Influence of First Return Stroke Current Distributions of Tropical and Temperate Regions on the Assessment of Backflashover Occurrence of Transmission Lines

The effect of first return stroke current distributions of tropical and temperate regions on the assessment of backflashover occurrence of transmission lines is analyzed by means of computational simulations. Current parameters and associated distributions derived from the measurements performed at Morro do Cachimbo station (MCS), Brazil, that comprise 51 negative cloud-to-ground flashes and median first stroke peak current of 43 kA are considered. The results were compared with those obtained from the application of current parameters derived in a temperate region at Mount San Salvatore station (MSS), Switzerland and the cumulative peak current of first strokes recommended by IEEE Std 1243. Sensitivity analyses were developed considering typical configurations of 138-kV and 230-kV transmission lines in a wide range of tower-footing grounding impedance and representative first stroke current waveform. The obtained results revealed about 44%-to-54% larger and 54%-to-28% lower backflashover probability related to the application of MCS peak current distribution data, in the 20-to-40-Ω tower-footing grounding impedance range, for the 138-kV and 230-kV transmission lines, respectively.