When there is overvoltage or undervoltage in the power supply line, the protector can quickly and safely cut off the circuit under the continuous high voltage shock, so as to avoid the occurrence of accidents caused by abnormal voltage being sent to the terminal electrical equipment. The internal circuit is automatically connected to ensure that the terminal electrical appliances work normally under unattended conditions. If the power supply line is struck by lightning, the protector will directly fuse after absorbing the sudden huge energy to protect the terminal electrical equipment.