Current and electromagnetic field associated with lightning-return strokes to tall towers

Rachidi, Farhad; Janischewskyj, W.; Hussein, A.M.; Nucci, Carlo Alberto; Guerrieri, S.; Kordi, Behzad; Chang, Jen‐Shih

doi:10.1109/15.942607

Cited by 295 publications

(172 citation statements)

References 19 publications

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“…We begin with the same assumptions made in recent studies [e.g., Guerrieri et al, 1998;Janischewskyj et al, 1996;Rachidi et al, 2001;Rakov, 2001;Rachidi et al, 2002]. A debate has recently arisen [e.g., Kordi et al, 2002;Thottappillil et al, 2001Thottappillil et al, , 2002 concerning the validity of a lossless transmission line assumption for the case of a vertical structure above a ground plane.…”

Section: Model Of a Vertically Extended Strike Objectmentioning

confidence: 99%

Determination of reflection coefficients at the top and bottom of elevated strike objects struck by lightning

et al. 2003

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[1] In this paper, we present an analysis of lightning return stroke currents along an elevated strike object. We derive closed form expressions, both in the frequency domain and in the time domain, to calculate the lightning current at any height along a strike object taking into account reflections at the top and at the bottom. The frequency dependence of reflection coefficients is taken into account. We also derive an expression to calculate the reflection coefficient as a function of frequency at the bottom of the lightning strike object from two currents measured at different heights along the strike object. We show that, if the current and its time derivative overlap with reflections at the top or bottom of the strike object, it is impossible to derive the reflection coefficient at the top of the strike object exactly from any number of simultaneous current measurements. We propose an extrapolation method to estimate this reflection coefficient. We propose a second method to calculate the top reflection coefficient from just one current derivative measurement if the current derivative and its reflections do not overlap significantly. We apply the proposed methodology to experimental data obtained on Peissenberg Tower (Germany) consisting of lightning currents measured at two heights. The results suggest that the reflection coefficient at ground level can be considered as practically constant in the frequency range 100 kHz to 800 kHz. Although the estimated ground and top reflection coefficients are in good overall agreement with values found in the literature, the estimated values for the top reflection coefficient from the extrapolation method are somewhat lower than those found employing the current derivative method; the differences are discussed.

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Section: Model Of a Vertically Extended Strike Objectmentioning

confidence: 99%

Determination of reflection coefficients at the top and bottom of elevated strike objects struck by lightning

et al. 2003

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“…If the lightning short-circuit current (see Section III above) is not influenced by the presence of towers, higher field peaks in the case of lightning strikes to towers might be due to: 1) the existence of two wavefronts propagating simultaneously in opposite directions from the junction point between the descending leader and upward connecting leader from the tower top, with the downward-moving wavefront traversing both the upward-connecting-leader channel and the tower (neglecting current reflection at the tower top); 2) the nearly doubling of the downward-moving current wave on reflection at the bottom of the tower (Section II); and 3) the propagation speed of current waves on the tower being nearly equal to the speed of light, which is higher than the propagation speed of return-stroke current wave in a lightning channel (Idone and Orville 1982 [33]; Wang et al 1999c [34]). Rachidi et al [9] noted, from their modeling of lightning strikes to the CN tower using the modified transmission line model with exponential current decay with height (MTLE model), that the radiation field component of the total field is most affected (enhanced) by the presence of the tower. Perhaps in support of this inference, many electric and magnetic fields measured at a distance of about 200 m from the 160-m high Peissenberg tower (Zundl 1994a,b [3], [35]), examples of which are given in Fig.…”

Section: Electromagnetic Fields Due To Lightning Strikesmentioning

confidence: 99%

Transient response of a tall object to lightning

Rakov

2001

IEEE Trans. Electromagn. Compat.

162

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Abstract-Experimental data showing the transient behavior of tall objects struck by lightning are reviewed. The influence of this transient behavior, illustrated by simple calculations, on measured lightning current and measured remote electromagnetic fields is discussed. The estimated equivalent impedance of the lightning channel at the time of the initial current peak is appreciably higher than the characteristic impedance of an ordinary tall object (a factor of 3 or so for both the Ostankino and Peissenberg towers and about a factor of 2 for the CN tower). The grounding impedance of a tower is typically lower than its characteristic impedance. Thus, the current reflection coefficient is negative at the top and positive at the bottom of the tower. The similarity of the statistical distributions of subsequent-return-stroke peak currents in: 1) natural downward lightning; 2) natural upward (object-initiated) lightning; and 3) rocket-triggered lightning measured at objects with heights ranging from 4.5 to 540 m suggests that current peaks are not significantly influenced by the presence of a tall object, provided that measurements are taken at the top of the object. This inference is consistent with modeling results of Melander who showed that the current peaks measured in Switzerland and Italy at the top of 70-m and 40-m towers, respectively, are essentially unaffected by the presence of the towers. If lightning current could be represented by an ideal current source, current at the top of the object would be equal to the source current at all times. The peak current measured at the bottom of a tall object is usually more strongly influenced by the transient process in the object than the peak current at the top. For example, peak currents measured in the lower part of the 540-m Ostankino tower are about a factor of two higher than the peak currents measured near the tower top because the current reflection coefficient at the bottom of the tower is near +1. Observations and modeling suggest that a tall metallic strike object replacing the lower part of lightning channel serves to enhance the lightning-radiated electromagnetic fields relative to the fields due to similar lightning discharges attached directly to ground, this effect being more pronounced for the sharper lightning current pulses.

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“…In the case of the Pulse function, applying the constraint using equation (6), n can be expressed in terms of 1 . By substituting n in the Pulse function equation (3) and its derivative, equation (5) …”

Section: Zero Crossingmentioning

confidence: 99%

“…Heidler function and its modified form have been widely used to simulate the lightning return-stroke current [1][2][3]. Furthermore, the derivative of Heidler function and the derivative of its modified form have been successfully used to simulate the lightning return-stroke current derivative, measured at the Toronto CN Tower [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Cn Tower Lightning Return-Stroke Current Simulation

Elrodesly¹

2012

JLR

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Different functions have been used to model the lightning return-stroke current with the aid of direct current measurements at tall structures. In this paper, a comparison between the Pulse function and Heilder function is carried out to find out the suitability of each of these functions for simulating the lightning return-stroke current, measured at the CN Tower. An automated system for determining the CN Tower lightning return-stroke current waveform parameters is introduced. The curve fitting technique of this system and the estimation of the initial values of the simulation function parameters are presented. An artificial lightning signal, free of noise and reflections, is used as a reference signal for evaluating the parameter extraction system. Finally, cumulative statistics of the CN Tower lightning return-stroke current waveform parameters (peak, maximum rate of rise, risetime, pulse width, decay time and charge) are derived using the Pulse function parameters.

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Current and electromagnetic field associated with lightning-return strokes to tall towers

Cited by 295 publications

References 19 publications

Determination of reflection coefficients at the top and bottom of elevated strike objects struck by lightning

Determination of reflection coefficients at the top and bottom of elevated strike objects struck by lightning

Transient response of a tall object to lightning

Cn Tower Lightning Return-Stroke Current Simulation

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