Resettable overvoltage and undervoltage protector and control method thereof

A self-recovery overvoltage and undervoltage protector comprises a detection circuit, a control module and a relay, the detection circuit collects and feeds back a current signal and a voltage signal of a main line, the control module drives the relay according to the current signal and the voltage signal, and the detection circuit comprises a voltage value and phase detection circuit which feeds back a voltage value and phase information to the control module. The control module obtains a current zero crossing point moment through the voltage value and the phase detection circuit, drives a contact of the relay to be switched off when the main line has overvoltage and undervoltage faults, drives the contact of the relay to be switched on when the main line is in a normal operation state, and enables the switching-on moment of the relay to be within 5 ms before the current zero crossing point moment; according to the control method of the self-recovery overvoltage and undervoltage protector, the current zero c