配电房工频磁场屏蔽方法分析

Analysis of power frequency magnetic field shielding methods for power distribution substation

以三相重载母排为配电房工频磁场源,以配电房自身楼层面作为屏蔽体,基于涡流场分析原理建立了配电房工频磁场计算的有限元模型,并采取局部加密的方法对有限元的剖分进行控制,从而实现对配电房及附近环境中的三维涡流场的有效计算。在此基础上选取设置了素混凝土层、单层钢筋网混凝土层、双层钢筋网混凝土层、钢板混凝土层4种屏蔽模型,采用有限元法对这4种屏蔽层模型进行仿真计算,对比研究其屏蔽效能。针对研究结果,以单层钢筋网混凝土为屏蔽层,进一步讨论了屏蔽效能与钢筋网格尺寸及钢筋直径之间的关系,并对钢板混凝土为屏蔽层时其屏蔽效能与钢板厚度的关系进行计算分析。最后得出结论:虽然钢板混凝土层的屏蔽效能最好,但是在适当选择钢筋网格数和钢筋直径的情况下,单层钢筋网混凝土结构可以满足经济性和环保安全的双方面要求。

Power frequency magnetic field which is generated by the underground power distribution substation of residence areas poses as a potential harm to human health. In view of this, the present study aims to analyze the magnetic field distribution and shielding for power distribution substation based on Finite Element Method （FEM）. Referential suggestions for magnetic shielding around power distribution room are proposed further. Based on the principles of eddy current field analysis, the Finite Element Model is employed to deal with the power frequency magnetic field of power distribution substation, where three-phase heavy-duty busbar is regarded as the source of power frequency magnetic field and its own floor is considered as the shield. The three-dimensional eddy current field in and near the power distribution substation has been efficiently calculated where the method of local refinement is applied to control the finite element subdivision. Through a series of setting, the following screening models have been constructed and studied with finite-element method： plain concrete layer, single-mat reinforced concrete layer, double-mat reinforced concrete layer and steel plate concrete layer. Some conclusions are drawn as follows： the shielding efficiency of plain concrete layer is the lowest, while the steel plate concrete is the most efficient shielding material among he studied shielding models. Compared with the single-mat reinforced concrete layer, the shielding efficiency of double-mat reinforced concrete layer is improved insignificantly. The shielding efficiency of the steel-plate concrete layer is improved with the increase of steel plate thickness. Nevertheless, the improvement of shielding efficiency of steel plate is not obvious as its thickness continue to increase. Considering the construction cost and shielding efficiency, single-mat reinforced concrete layer was selected as shielding layer to further discuss the relationship between the shielding properties and steel grid size as well as steel diameter. The simulation results indicate that single-mat reinforced concrete layer is able to meet the requirement of both economic and environmental safety aspects as long as proper steel grids and steel diameters are chosen.