地面建筑物对地闪回击通道附近电磁辐射环境的影响

Influence of buildings on the electromagnetic radiation environment near the lightning return strokes channel

采用有限电导率下的时域有限差分(FDTD)方法,分析了建筑物对地闪回击电磁环境的影响.结果发现建筑物对回击电场的影响较为明显,对磁场影响较小,建筑物高度hb=50 m时对磁场的影响不大于10%.建筑物顶部电场受自身高度的影响较大,屋顶中部的垂直电场随建筑物高度的增加而增大,水平电场随建筑物高度的增加而减小.建筑物高度为20、50和100 m时,屋顶中部的垂直电场分别约为地面处的1.3、1.7和2倍,水平电场约为地面处的0.9、0.8和0.7.电导率分别取0.001和0.1 s/m时对比发现,地表处的水平电场受电导率的影响较大,电导率越大,地表处水平电场的幅值越小,此时建筑物的存在对其影响不明显.地表以上一定高度处的水平电场则受观测点位置和建筑物的影响更加明显.

We analyzed the effect of tall buildings on the lightning return-stroke electromagnetic fields by using finite-difference time-domain（ FDTD） technique. Results show that tall buildings have obvious effect on the returnstroke electric fields and weak effect on magnetic fields（ less than 10% when the building is 50 m high）.The electric field at the top of buildings is closely related with the building height,and the vertical/horizontal component of the electric field gradually increases/decreases with the increase of building height.When the building is high as 20 m,50 m,and 100 m,the vertical electric field at the building top is 1. 3,1. 7,and 2 times of that at the ground level,respectively,while the horizontal one is 0. 9,0. 8,and 0. 7 times,respectively.We also analyzed the factors influencing the electric fields near tall buildings. The ground level horizontal electric field is obviously affected by the ground surface finite conductivity,the greater the soil conductivity,the faster the negative amplitude decays. While the horizontal electric field above the ground is affected by the buildings as well as the observation point location.