季节因素对发变电站地表高阻层安全效果的影响

Influence of Seasonal Factor on Seasonal Factor on Safety of Ground Surface High Resistivity Layer in Substations

发变电站接地系统可通过提高表层土壤电阻率来提高人体允许的跨步电压和接触电压，减小通过人体的电流，但季节因素将影响高阻层的安全性能，导致接触电压和跨步电压的改变，危及电力系统的安全稳定运行。文中采用数值计算方法分析季节因素对地表高阻层安全全性能的影响 采用ＤＬ／Ｔ６２１—１９９７标准中计算公式得到的允许跨步电压和接触电压过于偏高，高于ＩＥＥＥＳｔｄ８０—１９９７标准推荐公式的计算值、采用高阻层后，地网表面的接触电压在雨季明显减小；地网表面的接触电压在冰冻季节将高于没有采用高阻层的地网地表面的对应值。

The permissible step and tonuch voltage of grounding system for human body in suhstatinos may be increased byincrease of surface soil resistivity, and the current through human body may be correspondingly reduced. However, seasonalfactor may affect the safety characteristic of high ground resistivity layer. causing the change of step and touch voltage. Thepermissible step and touch voltage calculated from DI/T621-1997 standard formula seens too high, higher than that byIEEE Std80-1997 standard recommended formula. When using high resistivity layer. the touch voltage will be lower duringrainy season, but during cold season, it will be higher than those without using high resistivity layer.Therefore,the effect ofseasonal factor on safety of grounding system shall be considerde.