Induced voltages on overhead transmission lines because of nearby included lightning channel

Abstract

The power system networks can be adversely affected by indirect coupling with the cloud-to-ground lightning return stroke. In most computations of lightning-induced voltages on overhead transmission lines, the overhead transmission lines are considered as straight lines and the return stroke channel is assumed to be a straight and a vertical channel. However, in reality, the line is not straight and is not parallel to the ground level because of the sag produced by its weight. In addition, the lightning channel is most often inclined. This study studies the effect of conductors' sag as well as the inclination angle of the lightning channel on the lightning-induced voltage on the three-phase power lines because of inclined lightning channel. This study has been evolved, formulated and applied on Egyptian 500 kV three-phase transmission line. Moreover, the effect of the ground conductivity on induced overvoltages in case of sagged transmission lines is considered. It can be observed that, taking into account the effects of the ground conductivity, the presence of the ground wire and the sag of the transmission lines reduce the values of the calculated induced voltages.