基于土壤电阻率温度特性的接地极电热全耦合分析

Fully coupled analysis of current and temperature fields of grounding poles based on soil resistivity and temperature characteristics

接地极的温升问题可能会影响接地极的安全稳定运行,接地极在土壤中散流,在电流场的作用下产生焦耳热并进行热传导。实际上,土壤的参数会随着温度改变,导致电流场变化,进而影响热传导过程,即电流场与温度场之间相互影响。通过试验获取土壤的电阻率温度特性、导热系数和容积热容量数据并建立电流场和温度场的全耦合模型。将2种仿真计算结果与试验得到的温升、电压数据进行对比,结果发现:不考虑土壤电阻率温度特性时前期的结果与试验结果较为符合,后期的温升速率继续降低则与试验中后期温度迅速增加的现象相矛盾;仿真中考虑土壤电阻率温度特性时温升和电极电压仿真结果趋势均与试验结果趋势符合较好,且此时有助于削弱端部效应,所以应该将土壤电阻率温度特性引入接地极的发热分析。

The temperature rise problem of the grounding pole may affect the safe and stable operation of the grounding pole.The grounding current scatters in the soil,generates joule heat,and conducts heat conduction under the action of the current field.In fact,the parameters of the soil change with temperature,which causes the current field to change and affects the heat conduction process.Thus,the interaction between the current field and the temperature field occurs.Through the test,the temperature characteristics of resistivity,thermal conductivity and volumetric heat capacity data of the soil were obtained and the fully coupled model of the current field and the temperature field was established.The results of the two simulation models with and without considering the temperature characteristics of the soil were compared with the temperature rise and electrode voltage data obtained by the test.The results of the early period are consistent with the test results when the temperature resistivity of the soil is not considered.The subsequent decrease of the temperature rise rate is in contradiction with the rapid increase of the temperature in the middle and the end periods of the test.When the temperature characteristics of the soil resistivity are considered in the simulation,the trends of temperature rises and the electrode voltage simulation results are in good agreement with those of the test results,which helps to weaken the end effect.Therefore,the soil resistivity temperature characteristics should be introduced into the grounding electrode for heat analysis.