IEC 61643-332:2024 describes the theory of operation, principles for the selection and application of MOVs to be connected to power lines or telecommunication or signalling circuits, up to 1 000 V AC or 1 500 V DC. These SPCs are designed to protect apparatus or personnel, or both, from high transient voltages. This document applies to MOVs having two electrodes and voltage dependents elements with or without disconnectors. It does not apply to assemblies that include MOVs and their influence on the MOV's characteristics. This standard specifically discusses the zinc-oxide type of MOVs.