Abstract
Lightning-induced voltages are one of the main causes of shutdown in distribution lines. In this work, attention is focused on the effects of wideband modeling of electric grounding in the overvoltage calculation along insulator strings due to indirect lightning strikes. This study is done directly in the time-domain with the grounding being represented with an equivalent circuit accounting for its dynamics. Results show that the adoption of commonly adopted simplified grounding models, such as low-frequency resistance, may lead to an underestimation of the overvoltage. According to the results, differences in the order of 25% can be found in some studied cases.
Highlights
Transmission and Distribution Systems are highly affected and damaged by direct and indirect lightning events
Indirect events are not of interest for TS since the induced voltages are generally lower than the line Critical FlashOver voltage (CFO), but they are vital when dealing with Distribution Systems (DS), which are characterized by a low CFO
Based on the behaviors described in these figures, it is possible to verify that: (i) grounding can only be represented by R LF in the low-frequency range, where Z (ω ) tends to R LF ; (ii) the limit frequency of the low-frequency range increases with a reduction in conductivity; (iii) in the intermediate-frequency range there is a predominance of capacitive behavior of the grounding, verified by the decrease of
Summary
Transmission and Distribution Systems are highly affected and damaged by direct and indirect lightning events. Indirect events occur when lightning strikes the ground in the proximity of a power system; these events are much more frequent with respect to direct ones, but the overall voltage induced in the power system is usually much lower. Most works address lightning-induced voltages in DS model electric grounding as a constant value resistance R LF [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16] This parameter is associated with a low-frequency behavior, i.e., disregarding its electromagnetic dynamic.
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