Accelerated corona discharge performance of polymer compounds used in high voltage outdoor insulators

The results of a study aimed at evaluating the performance of several polymer compounds when exposed to low magnitude electrical discharges (corona) and high humidity levels are presented in this paper. Three different high temperature vulcanizing (HTV) silicone rubber (SiR) formulations were evaluated in a corona test cell. The magnitude and frequency of the corona discharges and the current flowing through the samples volume were recorded. The physical and chemical changes occurring on the compounds were monitored visually and by means of Fourier Transform Infrared (FTIR) spectroscopy. The results obtained from this study demonstrate that some HTV-SiR formulations used in high voltage outdoor insulation as housing materials may suffer from significant degradation even under the effect of relatively low magnitude corona discharges. On HTV-SiR compounds, such degradation process seems to be the moisture absorption characteristic of the polymer. These findings emphasize the importance of minimizing the occurrence of corona on non-ceramic insulators particularly when operating in outdoor environments.