垂直接地极温升模拟试验及仿真分析  

Modeling test and simulation analysis of temperature rise of vertical grounding electrode

作　　者：张延辉[1] 蔡汉生 胡上茂 刘刚 贾磊 鲁海亮[1] ZHANG Yanhui;CAI Hansheng;HU Shangmao;LIU Gang;JIA Lei;LU Hailiang(School of Electrical Engineering and Automation,Wuhan University,Wuhan 430072,China;Electric Power Research Institute,China Southern Power Grid,Guangzhou 510080,China)

机构地区：[1]武汉大学电气与自动化学院,湖北武汉430072 [2]南方电网科学研究院,广东广州510080

出　　处：《武汉大学学报（工学版）》2019年第11期1003-1010,共8页Engineering Journal of Wuhan University

基　　金：南方电网重大专项项目（编号：WY-KJXM-20150901）

摘　　要：通过模拟试验获得了直流输电系统垂直接地极在均匀土壤、双层土壤、包含焦炭的均匀土壤和包含焦炭的双层土壤4种情况下的温升规律,并建立有限元模型进行了仿真对比分析.结果表明:垂直接地极在均匀土壤中由于端部效应端部发热严重;在双层土壤中由于上层土壤电阻率高,导致电极顶端温升减小,底端温升进一步增大,试验结束时顶端和底端温差很大;在试验后期电极的温度迅速上升,结合接地极电压迅速上升的现象分析,认为是接地极附近的土壤因温度升高、水分逐渐蒸发、电阻率迅速增大所致;距离接地极12 cm处的土壤温升几乎为0,温升集中在接地极附近是因为土壤的导热系数比较小,在试验的有限时间里接地极产生的热量难以传递到较远位置;填充焦炭等效于增加接地极的半径,能显著降低垂直接地极的温升速率;增加土壤的导热系数能够降低接地极的温升速率和稳态温度,将土壤的导热系数从1 W/(m·℃)增加到10 W/(m·℃),2次试验的最大温升分别降低了25℃和32℃.因此对接地极进行填充焦炭处理和采用导热系数大的土壤是降低接地极温升的直接有效方法.Through modeling test measurements,the law of temperature rise of vertical grounding electrode under the four conditions of uniform soil,double-layered soil,homogeneous soil containing coke,and doublelayer soil containing coke is obtained;and then,a finite element model is established for simulation analysis.The results show that the vertical ground electrode has severe fever at the end due to the end effect when it is in the uniform soil.In the two-layer soil,due to the high resistivity of the upper layer soil,the temperature rise at the top end of the electrode is reduced,and the temperature rise at the bottom end is further increased,at the end of the test,the temperature difference between the top and bottom ends is very different at end of the test.The rapid increase in temperature at the end of the test,combined with the phenomenon of rapid rise in the voltage at the ground electrode,is considered to be due to the increase in temperature in the soil near the grounding electrode,moisture gradually evaporates and the resistivity increases rapidly.The temperature rise of the soil at 12 cm from the grounding electrode is almost zero,the temperature rise is concentrated near the grounding electrode because the thermal conductivity of the soil is relatively small,in the limited time used in the test,the heat generated by the grounding electrode is transmitted to a relatively small distance.Filling the coke is equivalent to increasing the radius of the grounding electrode can significantly reduce the temperature rise rate of the vertical grounding electrode.Increasing the thermal conductivity of the soil can reduce the temperature rise rate and the steady-state temperature of the grounding electrode,the thermal conductivity of the soil is increased from 1 W/(m·℃)to 10 W/(m·℃),and the maximum temperature rises of testsⅠandⅡare reduced by 25℃and 32℃,respectively.Therefore,the coke treatment of grounding electrode and the use of soil with high thermal conductivity are two direct and effective methods to

关 键 词：均匀土壤 双层土壤 焦炭 暂态温升 模拟试验 

分 类 号：TM723[电气工程—电力系统及自动化]