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High-Quality Ring Main Unit Manufacturer for Reliable Power Distribution
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11KV Medium Voltage Gas Insulated Switchgear
Cotenele is one of the main manufacturers of power distribution equipment in China,our products includes LV and MV switchgears,ring main units and their internal core components.The 11KV Medium Voltage Gas insulated Switchgear has a compact structure, is sturdy and durable, and has safe and stable performance. Widely used in urban power distribution, commercial buildings, wind and solar power plants, and industrial sites with limited space.
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
