典型故障条件下35 kV包裹绝缘护套母排电场分布研究

Study on the Electric Field Distribution of 35 kV Bus with Wrapped Insulation Sheath Under Typical Fault Conditions

绝缘护套包裹在变电站母排上起着防腐蚀和绝缘保护的作用,但有异物搭接在包裹绝缘护套的母排上时常发生相间短路事故,具体的事故原因并不明确,严重影响电网的安全、可靠运行。文中基于有限元计算方法,构建了典型故障条件下(气隙缺陷和搭接异物)包裹绝缘护套的母排模型,对包裹绝缘护套母排进行了三维工频电场计算,分析了绝缘护套内部气隙缺陷和外部异物搭接导致的绝缘护套内部和表面电场分布情况,并研究了绝缘护套厚度对电场分布的影响。结果表明:包裹绝缘护套的母排内部存在气隙缺陷和外部有异物搭接时,绝缘护套内部和表面均会发生电场畸变,电场畸变程度为:搭接金属>搭接潮湿树枝>搭接干燥树枝>热缩气隙;增加绝缘护套厚度有助于改善异物导致的绝缘护套表面和内部电场畸变,对金属异物导致的电场畸变可降低68%。

The insulating sheath is wrapped in the busbar of the substation to play the role of anti⁃corrosion and insu⁃lation protection.However,when a foreign object is lapped on the busbar of the insulated sheath,the phase⁃to⁃phase short⁃circuit accident often occurs.The specific cause of the accident is not clear,which seriously affects the grid,safe and reliable operation.Based on the finite element method,the busbar model of the wrapped insulation sheath under typical fault conditions(air gap defects and lapped foreign objects)is constructed.The three⁃dimensional pow⁃er frequency electric field calculation is carried out on the wrapped insulation sheath busbar,and the insulation pro⁃tection is analyzed.The internal and surface electric field distribution of the insulating sheath caused by the internal air gap defect and the external foreign matter overlap,and the influence of the thickness of the insulating sheath on the electric field distribution is studied.The results show that when there is air gap defect inside the busbar wrapped with insulating sheath and external foreign matter overlap,electric field distortion will occur in the inner and surface of the insulating sheath.The degree of electric field distortion is:lapped metal>lapped wet branch>lapped dry branches>heat shrinkable air gap;increasing the thickness of the insulating sheath will help to improve the electric field distortion on the surface and the inner part of the insulating sheath caused by foreign matters,which is different to the metal The distortion of electric field can be reduced by 68%.