Tall-Structure Lightning Return-Stroke Models

从电气工程师的角度来看，回击是闪电中最重要的事件，因为它会导致电力和电信网络中的大部分破坏和干扰。为了确定这些领域，闪电回击（LRS）模型必须构建。同时测量的雷电流，其相关的电磁场，和雷电通道特性的定量评估的雷电回击模型，并为新的模型的建设和评估是必要的。这种基于实验的验证和开发方法将增强我们对LRS过程的理解，有助于制定可以更成功地用于闪电检测算法的模型，并允许开发更复杂的防雷措施。加拿大国家电视塔，以其极端的高度，提出了在世界上最好的选择之一，进行这项调查。到1991年，五个测量站投入运行，同时记录所有相关的闪电参数，包括塔上的回击电流及其在塔以北2公里处产生的电磁场。在过去的几年里，CN塔和附属的雷电通道已经由一系列级联的均匀传输线（TL）段表示。在该模型中，在不断增长的回击通道的前端的电流反射被考虑在内。从测量的电流中确定了CN塔三个主要结构不连续处的反射系数。该模型的定量评价进行了比较的EM场，计算通过应用一个特定的LRS模型和测量2公里以外的塔。虽然这种比较验证了该TL模型的优点，但由于雷电流路径（高架物体和通道）的每一级到地面的距离不同，因此使用均匀TL段显然是一种近似。申请人计划将雷电流路径建模为一系列非均匀传输线，每个传输线具有随高度变化的特性阻抗。

From the point of view of electrical engineers, the return stroke is the most important event in a lightning flash, as it causes most of the destruction and disturbance in electrical and telecommunication networks. In order to determine these fields, a lightning return-stroke (LRS) model must be constructed. Simultaneous measurement of the lightning current, its associated electromagnetic field, and lightning channel characteristics are necessary for the quantitative evaluation of lightning return-stroke models, and for the construction and evaluation of new models. This experimentally-based verification and development method will enhance our understanding of the LRS process, help in the formulation of models that can be used more successfully in lightning detection algorithms, and permit the development of more sophisticated measures for lightning protection. The CN Tower, with its extreme height, presents one of the best options in the world to carry out this investigation. By 1991, five measurement stations were in operation to simultaneously record all relevant lightning parameters, including the return-stroke current at the tower and its generated electromagnetic (EM) field 2 km north of the tower. Over the past several years, the CN Tower and the attached lightning channel have been represented by a series of cascaded uniform transmission line (TL) segments. In this model, current reflections at the front of the continuously growing return-stroke channel were taken into consideration. Reflection coefficients at CN Tower's three major structural discontinuities were determined from the measured current. A quantitative evaluation of this model was carried out by comparing the EM field, computed by applying a particular LRS model and that measured 2 km away from the tower. Although this comparison verified the merits of this TL model, the use of uniform TL segments is clearly an approximation since the distance to ground of each level of the lightning current path (the elevated object and the channel) is different. The applicant is planning to model the lightning current path as a series of non-uniform transmission lines, each having its characteristic impedance that varies with height.