Measurement and simulation of partial discharge in oil impregnated pressboard with an electrical aging process

The continuous test on oil impregnated pressboard insulation with internal void defect was developed and the phase resolved partial discharge (PRPD) pattern of partial discharge (PD) signals during the electrical aging process was measured. Two different void structures which have different void volume were used in this experiment. It shows that the PD pattern could be classified into five stages and a great diversity in the first four stages is observed. The larger void volume leads to larger PD magnitude. The computer numerical simulation model which is based on a physical discharge process was used and the causes of PD pattern change were interpreted by comparison with computer numerical simulation results. The initial values and change tendency of gas pressure and surface conductivity were determined through experiment. The model parameters in different stages have been studied as well as the insight into the physical changes in the void during electrical aging. The results provide rules for the identification of the electrical aging stage through the partial discharge measurements.