The Influence of Frequency Dependence of Soil Parameters on Lightning Overvoltages in a 138-kV Transmission Line
Felipe Mendes de Vasconcellos1; Fernando Augusto Moreira1
1 Universidade Federal da Bahia
Resumo
This study evaluates the overvoltages developed due to lightning in a 138-kV transmission line comparing constant and frequency-dependent soil parameters. ATP (Alternative Transients Program) was used to simulate the influence of the frequency dependence of ground resistivity and permittivity on the overvoltages developed across insulators due to direct lightning strokes to the tower top, considering lightning current parameters measured at Morro do Cachimbo Station, in Brazil. The consideration of the frequency dependence of the soil parameters causes a percentage decrease of the overvoltage peaks when compared with constant soil parameters of around 15% and 33% for first strokes and 1.1% to 2.6% for subsequent strokes, considering values of soil resistivity of 500 Ω.m and 2500 Ω.m. Therefore, disregarding the frequency dependence of the soil parameters in simulations may lead to an overly conservative estimation of the lightning performance of the transmission line.
Palavras-chave: ATP; ground resistivity; ground permittivity; lightning; transmission line