基于有限元方法的直流输电接地极多层土壤地电位分布计算

高压直流输电单极-大地回路方式运行时入地电流会在接地极周围的土壤中产生强电场,会对接地极附近电网的电力设备和地下金属管线等产生影响。针对接地极周围实际土壤的分布情况,建立了典型土壤模型和多层土壤模型,采用有限元法对典型接地极的地电位分布进行计算。比较了采用典型土壤模型和采用多层土壤模型下的直流输电接地极的接地特性以及对地面电位分布的影响。计算结果表明,在极址附近,接地极所在层土壤电阻率对接地电阻和跨步电压的影响较大,在离接地极数十公里范围内,深层土壤电阻率对地表电位的影响较大。

Calculation of multi-layer soil earth surface potential distribution of HVDC due to finite element method

Strong electric field will be produced in the earth around the grounding poles when HVDC transmission system operates in ground-return mode, which will influence electrical equipment nearby and the metallic pipelines underground. This paper builds a model of multi-layer soil and a typical soil model on basis of actual distribution of soil around the grounding poles, and then calculates surface potential distribution of typical grounding poles by finite element method. The grounding characteristics of DC transmission grounding electrode and the influence on earth surface potential distribution of the two models are compared. The results show that, the ground resistance and the step voltage around the site are much affected by the soil resistivity where the grounding locates. While the ESP which is within the range of tens of meters, is affected by the deep soil resistivity.