Space Charge Simulation Model for Bilayer Oil-Impregnated Paper Insulation Based on Multiple Discrete Trap Energy Levels

Space charge-induced electric field distortion seriously threatens dielectric insulation properties. However, there are fewer simulation studies on the interfacial charge of the same dielectric structure, such as bilayer oil-impregnated paper. In this article, based on the bipolar carrier transport model, a multiple discrete trap energy levels carrier transport model is proposed to simulate the space charge distribution of the bilayer oil-impregnated paper structure, taking the fast charge migration process into account. The results show that the maximum error of charge distribution under positive and negative polarity applied voltage is about 7.42% and 3.93%, respectively, and the simulation results are in good agreement with the experimental results. The effect of relaxation polarization on the polarization current is analyzed, and the polarization current simulation values considering relaxation polarization agree well with the experimental values, with a maximum error of about 7.3%. We find that the fast charge migration process is the root cause and the main source of the interfacial charge accumulation of the same medium. The introduction of the fast migration process ensures that the polarity of the interfacial charge accumulation is the same as that of the semi-conducting electrode, and the interfacial charge peaks all have a tendency to shift from the semi-conducting electrode side to the metal electrode side. The study in this article can provide a mechanism explanation for characterizing the migration mechanism of bilayer oil-impregnated paper structure and the origin of interfacial charge accumulation.