Study on Electrical Properties of Epoxy/Paper Composites Under Thermal and Electrothermal Aging

Epoxy/paper composites are critical materials in drytype bushings for Ultra-High Voltage Direct Current (UHVDC) systems. Understanding the aging behavior of epoxy/paper composites under combined electrical and thermal stresses is crucial for ensuring the reliable operation of insulation systems. The study investigates the changes in dielectric properties and space charge distribution in epoxy/paper composites subjected to both thermal aging and electrothermal aging. The results show that both aging conditions lead to significant degradation in the electrical properties, but electrothermal aging causes more pronounced effects. Specifically, the relative permittivity initially decreases in thermal aging due to the decomposition of residual curing agents, but it increases as the material undergoes further aging. In electrothermal aging, the relative permittivity increases immediately due to the combined effects of thermal and electrical stresses, leading to structural damage and more pronounced interfacial polarization. Additionally, space charge accumulation is higher in electrothermal aging compared to thermal aging, as the electric field concentrates stress at internal interfaces, accelerating material degradation. These findings provide valuable insights into the aging mechanisms of epoxy/paper composites, highlighting the need to consider both electrical and thermal stresses in the design and operation of high-voltage equipment.