Numerical research on space charge behavior in composite insulation under electro-thermal coupled stress

Insulation failure due to interfacial charge buildup under high-frequency electro-thermal coupling stress has emerged as a critical limitation in the design of composite insulation systems. This research presents a novel numerical model tailored for space charge in composite insulation under high-frequency stress. A Gaussian-like interfacial trap distribution that takes into account surface state effects is introduced as a setup for interfacial transition states. Meanwhile, descriptive equations adapted to high-frequency characteristics are presented concerning injection, migration, and polarization environment, respectively. The dynamic behavior of space charge in PI/EP composite insulation and the resultant electric field distortion under varying polarization circumstances are examined. The results indicate that the level of interfacial charge buildup exhibits a positive correlation with both the field intensity and the frequency. The polarity of charge buildup at the interface differs under uni/bipolar stress. This also results in a distribution of the distortion field intensity related to the stress polarity. In addition, the main source of interfacial charge is the positive and negative ions from impurity dissolution in high-frequency condition. The interfacial charge buildup determines the extent of electric field distortion in the composite insulation. The related work is anticipated to offer assistance in elucidating the insulation failure process in high-frequency conditions.