Assessing the influence of peak current distributions of first return strokes on the lightning performance of transmission lines: Instrumented tower distributions versus standard distributions

Abstract

• The effect of peak current distributions on backflashover is shown. • Instrumented tower and standard distributions are adopted. • IEEE and CIGRE distributions overestimate backflashover for high voltage level TLs. • MCS distribution leads to largest BFOR probability for low insulation level TL. • A new formulation to reproduce high current region of MCS distribution is proposed. The influence of peak current distributions of first return strokes of instrumented towers and international standards on the calculated lightning performance of 138 kV and 500 kV transmission lines is evaluated. This performance, expressed by the backflashover probability, is determined by computational simulations using the Hybrid Electromagnetic model (HEM) and the Disruptive Effect method (DE). The performance is calculated considering the cumulative peak-current distributions obtained from direct measurements at the instrumented towers of Morro do Cachimbo (MCS) and Monte San Salvatore (MSS) stations and those provided by IEEE and CIGRE standards. According to the results, using the standard distributions yields larger backflashover probabilities of transmission lines of higher insulation level, in relation to those calculated using instrumented-tower distributions. Considering transmission lines of lower insulation level, the performances calculated using standard distributions are close to those obtained using MSS distribution, but yields lower backflashover probabilities in relation to those obtained using MCS distribution. The latter leads to backflashover probabilities about 40% and 47% larger than those obtained by using IEEE and CIGRE distributions, respectively, in the tower-footing impedance range of 20 Ω – 40 Ω.