Solid-insulated fully enclosed ring-network unit (hereinafter referred to as ring-network unit) is a fully sealed power supply unit. All live parts and switches are fully sealed in an epoxy plastic shell, and there is no gas in the shell. The whole switching device is not affected by the external environment, ensuring operation reliability and personal safety, and realizing maintenance-free. The ring network unit is divided into indoor and outdoor types. The outdoor type is a multi-channel loop-network power supply unit composed of indoor loop-network units enclosed in a metal shell. The ring-network unit is applicable to 12kV, 50Hz three-phase AC power distribution system, and is used for ring-network power supply or terminal power supply. The ring network unit can be installed in the distribution system of industrial and mining enterprises, residential quarters, schools, parks, etc., and can also be installed in the compact box-type substation for the control and protection of the distribution transformer. Therefore, both indoor and outdoor ring-network units can realize distribution automation.