Most of the available data concerning lightning current parameters were obtained by means of measurements made in temperate regions in the Northern Hemisphere. Considering the influence of regional aspects on such parameters, the need for references concerning lightning protection practices specifically in tropical zones requires dedicated data. An experimental investigation program has been carried on in Brazil since 1971 in order to provide data for characterization of local lightning current parameters. The authors of the present work are involved in that research. With such purpose, they have evaluated a significant amount of data, obtained by means of measurements taken at an instrumented tower located at “Morro do Cachimbo” Station, in Southeastern Brazil. The lightning current wave registers correspond to 157 strokes, which were measured during 13 years at the station. In this paper, the authors present a statistical evaluation of measured current waves, with particular interest in front wave parameters. The considered parameters (peak current, front duration and front steepness) are compared with those traditionally presented in literature. The cumulative frequency distributions and the correlation coefficients between parameters were determined. One main result was derived from this work, concerning the negative downward discharges: the median (and average) value of current peak measured at tower basis was found to be around 50% and 30% higher, respectively for the first and subsequent strokes, than the usual Berger references measured at tower top.

The response of grounding grids subjected to currents with typical waveforms of first and subsequent lightning return strokes is analyzed, based on experimental and simulated results. Parameters, which characterize this response, such as the grounding potential rise, impulse impedance, impulse coefficient, and effective grid area are determined for grids buried in soils of low, moderate, and high resistivity, varying the grid dimension and considering the frequency dependence of soil parameters. Based on such results, expressions to obtain the impulse impedance from the low-frequency resistance are derived.

The purpose of this paper is to introduce a modified approach for the electric field computation at the surface of overhead transmission line (TL) conductors through the finite-element method (FEM). The proposed strategy is based on a spatial transformation, well-known as Kelvin transformation, resulting in a special way to treat the unbounded domain. Unlike other applications of the FEM in TLs, the suggested procedure aims to reduce the computational domain and the solution time, allowing an efficient numerical evaluation of the electric potential gradients, without the need of geometric simplifications of the conductors. Comparative results show that a more realistic treatment offers a better understanding of how electric fields operate near real conductors and, in addition, that the proposed approach can be used to provide an accurate design for conductor systems in TLs.

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.