Effect of ambient temperature on electrical treeing and breakdown phenomenon of polypropylene with repetitive pulse voltage

In this paper, the treeing characteristics and breakdown phenomenon of polypropylene (PP) considering different temperatures with repetitive pulse voltage were investigated. The temperature varied from 50 to 130°C. The pulse amplitude ranging from 15 to 19 kV was applied. The tree initiation probability increases with the increase of temperature and the applied pulse amplitude. With the temperature increasing from 50 to 110°C, the growth rate of electrical trees increases, while it is the slowest at 130°C, which is explained by the differential scanning calorimetry (DSC) analysis result. Meanwhile, the growth rate and fractal dimension of electrical trees increase with the increase of pulse amplitude at the same temperature. It is found with the temperature increasing from 50 to 110°C, the fractal dimension of breakdown electrical trees increases, while it is smaller at 130°C than that at 110°C. The accumulated damage of breakdown electrical trees is independent with temperature. By using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX), agglomerated and dispersed particles which contain carbon and oxygen elements are observed in the breakdown channels. The chemical analyses of the breakdown channels by attenuated total reflection infrared (ATR-IR) spectrum show that it contains C=O and C-O groups.