土壤结构对直流入地电流分流特性的影响研究

高压直流输电系统单极大地回路运行时,从大地返回的直流电流通过接地网流入变压器中性点,从而引起变压器噪声增大、发热加剧等一系列不良后果。利用CDEGS软件对交直流互联系统进行建模仿真,直流输电系统以单极大地回线方式运行时,依据3种土壤分层结构分别计算了流经变压器中性点的直流电流量,得出了交流电网直流电流分布图。仿真结果表明:流经变压器中性点的直流电流因距离接地极的远近而变化,距离接地极越近,流经变压器中性点的直流电流量绝对值越大,近似呈对数函数形式分布;流经交流架空线路的直流电流值与土壤的分层结构、交流电网的拓扑结构以及距离直流接地极的远近相关。

The Influence of Soil Structure on Bifurcated Characteristics of DC Grounding Current

When a high voltage direct current(HVDC) transmission system works in single pole-ground mode,direct current returned from ground will flow into neural point of transformers through the grounding grid,which may lead to a series of harmful results,such as noise increasing and heat aggravation of the transformer.The model of AC-DC interconnected power system which works in single pole-ground mode is built,and simulation is carried out by using of CDEGS.Then,the values of direct current that flow into the neural point of transformer are calculated according to three kinds of soil structures,and the distribution diagrams of direct current for AC power grid are obtained.The simulation results show that the direct current at neural point of transformer varies according to the distance between transformer and grounding pole.It means that the nearer the distance,the bigger the absolute value of DC,whose distribution is similar to a logarithmic function.And the value of direct current flowing in AC overhead transmission lines is determined by soil layer structure,topology structure of the AC network,and the distance between AC overhead transmission line and grounding pole.