有限元法计算地中交流电流分布

Calculation of the Distribution of the AC Current in the Earth by the Finite Element Method

交流以大地为回路时,接地电流在大地通道中的分布对接地极的电位、地表电流密度产生较大的影响。针对传统近似模型的不足,采用有限元法对地中电流进行数值分析计算,根据计算结果得到地中电流轴、横向分布的规律,并通过改变参数分析电流的频率对地中电流分布的影响。结果表明,此法计算方便,数据精确直观,在交流下电流向导线集中分布,且随着交流频率的增加,地表电流迅速增大,深处电流迅速衰减。

When the electric current infloods from the grounding pole to the earth, the distribution of the electric current in the earth makes important influences to the potential of the grounding poles and the surface current density. In this paper, laws of the current distribution in the earth under Alternating Current are investigated. As the old near model has many insufficiencies, whose assumed condition is that the current is equal at the ground surface and at the same radius, so that the analytic solution can be carried out, the results from this conventional method could only reflect the currentchange with the depth in the earth, but not enough to reflect the current distribution at the ground surface. In this paper, the current in the earth is recalculated by finite element method. The finite element method has many advantages, the original model could be solved with no change, and the current in multiplex stratified soil or in special landform can be calculated as well. By analyzing the results we could find the laws, including the axial current distribution and the transverse current distribution, which are similar. Then the frequency is changed to analyze its influence to the current distribution. In conclusion, compare with the old near model, the results prove that the finite element calculating method is convenient, and its data is precise and visualized. The results also indicate that the current concentrates towards the transmission line under AC power frequency. The current in the ground surface raises fast and the current in the deep earth decays fast with the increase of the frequency.