基于边界元法的输电杆塔上分裂导线表面电场数值计算

Numerical Calculation of Bundle Conductor Surface Electric Field on Transmission Tower Based on Boundary Element Method

为了比较准确计算输电导线附近电磁环境,为优化杆塔和线路提供参考,对输电杆塔附近的分裂导线表面电场进行数值分析。根据杆塔的特点,设杆塔模型由一系列圆柱形导体组成,并把圆柱形导体设为线单元。把分裂导线圆柱形表面设成面单元,采用线-面混合边界元法把杆塔和导线作为一个系统进行计算。针对导线表面剖分单元的特点,在高斯积分方法上提出了改进措施,即在剖分单元比较长的方向上增加高斯点,减少计算内存提高效率。同时考虑计算模型两边输电导线的影响和大地镜像的影响。计算结果表明:采用线-面混合边界元法,可以比较准确有效地计算出杆塔附近导线表面电场分布;杆塔附近分裂导线表面电场会明显增大,并随着距离杆塔越来越远,杆塔影响迅速减小,中间相导线受杆塔影响比较大;正常高斯积分长宽比值小于16倍时才比较准确,改进高斯积分后,剖分单元长宽比值64倍时结果仍然比较准确,显著提高了计算精度和效率;当半无限长导线距离计算点较近时对计算结果产生的影响比较大,距离计算点较远时产生的影响比较小。

In order to accurately calculate the electromagnetic environment near transmission lines and provide a reference for optimizing the tower and the line, we numerically analyze the electric field on the surface of the bundle conductor near the transmission tower. According to the characteristics ofthe tower, assuming that tower model consists of a series of cylindrical conductors, a cylindrical conductor is set as a line element, and the bundle conductor surface is set as a plane element. The tower and wire system, as a whole, are calculated with the line-plane mixed boundary element method. According to the characteristics of the conductor surface subdivision unit, improvement measures are proposed on the Gauss integral method.Namely, increasing Gauss points on the long direction of the split unit to reduce the computational memory and improve efficiency, meanwhile, considering the effects of transmission lines on both sides of the calculation model and the earth mirror. The calculation results show that the line-plane boundary element method can calculate bundle conductor surface electric field distribution near the tower more accurately and effectively; Bundle conductor surface electric field near the tower will be significantly increased, and as it is more and more away from the tower, the tower impact decreases rapidly, and the influence of the towers in the middle phase conductor is relatively large. Under normal circumstances, when the aspect ratio is less than 16 times, the Gauss quadrature value of the calculation result is rather accurate. After Gaussian integral is improved, when the aspect ratio of split unit is 64 times, the value of the result is still relatively accurate. So, the accuracy and efficiency are significantly improved; When the distance between the semi-infinite wire and computing point is relatively close, the impact on the calculation result is relatively remarkable.When the distance is relatively far, the impact is relatively small.