phase-Resolved PD Analysis (PRPD) is carried out to study PD behaviour. In this paper, Pulse Sequence Analysis (PSA) patterns and the PD pulse waveform during electrical tree growth are analysed alongside the conventional approach (PRPD). Electrical trees in epoxy resin were conventionally grown in the laboratory and the PD activity recorded during the entire experiment. PD were measured using traditional wide-band detection to acquire the train of PD pulses, and High-Frequency Current Transformer (HFCT) to capture the pulse waveform. In addition, the electrical tree growth was monitored using an optical camera, to correlate the tree progression with the PD behaviour. The results showed that the PD behaviour changed after the tree bridges the insulation: PD amplitude stopped increasing and PSA plots showed a characteristic 45º line with the points. The frequency content of the current pulse waveform was similar amongst the stages of tree growth analysed. PRPD and PSA were sensitive to disclose when the tree reached the counter electrode. More research is needed to generalise the findings and use them for a more effective condition assessment of insulation systems affected by electrical trees.

Additional informations

Authors

SILVA, HIPPLER, DE ARAUJO NASCIMENTO, DA SILVA FILHO

Keywords

Electrical trees, partial discharges, PD, pulse waveform, pulse sequence