Estudo da sobretensão causada por descargas atmosféricas em linhas de distribuição de 69 kV

Abstract

This work displays in detail the modelling, using the graphical preprocessor ATPDraw, of a 69 kV overhead line, whose line supports consist in concrete poles. Both this operating voltage and this class of structure are infrequently approached in the literature. The overvoltage waveforms across the insulators caused by lightning strikes on the shield wire were analysed, considering two models of lightning sources, with 1 or 7 Heidler Functions. The grounding conductor along the concrete pole were modelled through a multiconductor model and represented as lossless transmission lines. Regarding the simulations scenarios, besides the effects of the soil resistivity variation, both regular and irregular grounding conditions were considered. The overvoltage peak values across the insulators for the 7 Heidler current source model were superior in 80 % of the cases, characterizing a more conservative approach. Major impacts were observed in both amplitude and shape of waveforms of the overvoltage across the insulators for the irregular grounding condition in the struck pole. Nevertheless, this effect was minimal for the overvoltage across the insulators of the struck pole considering the irregular grounding condition in the adjacent pole.