Charge Transport Model of Oil-Pressboard Composite Insulation Structure Considering Interface Barrier and Ion Migration

Charge accumulation at the interface of oil-pressboard insulation in converter transformers increases the risk of insulation failure. Current models overlook pressboard and oil individual characteristics and neglect heterojunction effects at the pressboard-oil interface in insulation. To address these issues, this article proposes a simulation model that combines the bipolar carrier model and the ion migration model to simulate the charge transport processes in insulating pressboard and transformer oil. The model takes into account the specific characteristics of each material within the composite insulation structure. Additionally, an interface charge transport model, based on the contact state of interface, has been developed to specifically address the oil-pressboard interface. The model accurately simulates the charge distribution within the oil-pressboard composite insulation structure. In terms of charge density distribution, the maximum deviation from the experimental data measured by the pulsed electroacoustic (PEA)-Kerr composite method is 11.21%. For the calculation of charge accumulation at the interface, the maximum error compared to the measured values is only 7.1%. We also utilize this model to provide a detailed explanation of the charge transport and accumulation behaviors at the microscopic level, revealing the underlying charge transport mechanisms in the oil-pressboard composite structure. These findings offer insights into the charge accumulation behavior within such insulation systems.