Dielectric frequency response of oil-paper composite insulation with transient moisture distribution

Because the temperature and load of transformer are variable, the moisture is usually inhomogeneous in oil-paper, especially for the traction transformer. In order to research the dielectric relaxation behavior of the oil-paper composite insulation with an inhomogeneous moisture distribution, it was proposed that a theoretical model for dielectric medium with an arbitrary distribution of conductivity and dielectric constant. The dielectric frequency response of oil-paper with transient moisture distribution was simulated by using the proposed model. The results show that transient moisture distribution caused the concentration polarization(CP), which enhanced the low-frequency relaxation. The model is validated against experimental data.