The broadband impedance spectroscopy is a promising cable fault location technique because of its high sensitivity, which has been applied to low voltage cables and distribution cables, however, there is a gap in the theoretical study of this method for locating defects in high voltage cables. In this paper, the effect of impedance spectroscopy on the occurrence of buffer layer ablation faults is analyzed by calculating the distribution parameters and the first end impedance based on the transmission line model for the broadband impedance spectroscopy. The analysis shows that the broadband impedance spectroscopy technique can detect high voltage cable faults, and the localization effect is more obvious when the fault affects the insulation shield, which has potential for field application.