500 kV输电铁塔覆冰风险评估与加固措施

Icing risk assessment and reinforcement measures of 500 kV transmission tower

输电线路覆冰可能导致输电铁塔倒塌、线路断线,严重威胁电网的安全稳定运行。针对某地区的典型覆冰线路,采用有限元仿真方法建立了500 kV塔线体系仿真模型,并对均匀覆冰下不同覆冰厚度和不同风速等工况进行仿真分析,统计25组仿真结果后获得了500 kV输电铁塔的薄弱点位置规律;然后,基于输电铁塔关键构件的轴向应力和节点位移,进行输电铁塔运行风险评估分析,并划分输电铁塔的运行风险状态;最后,进一步分析2类加固措施的效果,得到加固前后输电铁塔不同薄弱点位置处轴向应力和节点位移的变化关系。仿真结果表明:500 kV输电铁塔的薄弱点位置主要分布在铁塔塔头地线支架处、上下曲臂连接处、瓶颈处以及铁塔的塔身处;在均匀覆冰和风荷载作用下,关键构件的轴向应力和节点位移均呈非线性增加;拟合得到了输电铁塔安全、预警和危险状态临界表达式;增加构件横截面积的加固效果优于改变薄弱点角钢结构,后者加固前后输电铁塔薄弱点处的轴向应力和节点位移均无明显变化。

The existing of transmission line icing may lead to the collapse of the transmission tower and disconnection of the transmission line,which seriously threatens the safe and stable operation of power grid.In this paper,aiming at the typical icing lines in Guizhou,the simulation model of 500 kV tower-line system is established by finite element simulation method,and the simulation analysis of different icing thicknesses and different wind speeds under uniform icing is carried out.The weak point position rules of 500 kV transmission tower are obtained by counting 25 groups of simulation results.Then,based on the axial stress and node displacement of the weak components of the transmission tower,the operational risk assessment analysis of the transmission tower is carried out,and the operational risk state of the transmission tower is divided.Furthermore,the effect analysis of two kinds of reinforcement measures is carried out,and the relationship between axial stress and node displacement at different weak points of the transmission tower before and after reinforcement is obtained.The results show that the weak points of the 500 kV transmission tower are mainly distributed at the ground bracket of the tower head,the joint of the upper and lower curved arms,the bottle neck and the body of the tower.Under uniform icing and wind load,the axial stress and node displacement of key components increase nonlinearly.The critical expressions of safety,warning and dangerous state of the transmission tower are fitted.The reinforcing effect of increasing the cross-sectional area of components is better than that of changing the angle steel structure with weak points.The axial stress and joint displacement of the transmission tower at the weak point have no obvious change before and after reinforcement when changing the angle steel.