复合绝缘子界面缺陷对电场分布特性影响的仿真研究

Influence of interface defect on the electric field distribution of composite insulator

复合绝缘子的芯棒与护套粘接界面常常出现缺陷,畸变周围电场,影响绝缘子的电气和机械性能。为了研究不同缺陷形态下的绝缘子电场特性,文中以110kV复合绝缘子为考察对象,应用有限元分析软件COMSOL搭建了绝缘子三维模型,对电场分布进行了仿真计算,研究了界面出现气隙、水汽等缺陷对局部电场及绝缘子整体轴向电场分布特性的影响。结果表明:气隙处电场强度相比正常情况下显著增大,场强最大值与气隙跨度、厚度正相关,与气隙长度负相关,并基于气隙等效弧柱体模型给出了理论分析,修正了等效圆柱模型的不足;水分渗入能降低气隙场强,但同时严重畸变绝缘子轴向电场;护套受潮增重会使场强线性增加,超过一定程度会引发电晕放电,导致沿面闪络等事故。

Interface defect can be commonly found between the rod and the sheath of the composite insulator. The defect will distort the electric field nearby, which have a bad effect on the electricaland mechanical properties of the insulator.In order to study the electric field distributionof insulators under different fault conditions, a 3-D model of AC 110 kV composite insulator is established using the finite element analysis software COMSOL. The influences of the interface gap filled with air or water on the internal and the axial electric field distribution of the insulator are discussed. The results show that the electric field magnitude at the air gap increases significantly compared with the normal case. The maximum value of field is correlated positively with the gap span and thickness, and negatively with the gap length. Theoretical analysis based on the air gap equivalent arc cylinder model is given, and the deficiency of the equivalent cylinder model is corrected. Water permeation reduces the air gap field magnitude, meanwhile severely distorts axial electric field of the insulator. The field magnitude goes up linearly as the sheath damps, which may lead to corona discharge, causing flashover and other accidents, when the damping reaches a certain degree.