Temperature Dependence of Surface Electrode Degradation in Metallized Film Capacitors Under High Voltage Stress

Metallized film capacitors (MFCs) are critical components in advanced energy systems. With the trends toward miniaturization and high power density, MFCs are increasingly prone to internal heat accumulation and insufficient thermal dissipation, resulting in elevated operating temperatures and degraded performance. This study employs image processing techniques to quantitatively analyze the temperature dependence of surface electrode degradation in metallized films under high voltage stress. The concept of capacitance-reducing discharge (CRD) is proposed to comprehensively interpret the mechanism of electrode degradation. CRD includes three discharge types: self-healing (SH), flashover around SH points, and margin flashover. The results show that SH is the dominant contributor to capacitance reduction. While its morphological characteristics are relatively insensitive to temperature, the number increases with temperature, and the mean area shows a peak of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$26.4 \text{mm}^{2}$</tex> at 70° C before decreasing. In addition, flashover events are also identified as significant contributors to electrode degradation. As the temperature rises, the increased frequency of such discharges leads to more severe capacitance loss in MFCs.