温度梯度下电荷行为与直流沿面闪络的关联性

Relation Between Charge Behavior and DC Surface Flashover Under Temperature Gradient

现有的直流沿面闪络模型仍存在一些值得探索的不足之处,无法对一些直流沿闪现象进行完备的解释。为得出更完善的结论有必要对影响直流沿闪的关键因素进行研究。针对温度这一关键因素,利用电-热多物理场仿真方法,研究了温度梯度下,固体绝缘内部电荷及表面电荷积聚的现象。结果表明:在直流电场作用下,高压电极处电荷的注入会使高压电极附近的表面电势上升,当高压电极温度升高后,具有高电势的区域将随着体内与表面电荷的注入,高压电极处较高的表面电势逐渐向地电极扩张,该效果可视为高压电极向地电极的延伸,减小了沿面有效绝缘距离,从而降低了固体绝缘的沿闪电压。这些结果验证了"近似失效绝缘区"的概念。文中验证的"近似失效绝缘区"的概念能够用于解释直流作用下不明诱因的沿面闪络现象,对于今后高压直流绝缘设备设计研发具有一定的参考价值。

The existing DC flashover models still have some deficiencies,and cannot integrally explain some DC flashover phenomena.In this paper,the phenomenon of charge accumulation inside and on the surface of solid insulation under temperature gradient is studied by electrical-thermal multi-physical field simulation.The results show that,under the DC electric field,the surface potential near a high-voltage electrode can be increased by charge injection at the high-voltage electrode.When the temperature of the high-voltage electrode increases,the area with high potential will gradually extend to the grounded electrode with the charge injection from the body and the surface.This effect can be regarded as the extension of the high-voltage electrode to the grounded electrode,which reduces the effective insulation distance along the surface,and thus reduces the effective insulation distance along the surface.These results validate the concept of"analogous ineffective region".The concept of"analogous ineffective region"verified in this paper can be used to explain the unidentified cause of surface flashover under DC.The results can provide a certain reference for the future design of HVDC insulation equipment.