ESTIMATION OF VOLTAGE DROP IN INDUCTIVE REACTANCE OF CONNECTING WIRES OF SURGE ARRESTERS

Purpose. The results of studying the voltage drop in the inductive ractance of the connecting wires of surge arresters installed in open switchgear are presented. Methodology. Free software for circuit simulation was used to solve electri- cal circuits with nonlinear parameters. To take into account the differences between the negative and positive lightning current impulses, the oscillograms of real lightning currents were digitized using free specialized software. Results. The duration of the impulse front (as well as the total impulse duration) of the positive lightning significantly exceeds the corresponding parameters of the negative lightning current, so the charge carried by the positive lightning significantly exceeds the charge carried by the negative lightning. For these reasons, positive lightning, although less common than ЕЛЕКТРОЕНЕРГЕТИКА, ЕЛЕКТРОТЕХНІКА ТА ЕЛЕКТРОМЕХАНІКА Вісник КрНУ імені Михайла Остроградського. Випуск 4/2021 (129) 162 negative lightning, is more dangerous. It is found that due to the slower front of the impulse, the voltage drop in induc- tive reactance of connecting wires of the surge arresters in the case of positive lightning in 8-11 times less than in the case of negative lightning. Analytical formulas for calculating the inductance of the connecting wires, which take into account the geometric dimensions of the wires, provide more accurate results than the average inductance value of 1.3 μH/m given in the literature. Originality. The approach takes into account the differences between impulses of light- ning currents of negative and positive polarity, which cannot be achieved with use of the approximation of lightning currents by simplified mathematical expressions. Practical value. It is found that voltage drops in the inductive reac- tance will be more dangerous in case of long wire lengths and negative lightning current impulses with a steep front. Conclusions. Further development of the proposed approach is seen in its use for the analysis of circuits for protection of electrical equipment of high-voltage electrical networks from lightning overvoltages using surge arresters. Refer- ences 15, figures 10.