直流电流密度对土壤电阻率的影响

The Impact of DC Current Density on Soil Resistivity

高压直流输电系统的接地电流在1000A以上,为确保直流接地系统的安全运行,该文对直流电流密度与土壤电阻率的关系进行了研究。首先,利用多孔介质模型分析直流条件下土壤的导电机制,得出土壤电阻率的计算公式以及直流电流密度对土壤电阻率的影响规律。然后设计相应的实验进行定量分析,认为离子携带的总电荷数|zi|Ci以及离子迁移能力μi是影响土壤电阻率的主要因素,这种影响可以按直流电流密度的大小分为3个区段,第1个区段内土壤电阻率不随电流密度变化;第2个区段内土壤电阻率随电流密度增大而快速上升;在第3个区段,土壤电阻率随着电流密度的上升而快速下降。文中对造成这种现象的原因进行解释,并建立简化数学模型,该模型可以对不同直流电流密度下的土壤电阻率进行近似计算。

The grounding grip of high voltage direct current（HVDC） power system was working in large currents more than 1 000 A for long-term. Therefore, an analysis was given to definitude the relationship of current density and soil resistivity. In the first part, an expression of soil conductive mechanisms was given using porous media and a discussion was given about the effect of DC current density on soil resistivity. Then, an experiment was done on prove it. At last, a model was made about the relationship of current density and soil resistivity. Soil resistivity is determined by two parameters, the total of charges │zi│Ci and ionic mobility μi. The effect of DC current density on soil resistivity can be divided into three parts： when DC current density rises, soil resistivity rises slowly in the fast part and rises fast in the second part. In the third part, soil resistivity drops while current density rising. The model describing this effect can be used to calculate the soil resistivity of HVDC grounding system on any current.