垂直双层土壤中引外接地对降低接地阻抗的作用研究

Study on the Effect of External Grounding on Reducing Grounding Impedance in Vertical Double-Layer Soil

笔者研究了引外接地在垂直双层土壤中有效长度,以验证GB 50065中所说变电站2km范围内有低土壤电阻率地区时可采用引外接地的可行性。研究采用CDEGS软件进行仿真,结果表明辅助接地网的降阻效率随引外长度增加而减小,有效降阻的最大引外长度(η≥10%)在400~800m之间。辅助接地网的降阻效率还受到两侧土壤电阻率比值k、接地导体材质、接地网边长以及接地导体半径等因素的影响。因此当辅助接地网距变电站主接地网2km时已无实际效果。

The author studies the effective length of external grounding in vertical double-layer soil to verify the conclusion in GB 50065 that external grounding can be used when there are low soil resistivity areas within 2 km from the substation.The software CDEGS is used in the simulation,and the results show that the resistance reduction efficiency of the auxiliary grounding grid decreases while the lead out length increases.And the maximum effective resistance reduction length(η≥10%)is between 400m and 800m.The resistance reduction efficiency of auxiliary grounding grid is also affected by the soil resistivity ratio k,the material or radius of grounding conductor,and the side length of grounding grid.Therefore,there is no practical effect when the auxiliary grounding grid is 2km far away from the main grounding grid.