Study and characterization of PD in impregnated polypropylene capacitors

Measurements of partial discharge (PD) in models of impregnated polypropyle ne capacitors with and without specific defects have been conducted. Two di fferent regimes of discharges (in the liquid and in gas bubbles) are illust rated. The effect of temperature on the decrease of the insulation property is underlined. Four specific defects have been artificially introduced in the test cell (poor impregnation, bad contact, fold in the polypropylene (P P) film, cavity). The relevance of parameters such as skewness and kurtosis to characterize PD distributions is discussed. New parameters based upon t he mean position of the PD in the voltage phase are proposed for a better r ecognition of the defects inducing PD.