非线性电导涂层对直流GIL绝缘子空间/表面电荷和沿面电场的调控研究

Study on regulation of space/surface charge and surface electric field ofDC GIL insulator by nonlinear conductive coating

空间/表面电荷积聚是导致直流GIL绝缘子沿面闪络电压降低的潜在原因,涂敷非线性电导涂层是提升沿面绝缘性能的有效方法。本文建立了电场依赖性非线性电导涂层对绝缘子空间/表面电荷及沿面电场调控的数学模型,综合考虑了绝缘气体电流密度以及绝缘子固体电导率与电场强度的非线性关系,通过该模型研究了温度梯度分布下绝缘子内部电荷的分布规律,以及非线性电导涂层对绝缘子表面电荷积聚的影响机制。结果表明:非线性电导涂层对空间电荷消散有明显的促进作用,高压电极附近的同极性电荷主导了表面电荷分布;由于表面电荷分布和切向电场的改善,绝缘子的沿面闪络性能得到提高;在绝缘子与涂层界面之间会积聚正电荷,并从高压电极向地电极逐步递减。

Space/surface charge accumulation is a potential cause for the decrease of surface flashover voltage of DC GIL insulators.Applying nonlinear conductive coating is an effective method to improve the surface insulation performance.In this paper,a mathematical model was established for the regulation of space/surface charge and surface electric field of insulator by electric field dependent nonlinear con-ductive coating.The nonlinear relationships between the current density of insulating gas and the solid conductivity of insulator and the electric field intensity were comprehensively considered.The internal charge distribution law of insulator under temperature gradient distribution and the influence mechanism of nonlinear conductive coating on the surface charge accumulation of insulator were studied through this model.The results show that the nonlinear conductive coating promotes the dissipation of space charge obviously,and the homopolar charge near the high voltage electrode dominates the surface charge distribution.Due to the improvements of surface charge distribution and tangential electric field,the surface flashover performance improves.The positive charge may accumulate between the insulator and the coating interface,and decrease gradually from the high voltage electrode to the ground electrode.