Overvoltages caused by direct lightning strokes to a hybrid overhead line

•Tower and insulator models validated through comparisons with experimental results.•Systematic evaluation of the effects of several parameters on the MV circuit voltages.•Critical currents calculated for different combinations of soil resistivity and ground impedance.•Subsequent strokes are unlikely to cause backflashovers in the HV and MV circuits.•HV and MV circuits are shown to have excellent lightning performances. This paper presents an analysis of the overvoltages caused by direct lightning strokes to a hybrid overhead line with 138 kV, 13.8 kV, and 220 V circuits. The primary focus is on medium voltage line overvoltages and their dependence on key parameters, including ground impedance, soil resistivity, stroke current front time, conductor characteristics, lightning channel impedance, insulator capacitance, conductors' sags, and tower surge impedance. Using specific models for the transmission tower and high-voltage insulators, validated through laboratory tests and EMTP simulations, critical currents are determined for varying soil resistivity and impulse impedances. The analysis confirms the line robust performance against stroke-induced backflashovers.