Far-field-current relationship based on the TL model for lightning return strokes to elevated strike objects
Far-field-current relationship based on the TL model for lightning return strokes to elevated strike objects
复制标题
DOI：
10.1109/temc.2004.842102
复制
发表时间：
2005-02
影响因子：
2.1
通讯作者：
J. Bermudez;F. Rachidi;M. Rubinstein;W. Janischewskyj;V. Shostak;D. Pavanello;Jen Shih Chang;A. Hus
中科院分区：
文献类型：
--
作者：
J. Bermudez;F. Rachidi;M. Rubinstein;W. Janischewskyj;V. Shostak;D. Pavanello;Jen Shih Chang;A. Hus
考虑到高架雷击物体的影响，提出了有关雷电回击电流和远辐射电场和磁场的新一般表达式，该物体的存在被包含为传输线（TL）模型的扩展。针对高物体和电矮物体的情况导出了特定方程。导出的表达式表明，对于高层结构（当塔内从顶部到底部的往返传播时间大于当前的零到峰值上升时间时），远场通过相对于地面发起的理想回程的一个因子而增强。增强因子可以用回程波前速度 v、真空中的光速 c 以及高架撞击物体顶部的当前反射系数来表示。对于该顶部反射系数通常为负值，雷击高塔会导致远电磁场显着增强。还针对电短塔和非常长的回程电流波前提出了与远电磁场和回程电流相关的表达式。对于在地面 (h=0) 处发起回程的情况，这些表达式代表了经典 TL 模型的概括，其中现在考虑了地面的反射。我们还描述了 2000 年和 2001 年期间对 553 米高的多伦多加拿大国家 (CN) 塔的雷击相关的两个距离处的回击电流及其相关电场和磁场的同步测量。针对高击中物体的导出表达式与获得的与雷击加拿大国家电视塔相关的同时测量的电流和场组进行了测试，并发现了合理的一致性。此外，研究表明，与雷击地面相比，雷击对 553 米高的结构辐射的电磁场峰值对回击速度值相对不敏感。
New general expressions relating lightning return stroke currents and far radiated electric and magnetic fields are proposed, taking into account the effect of an elevated strike object, whose presence is included as an extension to the transmission line (TL) model. Specific equations are derived for the case of tall and electrically short objects. The derived expressions show that, for tall structures (when the round-trip propagation time from top to bottom within the tower is greater than the current zero-to-peak risetime), the far field is enhanced through a factor with respect to an ideal return stroke initiated at ground level. The enhancement factor can be expressed in terms of the return stroke wavefront speed v, the speed of light in vacuum c, and the current reflection coefficient at the top of the elevated strike object. For typically negative values of this top reflection coefficient, lightning strikes to tall towers result in a significant enhancement of the far electromagnetic field. Expressions relating the far electromagnetic field and the return stroke current are also presented for electrically short towers and for very long return stroke current wavefronts. For the case of return strokes initiated at ground level (h=0), these expressions represent a generalization of the classical TL model, in which the reflections at the ground are now taken into account. We describe also simultaneous measurements of return stroke current and its associated electric and magnetic fields at two distances related with lightning strikes to the 553-m-high Toronto Canadian National (CN) Tower performed during 2000 and 2001. The derived expressions for tall strike objects are tested versus obtained sets of simultaneously measured currents and fields associated with lightning strikes to the CN Tower, and a reasonable agreement is found. Additionally, it is shown that the peak of the electromagnetic field radiated by a lightning strike to a 553-m-high structure is relatively insensitive to the value of the return stroke velocity, in contrast to the lightning strikes to ground.