500kV同塔4回输电线路绕击的耐雷性能

为研究同塔4回输电线路绕击耐雷性能,采用改进电气几何模型对其进行了分析。同塔4回输电线路导线数目多,避雷线需同时保护多相导线,因此必须通过确定雷电绕击的范围以得到绕击计算时所需的击距系数k、临界击距rsc、最大击距rsmax、年落雷次数N和雷击击距为r的概率等基本条件。在实际分析验证典型塔型的基础上建立了计算模型,改变相应参数得出绕击跳闸率n与杆塔高度hc、避雷线保护角θs、地面倾角θg、击距系数k等的对应变化关系。结果表明,n随hc增加、θs增大、θg增大、k减小而增大,采用负θs和降低hc是提高500kV同塔4回线路绕击耐雷性能的有效办法。

Lightning Protection Performance of 500 kV Quadruple-circuit Transmission Lines on the Same Tower

The performance of shielding failure of 500 kV quadruple-circuit overhead AC transmission lines on the same tower with the revised electric geometry model (EGM) method is analyzed, and the problem of shielding for transmission lines by ground wires is discussed. In the process of studying the performance of shielding failure of 500 kV quadruple-circuit transmission lines on the same tower, there are many conductors on the tower, consequently, the ground wires should protect multiple phases conductors at the same time, so the basic parameters for shielding failure calculation,such as striking distance factor, critical striking distance, maximal striking distance, quantity of lightning on the transmission lines, the probability of r (the striking distance) , and so on, must be gotten by ensuring the range of lightning shielding failure. The revised EGM method is adopted to calculate the shielding failure flashover rate and model reasonably on the basis of the analysis on the tower style by changing the corresponding parameters, and the relationship between shielding failure flashover rate and each factors such as the height of tower, the protection angle, ground obliquity and striking distance factor is achieved. A conclusion is drawn that the shielding failure flashover rate will become larger when the height of tower, the protection angle, the ground obliquity become larger and the striking distance factor become smaller. The results show that negative protection angle and lower height of tower are effective methods to improve the performance of shielding failure of 500 kV quadruple-circuit transmission lines on the same tower.