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Ring Main Units (RMU)
10 Series · 15 Models
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Ring Main Units (RMU) Overview
Ring main units (RMUs) are compact, sealed switchgear that feed and protect medium-voltage ring networks. QDTB RMUs integrate load break switches, circuit breakers, and earth switches in gas-insulated (SF6) enclosures rated 12/24 kV up to 630 A per IEC 62271-200. The sealed-for-life design needs essentially no maintenance and occupies roughly one-third the footprint of conventional air-insulated gear, while modular construction allows additional compartments to be added as the network grows.
Available Series
SRM12 Series
The SRM12 series ring main units with integrated FTU combine primary switching equipment with secondary automation. Factory tested with primary and secondary systems merged into one device for fast deployment in distribution automation projects.
XGN15 Series
The XGN15 series ring main units with integrated FTU combine switching equipment with feeder automation terminals. Primary and secondary systems merged into one factory-tested device for rapid deployment in smart grid distribution networks.
FLN36 Series
The FLN36 series ring main units with integrated FTU represent the convergence of primary equipment and secondary automation. Factory tested with all protection and monitoring functions pre-configured for fast deployment in distribution networks.
SM6 Series
The SM6 series SF6 ring main units feature sealed SF6 gas insulation tanks for maintenance-free operation in urban power distribution networks. Modular design with load break switch and fuse or vacuum circuit breaker protection options.
RM6 Series
The RM6 series SF6 gas-insulated ring main units provide reliable medium voltage switching for distribution networks. All-in-one sealed SF6 tank design ensures long-term maintenance-free performance with load break switch and fuse combination protection.
SafeRing Series
The SafeRing series represents ABB-compatible SF6 gas-insulated compact ring main units with advanced safety features. Fully sealed design with SF6 insulation provides excellent performance in harsh environments while ensuring operator safety.
8DJH Series
The 8DJH series SF6 gas-insulated switchgear provides reliable medium voltage switching for urban distribution networks. Features sealed SF6 tank design with load break switch and vacuum circuit breaker protection modules for maintenance-free operation.
GXS Series
The GXS series solid-insulated ring main units represent the next generation of SF6-free, environmentally friendly switchgear. Features epoxy-encapsulated live parts eliminating SF6 gas, ideal for eco-buildings and environmentally sensitive applications.
XGN Series
The XGN series solid-insulated ring main units provide SF6-free, environmentally friendly medium voltage switching. Features epoxy encapsulation of all live parts, eliminating greenhouse gas emissions while maintaining reliable switching performance.
VCB Ring Main Units Series
VCB ring main units use vacuum circuit breakers for the transformer and feeder protection ways, providing full breaking capacity instead of load-break switching alone. Rated 12–24 kV, 630–1250 A with circuit-breaker protection modules, for distribution networks requiring fault interruption at each way.
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Certification
The values below are computed from what you selected above. Anything that cannot be computed yet is shown as an em dash — never as zero.
Iₙ = S / (√3·U) · I_sc = 100·Iₙ / uₖ · S_sc = √3·U·I_sc · I_p = k·Iₖ
Still required to complete the calculation: rated capacity S, impedance voltage uₖ, short-time or peak withstand current.
Per-model values (P0 / Pk / uₖ declared by the factory, losses, noise, temperature rise, dimensions, weight) are not in the product library: those rows stay at an em dash until the factory parameter sheet is supplied. An em dash means the value is unavailable — it is never rendered as zero.
Reference prices are for estimation only and do not constitute a formal offer.
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Application Scenarios
Urban Ring Networks
Primary switchgear with automatic fault isolation.
Wind Power
MV switchgear for wind farm collection.
Solar Plants
MV distribution for PV plants.
Commercial
Compact RMU for developments.
Industrial
Factory substation switchgear.
Infrastructure
Railway and airport distribution.
Technical Advantages
Gas-Insulated
SF6/clean air, maintenance-free 30+ years.
Modular
2-6 compartments configurable.
