Overvoltages in a 400 kV Transmission Line with Y-shaped Composite Pylon: Impact of Line Parameter Calculation Formulations

This paper assesses the impact of employing two distinct formulations, derived from different definitions for the overhead conductor voltages, in calculating transmission line parameters for assessing lightning-induced overvoltages in overhead lines installed on a composite material transmission tower featuring a $\mathbf{Y}$-shaped composite pylon. One of the formulations uses Pettersson’s equations, which are based on the definition of voltage on conductors, providing a physically more consistent approach. While the other formulation uses Carson’s equations, which are based on the definition of potential on conductors, offering a physically less consistent approach, this latter formulation is typically used in EMT-type programs. The results reveal significant differences between the physically more consistent formulation and those typically employed in EMT-type programs when comparing lightning-induced overvoltages in overhead lines installed on a Y-shaped pylon. These differences become more pronounced with increasing soil resistivity and may be crucial in determining occurrences of backflashover on the line.