采用有限体积法的特高压直流输电系统接地极稳态温度场仿真分析

在接地极计算中,需要计算的不仅仅是接地极附近的电流场,由电流场引发的温度场也需要同时计算。为此,介绍了采用有限体积法的特高压直流输电接地极稳态温度场计算方法。首先将场域在3维空间内划分为若干个互不重叠的单元,每个单元用中心点代替;然后根据热平衡方程,推导出描述温度场的离散方程组;最后求解方程,得到场域内所有节点的温度,从而获得稳态温度场中的最高温度。在对同1个模型的稳态温度场计算中,通过比较该算法以及MATLAB计算结果,验证了有限体积法的正确性。将该算法用于实际工程中接地极稳态温度场的计算,通过对比若干组计算结果,得到了土壤最高稳态温升与接地电阻的平方、入地电流的平方成正比,与土壤热导率成反相关的结论。最后对于实际工程的应用中,提出通过减小接地极的接地电阻来减小土壤最高稳态温升的合理建议。

Steady-state Temperature Field Simulation Analysis of Ultra High Voltage DC Transmission System Grounding Electrode Using Finite Volume Method

In grounding electrode computation of ultra high voltage DC(UHV DC) system,not only the current field should be taken into account,but also the temperature field should be calculated.A method was described for calculating the temperature field near the grounding electrode of an UHV DC system by using finite volume method(FVM).Firstly,the grounding electrode field was divided into a number of non-overlapping blocks in 3D space and each block was represented by its center.Then the mathematical equation describing the temperature field was established according to the thermal equilibrium principle.Finally,the steady-state temperature field could be obtained by solving the above equation.Thus the maximum temperature could also be acquired.The comparison between the result of FVM and that of MATLAB verified accuracy of the finite volume method.In addition,the method was applied in an actual project,and the conclusion was that the maximum temperature was in proportion to the square of the grounding resistance and the square of the current into earth,and was reversely correlated with the thermal conductivity.At last,in practical application,it was suggested that decreasing grounding resistance in grounding electrode could inhibit the maximum temperature rise of soil.