交直流互联系统直流电流分布与多层土壤参数的关系

分层土壤参数是影响交直流互联系统直流电流分布的重要因素．将各层土壤的电阻率及厚度作为自变量，变压器中性点的直流电流作为因变量，利用二元函数的三维曲面及等值线来描述变压器中性点直流电流与各层土壤参数的关系；基于此，研究多层土壤参数同时变化时，交直流互联系统直流电流分布与地理位置的关系．结果表明：变压器中性点的直流电流分别与第l层土壤电阻率比厚度、第2层土壤电阻率乘厚度、第3层土壤电阻率比厚度相关；当第1层土壤电阻率取最小值、厚度取最大值，第2—4层土壤电阻率全部取最大值、厚度全部取最小值时，各站点变压器中性点的直流电流相对较大；距离接地极越远，不同站点变压器中性点的直流电流差距越小．

Relationship Between DC Current Distribution and Multilayer Soil Parameters in AC-DC Interconnected Power System

Stratified soil parameters are an important factor in affecting the DC current distribution in the AC-DC interconnected power system. The resistivity and thickness of each soil layer taken as independent variables and the DC current of transformer neutral point regarded as dependent variable, the 3D surface and isoline of the binary function were used to describe the relationship between the DC current of transformer neutral point and the parameter of each soil layer. And then, the relationship between the DC current distribution in the AC-DC interconnected power system and the geographical position was studied, with multilayer soil parameters changing at the same time. The results showed that the DC current of transformer neutral point was related to the ratio of resistivity to thickness of the first layer, the product of resistivity and thickness of the second layer, and the ratio of resistivity to thickness of the third layer, respectively. The DC current of each substation was relatively larger when the resistivity and thickness of the first layer took the minimum and maximum value, and those of the second, third and fourth layers took the maxi- mum and minimum values, respectively. The greater the distance from DC grounding electrode is, the smaller the DC current difference of transformer neutral point at different sites will be.