Improved carrier mobility dependent surface charge am flashover voltage of polypropylene film under DC and pulse voltages

The surface charges that accumulate on polypropylene (PP) film can induce electrical field distortion and surface flashover, which accelerate the electrical aging of a capacitor. This paper investigated the effect of combined voltage on the surface charge behaviors and flashover voltage and a modification method to inhibit the accumulation of surface charge. The carrier mobility in different conditions was calculated using a surface potential decay process to analyze the transportation of surface charges. Samples that were fluorinated for 15, 30, 45 and 60 min and unfluorinated samples were prepared prior to experiments. The samples were corona charged with a pair of needle-plate electrodes by DC voltage and a combination of DC voltage and pulse voltage. The flashover experiments were performed under DC voltage, pulse voltage and superimposed voltage in atmospheric air. The results indicate that the maximum carrier mobility and maximum flashover voltage can be obtained when the samples are surface modified for 45 min. The surface charge density decreases with an increase in the carrier mobility under DC voltage. Under a combination of DC voltage and pulse voltage, the initial surface charge density is influenced by both the carrier mobility and the pulse voltage. The results suggest that surface modification for a certain time can significantly inhibit the surface charge accumulation, improve the carrier mobility and increase the flashover voltage.