Since the overvoltage and undervoltage protection devices adopts high speed low power micro processor design as the core, the magnetic latching relay main circuit, modular double standard, when the power supply line overvoltage and undervoltage protection devices, to continue to shock quickly and safely cut off the circuit, to avoid the occurrence of abnormal voltage into the terminal electrical accident and when the voltage protector will resume normal, within the specified time automatically switch on the circuit to ensure the normal operation of terminal electrical equipment in unmanned condition.

Overvoltage and undervoltage protection devices is suitable for single phase AC voltage 220V, frequency 50Hz, rated operating current 60A or less user or load. Protection of single-phase power supply equipment as a result of single-phase line over voltage due to neutral line fault. The utility model is mainly used for the protection of the distribution line of a household partition box or an electric equipment needing to protect single-phase power supply equipment.