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High-Quality Ring Main Unit Manufacturer for Reliable Power Distribution
A Ring Main Unit is a type of medium-voltage switchgear used in power distribution networks. It is a compact, factory-assembled, metal-enclosed set of switchgear components (such as load-break switches, fuses, and busbars), typically applied at rated voltage levels from 10 kV to 40.5 kV.
Ring main units can be divided into gas-insulated RMUs and environmentally friendly RMUs based on the insulation medium. Gas-insulated RMUs typically use SF₆ as the insulating and arc-quenching medium, while eco-friendly RMUs adopt environmentally friendly gases such as dry air, N₂, or other green gas mixtures, as well as vacuum interruption technology. There is also a type of solid-insulated RMU, which generally uses epoxy resin as the insulation material.
Ring main units can be divided into gas-insulated RMUs and environmentally friendly RMUs based on the insulation medium. Gas-insulated RMUs typically use SF₆ as the insulating and arc-quenching medium, while eco-friendly RMUs adopt environmentally friendly gases such as dry air, N₂, or other green gas mixtures, as well as vacuum interruption technology. There is also a type of solid-insulated RMU, which generally uses epoxy resin as the insulation material.
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11KV RMU Medium Voltage Ring Main Unit MV Switchgear
Cotenele is a large manufacturer and supplier of medium voltage ring main units and their internal core components in China,Our medium-voltage RMUs mainly exported to regions such as Europe and the Middle East.The XGN66-12 series 11KV RMU Medium Voltage Ring Main Unit MV Switchgear is an indoor fixed AC metal-enclosed switchgear designed for 3.6–40.5 kV, 50 Hz three-phase power systems. It is widely used for power distribution, circuit control, and protection in applications such as substations, industrial plants, high-rise buildings, residential communities, and pad-mounted transformers.
33KV RMU MV Gas Insulated Ring Main Switchgear
Cotenele is one of the main suppliers of HXGN-40.5 series 33KV RMU MV Gas Insulated Ring Main Switchgear to State Grid Corporation of China. Our ring main unit products are not only sold domestically, but also exported to multiple countries and regions in Africa, Europe, and the Middle East. The HXGN-40.5 series 35KV medium-voltage ring main unit is a 50Hz AC three-phase indoor medium-voltage distribution equipment. It has the characteristics of safe use, unaffected by climate, easy installation, minimal maintenance, and compact size, and is suitable for installation in box type substations.
22KV Medium Voltage Ring Main Unit RMU Panel
Cotenele is a large manufacturer and supplier for the medium-voltage ring main units and switchgearsin China,all internal components in these medium-voltage switchgears also manufactured by ourselves. The XGN15-24 series 22KV Medium Voltage Ring Main Unit RMU Panel is a box type fixed metal enclosed ring network switchgear widely used in 20kV voltage level distribution systems. The ring main units have features such as compact structure, modular design, and good operational safety,and are widely employed many industrial and civilian power distribution projects.
11KV Medium Voltage RMU Electrical Panels
Cotenele is a manufacturer of medium-voltage switchgears and their internal core components,our products include medium-voltage panels,ring main units,vacuum circuit breakers,load break switches and operating mechanisms.The HXGN17-12 series 11KV Medium Voltage RMU Electrical Panels is a widely used and technologically mature 10kV indoor box type fixed AC metal enclosed ring network switchgear. It is mainly used in three-phase AC 50Hz, rated voltage 12kV distribution systems, responsible for the reception, distribution, control, and protection of electrical energy, and is widely used in ring network power supply and terminal power supply scenarios.
11KV Medium Voltage Ring Main Unit MV Panels
The 11KV Medium Voltage Ring Main Unit MV Panels is a compact distribution switchgear mainly installed in indoor or outdoor substations, usually used to control transformers. Cotenele is one of the main suppliers of China State Grid and Southern Power Grid. The ring main units we produce mainly include environmentally friendly ring main units and gas-insulated ring main units. The HXGN15-12 is the gas-insulated RMU,this modular ring main unit has a simple structure, flexible operation, reliable interlocking, easy installation, and free combination. It is suitable for occasions such as airports and railways that require high automation of power distribution.
22KV MV Gas Insulated Gis Switchgear
Cotenele not only manufactures switchgear with voltage levels of 12kV, but also medium-voltage switchgear with voltage levels ranging from 3.6kV to 40.5kV, including 24kV gas-insulatde ring main unit.The 22KV MV Gas Insulated Gis Switchgear is a rated voltage 24kv gas-insulated ring main unit (RMU) ,which features a compact, fully sealed switchgear, This design makes the RMU immune to environmental contamination, humidity, and dust, ensuring high reliability and safety.
What is a Ring Main Unit?
A Ring Main Unit (RMU) is a set of medium-voltage switchgear used in distribution networks. It integrates key components such as load switches and fuses into a metal or non-metal enclosure.
It is named after its common application in ring-type distribution networks, which provide high power supply reliability. In such a ring configuration, the distribution lines form a closed loop, allowing power to be supplied from both directions.
When a fault occurs on one section of the line, the faulty section can be quickly isolated, and power can be restored from the opposite side, minimizing the outage range.
RMU Insulation Types
- SF₆ gas-insulated type (excellent performance but high greenhouse impact, still widely used)
- Solid-insulated type (environmentally friendly and safe, gradually replacing SF₆)
- Air-insulated type (lower cost but larger size)
- Environmentally friendly gas-insulated type (future development trend)
RMUs are widely used in urban distribution networks, commercial buildings, industrial and mining enterprises, infrastructure projects, and renewable energy systems.
