Abstract This paper studies the influence of different parameters on the shielding failure of high voltage direct current (HVDC) transmission lines. A numerical analysis model considering the developing process of the downward lightning leader based on electromagnetic field theory is used to estimate the lateral striking distance to the transmission line. The influences of different factors (different parameters of the downward lightning leader, HVDC transmission line, and weather conditions) on the shielding failure of the HVDC transmission line (TL) have been considered in this analysis. The results show that the dimensions of the transmission line strongly affect the analysed results of the HVDC–TL shielding failure.