1100 kV直流SF6气体绝缘穿墙套管电场仿真分析

Electric Field Simulation and Analysis of 1 100 kV DC SF6 Gas-insulated Wall Bushing

国产1100 kV直流SF6气体绝缘穿墙套管首次采用双层内屏蔽结构。为此,提出了1种气体电流密度计算方法用于仿真直流电压下的套管电场分布,对工频和直流电压下分别采用单层和双层内屏蔽结构时的套管电场分布进行了仿真分析,探讨了双层内屏蔽结构的电场调控能力,仿真分析了气体电离对电场分布的影响。结果表明:直流电压下套管外部表面电场分布不受内屏蔽电极配置方式的影响,但双层屏蔽结构相对于单层屏蔽结构能够减小套管内部电极的表面场强;套管外部空气电离达到一定程度后将引发屏蔽环表面起始的闪络,内部SF6气体电离达到一定程度后则更容易发生电离区附近的套管表面电晕放电。

A structure of double-layer inner shields is adopted in domestic 1100 kV DC SF6 gas-insulated wall bushing for the first time.Therefore,a calculation method of gaseous current density was proposed to simulate the electric field distribution of bushing.The electric field distributions of bushing with single-layer and double-layer inner shields under power frequency and DC voltages were simulated and analyzed.The electric field control ability of double-layer inner shields was discussed.The impact of gas ionization for electric field distribution was simulated and analyzed.The results show that the outer surface electric field distributions of bushing are not affected by inner shields.Compared with single-layer inner shields,double-layer inner shields can decrease the surface electric fields of inner electrodes.When the outer air ionization of bushing achieves a certain level,the flashover from grading ring surface will be triggered,and a certain level of inner SF6 gas ionization will more likely to result in the corona on insulator surface near the ionization region.