建筑物高度对地闪回击电磁场影响的模拟

基于三维时域有限差分数值算法（3D-FDTD）建立了雷击高建筑物电磁场传播模型，研究了负地闪击中不同高度建筑物时回击垂直电场、角向磁场以及水平电场沿地表的传播规律。模拟结果表明:建筑物的高度对雷电电场峰值的影响显著，如当建筑物高度从100 m增加至600 m时，在距离d=100 m位置的垂直电场峰值减小了63%，水平电场正极性峰值的增加比例为84%、负极性峰值的绝对值增加比例高达130%；观测位置不变时，角向磁场峰值和水平电场正极性峰值均会随着建筑物高度的增加而增大；对于距离d=100 m，300 m时，垂直电场的峰值随着建筑物高度的增加而减小，而d=500 m时，垂直电场峰值随着建筑物高度的增加呈现出先增大后减小的趋势；此外，建筑物高度会影响垂直电场峰值对距离的敏感程度，建筑物越低（高），相应的垂直电场峰值随着观测距离增大衰减越快（慢）。该文研究结果能够为现代化城市中高建筑物附近线缆、室外设备等的雷电防护方案设计提供参考。

Simulation of Structure Height Influences on Electromagnetic Field of Lightning Return Stroke

With the development of economy and society and the continuous acceleration of urbanization, there are more and more tall-objects in urban area. Tall-objects can attract nearby downward lightning and trigger upward lightning. When a thunderstorm occurs, tall-object may be struck multiple times, which lead to a severe lightning electromagnetic environment in the vicinity. Therefore, the study of lightning striking to tall-object is of significance to the lightning protection of nearby equipment and cables.An electromagnetic model of lightning striking to tall-object is developed based on the three-dimensional finite-difference time-domain (FDTD) numerical method. Using FDTD method, the propagation law of lightning vertical electric field, the azimuthal magnetic field and the horizontal electric field along the ground surface, produced by negative cloud-to-ground lightning flash to tall-object, is investigated considering cases of different heights (100-600 m) of tall-objects.The amplitude of lightning short-circuit current waveform is 11 kA, and the corresponding 10%-to-90% rise-time is 0.15 μs. Simulation results show that the height of the tall-object plays an important role on the peak value of lightning electric field. For example, for the case of distance d=100 m, the peak value of vertical electric field decreases from 8.59 kV·m-1 to 3.41 kV·m-1 with the height of the tall-object increasing from 100 m to 600 m (decrement:63%). Moreover, for horizontal electric field, the positive peak value increases from 0.7 kV·m-1 to 1.29 kV·m-1 (increment:84%), and the amplitude of negative peak increases up to 130%. The peak value of azimuthal magnetic field and horizontal electric field will increase with the tall-object height, when the distance of the observation point is constant. However, for the case of distance d=100 m, 300 m, the vertical electric field peak will decrease with the tall-object height increasing. Furthermore, for the case of d=500 m, the vertical electric field peak increase first and then decrease with the height. In addition, the tall-object height has an effect on the dependence of vertical electric field peak on distance d. For relative lower/taller strike object, the peak value of the corresponding vertical electric field attenuates quickly/slowly with the observation distance d. Results obtained are very useful for lightning protection design of power cables and electronic equipment in the vicinity of tall objects.