交流500kV复合绝缘子内部缺陷对轴向电场分布的影响

复合绝缘子的芯棒和护套间的胶接界面贯通于绝缘子两端,是内绝缘的组成部分。一旦芯棒和护套粘接不紧密,在界面形成的间隙将畸变周围电场分布,高场强的长期作用将对芯棒机械性能造成影响。为了研究界面缺陷对电场分布的影响,以南方电网某交流500kV线路复合绝缘子断裂事故为研究对象,应用有限元分析软件ANSYS建立了该断裂复合绝缘子的整体模型和子模型,计算了芯棒表面存在缺陷时的电场分布。结果表明:气隙处电场强度增大,但不足以引发局部放电。水分渗入后,缺陷尺寸足够大时电场强度将会超过空气的击穿场强,导致局部放电,进一步加速界面粘接性的劣化;护套破损后内部芯棒暴露,芯棒蚀损使得机械性能降低,最终将引发断裂掉串。

Internal Defects Influence of 500kV AC Composite Insulator on the Electric Field Distribution Along the Axis

The bonding interface between the rod and the sheath of composite insulators,which through both ends of the insulator is an integral part of the inner insulation.If the bonding of the composite insulators’ rod and sheath is not closely,the air gap between the rod and sheath will affect the electric field,and the mechanical properties of the rod will be reduced in the high intensity electric fields for a long time.On the basis of a rupture accidents of a 500 kV AC composite insulator,in order to calculate the distribution of electric field,we established a overall model and a sub-model by using the ANSYS code,and analyzed the influence of air gap.The simulation results show that the electric field around the air gap increases remarkably but is not high enough to cause partial discharge.Water can infiltrate into the gap,and strength of the electric field around the gap is higher than that of the air breakdown field,causing partial discharge and reducing the adhesion of the interface.When mandrel is exposed after the shealth being damaged,erosion can influence its mechanical properties,and finally cause breakage.