高精度上流有限元法在特高压直流输电线路离子流场计算中的应用

Application of the High Precision Upstream FEM to Calculation of the Ionized Field of HVDC Transmission Line

在对高压直流(HVDC)输电线路下的电磁环境进行预测时,地面合成场强和离子流密度的计算问题实际上是一个多维非线性问题。在对剖分单元进行处理时,为了解决传统的有限元方法、上流有限元法采取线性假设与线性插值,存在计算量大、精度差、算法效率低的问题,提出一种新的非线性空间电荷密度插值方法,从理论上推导了算法的实现过程,并基于上流有限元方法对离子电流密度方程进行迭代求解。采用该算法对现场运行的±500 k V和±800 k V输电线路离子流场进行了理论计算与现场实地测量,并将理论计算结果与实际测量结果进行了对比,结果表明:所提出的算法能在减少计算量的同时提高计算的准确度。针对风速对双极离子流场影响的研究较少的情况,研究讨论了不同风速影响下的双极离子流场问题,得到了风速对双极离子流场地面最大合成场强和离子流密度影响的规律,为新的直流输电线路的设计提供了有力的参考。

The calculation of ground-level electric field and ion current density under HVDC transmission line is actually a multidimensional nonlinear problem when predicting the electromagnetic environment. When processing the subdivision element, some limitations, like the huge computation, complex algorithm and low accuracy of calculation, exist in the traditional finite element method and upstream FEM by using linear hypothesis and linear interpolation. To solve the problems above, we propose and introduce a new method based on quadratic nonlinear interpolation of space charge density to calculate the ground-level electric field and ion current density under HVDC transmission line. Then the upstream FEM method is applied to solve the current continuity equation. After the validity of the method is verified using a test model, the engineering measurement experiment under the running ±500 k V and ±800 k V transmission lines is carried out, which demonstrates further that the proposed method is effective. Due to the fact that little is known about the impact of wind speed on the bipolar ion flow field at present, we discuss the problem of bipolar ion flow field under different wind speed, and analyze the law of the influence for the grand-level electric field and ion current density. The results can provide powerful references for the new design of DC transmission line.