Changes in PD pattern and PD current shape for a void in LDPE

Partial Discharge is closely related to the degradation of insulating materials and the lifetime of high-voltage power apparatus and cables. Therefore, it is important to understand the PD behaviors in the aging process. In this paper, partial discharges and their current shapes of low-density polyethylene (LDPE) with a disc shaped void were measured. This measurement was achieved by the time-resolved method based on a fast digital signal processing technique. The PD current shape and PD magnitude give us information about the mechanisms of PD. Not only the parameters of current shape, for examples, pulse height, pulse width, rise time and kurtosis were calculated, but also the power spectra of PD pulse were analyzed by the software developed for this experiment. Especially, several parameters such as frequency peak were proposed as new pulse shape parameters. These PD parameters changed with aging. Such changes in PD characteristics will be applicable to the insulation diagnosis