典型覆冰形状下输电线路风荷载影响研究

Influence of Wind Loads on Transmission Lines Under Typical Ice Shapes

风荷载对输电线路覆冰监测精度的影响显著,需要对不同覆冰形状下导线风荷载进行研究。该文总结了6种线路典型冰形,通过计算流体力学方法得到各覆冰形状下导线的气动阻力系数,在此基础上研究了覆冰发展过程中覆冰形状、扭转角和覆冰类型对导线风荷载的影响规律,并计算了各气象冰区下不同冰形的覆冰增大系数,与现行规范进行比较并给出了取值建议。结果表明,各冰形气动阻力系数受到冰厚、扭转角、风速的影响,新月和扇形覆冰阻力系数受三者影响均较大,D形和椭圆形主要受到扭转角的影响,而圆形覆冰受三者影响均很小;在导线覆冰发展过程中,新月形和椭圆形覆冰在扭转角为90°时风荷载最大,0°时最小,扇形和D形覆冰则在扭转角为0°时最大,60°和90°时最小,且混合淞的风荷载大于雨凇;对于同一条输电线路,其风荷载在新月形和椭圆形覆冰且扭转角为90°时达到最大;对于各气象区,采用现行规范中的覆冰增大系数取值进行输电线路设计将会在部分冰形覆冰情况下存在风险和隐患,对于大多数普通线路,建议结合不同冰区的主要冰形和不同线路类型的扭转情况,并综合考量经济性和安全性进行系数选取,针对重要枢纽线路,需要保证任何覆冰情况下均安全运行,推荐取值为3.5~3.6。

As the wind loads affect greatly on the monitoring accuracy of the transmission line icing,it is necessary to study the wind loads of the conductors under different ice shapes.In this paper,by summarizing six typical ice shapes of the lines,the aerodynamic drag coefficients of the conductors under each of the ice-covered shapes are obtained by means of the computational fluid dynamics.The influence of the ice shapes,the torsion angles and the icing types on the wind loads of the conductors in the icing development process is studied.The icing increase coefficients of different ice shapes under each of the meteorological ice areas are calculated and compared with the current norms,giving the value suggestions.The results show that the aerodynamic drag coefficients of each of the ice shapes are affected by the ice thicknesses,the torsion angles,and the wind speeds.The ice-covered drag coefficients of the crescent-and the fan-shaped types are greatly affected by the above three factors,the D-shaped and the ellipse types are mainly affected by the torsion angles,while the circular icing is less affected by the three;The crescent and the elliptical wind loads reach the maximum when the torsion angle is 90°,and the minimum at 0°.The fan-shaped and the D-shaped wind loads reach the maximum at the torsion angle of 0°,and the minimum at 60°and 90°.The wind load of the mixed icing is greater than that of the glaze icing;The wind load of the transmission line reaches the maximum when the ice-covered shape is crescent and ellipse and the torsion angle is 90°;For every meteorological region,the design of the transmission lines using the value of the icing increase coefficient in the current code will cause risks or hidden dangers in the case of partial icing.For most ordinary lines,it is recommended to combine the main ice shapes in different ice regions and the torsion of different line types,and comprehensively consider the economy and safety to select the coefficient.For important hub lines,it is necessary to ensure the safe operation under any icing conditions with the recommended value as 3.5~3.6.