The paper presents an analysis of the effectiveness of overvoltage protection of the jacket of a single-core cable. The protection in question consists of a surge arrester, which is connected between the conductive sheath of the cable and the ground. The theory of calculations for overvoltages of atmospheric origin is presented. It was applied to the single-core cables that make up the 110 kV cable connection for aggregate 1 in HPP Zakucac.