Statistical analysis of pulse parameters and diagnose of aging state based on partial discharge in paper-oil insulation

The partial discharges (PDs) in paper-oil insulation with different aging degrees show various features according to the variation in material behaviors. Hence, we established a PD measurement system with strong anti-interference capability in laboratory, prepared internal defect models of paper-oil with six different aging degrees, and measured of single PD pulses of the models in order to obtain statistical features of PD pulse parameters that can indicate the degradation level of oil-impregnated paper. The results show that, despite the obvious randomness of the PD intensity, both the rise time of PD pulses and the full width at the half maximum decrease with the increase of aging degree. This pattern can be used to determine the aging degrees of pressboards. The results can be taken as a new approach for determining the aging degree of paper-oil insulation.