Temperature-dependent surface charge behavior of polypropylene film under DC and pulse voltages

Abstract

Film capacitors are constructed with polymer films as the dielectric material, among which polypropylene (PP) has the highest breakdown strength and excellent thermal performance. Accumulation of static charge on the polymer film surface between electrode segments may induce surface discharge causing energy loss and accelerating electrical aging of insulation material in the capacitor. In the application of pulsed power systems, the capacitor faces temperature rise and multiple electrical stresses, which will influence the surface charge behavior of the polymer film. The paper is dedicated to research on the influence of temperature and different voltage waveforms on the surface charge and trap characteristics of PP film. The PP film was corona charged with needle-plate electrodes by DC voltage and combination of DC and pulse voltage, respectively, and the surface potential decay was conducted at different temperature. It is found that the rise of temperature can significantly enhance de-trapping of the surface charge in deep traps, thus accelerating the surface charge decay. Under DC voltage, the accumulation of surface charge shows no relation with temperature, while the decay is dominated by both electric field and temperature. Under multi-stress of DC and pulse voltage, however, the surface charge accumulation is influenced by temperature due to its impact on surface charge coupling. And the decay of surface charge becomes complicated with coupling process as well, in which the electrical field, trap level and density show inconsistency with the decay under different temperature.