Quantitative relationship between aging condition of transformer oil-paper insulation and large time constant of extend Debye model

Since how to quantify the aging condition of transformer oil-paper insulation by PDC(Polarization and Depolarization Current) method needs further research, several oil-paper insulation specimens with different aging conditions and different moisture contents are prepared by a series of accelerated thermal aging and moisture absorption experiments, and their PDC diagrams are measured. The extended Debye model is adopted to fit the PDC diagram and the model parameters are obtained. The influence of oil-paper aging on the model parameters is studied, and the time-domain dielectric characteristic parameter, i.e. the large time constant of extend Debye model is proposed to quantify the aging condition of transformer pressboards. Results of research show that, there is better exponential relationship between the large time constant of extend Debye model and DP(Degree of Polymerization) and the large time constant is immune to the insulation size.