Internal Core Components
- Load-break switch (for making and breaking load current)
- Fuse (for interrupting fault current)
- Earthing switch (for maintenance safety)
Why is it Called a Ring Network?
In traditional power distribution systems, electricity is supplied in a radial structure from a single substation. If a fault occurs, downstream users experience outages.
A ring network connects multiple RMU cabinets into a closed-loop circuit. Under normal operation, the system runs in an open-loop state, allowing power supply from both directions without forming a short circuit.
When a fault occurs, the faulty section is isolated, and the normally open point is closed to restore power from the opposite direction, improving reliability and flexibility.
Construction and Key Components
Load-break Switch (C-unit)
Can safely make and break normal load current but cannot interrupt short-circuit currents.
Fuse (F-unit)
Combined with load-break switch for transformer protection. In fault conditions, the fuse operates and trips the switch.
Circuit Breaker (V-unit)
Uses vacuum circuit breakers to interrupt fault currents. Typically used for incoming circuits and critical loads.
Fully Insulated and Sealed Design
Modern RMUs use SF₆ gas or environmentally friendly gases in a sealed tank structure. This ensures compact design, high reliability, and resistance to dust, humidity, and pollution.
Main Application Areas
- Residential complexes
- Commercial buildings
- Urban distribution networks
- Industrial parks and factories
Classification of Ring Main Units
By Insulation Medium
- SF₆ gas-insulated type
- Solid-insulated type
- Air-insulated type
- Environmentally friendly gas-insulated type
| Type | Insulation Medium | Key Characteristics | Environmental Note |
| SF₆-Insulated RMU | Sulfur hexafluoride(SF₆) | Compact,fully sealed,unaffected byenvironmental conditions,long maintenanceintervals. | SF₆ has high global warming potential; utilities are transitioning to alternatives. |
| Eco-Friendly Gas-insulated RMU | Natural or low-GWP gases(dry air,nitrogen, fluoronitrile/fluoroketone mixtures) | Same compact footprint as SF₆units,significantly reduced environmental impact | Often called"green gas"or "eco-friendly"RMUs. |
| Air-Insulated RMU (AIR) | Ambient air | Larger footprint,lower upfront cost,easyvisual inspection. | Typically used indoors where space is not critical. |
| Solid-Insulated RMU | Solid dielectric materials(e.g.,epoxy resin) | No greenhouse gases,completely sealedagainst moisture and pollution,compact,minimal maintenance. | Often classified under the eco-friendly category. |
By Functional Unit
- C-unit: Load-break switch unit
- F-unit: Switch-fuse combination unit
- V-unit: Vacuum circuit breaker unit
- G-unit: Sectionalizer or isolation unit
| Unit Type | Core Components | Function |
| C-Unit | Circuit Breaker | Makes,carries,and breaks both normal load currents and short-circuit currents.Used for feeder protection where frequent fault interruption is required. |
| F-Unit | Load-Break Switch +FuseCombination | The load-break switch handles normal load currents;the fuse provides short-circuit protection.Commonly used for transformer feeder units. |
| V-Unit | Vacuum Circuit Breaker | Similar to C but specifically using vacuum interrupters.Suitable for applications requiring fast and reliable fault clearing. |
| G-Unit | Disconnector(lsolator) | Provides visible isolation and earthing but cannot break load current or fault current. Used as an incoming/outgoing isolation point or for sectionalizing. |
| SL/S-Unit | Load-Break Switch (Standalone) | Makes and breaks normal load currents but does not include a fuse.Used for ring-in /ring-out units in a loop. |
RMU vs Metal-Clad Switchgear
Metal-clad switchgear uses fully separated compartments for busbar, circuit breaker, and cable sections, providing high safety and visibility of isolation points.
RMUs, on the other hand, are compact, fully sealed systems designed for distribution networks requiring reliability, small footprint, and minimal maintenance.
| Feature | Ring Main Unit(RMU) | Metal-Clad Switchgear (e.g.,KYN) |
| Footprint | Compact;width typically 300-600 mm | Larger;width typically 800-1000 mm |
| Insulation | Mostly gas-insulated(SF₆or alternatives)in sealed tanks | Mostly air-insulated with visible busbars |
| Primary switches | Load-break switch +fuses (predominantly) | Vacuum circuit breakers(predominantly) |
| Cost | Lower,due to simplicity and compactness | Higher,with more advanced protection |
| Typical Role | Secondary distribution,ring networks,compact substations | Primary distribution,substation feeders, direct starting of large motors |
Why Choose Cotenele?
Cotenele is an important partner of the State Grid Corporation of China. We operate a self-owned factory covering over 30,000 square meters.
Our product range includes gas-insulated switchgear, environmentally friendly switchgear, and ring main units with rated voltages from 12 kV to 40.5 kV.
All internal components are manufactured in-house. We are certified with ISO9001, ISO14001, and ISO18001.
Our products are widely used in power, railway, petrochemical, and municipal construction industries. Our headquarters is located in Liushi Town, Yueqing City, Wenzhou, known as the “Electrical Capital” of China.
A Ring Main Unit is a compact and highly reliable medium-voltage switchgear solution. It enables ring-type network operation, improving power supply reliability and operational flexibility.
Modern RMU technology is evolving toward:
- SF₆-free environmentally friendly insulation systems
- Integration with digital monitoring and remote control systems
