Effect of additives on the electrical aging of impregnatedpolypropylene films

摘要

In relation to the aging of power capacitors, the authors studynthe degradation of polypropylene (PP) films impregnated with an aromaticnliquid at high AC electric fields. An investigation at 135 V_rmsnμm^-1, 80° C, and with O₂-saturatednbenzyltoluene as impregnant has been conducted. By measuring thenthreshold voltage for discharge detection in a capacitor model thenauthors have verified that the aging field was about 75% lower than thendischarge threshold. In these conditions the model lifetime is reducednto about 200 hr. PP degradation has been evaluated based on filmnbreakdown voltage and Fourier-transform infrared microspectrometrynresults. Various additives to the liquid have been tested in order tondetermine the degradation mechanism. Without any detected discharges, anlarge degradation under AC high electric fields is observed. Thendecrease of breakdown voltage is more than 25%. Oxygen increases thendegradation kinetics, but the main degradation factor is the highnelectric field