双层高土壤电阻率地区发变电站接地网的分析

Analysis on Grounding Grid for Power Plants and Substations at Regions with High Soil Resistivity of Double Layer

高土壤电阻率地区存在土壤垂直分层现象。为了均匀地表的电位分布．应进一步降低接触电压和跨步电压。采用接地设计软件CDEGS分析了发、变电站接地网不等间距布置方式压缩比的选取对接地电阻。接触、跨步电压的影响。讨论了不等间距接地网导体根数的选取原则，分析了青海某高土壤电阻率地区变电站接地网不同布置形式对接地网接地电阻、短路电流、接触电压以及地表电位的影响。分析表明．最优压缩比与上层土壤厚度、反射系数和接地网边长有关；在设计接地网时，只需考虑接触电压的最大值就能够达到安全要求：对于100m×100m的接地网，其导体根数不少于10根。可保证导体上的泄漏电流密度更均匀，并显著地减小接地网接地电阻及地表电位，达到了对接地网的安全要求。

Vertical lamination of soil takes place at high soil resistivity regions. To equalize the potential distribution on the earth surface, it is necessary to decrease the touch voltage and step voltage. The effect of compression ratio of unequal grounding grid spacing on grounding resistance, touch voltage and step voltage was evaluated using CDEGS designing program. The criteria of conductor number selection for grounding grid of unequal spacing were discussed and effect of different arrangement of grounding grid of power stations at high soil resistivity region Qinghai province on grounding resistance of grounding grid, short-circuit current, touch voltage and earth surface potential was evaluated. The analysis shows that the optimum compression ratio is correlated with thickness of top soil layer, reflection factor and length of grounding grid. The safety requirement can be ensured only with consideration of maximum touch voltage. Conductors at least 10 for grinding grid 100 m×100 m can ensure uniform leakage current density, apparently decrease grid grounding resistance and potential on soil surface, meeting the safety requirements for grounding grid.