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为了研究闪电脉冲电磁场(LEMP)在地下传播的过程与空间分布特性,本文采用一种改进的时域有限差分法(FDTD)计算了LEMP在整个地下空间的传播过程.与以往发表的研究只局限在个别观察点的讨论不同,本文通过计算得到了空间中所有网格位置上的电磁场、时间导数、功率密度和能量密度及它们的峰值,并将它们按照空间坐标表示在相应的分布彩图中.发现在靠近地表和远离闪电通道的区域内,LEMP的各个分量同时在平行和垂直地面的两个方向上呈指数型衰减.其中磁场与水平电场的峰值在整个空间极性统一,且呈现类双指数形分布.而垂直电场在地下的峰值分为极性相反的两个区域,并且靠近闪电通道的区域呈类球状分布.其他特性参量也有类似以上的空间分布特点.并且本文通过对不同大地电导率、电容率、放电通道模型和基电流情况的计算,发现虽然在个别情况下LEMP在地下空间的数值整体增大,但整体分布特征并未改变.即使是在水平或垂直分层大地的情况下,同一层内部仍然具有相同的分布规律.甚至是在击中避雷针情况下,LEMP在地下空间的分布特点也仍然未变.而这些分布规律和特征的发现和利用,将为地下管线、设备、线缆的电磁防护设计与位置规划提供重要的支持.
In order to study the process and spatial distribution characteristics of lightning impulse electromagnetic field (LEMP) propagating underground, an improved time domain finite difference method (FDTD) was used to calculate the propagation of LEMP in the entire subsurface space. The discussion at individual observation points is different. In this paper, the electromagnetic fields, time derivatives, power density, energy density and their peak values of all the grid positions in space are calculated and expressed in the corresponding color map according to the spatial coordinates It is found that the LEMP components attenuate exponentially in both directions parallel and perpendicular to the ground near the surface and away from the lightning channel, where the peak values of the magnetic field and the horizontal electric field are uniform across the entire space, Double exponential distribution.The vertical electric field in the underground peak is divided into two opposite polarity regions, and near the lightning passage area was spherical distribution, and other characteristics of the parameters also have the above spatial distribution characteristics.This paper through the different earth Conductivity, permittivity, discharge channel model and the calculation of base current conditions, it is found that although in individual cases L EMP in the overall increase in the numerical value of the underground space, but the overall distribution of features has not changed even in the case of horizontal or vertical stratification of the same layer within the same distribution still have the law, even in the case of lightning rod hit, The distribution characteristics of LEMP in underground space also remain unchanged, and the discovery and utilization of these distribution rules and features will provide important support for the design of electromagnetic protection and location planning of underground pipelines, equipment and cables.