冰冻土壤中垂直接地极的接地电阻变化规律

Grounding Resistance Change Rule of Vertical Grounding Electrode in Frozen Soil

单根垂直接地极在均匀土壤冰冻前后工频接地电阻值的变化会影响防雷接地检测的误差和防雷接地的效果。鉴于此，利用CDEGS软件对单根垂直接地极在均匀土壤产生冻土前、后的接地电阻值R1、R2进行了仿真。分析仿真数据得出：影响该接地电阻值的主要因素有反射系数、冻土厚度和垂直接地极的长度；当垂直接地极在冻土层时，R1与R2之间满足线性变化的关系式；当垂直接地极穿过冻土层时，R1与R2之间满足非线性变化的关系式；与CDEGS的仿真值相比，垂直接地极在冻土层时，采用提出的拟合公式得到接地电阻的相对误差在±5％左右；垂直接地极穿过冻土层时，采用提出的拟合公式得到接地电阻相对误差绝对值在5％-10％左右。

For a single vertical grounding electrode, its power frequency grounding resistance in homogeneous soil is different before and after soil freezing. This will affect the error of grounding resistance test as well as the effect of groun- ding measures. Therefore, through simulation in CDEGS, we calculated the grounding resistance of single vertical grounding electrode in frozen and unfrozen soil, denoted by R1 and R2, respectively. According to the results, R1 and R2 are mainly influenced by three factors, namely, the reflection coefficient, the thickness of frozen soil and the length of the vertical grounding electrode. When the electrode length is no more than the thickness of frozen soil, there is a linear rela- tionship between R1 and R2; otherwise, the relationship would be nonlinear. We proposed equations for fitting the resistance, by which we obtained fitted R1 and R2 with relative error around ±5% when the electrode length is no more than the thickness of frozen soil, compared with the simulative results in CDEGS simulation values; when the electrode length is larger than the thickness of frozen soil, the abosolute value of error would be between 5% and 10%.