Protection
Complete switching in one sealed unit.
Smart Grid
Motorized operation and remote monitoring.
FAQ - Ring Main Units (RMU)
What is the difference between SF6 and air-insulated RMUs?
How many feeders can an RMU support?
What is the difference between a load break switch and a circuit breaker?
Are RMUs suitable for renewable energy projects?
What capacity and voltage range is available for Ring Main Units (RMU)?
What is the minimum order quantity (MOQ) for Ring Main Units (RMU)?
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SF6 Gas-Insulated vs Air-Insulated vs VCB Ring Main Unit: How to Choose
| SF6 Gas-Insulated | Air-Insulated | VCB Ring Main Unit | |
|---|---|---|---|
| Insulation & enclosure | Sealed-for-life SF6 tank with no live parts exposed | Air clearance between phases inside a metal enclosure | Vacuum breaker ways in a sealed or open enclosure |
| Footprint | About one-third the footprint of air-insulated gear | Larger, because air clearances set the spacing | Between the two, driven by the breaker ways |
| Maintenance | Essentially maintenance-free over the sealed life | Busbars and contacts inspectable, so periodic checks are possible | Breaker mechanisms need routine inspection |
| Fault clearing | Load break switches clear load current; fuses or relays clear faults | Depends on the fitted switch and fuse combination | Vacuum breaker clears fault current under relay protection |
| Extension | Modular ways added as the ring grows | Additional panels bolted on at air clearance | Extra breaker or switch ways added in the same line-up |
| Protection & automation | Relay or fuse based, with smart-grid options | Relay based, straightforward to instrument | Relay based, with full overcurrent and earth fault |
| Typical application | Urban ring networks and compact kiosks | Industrial and commercial MV rooms | Wind and solar collectors, plant substations |
Where QDTB® Ring Main Units Are Specified
Ring main units sit on medium-voltage ring networks where two feeds must reach the same load point: urban distribution rings, commercial complexes and industrial estates. The sealed design is what allows a compact kiosk at the roadside instead of a masonry switch room, and the ring arrangement keeps the load supplied while one side is isolated.
Wind and solar collector networks use an RMU at each string or turbine because the unit is sealed for life and needs no maintenance visit in an unmanned plant. The 2 to 6 way layouts cover the usual ring-in, ring-out, transformer and spare positions, and a modular frame adds ways as the plant is extended.
Industrial and commercial MV rooms select air-insulated or vacuum breaker ways where the operator wants inspectable busbars or full fault-current breaking. Extensible modular designs are chosen where the network will grow in stages and the switch room cannot be rebuilt later.
Every unit is rated 12 kV to 24 kV up to 630 A to IEC 62271-200 and GB 3906. Fuse-switch, load break switch or vacuum breaker ways are chosen against the protection study rather than taken as a catalogue default.
Frequently Asked Questions
What is the difference between SF6 and air-insulated RMUs?
SF6 RMUs are sealed and gas-insulated, giving a smaller footprint and maintenance-free operation. Air-insulated RMUs are simpler and lower-cost but larger and need periodic inspection.
How many feeders can an RMU support?
A typical RMU supports 2 to 6 ways. Modular QDTB designs let you add load break or circuit breaker compartments as the network expands.
What is the difference between a load break switch and a circuit breaker?
A load break switch makes and breaks normal load current only. A circuit breaker also interrupts fault currents and can be triggered by protection relays for automatic fault isolation.
Are RMUs suitable for renewable energy projects?
Yes. Their compact sealed design and low maintenance make RMUs well suited for wind, solar, and storage collection networks where space is limited.
What capacity and voltage range is available for Ring Main Units (RMU)?
QDTB® supplies Ring Main Units (RMU) with voltage ratings from 12 kV to 24 kV.
What is the minimum order quantity (MOQ) for Ring Main Units (RMU)?
One unit for standard products. Custom-designed equipment is quoted on specifications — send your parameters or drawings and our sales team will confirm the MOQ for your configuration.