土壤结构对流入变压器中性点直流电流的影响

Influence of Soil Structure on Direct Current Flowing Into Neutral Point of Power Transformer

当直流输电系统单极大地回路运行时,会在直流接地极附近的中性点接地变压器中流过较大直流电流,从而导致变压器直流偏磁等一系列后果。采用复合分层土壤结构模型,基于特定的计算模型,对直流接地极流入直流电流时引起的地中电流场分布和地电位分布进行计算,分析流入变压器中性点的直流电流。同时通过改变土壤结构模型参数,分析不同土壤结构配置下流入变压器中性点直流电流的变化。研究表明,土壤结构对流入变压器中性点的直流电流影响较大,因此在精确计算流入变压器中性点的直流电流时应考虑土壤情况的复杂性。研究结果为实际工程中直流接地极附近变电站选址提供理论参考。

When a high voltage direct current（HVDC） transmission system operates in ground-return mode, large currents will flow through the neutral earthed transformers near the HVDC grounding electrode, which may lead to a series of harmful results such as DC biases of transformers. Based on specified model, the influence of soil structure configuration on direct current flowing through transformer＇s neutral point is analyzed. Complex soil structure with horizontal and vertical combined-layer model is taken into account. The results show that soil structure has notable effect on the direct current flowing through transformer＇s neutral point. So when accurately calculating the direct current, the complexity of soil structure should be considered. The results also provide a theoretical reference for selection of substations near the HVDC ground electrode.