Comparative Analysis of the Conductivity Model and Charge Transport Model for Simulating Space Charge Characteristics of Transformer Oil-Impregnated Paper

Space charge accumulation in the transformer oil-impregnated paper results in the distortion of the electric field, which may lead to accelerated ageing of the material due to partial discharges. The core inner mechanism of charge transport and space charge accumulation and their effects on the electric field distortion are not clearly explained in the relevant papers reported in the literature. In this article, the conductivity and the bipolar charge transport (BCT) models are simulated using the finite element method for calculating the distribution of space charge and electric field in the insulating paper. Also, the results obtained from both models are correlated with the established experimental results. The effect of thermal transients on the field and space charge distribution is also studied, indicating that higher temperature results in an increased breakdown probability of the insulation. The physical processes, such as charge injection, migration, and recombination, are discussed along with the charge distribution. The results obtained from the BCT model seem to be more realistic. Finally, the limitations, advantages, and applicability of both models are discussed. This study will be helpful in the design and analysis of the insulation system with oil-impregnated paper and provide an advertencefor the simulation of space charge dynamics with optimised parameters.