Effects of Charging/Discharging Cycles on Breakdown Characteristics of Polypropylene Film

摘要

With the high-speed development of smart grid and microgrid in China, high energy density capacitor (HEDC) becomes one of the most important storage components in the electrical system, in which the dielectric reliability of polypropylene (PP) film is a critical factor affecting the operating reliability. During the lifetime of PP, it is generally known that charging/discharging cycles can increase the ageing occurrence, even the breakdown. In this paper, the charging/discharging experiments were conducted based on polarization and depolarization current method, and the breakdown experiments were constructed with different electric-field patterns and electrode spaces. After the charging/discharging experiments, the breakdown voltage and breakdown currents were measured. The images of breakdown craters were captured through applying a monocular-video-zoom microscope, and then quantitatively characterized by using an image-pattern-identification technique to obtain the breakdown characteristics of PP films. The results obtained show that both charging/discharging cycles and electric-field patterns have significant influence on the breakdown characteristics of PP films. With increasing the electrode space and uniformity of electric field, the breakdown voltage, breakdown energy and breakdown degree all show the increasing tendency. While with the increase in the charging/discharging cycles, the breakdown voltage, breakdown energy and breakdown degree show the decreasing tendency.