Reliable power distribution serves as the backbone of modern infrastructure, and the Switchgear Ring Main Unit (RMU) is the missing piece of the puzzle that guarantees it. For urban grids, industrial plants, or even renewable energy worksites, RMUs enable a nearly flawless flow of electricity with superior protective devices. But what makes them so important? In our guide, we will discuss RMU’s core features and assets and what makes it a worthy investment. So, it’s wise not to skip!
1) What is a Ring Main Unit (RMU) ?
“A Ring Main Unit (RMU) is an intelligent switchgear system installed in Medium Voltage Power Distribution networks which is compact and enclosed.”
It guarantees continuous and reliable electricity supply through the establishment of a looped interconnection of power sources. This minimizes the downtime of the connected units by rerouting the power in case of faults.
They are widely used in commercial buildings, industrial facilities, utility networks, and even quarreling offices. Apart from boasting a compact outer shell, which makes it easier to fit into space-constrained areas, the sealed design also improves safety by protecting direct touch on electrical parts.
These units are constructed to switch, protect, and control tasks in a highly effective manner. It is common for them to have parts such as load break switches, circuit breakers, earth switches, and protection relays that must work in unison together to ensure smooth electrical operating activities.
2) Structure and Components of a Ring Main Unit (RMU)
A Ring Main Unit (RMU) is a compact modular assembly designed for medium voltage power distribution switchgear. It integrates engineering features associated with operational control, protection, and control of electrical networks in confined spaces. Their reliability and efficiency make RMUs important in industrial plants, commercial buildings, and utility grids.
Key Components of an RMU
i) Load Break Switch: The load break switch allows disconnection of electrical loads under normal circumstances. It empowers network operators to secure some sections of the entire network while the network continues to function normally during the servicing of some components.
ii) Circuit Breaker: A circuit breaker is designed to automatically disconnect the circuit from the power supply in case of faults like short circuits or overload. This aids in protecting the network from various perils, damaging the equipment, and improving network safety.
iii) Earth Switch: During the servicing of electrical equipment, the earth switch serves as an electrical component that ground and prevents inadvertent electric shocks during electro-mechanical servicing of the system.
iv) Protection Relays: Overload protection relays scan the system for operational errors, like overloads or faults, within the machinery. When critical failures and equipment destruction are likely to occur, overload protection relays initiate command cycles to open the circuit breaker.
v) Busbar System: The busbar system is a component in the RMU with the highest bulk resistance. As such, it serves as the primary current distributing point within the RMU, ensuring continuity between its elements. It saves more energy while increasing the reliability of the system.
Abhijeet Deshpande who works at TATA powers shared in a Quora post that RMU is used in the grid to prevent interruptions in power supply. He further said that they are also used to distribute load to more than one load.
Types of Insulation in RMUs
a) Gas-Insulated RMU (SF6-Based)
SF6 gas-insulated RMUs use sulfur hexafluoride gas as a primary thermal insulating medium. For instance, SF6 has superb dielectric strength in very compact structures. This makes these RMUs extremely resistant to environmental conditions, such as moisture and dust, which is perfect for harsh environments.
b) Air-Insulated RMU
The use of dry air or other gases for thermal insulation instead of SF6 characterizes air-insulated RMUs. They are relatively environmentally friendly and easier to maneuver. Although bulkier, these RMUs are preferred in areas where space is not a concern.
3) Working Principle of Ring Main Unit (RMU) Switchgear
The Ring Main Unit (RMU) is a medium voltage switchgear that is specially designed for compactness. It is built in a way that ensures a constant electric supply through a loopy network that allows power flow from diverse directions. This feature increases reliability and minimizes downtime in case of faults. Let’s discuss how RMU works;
- Power Distribution within a Ring Network
Several electricity sources are connected to an RMU in a loop configuration. This means that in case one source or feeder fails, the system ensures that the power continues to the electric supply by re-routing the electricity through an alternate route.
- Load Switching and Fault Protection
- The load break switch can connect or disconnect an electrical load either partially or completely without interrupting service.
- The automated lens switches away faulty sections of powered equipment in over currents and short-circuiting thereby preventing damage.
- Protection relays constantly scan the system and command the trip current of the circuit breaker when they notice fault conditions, so they ensure speedy isolation.
