Study on the time domain dielectric properties of oil-impregnated paper with non-uniform aging based on the modified Debye model

Temperature gradient inside oil-immersed transformers will cause non-uniform aging of the paper. In order to simulate non-uniform aging process of oil-immersed paper, a test platform is established in laboratory. We measured polarization/depolarization currents of test samples. Finally we identified its equivalent model parameters. The results indicate that: Polarization/depolarization currents of insulation paper near heat source move to the top left with higher conductivity and higher polarization response speed. Polarization resistance and time constant in isothermal zone near heat source has minimum value and parameters exists relation between extended Debye model and modified Debye model. Extended Debye model can only assess average aging condition of insulation paper. It will appear aging overvalued area and aging undervalued area when using extended Debye model for paper condition assessment with up nearly 50% deviation.