干燥空气绝缘开关柜中应用的固封极柱绝缘结构设计及优化

Design and Optimization of Insulation Structure for Embedded Pole Used in Dry Air Insulation Switchgear Cabinet

为了实现气体绝缘开关柜的绝缘介质由SF6向干燥空气等环保型气体转变,开发一种结构小型化、绝缘水平满足要求的干燥空气绝缘开关柜中使用的固封极柱是亟需解决的问题。文中分析了40.5 kV SF6固封极柱置于干燥空气绝缘开关柜中的相间及对地电场分布,结果显示灭弧室动、静端盖板以及绝缘拉杆附近的气—固沿面电场严重超标,易造成沿面闪络。依据气—固复合绝缘理论,采取增加均压屏蔽网、改进绝缘壳体外观结构、重新设计绝缘拉杆等措施进行电场优化。通过仿真分析,优化设计后的固封极柱灭弧室端盖附近沿面最大场强由3.4 kV/mm降至2.03 kV/mm,绝缘拉杆沿面最大场强由4.1 kV/mm降至1.7 kV/mm。对优化前后的固封极柱进行了局部放电和雷电冲击耐压试验,局部放电试验的起弧电压由35 kV提升到62 kV,雷电冲击耐压试验的峰值耐受电压由145 kV提升到218 kV,证明了优化方案的可行性,为后续40.5 kV及更高电压等级的类似固封极柱的研发及优化提供了有关参考。

For achieving the transition of the dielectric medium of gas insulated switchgear cabinet from SF6 to such environmentally friendly gas as dry air,it is an urgent issue to develop an embedded pole for dry air insulated switch⁃gear cabinet with a smart structure and insulation level meeting requirement.In this paper,the electric field distribu⁃tion of phase⁃to⁃phase and phase⁃to⁃ground of 40.5 kV SF6 embedded pole which is placed in the air insulated switch⁃gear is analyzed.The result shows that the gas⁃solid surface electric field near the moving and static end cover as well as insulation rod of the arc interrupter seriously exceeds the standard,which is likely to cause surface flash⁃over.Based on gas⁃solid composite insulation theory,the electric field is optimized by such measures as adding grading shield network,improving appearance structure of insulation enclosure and redesigning insulation rod ect.Through simulation analysis,maximum field strength along the surface near the cover of arc interrupter after the optimal de⁃sign is reduced from 3.4 kV/mm to 2.03 kV/mm,and the maximum field strength along the insulation rod is reduced from 4.1 kV/mm to 1.7 kV/mm.Partial discharge and lightning impulse tests are performed on the embedded poles be⁃fore and after optimization.The arcing ignition voltage of the partial discharge test is increased from 35 kV to 62 kV,and the peak withstand voltage of lightning impulse test is increased from 145 kV to 218 kV,which proves the feasi⁃bility of the optimized scheme and provides a reference for the subsequent development and optimization of similar embedded poles at 40.5 kV and above.