冰冻季节对发变电站接地系统安全性能的影响

采用数值计算方法分析了冰冻季节形成的地表高阻层对地网安全性能的影响。接地系统的接地电阻、接触电压及跨步电压随高阻层的厚度或电阻率的增加而增加。当高阻层的厚度小于地网埋深时 ,基本上对地网的安全性能无影响 ;而当高阻层厚度超过地网的埋深时 ,接地电阻、接触电压和跨步电压大幅度增加 ,导致地网安全性能下降。因此应合理地估计变电站所在地的高阻层厚度 ,将地网埋在高阻层之下 ,确保地网的安全性能基本上不受季节影响。分析结果将为电力部门提供设计依据 ,提高电力系统运行的可靠性。

Influence of freezing conditions on the safety of grounding systems

High resistivity soil layer forms when the ground freezes during the winter. The influence of the high resistivity layer on the safety of grounding system was analyzed numerically. The grounding resistance and the step and touch voltages of the grounding system increase with the thickness or resistivity of the high resistivity soil layer. If the thickness of the high resistivity soil layer is smaller than the burial depth of the grounding grid, the safety of the grounding system is not affected; but when the thickness exceeds the burial depth of the grounding grid, the grounding resistance and the step and touch voltages increase greatly and the safety of the grounding system is greatly reduced. So the thickness of the high resistivity soil layer at a substation should be accurately estimated and the grounding grid should be buried below the high resistivity soil layer so the safety of the grounding system would be assured throughout the year. The results provide a design basis for power systems.