模拟电荷法计算特高压架空线路3维工频电场

为研究杆塔及导线弧垂对架空线路周围工频电场分布的影响,并检验2维计算模型的合理性与适用性,首先基于模拟电荷法建立考虑杆塔及导线弧垂的3维架空线路工频电场计算模型(它以线电荷单元为模拟电荷布置在各导线和杆塔铁棒轴线上,解析计算线电荷单元的电位系数,并叠加得到总体电位系数矩阵,从而可解得各节点的线电荷),然后据此计算了特高压线路相导线表面及地面上1m高平面内的3维工频电场。结果表明,地面上1m处平面内场强分布受弧垂影响很大,3维模型比2维模型更全面、准确地反映了这种不均匀分布状况;各相导线表面场强最大值在杆塔附近均有微弱变化,但并不显著;地面上1m处场强在杆塔附近增大,但在远离杆塔的区域基本不受杆塔影响。

Calculation of Three-dimensional Harmonic Electric Field Around Ultra High Voltage Overhead Line Based on the Charge Simulation Method

The knowledge of harmonic electric field around ultra high voltage transmission line is very important for the line designers. For example, the magnitude of electric field on the surface of phase conductor (Es) is a parameter of most concern that determines audible noise, radio interference and corona loss. Beneath the line, the knowledge of the distribution of electric field in the plane 1m above the ground (Eg) is significant for the design of the corridor width and conductor arrangement. In order to study the effects of tower and sag of conductor on the harmonic electric field distribution around the overhead line and verify the rationality and applicability of two-dimensional model, a three-dimensional overhead line model considering the tower and sag of conductor is built based on the charge simulation method (CSM). In this method, some linear charge elements are treated as the simulating charges and placed in each conductor's axes. Then the global potential coefficient matrix is obtained by the superposition of each element's contribution. The linear charge on each node is solved and the electric field on arbitrary points can be calculated analytically. Based on the proposed method, some examples are given to analyze the harmonic electric field on phase conductor surface (E s) and in the plane 1m above the ground (E g). The results of 3D model show that E g is unevenly distributed across the plane, which means the effect of the sag of conductor can't be neglected. And E g near the tower is enhanced due to the existence of the grounding tower. While the tower has little effects on E s and there is no significant value change found near the tower. The proposed method is effective in the three-dimensional harmonic electric field calculation for the overhead line, which may be helpful to the design of ultra high voltage transmission line.