Numerical electromagnetic analysis of transient induced voltages associated with lightning to tall s.pdf

Journal of Electrostatics 60 (2004) 141–147 Numerical electromagnetic analysis of transient induced voltages associated with lightning to tall structure$ Ramesh K. Pokharela,*, Yoshihiro Babab, Masaru Ishiia aUniversity of Tokyo, Tokyo, Japan bDoshisha University, Kyoto, Japan Abstract In the present paper, transient-induced voltages on a distribution line over finitely conducting ground, which are associated with lightning to a 200-m high stack, have been analyzed by Numerical Electromagnetics Code (NEC-2). An electromagnetic model (EM) of a lightning channel, which contains additional distributed inductance to simulate the reduced propagation velocity of lightning current, has been employed. Validity of the employed model which incorporates a tall structure and a lightning channel has been discussed by comparing calculation with measurements. r 2004 Elsevier B.V. All rights reserved. Keywords: LEMP; Lightning-induced voltage; Numerical electromagnetic field analysis; Return stroke; Tall structure 1. Introduction Lightning often strikes tall structures such as chimneys that might be close to distribution lines. In such cases, a tall structure as well as a lightning channel should be modeled reasonably to evaluate electromagnetic fields around them [1–4]. Recently, lightning currents have been measured on freestanding tall structures simultaneously with the associated electromagnetic fields, and they were analyzed ARTICLE IN PRESS $This work was presented at the 26th International Conference on Lightning Protection, Cracow, Poland, 2–6 September 2002. *Corresponding author. Current address: Aoayma Gakuin University, Tokyo, Japan. E-mail addresses: pokharel@ee.aoyama.ac.jp (R.K. Pokharel), ybaba@mail.doshisha.ac.jp (Y. Baba), ishii@iis.u-tokyo.ac.jp (M. Ishii). 0304-3886/$ - see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.elstat.2004.01.019 [1–3]. Most of the analyses employed single or cascaded lossless transmission lines specifying surge im