Application of the antenna theory model to a tall tower struck by lightning

Abstract

[1] The interaction of lightning with the 553-m high CN Tower in Toronto is modeled using the antenna theory model. A simple lossless wire structure is used to represent the tower. The return-stroke channel is modeled as a lossy vertical antenna attached to the tower top. The lossy antenna and the wire structure representing the tower are assumed to be fed at their junction point by a voltage source. The voltage waveform of this source is selected so that the source current resembles a typical lightning current waveform not influenced by the presence of the tall strike object. An electric field integral equation in the time domain is employed to calculate the lightning return stroke current distribution along the CN Tower and along the lightning channel. The equation is solved numerically using the method of moments. The lightning current flowing in the tower at the 474-m level above ground, predicted by the antenna theory (AT) model, compares favorably with the measurements conducted at the CN Tower. Once the temporal and spatial distributions of the current along the tower and along the lightning channel are determined, the corresponding remote electromagnetic fields are computed. Waveshapes of modelpredicted electric and magnetic fields at a distance of 2 km from the tower are in good agreement with measurements. The contribution of the tower to the electric and magnetic fields at 2 km is about four to five times the contribution of the lightning channel.

Electromagnetic compatibility issues of wind turbine analysis and design

“…Furthermore, the lightning channel is represented by a lossy vertical wire antenna, neglecting the corona effect. Note that the resistance per unit channel length is assumed to be 0.07 Ω/m, as in [19], the wire radius is a = 10 cm. For the sake of simplicity, the current wave along the channel is assumed to propagate at the velocity of light although the realistic current propagation velocity is by the factor of two or three less than in the model used in this work.…”

“…Within the framework of engineering models, the presence of a tall object has been considered by the use of a uniform, lossless transmission line representation [12,13]. The AT models [14][15][16][17][18][19] have been mostly applied in the analysis of lightning strikes to CN tower in Toronto, e.g. [18] or similar towers, e.g.…”

“…[18] or similar towers, e.g. [19]. The formulation can be posed in either the time [14,19] or the frequency domain [15][16][17][18], respectively.…”

“…[19]. The formulation can be posed in either the time [14,19] or the frequency domain [15][16][17][18], respectively. It is worth noting that a Numerical Electromagnetic Code is commonly used for current distribution calculation assuming the ground to be perfectly conducting (PEC) [14].…”

On the Mechanism of Attenuation of Current Waves Propagating Along a Vertical Perfectly Conducting Wire Above Ground: Application to Lightning

“…Models based on this approach are referred to as electromagnetic models (e.g., Rakov and Uman [3]). In these models (e.g., Podgorski and Landt [4], Moini et al [5], Kordi et al [6], Baba and Rakov [7]), lightning return stroke channel is represented by a vertical conductor of nonzero thickness. It has been shown that a current pulse attenuates as it propagates along such a conductor, even in the absence of ohmic losses, when it is excited at its bottom by a lumped voltage source (Bantin [8]; Kordi et al [9], [10]; Baba and Ishii [11]) or by a lumped current source (Grcev et al [12], and Baba and Rakov [7]).…”