Transient Lightning Impulse Performance Analysis for Composite Transmission Line Tower

In this paper, the transient impulse performances of a 330-kV composite transmission line tower under direct lightning strokes are comprehensively presented. An equivalent distributed parameter model combined with lumped capacitance elements for the tower is established. The wave impedances of the hybrid model are determined by using analytic equations. The lumped capacitances are calculated by 3-D finite element method (FEM). An accurate model for extended grounding structure (EGS) of the tower base considering the soil ionization is used to simulate its impulse performances. The wave process of the tower is analyzed by using the electromagnetic transient program (EMTP). The proper grounding conductor system is determined for the case of a superior lightning impulse performance considering three diverse grounding configurations. The influence of radius of the grounding conductor is assessed. The numerical electromagnetic field analysis, finite-difference time-domain (FDTD) simulation is applied to verify the validity of the presented hybrid model. Then, the influence of the wave-front time of the lightning current, the soil resistivity, the dimension of the EGS, and their combined effect on the transient impulse performances for the EGS are analyzed and discussed.