Degradation of polypropylene films in metallized film capacitors under repetitive intense pulsed electric fields

Abstract Repetitive microsecond pulsed electric fields impose severe challenges on the reliability of metallized polypropylene (PP) film capacitors. However, the degradation mechanism of PP films under this condition and the influence on capacitor performance remain insufficiently clarified. In this paper, the degradation behavior of PP films under prolonged intense pulsed electric fields is investigated. A quantitative capacitance loss evaluation method based on image processing is proposed for metallized PP films. The results show that high field pulsed stressing induces oxygen-containing groups and unsaturated structures, weakens the carrier trapping effect of deep traps, and enhances carrier transport. The discharged energy density decreases by up to 67.7%, accompanied by reduced charge–discharge efficiency. For metallized films, PP film degradation promotes local breakdown and self-healing events, while more energetic self-healing discharges under higher fields further aggravate electrode clearing. This coupled degradation process leads to a maximum capacitance loss of 12.31%. This study clarifies the degradation chain from PP film structural deterioration and carrier transport enhancement to capacitance loss, providing a basis for reliability evaluation of metallized film capacitors under repetitive microsecond pulsed electric fields.