Three-phase four-wire overvoltage and undervoltage protector

The invention discloses a three-phase four-wire overvoltage and undervoltage protector, which solves the problems of unreasonable spatial layout, large size, unstable quality and the like of the existing overvoltage and undervoltage protector. The three-phase four-wire overvoltage and undervoltage protector comprises a shell, a relay control module, and an inlet end and an outlet end of a zero line, a metal connecting piece is connected between the inlet end and the outlet end of the zero line, the metal connecting piece crosses over the relay control module to connect the two ends, and the inner side face of the shell is close to the left side face and the right side face of the relay control module. The connection mode of a zero line in a protector product is changed, the inlet end and the outlet end of the zero line are connected through the metal connecting piece, the metal connecting piece is arranged above the relay control module in a crossing mode, the size of an original soft braided wire is saved, t