ainly used for the protection of over-voltage, under-voltage or over-current in the incoming line of residential household box or the distribution line which needs to protect single-phase electrical equipment. Its main feature is that the line appears overvoltage or undervoltage, overcurrent status, the product can instantly cut off the power supply, protect the electrical equipment from damage; when the line voltage returns to normal, the protector can automatically and normally turn on the power supply.