地闪雷电电磁脉冲在大地中的分布研究

为研究地闪雷电电磁脉冲(LEMP)在大地中的分布规律,采用二维时域有限差分法计算了在雷电通道不同距离处、不同大地电参数条件下LEMP在地下不同深度的分布,并与其他高功率电磁环境在大地中的衰减情况作了对比.计算结果表明:随距离增大,大地中LEMP场分量迅速衰减;大地电导率较大时,电场分量衰减很大;大地电容率的变化主要影响LEMP的垂直电场分量,随大地电容率的增大,垂直电场分量明显减小;随深度的增大,电场分量衰减增大,其高频成分的衰减尤为显著,低频成分则衰减很小.由此可知,对电线电缆实施简单的埋地处理并不能有效防止LEMP的耦合效应.

Distribution of cloud-to-ground lightning electromagnetic pulse fields under the ground

In order to find out the distribution of lightning electromagnetic pulse (LEMP) fields under the ground, the two-dimensional finite-difference time-domain method is used to calculate LEMP under the ground. The distributions of LEMP under the ground are calculated in the cases of different distances from the lightning channel, different ground conductivities, different ground permittivities and different depths. The attenuations of lightning fields in the ground are compared with those of other high-power electromagnetic environments. The calculated results show the following points: the LEMP dramatically attenuates as the distance increases; the attenuation of the electric component is significant when the ground conductivity is reasonably high; the change of ground permittivity mainly causes the change of vertical electric field component, which decreases as the ground permittivity increases; the attenuation of the high frequency electric component increases and that of the low frequency electric component invisibly changes as the depth increases.