Study on DC Surface Flashover at the Clear Edge of Metallized Polypropylene Films

The surface flashover may occur at the clear edge of metallized films, affecting the insulation performance of metallized film capacitors (MFCs). In this article, an experimental setup was established to investigate the dc surface flashover characteristics of the metallized polypropylene film for MFCs. The effects of voltage setting, parallel capacitance, interlayer pressure, experiment temperature, and clear edge width on the flashover characteristics of metallized films were studied experimentally. The results reveal that, different voltage setting methods affect the surface flashover voltage, with a relatively stable disparity of 14.03%; parallel capacitance has little effect on the flashover characteristics in the range of 0–60
$\mu \text{F}$
; the surface flashover voltage and field strength are positively correlated with the interlayer pressure in the range of 50–800 kPa, and negatively correlated with the experiment temperature in the range of 30 °C–90 °C; as the clear edge width of the metallized film increases from 0.5 to 2.5 mm, the flashover field strength substantially decreases by 49.39% and gradually slows down to saturation. In terms of clear edge design, the width should be determined by the surface flashover voltage under the second voltage setting method; the effect of parallel capacitance on surface flashover can be ignored; measures should be taken to increase the interlayer pressure of outer films, such as increasing the turns of wrapped film outside; the clear edge width should be increased for MFCs operating at high temperature and can be selected according to the experimental data in this article.