On validation of FCCFs for lightning striking tall objects considering propagation effect of finitely conducting earth

Abstract

In this paper we have studied the accuracy of field-tocurrent conversion factors (FCCFs) presented by Baba and Rakov for currents inferred from electromagnetic field produced by lightning strike to tall objects, considering the perfectly and finitely conducting ground, respectively. For the perfectly conducting ground, the different FCCFs for the peak currents have different accuracy ranging from about underestimation of 18% to overestimation of 10% for the reflection coefficients at the two ends of object t =-0.5 and b =1.0, and from about underestimation of 25% to overestimation of 10% for  t =-0.5 and b =0.7, and their accuracy decreases with the increase of current risetime RT. For the finite conductivity with 0.01 S/m and 0.001 S/m, FCCFs will cause many errors if we do not take into account the propagation effect along the finitely conducting ground, and their errors obviously increase with the decrease of the conductivity. For example, for t =-0.5 and b =1.0, , the errors are about 20% when the conductivity is 0.01 S/m while the errors are about 55% when the conductivity is 0.001 S/m for lightning strike to the 168-m-high object. Therefore, we revised FCCFs by considering the propagation effect of finite conductivity on the electromagnetic field radiated by lightning strike to tall objects, and found that our revised FCCFs have much better accuracy for the lossy ground than that presented by Baba and Rakov.

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

“…Direct measurements of lightning currents can be obtained either using instrumented towers (e.g., Berger, 1975;Diendorfer et al, 2009;Heidler et al, 2015;Romero et al, 2013;Visacro et al, 2004) or using artificial initiation of lightning from natural thunderclouds (e.g., Qie et al, 2011;Thottappillil et al, 1995). Besides, information on lightning current can be remotely inferred from lightning location systems using empirical (e.g., Rakov et al, 1992) or theoretical (e.g., He et al, 2014;Rachidi & Thottappillil, 1993;Zhang et al, 2014) equations. The estimation of lightning current parameters from remote field measurements is affected by the conditions of the propagation path of the electromagnetic fields.…”

An Analysis of Current and Electric Field Pulses Associated With Upward Negative Lightning Flashes Initiated from the Säntis Tower

“…Characteristics and mechanisms of lightning flashes initiated from tall structures have been studied for nearly eight decades (e.g., Baba & Rakov, ; Berger, ; Bermudez et al, ; He et al, ; Heidler & Paul, ; McEachron, ; Miki et al, ; Mosaddeghi et al, ; Pavanello et al, ; Rachidi et al, ; Wang et al, ; Zhang et al, ; Zhou et al, ). The percentage of upward flashes initiated from tall towers depends on a number of factors such as the height of the structure, the topographical conditions, and the presence of other tall structures in the vicinity (Smorgonskiy et al, ).…”