复合绝缘子沿面电场影响因素分析

Analysis on Influencing Factors of Surface Electrical Field of Composite Insulator

研究不同状态下的绝缘子表面电场特征对提高绝缘子可靠性具有重要意义。笔者以220 kV交流复合绝缘子为例,借助于COMSOL有限元软件,对电场分布进行了计算分析,研究了均压环、表面污秽及内部缺陷对绝缘子沿面电场分布的影响。计算结果表明:加装均压环可以大大降低沿面最大电场强度,有效改善表面电场不均匀程度;污秽条件下,伞群和护套交接处电场畸变严重,但畸变程度不足以引发局部放电;粘结面存在空气隙时,气隙附近电场明显畸变,护套内外存在一个较大的电场梯度,当达到一定程度时会造成护套击穿。

To enhance insulator reliability, a model of 220 kV AC composite insulator simulate the surface electrical field of the composite insulator. The influences of grading is established to ring, surface filth and internal defect on electrical field distribution are analyzed with the software COMSOL. The results reveal that： （1）grading ring can lower the maximum surface electrical field greatly, and improve the nonuniformity of surface electric field effectively; （2）when the insulator is covered with filth, the electrical field at the junction of the umbrella and the sheath distorts seriously, but the distortion degree is not enough to cause partial discharge; and （3）internal defect in the insulator results in clear destortion of electrical field around it, and a large electric field gradient exists on the sheath, which will cause sheath breakdown when the gradient reaches a certain degree.