基于薄壳理论的直流接地极电热动态耦合有限元模型

发布时间：2019-01-01 19:27

【摘要】：超/特高压直流输电工程中共用接地极技术的应用日趋普遍,单极大地运行方式下直流接地极承载的入地电流大幅增加。考虑直流接地极散流时土壤中温度场和电场的相互影响,准确计算其接地参数及电流场分布是直流接地极优化设计及后续相关课题研究的基础。提出了基于薄壳理论的直流接地极电热动态耦合有限元数值计算方法。在土壤中恒定电场与温度场耦合的基础上,分别通过将土壤电参数和热参数:电阻率、比热容和热导率设置为上一时刻该单元土壤温度的函数,实现由时变的温度分布控制土壤参数,准确地模拟散流过程中土壤电场、热场相互影响、相互耦合的动态过程;同时在数值计算过程引入"薄壳"理论,将接地导体用具有一定虚拟厚度的二维面代替,采用三角形单元离散,解决了直流接地极截面尺寸与求解区域差异巨大而带来的计算量大、求解困难的问题。最后,将数值计算结果与文献试验测量结果对比,验证了文中算法的有效性。并基于文中算法分析了土壤参数温度特性对接地极性能的影响,认为考虑土壤参数温度时变特性时,在一定范围内,较高土壤电阻率地区直流接地系统的接地电阻随运行时间有较明显的增大现象。
[Abstract]:The application of common earth-pole technology in UHV / UHV HVDC transmission projects is becoming more and more common, and the earth-entering current carried by DC earth-pole is greatly increased under the monopole operation mode. Considering the interaction between the temperature field and electric field in the soil during the DC earth pole dispersion, the accurate calculation of the grounding parameters and the distribution of the current field is the basis of the optimum design of the DC earth pole and the research of the related topics. A finite element numerical method based on thin shell theory is proposed for dynamic electrothermal coupling of DC earth electrodes. On the basis of the coupling of constant electric field and temperature field in soil, the electrical and thermal parameters of soil are set as the function of soil temperature at the last moment by setting the electrical and thermal parameters of the soil: resistivity, specific heat capacity and thermal conductivity, respectively. The soil parameters are controlled by time-varying temperature distribution, and the dynamic process of soil electric field and thermal field interaction and coupling are simulated accurately. At the same time, the theory of "thin shell" is introduced into the numerical calculation process, and the grounding conductor is replaced by a two-dimensional plane with a certain virtual thickness, and the triangular element is used to discretize the ground conductor. The problem of large computation and difficult solution caused by the huge difference between the size of DC earth pole section and the solution area is solved. Finally, the effectiveness of the proposed algorithm is verified by comparing the numerical results with the experimental results. Based on the algorithm, the influence of soil temperature characteristics on the performance of the earth pole is analyzed, and it is considered that the time-varying temperature of soil parameters is in a certain range. The grounding resistance of DC grounding system in high soil resistivity area increases obviously with operation time.
【作者单位】：郑州大学电气工程学院;
【基金】：国家自然科学基金项目(51307152)~~
【分类号】：TM721.1;TM862

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