影响双层土壤中垂直接地极性能的研究

Study of Influence Factors of Dual-layered Soil on Vertical Grounding Rod Performance

在土壤电阻率较高、占地面积较小的变电站,仅靠水平接地网,接地电阻往往不能满足国家有关规定的要求,需要采取降阻措施。在变电站双层土壤结构中,采用接地设计软件CDEGS分析了上层土壤电阻率、反射系数、上层土壤厚度及垂直接地极长度变化对降阻率的影响。结果表明,上层土壤电阻率不同,对降阻率的影响较小;降阻率随反射系数增大而减少;垂直接地极长度小于上层土壤厚度时,反射系数对降阻率的影响非常小;随垂直接地极长度的增加,降阻率逐渐增大,但增大到一定长度后趋向饱和。反射系数为负时,穿入下层土壤的垂直接地极能有效地降低接地电阻。

At substation having high soil resistivity and small site area the grounding resistance only horizontal grounding grid can not meet the requirement of relevant regulations for grounding resistance, and resistance-reduction measure is needed. Using CDEGS program, the author analyzed the in- fluence of variation conserning resistivity of upper soil layer, reflection factor, thickeness of upper soil layer and length of vertical grounding rods on resistance reduction rate. The result shows that different resistivity of upper layer effects a little the resistance reduction rate which drops as the reflection rate lists, very small effect of reflection factor formed on resistivity reduction the resistance reduction, rate increases as the length of vertical grounding rod increases, tending to saturation in certain rising extent. The vertical grounding rod planting in lower soil layer can considerally reduce the grounding resistance when the reflection factor is negative.