Influence of temperature on polarization and depolarization current of oil-paper insulation

Temperature is one of the most crucial factors that influence the field measurement results of dielectric response methods. The distribution of moisture between oil and paper in a transformer insulation system is also highly temperature dependent. This research tests were carried out in a home-made oil/paper insulation system, which made it possible to regulate and control the temperature and humidity. Polarization and depolarization current of oil/paper samples with different moisture content are measured at different temperature. Research results show that both polarization and depolarization current increase with temperature. An inflection point appears in the depolarization current when moisture content is lower, and the time of inflection point shifts to lower with temperature increased. A master curve can be formed by shifting the polarization and depolarization current at different temperature when water content is lower, and the influence of temperature can be eliminated in this way. However, this is not feasible when moisture content is higher. Both time-shift factor and amplitude-shift factor meets the Arrhenius equation, and the activation energy of oil paper samples solved by these factors are almost the same.