ВПЛИВ НА НЕЛІНІЙНИЙ ОБМЕЖУВАЧ ПЕРЕНАПРУГ СТРУМІВ БЛИСКАВКИ НЕГАТИВНОЇ ТА ПОЗИТИВНОЇ ПОЛЯРНОСТІ

Abstract

Purpose. The study of surge arrester models using oscillograms of real lightning currents and taking into account the polarity of lightning has been further developed. Methodology. Methods of circuit simulation for electrical scheme modes, free software for digitizing a bitmap graphic image of a lightning current oscillogram and converting it into an array of points are used. Results. A studying the model of a typical surge arrester with a nominal discharge current of 10 kA, intended for use in a 10 kV network was carried out. A well-known dynamic (frequency-dependent) model proposed by the IEEE working group was used to simulate the surge arrester. Oscillograms of real lightning currents of negative and positive polarity which were recorded on special towers were digitized. Using a free circuit simulation program, the residual voltage at the terminals of the surge arrester was determined and the energy that the surge arrester should absorb in the event that lightning currents of different waveforms and polarities flow through it, but with the same amplitude of 10 kA. It has been found that positive lightning strikes are potentially more dangerous than negative lightning strikes. It was shown that before the ending of the positive lightning current, the surge arrester have to absorb more than ten times more energy than before the ending of the negative lightning current of the same amplitude. Further development of the proposed approach is seen in its use for the tasks of improving the lightning protection of overhead power lines and protecting the high-voltage insulation of electrical equipment of substations from lightning overvoltage. Originality. The approach takes into account the differences between impulses of lightning currents of negative and positive polarity, which cannot be achieved when using the approximation of lightning currents by simplified expressions. Practical value. The use of the proposed approach improves the accuracy and visualization of research, since it takes into account the actual features of the lightning current curve. References 20, figures 12.