界面电荷注入与积聚行为对直流GIS/GIL绝缘子沿面电场的影响分析

Analysis on Influence of Interface Charge Injection and Accumulation Behavior on Surface Electric Field Distribution of DC GIS/GIL Insulating Spacer

气体绝缘组合电器(gas insulated switchgear,GIS)和气体绝缘金属封闭输电线路(gas insulated metalenclosed transmission line,GIL)运行电流大,设备内部存在明显的温度梯度分布,造成高压电极附近电荷的注入与迁移加剧,导致绝缘子内空间及表面电荷的积聚,畸变电场,容易诱发沿面闪络故障。为此文中建立了电—热耦合应力下直流盆式绝缘子内的电荷注入与积聚模型,研究了考虑电荷注入和迁移特性的绝缘子空间电荷及表面电荷积聚情况,并分析了不同负载电流下绝缘子沿面电场分布规律。研究结果表明:温度梯度下,导体—绝缘界面电荷注入会造成绝缘子内部同极性空间电荷的积聚,并且空间电荷积聚密度会随着负载电流的增大而增大;空间电荷的积聚会减弱高压电极附近电场强度,增强绝缘子凸侧表面法向电场强度,加剧表面电荷的积聚;空间及表面电荷的积聚会使绝缘子表面电势上升,导致接地电极附近电势差增大,电场强度显著增大,地电极三结合点处的场强由空载条件下的1.71 kV/mm增长为额定电流作用下的3.47 kV/mm,增加了103%。该研究结果有助于理解温度梯度下直流绝缘子表面电场畸变机理,并对直流绝缘子的优化设计和安全运行有一定的参考价值。

Gas insulated switchgear(GIS)and gas insulated metal-enclosed transmission line(GIL)have large operating currentand obvious temperature gradient distribution inside the equipment,intensifying thecharge injection and the migration near high voltage electrode,causing the charge accumulation in the space and surface of insulator,distorting the electric fieldandeasily inducing flashover along the surface.To this end,a charge injection and accumulation model in a DC insulating spacer under electrical-thermal coupling stress is set up,the space charge and surface charge accumulation of the insulator considering the charge injection and migration characteristics is considered and the surface electric field distribution of the insulator under different load currents is analyzed.The research results show that under temperature gradients,charge injection at the conductor-insulation interface will cause the accumulation of space charges of the same polarity inside the spacer,and the accumulation density of space charges will increase with the increase of load current.The accumulation of space charges can weaken the electric field intensity near the high-voltage electrode,enhance the normal electric field intensity on the convex side of the spacer and intensify the accumulation of surface charges.The accumulation of space and surface charges increases the surface potential of the spacer,resulting in an increase of the potential difference near the ground electrodeand a significant increase in electric field strength.The field strength at the three junctions of the ground electrode is increased 103%,namely from 1.71 kV/mm at no-load conditions to 3.47 kV/mm under the action of rated current.The research results are helpful to understand the mechanism of surface electric field distortion of DC insulating spacer under temperature gradientand have certain reference for the optimal design and safe operation of DC insulating spacer.