1. Definition of RMU (Ring Main Unit)
A Ring Main Unit (RMU) is a medium-voltage switchgear (typically rated from 12kV to 36kV) designed in a sealed, compact form, used for switching, protection, and control of distribution networks in ring configurations. RMUs are generally insulated with SF6 gas or vacuum to ensure high safety, reliability, and space efficiency.
Main Functions of RMU:
- Switching, protection, and distribution of medium-voltage power to downstream loads.
- Isolation and protection of faulty sections to maintain power supply continuity.
- Space optimization with a compact design, suitable for distribution substations in residential, commercial, industrial areas, and renewable energy applications.
TypicalRing-type switchgear Components:
- LBS (Load Break Switch) Compartment: For load switching under normal conditions.
- CB (Circuit Breaker) Compartment: For fault interruption (e.g., short-circuit protection).
- Fuse Compartment: Overcurrent protection using switch-fuse combinations.
- Insulation System: SF6 gas or vacuum insulation for electrical isolation.
- Operating Mechanism: Manual or motorized operation for switching.
- RTU (Remote Terminal Unit): Enables SCADA integration, remote monitoring, and control.
2. Comparison Between Extensible and Non-Extensible RMU
| Criteria | Non-Extensible | Extensible |
| Diagram Example |  |  |
| Definition | Fixed configuration Medium-voltage ring unit, no further module expansion possible after installation. | It designed with provisions for future extension by adding modules. |
| Applications | Small substations with stable, fixed load requirements. | Industrial parks, factories, and distribution networks with potential future expansion. |
| Configuration Flexibility | Fixed number of functional compartments. | Flexible configuration with additional modules (LBS, CB, Fuse) as required. |
| Initial Investment | Lower initial capital expenditure. | Higher initial cost but optimized for long-term scalability. |
| Installation & Operation | Simple, fast installation with lower technical complexity. | More complex installation, requires higher technical capability. |
| Footprint & Dimensions | Compact design, minimal installation space. | Larger footprint due to modular extension capability. |
| Long-term Economic Efficiency | Economical for static systems with no expansion needs. | Cost-effective for networks requiring scalability and long-term upgrades. |
3. Conclusion
- Non-Extensible RMUs are suitable for projects with fixed capacity, where future expansion is not anticipated.
- Extensible RMUs are ideal for projects with scalability requirements, providing a future-proof solution for growing infrastructure.
4. Key Advantages of Using RMU in Modern Power Systems
Beyond their technical functions, Ring main switchgears play a critical role in the modernization of medium-voltage distribution systems. Their importance has grown in line with the demands of smart grids and distributed energy networks. The main advantages include:
- ✅ Increased Network Reliability: By enabling sectionalization, RMUs help isolate faults, reducing downtime and maintaining supply continuity.
- ✅ Enhanced Operator Safety: Loop distribution unit are fully enclosed, insulated systems, protecting maintenance staff from arc faults and electrical exposure.
- ✅ SCADA Compatibility: Integration with RTUs and intelligent controls allows real-time monitoring, remote operation, and predictive maintenance.
- ✅ Low Maintenance Requirements: The sealed structure and gas/vacuum insulation drastically reduce the need for regular service, saving OPEX costs.
- ✅ Support for Renewable Energy Integration: RMUs provide compact and reliable switching solutions for distributed solar, wind, and battery energy storage systems.
These strengths position RMUs as a foundational component in the next generation of smart, resilient electrical infrastructure.
5. Technical Consultation and Product Quotation
LS ELECTRIC offers a comprehensive range of SF6 Gas Insulated Ring Main Units (RMU), fully compliant with IEC 62271-200 standards. Our product line includes both Extensible RMUs and Non-Extensible RMUs, built to meet the specific needs of diverse electrical distribution environments.
With LS ELECTRIC’s cutting-edge engineering and global manufacturing standards, our Sealed distribution unit ensure:
- Enhanced personnel safety with fully insulated, arc-proof enclosures.
- Seamless SCADA integration and intelligent automation features.
- Proven durability in harsh environments, including high humidity, dust, and outdoor installations.
- Flexible panel configurations, available in multiple footprints to match any substation design.
Whether your project demands compact simplicity or long-term expansion capabilities, LS ELECTRIC has a reliable, scalable solution for you.
For further technical consultation and product quotation, please contact at:
- Hotline: 18006870
- Email: hamh@ls-electric.com.vn
