Outdoor Ring Main Unit for MV Distribution Sites

An outdoor ring main unit is a medium voltage switchgear solution used when feeder switching and transformer protection equipment needs to be installed outside a traditional indoor switchgear room. It is commonly applied in outdoor substations, compact transformer stations, renewable energy collection areas, industrial distribution yards, utility feeder points, and infrastructure power supply systems.
The main function of an outdoor ring main unit is to connect medium voltage cables, control incoming and outgoing feeders, protect transformer circuits, provide earthing operation, and isolate circuit sections for maintenance. In ring network or radial distribution systems, the RMU helps organize feeder control in a compact arrangement while keeping the operating interface clear for site personnel

Outdoor installation requires more mechanical and environmental review than indoor RMU installation. For an outdoor ring main unit, buyers should consider enclosure protection level, rain shielding, dust prevention, corrosion environment, foundation height, cable trench position, grounding connection, drainage, ventilation, anti-condensation design, lifting method, and maintenance space. These details influence site installation as much as the electrical parameters.
TSTY supports different technical routes for outdoor ring main unit projects. SF6 gas insulated RMU can be selected where compact design and sealed insulation are required. Environmentally friendly gas insulated RMU can be discussed for projects with specific environmental preferences. Solid insulated ring main unit may be considered when the buyer prefers solid insulation technology. HXGN-12 or other MV switchgear options can be reviewed for conventional distribution layouts.
The configuration of an outdoor ring main unit should follow the single-line diagram. Common arrangements include one incoming and one outgoing feeder with transformer protection, two incoming feeders with one transformer feeder, multiple outgoing feeder circuits, metering sections, and circuit breaker protection units. For transformer feeder protection, fuse combination units or vacuum circuit breaker units may be selected according to transformer capacity and protection requirements.
An outdoor ring main unit is often supplied as part of a complete distribution system. It may be installed beside an oil-immersed transformer, inside a compact substation, near a pad-mounted transformer, or within a renewable energy step-up station. When the RMU is used with transformers and low-voltage cabinets, interface details such as cable termination space, busbar arrangement, enclosure layout, transformer capacity, and protection coordination should be confirmed before production.
Before requesting a quotation, buyers should provide rated voltage, rated current, short-circuit withstand level, feeder quantity, cable direction, single-line diagram, protection relay requirements, metering needs, enclosure requirement, installation altitude, ambient temperature, humidity, pollution level, coastal exposure if applicable, and local standard requirements. For export projects, TSTY can provide datasheets, general arrangement drawings, routine test reports, packing details, nameplate information, and other agreed technical documents.