特高压直流GIL盆式绝缘子表面电荷分布特性仿真研究

Simulation Study on Surface Charge Distribution Characteristics of UHV DC GIL Basin Insulators

为了满足大容量长距离输电的要求,近年来,中国加快特高压直流输电工程的建设,对气体绝缘金属封闭输电线路(gas-insulated metal-enclosed transmission lines,GIL)的需求日益迫切。限制直流GIL实际投运的关键壁垒之一是绝缘子表面积聚的电荷会增加沿面闪络电压降低的概率,故研究特高压直流GIL盆式绝缘子表面电荷分布特性存在必要性。因此,基于SF_6气体中正负离子的输运方程,利用COMSOL Multiphysics建立了真型特高压直流GIL盆式绝缘子表面电荷积聚模型,分别研究了电压幅值和电压极性对绝缘子表面电荷分布特性的影响规律以及气固界面电荷对GIL试验单元空间电场分布的影响规律。从仿真结果可知,正负电荷在盆式绝缘子内外侧均有分布,但分布特性存在一定的差异,外施电压为-800 kV时,最大正负电荷密度分别出现在绝缘子的外表面和内表面,数值分别为+19.64μC·m^(-2)和-22.93μC·m^(-2);表面电荷的积聚程度和高场强区域面积均与电压幅值呈正相关;仿真结果还表明绝缘子沿面耐受电压具有极性效应,即负极性直流耐受电压较低。

To meet the requirements of large capacity and long distance transmissions,in recent years,the processof UHV DC transmission projects accelerates in China,the demand for gas-insulated metal-enclosed transmission line（GIL）becomes urgent. But one of the key barriers is the insulator surface charge accumulation may reduce the sur-face flashover voltage,so it is necessary to study the surface charge accumulation effect on UHV DC GIL insulator.Therefore,based on the positive and negative ions transport equations in SF_6 gas,a simulation model is establishedto investigate the surface charge accumulation characteristics of insulator in UHV DC GIL test unit of Chinese EPRI.From the simulation results,both positive and negative charges accumulate on the inner surface and the outer surfaceof the cone-type spacer,but the charge distribution of each surface is different. And the surface charge density is close-ly related to the magnitude of the applied voltage,when the -800 kV voltage is applied,the maximum positive chargedensity ＋19.64 μC·m（-2） and the maximum negative charge density-22.93 μC·m（-2） are on the outer surface and inner sur-face of the insulator,respectively. Results also show that the negative withstand voltage of the insulator is lower.