Determination of lightning currents from far electromagnetic fields : effect of a strike object

Bermudez, José Luis (School of Management and Engineering Vaud, HES-SO // University of Applied Sciences Western Switzerland) ; Rachidi, Farhad (EPFL, Lausanne, Switzerland) ; Janischewskyj, Wasyl (University of Toronto, Toronto, Canada) ; Shostak, Volodymyr O. (Kyiv Polytechnic Institute, Kiev, Ukraine) ; Rubinstein, Marcos (School of Management and Engineering Vaud, HES-SO // University of Applied Sciences Western Switzerland) ; Pavanello, Davide (EPFL, Lausanne, Switzerland) ; Hussein, Ali M. (Ryerson University, Electrical and Computer Engineering Department, Toronto, Canada) ; Chang, Jen-Shih (McMaster University, Hamilton, Canada) ; Paolone, Mario (University of Bologna, Bologna, Switzerland)

We discuss in this paper the influence of the presence of an elevated strike object on the peak of the lightning return stroke current determined from remote field measurements. We develop analytical expressions relating the lightning return stroke channel-base current and the far electromagnetic field for different specific cases, namely, (1) ground-initiated return strokes (classical transmission line (TL) model), (2) ground-initiated return strokes including possible reflections at ground level, (3) tall strike objects for which the current's zero-to-peak time is smaller than the travel time along the object, and (4) electrically short strike objects. It is shown that for tall structures, the field enhancement relative to a return stroke initiated at ground level is expressed through a factor equal to ktall = [1+c/v(1-2ρt)]/(1-ρt), where v and c are the return stroke front speed and the speed of light in vacuum, respectively, and ρt is the top reflection coefficient. For very short towers and/or very slow return stroke current wavefronts, when the condition tf ⪢ h/c applies, expressions relating the far electromagnetic field and the return stroke current were also derived. For case (2), return strokes initiated at ground level, the field enhancement relative to a return stroke initiated at ground level, case (1), is expressed through a factor equal to kshort =(1+(c/v) ρch-g)/(1+ρch-g), where ρch–g represents the reflection coefficient between the lightning channel and the grounding impedance.


Keywords:
Article Type:
scientifique
Faculty:
Ingénierie et Architecture
School:
HEIG-VD
Institute:
IICT - Institut des Technologies de l'Information et de la Communication
Date:
2007-05
Pagination:
7 p.
Published in:
Journal of Electrostatics
Numeration (vol. no.):
2007, vol. 65, no. 5-6, pp. 289-295
DOI:
ISSN:
0304-3886
Appears in Collection:

Note: The status of this file is: restricted


 Record created 2020-07-07, last modified 2020-07-09

Fulltext:
Download fulltext
PDF

Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)