- Earthing for Protection
When servicing the switch, the earth switch grounds the circuit and keeps it at earth potential eliminating the possibility of voltage remaining in the circuit. This averts dangerous electric shocks, protecting the maintenance workers.
- Busbar System for Power Flow
The busbar system manages the distribution of electricity in the RMU, helping to maintain an uninterrupted flow of current in both the incoming and outgoing feeders.
4) Types of Ring Main Unit (RMU) Switchgear
i) Gas Insulated RMU (GIS RMU)
GIS RMUs are equipped with SF6 gas insulation showing high efficiency, compact size, and reliable performance. They are commonly found in sealed urban power distribution networks and industrial facilities because their low-maintenance design is not susceptible to dust or moisture.
On the contrary, SF6 gas is known to be a greenhouse gas, needing adequate measures for handling and disposal. Although GIS RMUs are more expensive, their longevity and minimized servicing requirements outweigh initial costs.
ii) Air Insulated RMU (AIS RMU)
Unlike the previous example, AIS RMUs are more environmentally friendly as they use dry air or other gasses instead of SF6. This makes them cheap and cost-effective. They can be found in rural or industrial regions where space permits. They still have a cheaper initial cost, but AIS RMUs have a lower performance output from regular maintenance needed to keep dust and moisture from fouling their systems.
Well, their bigger profile makes it hard to work within compact installation areas.
iii) Compact RMU vs. Modular RMU
Compact RMU is a single-unit solution designed for small commercial and residential use thus making it space efficient. As a result, it is also quick and easy to install and requires little maintenance.
A modular RMU has multiple sections which allow for expansion and customization. This type is applicable in large industrial networks but needs more room and investment.
These solutions Compact and low-maintenance GIS RMUs, eco-friendly and economic AIS RMUs, as well as compact or modular RMUs are selected based on scalability and space restrictions.
5) Applications of RMU Switchgear
Due to their compact size, reliable construction, and the efficient provision of fault protection, Ring Main Unit RMU switchgear is used extensively in medium voltage power distribution for control and metering purposes. Its use is common across industries as well as in infrastructure projects.
- Power Distribution for Cities And Towns: RMUs are perfect for cities or commercial zones, which have limited space. They provide a stable power supply in residential complexes, shopping malls, and office buildings. In addition, they help protect these structures from voltage fluctuations and power failures.
- Industrial Buildings: Manufacturing plants and factories have capital-intensive heavy machinery that requires power to be delivered continuously. Switching RMUs helps avoid outages while controlling loads, providing an efficient solution to steel plants, chemical industries, and automotive manufacturing.
- Projects on Renewable Energy Sources: Solar and wind farms incorporate the use of RMUs to manage the inflow of power and hinder the disruption of energy flow. Their ability to fault towards the unit ensures smooth operation with solar fields and wind power stations.
- Underground and Compact Substations: Maintenance-free sealing RMU technology makes it practical for use in underground power networks including metro stations, tunnels and transport hubs.
- Healthcare and Data Centers: Healthcare facilities, like hospitals, and IT infrastructure, like data centers, rely on power continuously being available. RMUs minimize system downtime via automatic fault detection and switching, meaning critical medical devices and IT systems can be kept safe.
6) Advantages of Using a Ring Main Unit (RMU)
RMU switchgear comes with numerous advantages making it ideal for medium-voltage power distribution.
+ Compact and Space Saving: RMUs are modular, allowing for easy installation in compact areas devoid of space, like urban regions, underground substations and even industries.
+ Superior Power Reliability: Through automated switching between different power sources, RMUs can provide stable electricity.
+ Increased Safety: Personnel protection along with electrical hazard mitigation can be done with RMUs as they come with integrated circuit breakers, load breaks and earth switches. Extra protection is provided for the operator as the enclosed casing is sealed.
+ Low Maintenance and Longevity: The sealed insulation of the RMU reduces dust, moisture, and environmental damage, resulting in lower maintenance costs and an extended operational lifespan. This makes them a working option financially.
+ Fast Fault Detection and Isolation: RMUs save time and minimize power interruptions by quickly detecting and isolating faulty sections. This enhances reliability within the power network as well as saves on downtime costs for commercial and industrial use.
