Investigation of lossy ground in lightning induced over-voltage at presence of surge arrester in CST software

Abstract

The lightning over-voltage causes flashovers along the overhead lines and insulation failures in power system equipment. It is important to evaluate the lightning to mitigate its effects and improve the reliability of system. This study focuses on evaluating the effects of the indirect lightning strikes on medium-voltage (MV) lines. A 5 km line has been chosen in Electrical Company of Iran to study the lightning-induced over-voltage in different conditions. The amplitude and waveforms of the lightning-induced voltage are affected by many factors, such as distance between the lightning strike point and the line, soil resistivity, surge arrester spacing, earth resistance etc. The back-flow strikes are analysed in this study. Effects of the earth resistivity and location of the strike on back-flow strikes and wave shape of lightning-induced voltages are studied in CST software. After fitting the induced waveform, the distribution line has been modelled in EMTP-RV software. Overvoltage protection can be basically achieved by limiting the over-voltage at the equipment location such as one non-linear element (MO surge arrester). The influence of line and lightning parameters on the effectiveness of surge arresters in terms of the reduction of the induced voltage magnitude is analysed.