同塔交直流输电线路混合电场研究

Research on Hybrid Electric Field Caused by HVAC and HVDC Transmission Lines Erected on the Same Tower

高压交流与高压直流输电线路同杆塔架设能够有效缓解输电走廊紧缺问题。同塔交直流线路产生的混合电场的复杂性及其预测的困难性,成为制约该种线路设计和发展的关键因素。考虑了交流导线电晕放电和直流导线电晕放电之间的相互影响,基于上流有限元法,提出了种交直流线路同塔架设时混合电场的时域计算方法,通过试验线段的实验验证了算法的有效性;对不同等级交流电压情况下地面电场和离子流密度进行了计算,计算结果表明,交流线路对直流合成电场有明显的"屏蔽作用",且交流电压越高,地面电场直流分量和离子流密度越小;同时对空间电荷的运动轨迹进行了模拟,得到了交流电场对直流离子流场的作用机制,交流导线对空间电荷的吸引是导致地面电场直流分量和离子流密度减小的重要原因。

Erecting HVAC and HVDC transmission lines on the same tower can alleviate the scarcity of transmission corridor. The complexity of the hybrid electric field caused by HVAC and HVDC transmission lines erected on the same tower and the difficulty of predicting it already become the key factors restricting the design and development of such a kind of transmission lines. Considering the interaction between corona discharge of HVAC transmission line and that of HVDC transmission line and based on upstream finite element method, a time-domain computing method for hybrid electric field caused by HVDC line and HVAC line on the same tower is proposed, and the effectiveness of the proposed computing method is validated by experimental verification of test line. The ground electric filed and the density of ion flow under different AC voltage classes are calculated, and calculation results show that the HVAC transmission line can play an evident shielding effect on electric field produced by DC line, and the higher the AC voltage is, the lower the DC component of ground electric field and the density of ion current will be; at the same time, the motion trajectory of space charge is simulated and the action mechanism of AC electric field on DC ion flow field is attained, and it is proved that the attraction of AC conductors for space charge is the important reason leading to the reduction of both DC component of ground electric field and ion flow density.