Equipped with compact design, safety measures, unmatched reliability, and low maintenance requirements, RMUs are vital for modern power distribution infrastructure.
7) Key Considerations When Selecting an RMU
Proper selection of the ring main unit (RMU) switchgear is crucial because it affects the distribution of power, efficiency, and reliability over time. Take note of the following items:
! Voltage and Current Ratings: The selected RMU must have the correct voltage and current rating for the corresponding power system. Selecting an incompatible rating can result in destruction or ineffectiveness in the electrical network.
! Type of Insulation: Most RMUs come as gas-insulated (SF6-based) or air-insulated. While gas-insulated RMUs offer better protection and compact design, air-insulated RMUs are more cost-effective and environmentally friendly.
! Protection from Faults and Safety Features: The presence of circuit breakers, load breaks, and earth switches as components of an RMU guarantees better operator safety and fault isolation. There is also a complement of advanced protection relays that ensure Electrical Faults are detected and managed effectively.
! The Installation Site: Compact RMUs are preferred in densely populated urban and industrial regions. Sealed and weatherproof RMUs are also enclosed to ensure they work well in harsher environments so they can be more durable long-term.
! Scalability and Maintenance Needs: Modular RMUs are flexible because they are easily expandable. Also, an RMU that requires low maintenance assists in reducing expenditure on operational costs in the long run.
8) Eberry Ring Main Unit Switchgear Solution
Eberry Electric designs and manufactures Ring Main Unit (RMU) switchgear specially tailored to medium voltage networks for reliable, safe, and efficient power distribution.
- Key Features of Eberry’s RMU Switchgear:
+ Compact and Customizable Design: The RMUs are designed as compact devices that allow for easy installation in confined areas. Custom panels, materials, configurations, and labels are also offered to fulfill the needs of the customers.
+Enhanced Protection and Fault Isolation: Eberry’s RMUs are sophisticated with advanced protection features, enabling better system reliability as a result of minimal downtime caused by effective fault isolation.
+Modular Configuration: Incorporating modular design, the RMUs have the flexibility to be configured to different voltage and current levels, so, expansion is easy for the future.
+Durability in Diverse Environments: The high-quality materials of these RMUs provide them with excellent resistance to the environment’s threats of dust, moisture, and corrosion. This enables their use in a variety of weather conditions.
- Product Offerings:
Eberry Electric provides an RMU product line that comprises of:
- Fully insulated and Fully enclosed Main Ring Unit Switchgear: These are designed with an emphasis on safety and dependability during Medium voltage distribution.
- YM-GTXGN-12 Solid Insulation Ring Main Unit Switchgear: This unit has solid insulation designed for better protection and effective functioning.
- XGN15-12 24KV SF6 Ring Main Unit RMU Cabinet: This employs an SF6 gas insulator. SF6 gas is excellent for insulating electricity as well as extinguishing electric arcs. It is suitable for 12kV and 24kV uses.
Eberry has provided solutions with a combined effectiveness and economy that address the medium voltage distribution needs of substations, as well as urban power grid and industrial facilities.
9) FAQ
1. How does an RMU function in a ring main system?
An RMU creates a looped network, enabling the continuous flow of power through multiple sources, which increases reliability and reduces downtime. Electricity can be distributed from various directions, allowing for rapid fault isolation and enhancing overall reliability.
2. How do RMUs differ from conventional VCB switchgear?
While VCB switchgear employs vacuum circuit breakers as the handling devices for high-voltage switchgear, RMUs are gas-insulated and compact units allocated for distributed networks. RMUs are better suited for isolating faults, while VCBs manage heavier short-circuit currents.
3. How does an RMU handle fault conditions?
An RMU equipped with protection relays could isolate faults, detect faults, and handle them using circuit breakers and load break switches. This guards against total failure of the system.
10) Conclusion
To conclude, a Ring Main Unit (RMU) switchgear provides the best efficiency and reliability in modern power distribution systems. It has extensive application in industries and utilities due to its ability to improve safety, reduce downtime, and enhance versatility.
Well, with the right options, RMU guarantees improved performance and system stability for a long time. At Eberry Electric, we ensure durability and efficiency in all our high-quality RMU solutions. Check out our products and find the best fit for your power distribution needs.
