季节性冻土对变电站接地系统分流系数的影响

季节冻土将改变土壤模型,导致杆塔接地电阻和变电站接地电阻的变化,从而导致最大入地电流随季节变化。文章采用数值计算方法分析了存在季节冻土时变电站接地系统埋设深度、杆塔接地装置埋深、垂直接地极、局部冻土、变电站进出线回数等因素对变电站分流系数的影响。分析结果表明:存在季节冻土层时,如果冻土层的厚度超过接地网的埋深,将使最大入地短路电流增加;变电站进出线为10回时,变电站分流系数大约增加30%;接地网增加垂直接地极能够减轻季节冻土对分流系数的影响。

Influences of Seasonal Frozen Soil Layer on Current Division Factor of Substation Grounding System

Seasonal frozen soil makes soil characteristics altered, so it leads to seasonal characteristics of the maximum ground fault current because the grounding resistances of substation grounding system and tower footing varies with seasonal factors. When seasonal frozen soil layer exists, the influences of different factors, such as the burial depth of tower footing grounding device, the number and buried depth of vertical grounding rods, local frozen soil and the number of incoming and outgoing lines of substation, on current division factor of substation are researched by numerical analysis method. The analysis results show that when seasonal frozen soil layer exists, if the thickness of the frozen soil layer exceeds the buried depth of grounding mesh, the maximum short circuit current flowing into the ground increases. When the number of incoming and outgoing lines of substation is ten circuits, the current division factor of substation may approximately increase by 30%. The influence of seasonal frozen soil layer on current division factor can be eliminated by adding vertical grounding rods into grounding devices.