考虑高山影响的UHVDC单极大地运行感应电势分析

特高压直流输电系统单极—大地回路运行时,会使附近交流电网遭受直流偏磁危害,地表电位的准确求解是预防和治理直流偏磁危害的重要环节。针对高山对感应电势的影响,首先建立了考虑高山影响的复合土壤结构模型,并运用镜像法与行波法推导出感应电势的计算公式,分析了大地参数对感应电势分布的影响,发现高山的存在抬高了高山与直流接地极之间的感应电势,增大了高山两侧的感应电势差。进而以±800kV天中特高压直流输电工程为例,在Matlab中搭建模型计算哈密地区交流电网中直流电流分布情况。结果表明,各变电站接地极的直流电流仿真值与实测值相符。

Analysis of Induced Potential Caused by Ground Return Operation Mode of UHVDC System Considering Mountain Influence

When the UHVDC system is operated with unipolar-earth loop, the nearby AC network will suffer from DC bias hazard. The accurate solution of surface potential is an important link to prevent and control DC bias hazard. Aiming at the influence of high mountains on induced potential, a composite soil structure model is established considering the influence of high mountains. And then the calculation formula of induced potential is deduced by using image method and traveling wave method. The influence of geodetic parameters on the distribution of induced potential is analyzed. The simulation results show that the existence of high mountains elevates the distribution of induced potential between high mountains and DC grounding poles. The induced potential between the two sides of the mountain increases the difference of the induced potential between the two sides of the mountain. Finally, taking (±800 kV) Tianzhong UHVDC transmission project as an example, a model is built in Matlab to calculate the DC current distribution in the AC network in Hami area. The results show that the DC current simulation values of the grounding poles in each substation are consistent with the measured values.