Partial discharge patterns and their temporal change in polyethylene and polyimide. Effects of sample condition, chemical structure and gap atmosphere

Recently, many researchers tried to utilize partial discharge (PD) /spl phi/-q-n patterns for degradation diagnosis. The PD pattern is affected not only by the state of degradation but also by many other factors such as the sample condition, the gas constituent in the gap, and so on. Therefore, the precise knowledge of PD patterns and the mechanisms behind is necessary to implement accurate degradation diagnosis by PD pattern recognition. By using a computer-aided PD measurement system, we measured temporal change of partial discharge (PD) pattern of low-density polyethylene (PE) and polyimide (PI) films up to breakdown. Effects of chemical structure and condition of the samples as well as the gap atmosphere were studied. Effects of frequency acceleration on the PD pattern is also discussed.