Modelagem matemática de correntes na torre da estação Morro do Cachimbo (Brasil)

Abstract

The effect of an elevated strike object on the measured current in the top and the bottom of Morro do Cachimbo (MCS) station instrumented tower is modeled, considering a current divisor applied at the tower top, and that the channel current is supplied by the current source located at the attachment point. The mathematical formulations of the engineering models were applied in order to distinguish if the estimated current at the tower top or bottom is different considering the same event. The developed model for lightning striking short and long electrically towers, was applied to the Morro do Cachimbo (MCS), Mount San Salvatore (MSS) stations, and Mount Peissenberg tower (MPT). The mean return stroke current curve, computed from the experimental data acquired at the Morro do Cachimbo tower, was modeled by a Heidler Current Function and applied to the model for different wave reflection coefficients, locations of the current sensors and the tower heights. The results of modeling appear to be in accordance with a model based on the distributed current source along the lightning channel. The distribution current source model is expressed in terms of the ‘undisturbed’ current, object height, and current reflection coefficients at the top and the bottom of the object. It was considered the distributed-source representation of the lightning channel including a self-consistent treatment of the impedance discontinuity at the channel base and the tower top. We conclude that the location of measuring instrument on the tower (bottom or top) causes no significant differences in the first return stroke current peak. On the other hand, for the subsequent return stroke, the location of measuring instrument on the tower (bottom or top) causes differences in the estimated current peak at the tower base from 20% to 30% greater than the estimated current peak at the tower top.