EFFECT OF LIGHTNING CURRENTS OF NEGATIVE AND POSITIVE POLARITY ON SURGE ARRESTERS IN PARALLEL CONNECTION

Purpose. Studying the effect of non-identical protective characteristics of surge arresters on the efficiency of several arresters in parallel connection. Methodology. Free software for circuit simulation was used to solve electrical circuits with nonlinear parameters. To simulate the effect closest to real conditions, oscillograms of real lightning currents, digitized using free specialized software, were used. Results. The study of the parallel connection of two typical surge arresters designed for high-voltage networks of voltage class 110 kV was performed. To analyze the effect of non- identical protective characteristics, the residual voltage of one of the arrester was varied as a percentage of the residual voltage of the other one. It was found that when the difference between the residual voltages of the surge arresters ex- ceeds 6%, the current distribution through the surge arresters can reach a ratio of 1:4. Deliberate parallel connection of surge arresters is an effective solution to increase energy handling capability, provided that the residual voltages of the surge arresters are as close as possible. It was shown that a small difference in residual voltages is more dangerous in the case of positive lightning, which is characterized by a longer current impulse duration than negative lightning. It was shown that at the same amplitude of lightning currents, at struck by a positive lightning the surge arrester should absorb energy 10 times more, than at struck by a negative lightning. 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 mathematical expressions. Practical value. The use of the proposed approach allows a more in-depth analyzing the various schemes of protection of electrical networks against overvoltages, because it takes into account the actual features of the lightning current curve. Conclusions. Further development of the proposed approach is seen in its use both in the selection of surge arresters to protect electrical equip- ment of high-voltage electrical networks, and in the educational process.