Research on the Insulation Failure Mechanism at the Interface between Sheath and Core Rod of Composite Insulators
Zhang Yuming1, Geng Jianghai1, Hou Sizu2, He Zhongfeng1, Liu Yunpeng1
1. Hebei Key Laboratory of Power Transmission Equipment Security Defense North China Electric Power University Baoding 071003 China; 2. Hebei Key Laboratory of Power Internet of Things Technology North China Electric Power University Baoding 071003 China
Abstract：Composite insulators are widely used in China's overhead transmission lines, playing a significant role in addressing the issues of flashover caused by pollution and ensuring the safe operation of the power grid. At the same time, challenges arise in the operation of composite insulators, including service lives shorter than expected, high replacement costs, and frequent faults due to abnormal heating and string failure in high-humidity and high-temperature areas, which pose severe threats to the safe and stable operation of the power system. The interface region, being a vulnerable link in the composite insulator system of high temperature vulcanized silicone rubber (HTV) sheath and fiberglass reinforced plastic (FRP) core rod, is prone to initial defects that trigger insulation damage. Therefore, it is necessary to study the changes in the interface condition and its effect on interface insulation during the failure evolution process of the insulator. This paper establishes a numerical contact model for the HTV-FRP composite insulator interface and analyzes the impact of different failure levels and the dielectric environment within different cavities on the electric field distribution at the interface. A short test sample of the composite insulator, suitable for partial discharge and breakdown characteristic testing at the interface, was designed and fabricated. Different interface failure levels were obtained through wet-heat accelerated aging, and the influence of interface failure on partial discharge and breakdown characteristics was tested and analyzed. Finally, phase-field simulations were conducted to model the evolution of HTV-FRP interface insulation damage, and interface discharge degradation experiments were carried out to validate the phase-field simulation results. The research results show that with the increase in the cavity size at the HTV-FRP interface, the distortion of the electric field at the interface gradually intensifies. The moisture inside the cavity and the carbonization of the inner surface materials exacerbate the electric field distortion. As the cavity size at the HTV-FRP interface increases, the electric field distortion intensifies, and the discharge amplitude at the interface increases. This leads to a higher probability of initial electron generation, thereby increasing the likelihood of discharge channel formation. This phenomenon is manifested as a decrease in the initiation voltage for partial discharge in the cavity. At the same external voltage, larger cavities exhibit more intense discharges, and the breakdown voltage of the HTV-FRP interface continually decreases. Continuous cavity discharge at the interface forms conductive paths, facilitating breakdown. The presence of moisture influences the amplitude and phase distribution of partial discharge. In extreme cases, the HTV-FRP interface undergoes an insulation failure evolution process from initial cavity partial discharge to overall interface breakdown under electrical stress, and the wet-heat environment accelerates this process. In summary, the axial insulation failure of the composite insulator HTV-FRP interface can be divided into three stages based on its development sequence and characteristics: corona discharge within the cavity, contact point insulation failure, and rapid development of the electroerosion discharge channel. During this process, the bonding performance of the HTV-FRP interface and the HTV sheath's ability to prevent moisture intrusion become key factors restricting the long-term safe operation of composite insulators. The conclusions of this study provide a foundation and basis for further research on the degradation mechanisms of composite insulators and improving their long-term operational reliability.
张育铭, 耿江海, 侯思祖, 何中峰, 刘云鹏. 复合绝缘子护套和芯棒交界面绝缘失效机制研究[J]. 电工技术学报, 2026, 41(5): 1738-1752.
Zhang Yuming, Geng Jianghai, Hou Sizu, He Zhongfeng, Liu Yunpeng. Research on the Insulation Failure Mechanism at the Interface between Sheath and Core Rod of Composite Insulators. Transactions of China Electrotechnical Society, 2026, 41(5): 1738-1752.
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2026, Vol. 41 
