Polyphase overvoltage/undervoltage fault protective apparatus with self-reset function

Disclosed is a polyphase overvoltage/undervoltage fault protective apparatus with a self-reset function. The apparatus comprises a relay circuit board connected with multiple relays, a master control circuit board and an N-pole assembly. The control pins of the multiple relays are welded to the relay circuit board in parallel so as to form a polyphase overvoltage/undervoltage fault relay protective assembly, and two signal lines are led out from the relay circuit board to be connected with the master control circuit board. When an overvoltage or undervoltage circuit fault is generated in a polyphase main current loop, the master control circuit board detects the circuit fault and simultaneously transmits control signals to the multiple relays through the two signal lines, and the multiple relays are released simultaneously so as to disconnect the polyphase main current loop. When voltage in the polyphase main current loop returns to normal, the multiple relays are simultaneously automatically connected with the polyphase main current loop.