Many low voltage switch cabinets in the auxiliary and power distribution systems of power plants and large users are the core equipment of the whole power supply equipment and crucial to safety operation of the whole plant/power distribution system.

However, the low and medium buses are not specially protected in the conventional protection configuration scheme and generally protected by the backup protection setting of the incoming switch; the protection of the incoming and outgoing switches shall be mutually coordinated, so the low and medium bus failure in the auxiliary/power distribution system shall be subject to delay cutting.