Effect of tall instrumented towers on the statistical distributions of lightning current parameters and its influence on the power system lightning performance assessment

Abstract

Abstract-Statistical distributions of lightning current amplitude, time-to-peak value and other lightning current parameters, used in power system insulation coordination, are based on experimental data obtained by means of tall instrumented towers. It is, however, generally accepted that these distributions are affected by the presence of the tower due to its attractive radius. Current amplitudes, in particular, are biased towards higher values with respect to those that would refer to flashes at ground. In this paper we propose a procedure, based on the Monte Carlo method, that allows to infer the statistical distributions of lightning current parameters at ground level starting from the 'classical' ones, i.e. those obtained from data measured using tall instrumented towers. The procedure is more general than others proposed in the literature for the same purpose, in that it can be applied whatever attractive radius expression is used. The procedure is applied to quantify the tower bias on the classical statistical distribution of lightning current amplitude for a number of available attractive radius expressions. Additionally, the comparison between the indirect-lightning performances of an overhead line, inferred by adopting both the classical, toweraffected, and the unaffected statistical distributions at ground of the lightning current amplitude, is given.

Highly intense lightning over the oceans: Estimated peak currents from global GLD360 observations

“…We reiterate that the peak current calibration for first strokes is less certain than for subsequent strokes in existing channels, so the absolute values reported here for the peak current of first detected strokes may be less accurate. Strokes preceded by stepped leaders have different attachment and return stroke dynamics [ Borghetti et al , ; Bazelyan and Chichinskiy , ], and so the empirical correction factor derived for the NLDN from rocket‐triggered experiments and, by extension, GLD360, do not necessarily translate to actual peak currents of first strokes. Furthermore, peak current estimates for NLDN have only been validated for subsequent strokes with peak current magnitudes less than ~45 kA [ Jerauld et al , ; Nag et al , ], and linearity is assumed for strokes with a larger peak current.…”

Reconsidering insulation coordination and simulation under the effect of pollution due to climate change

“…The air gap required to protect overhead transmission lines against lightning is determined according to lightning voltage and various factors. If lightning hits the tower, the resulting overvoltage may discharge into conductors through tower arm and insulator chains, leading to an interruption in the transmission line . To reduce the risk of sparks, the air gap should not be less than a certain amount.…”

"Avaliação de correntes de descargas atmosféricas através de medições diretas em estruturas altas"

“…15. Correntes "pura" e "contaminada" para Z ch = 2,5 kΩ (h t = 62,5 m com h s = 0m, Z t = 275 Ω e R g = 5 Ω).Observa-se através daFigura 4.13 que existe certa diferença entre os tempos de frente das correntes "pura" e "contaminada".…”

“…15. Correntes "contaminada" e "descontaminada" com aplicação de "FFT smoothing" (h t = 62,5 m, h s = 0 m, Z t = 275 Ω, Z ch = 1 kΩ e R g = 5 Ω).Na Figura 5.15 tem-se que Icont-smoth-0us corresponde à corrente "contaminada" e Idescontsmoth-0us à corrente "descontaminada", ambos com aplicação do filtro "FFT smoothing".…”