The case of a self-provided generator sending power to the municipal network is called a reverse power supply. There are two kinds of serious consequences. a) If the municipal power grid is not cut off, the municipal power supply and the self-provided generator power supply will produce non-synchronous operation, which will destroy the unit. If the self-provided generator capacity is large, it will also make the municipal power grid shock. b) City network power outage is being tested, its own generator back power. It will electrocute some of the inspection staff.