非均匀土壤中变电站接地网优化设计

Optimal design of grounding grids of substations in nonuniform soils

为了均匀地表面的电位分布 ,进一步降低接触电压和跨步电压 ,更好地保障人身和设备的安全 ,论文提出了接地系统优化设计方法。论文采用数值计算的方法分析了双层土壤结构时土壤反射系数、上层土壤厚度及地网面积大小等因素对地网最优布置的影响规律。分析表明 ,确定最优压缩比应以接触电压达到最小值为目标函数。最优压缩比随反射系数的增大而减小 ,下层土壤电阻率小于上层土壤电阻率时的最优布置的水平导体 ,比下层土壤电阻率大于上层土壤电阻率时的最优布置的水平导体分布得更加均匀。分析得到了双层土壤结构时 ,使地网优化布置的最优压缩比的计算公式 ,便于工程设计人员采用 。

To equalize the potential and decrease touch voltage and step voltage on the earth's surface, an optimum design of grounding systems is proposed in this paper. The influences of the reflective coefficient of the double layer soil, the top layer soil thickness and the grounding grid area on the optimum arrangement are analyzed numerically. The results show that the optimum compression ratio (OCR) occurs when the target function of the touch voltage reaches a minimum. The OCR decreases with increasing reflective coefficient. When the bottom layer soil resistivity is smaller than that of the top layer soil, the horizontal conductors are more uniform than when the soil resistivity of the bottom layer soil is higher than that of the top layer soil. The formulas to calculate the OCR of the double layer soil structure that were obtained analytically provide a reference for engineers to design grounding systems of substations with high safety.