The 11kV Ring Main Unit (RMU) is a compact medium-voltage switchgear solution designed for reliable power distribution, ring network systems and secondary distribution applications. It integrates load break switches, vacuum circuit breakers, earthing switches and other protection or measurement components into a compact and highly reliable switchgear assembly.
CHNGS 11kV RMU is designed for 11kV medium-voltage distribution networks and can be configured with different combinations of Load Break Switches (LBS), Vacuum Circuit Breakers (VCB), fuse switches and earthing switches according to the requirements of the power distribution system.
The RMU can be supplied in SF6-insulated or solid-insulated configurations, with options for motorized operation, remote monitoring, fault indicators and SCADA integration.
The sealed gas tank used in gas-insulated RMUs can provide high protection against dust, humidity and environmental conditions. Typical RMU designs use an IP67-rated sealed tank, while the external enclosure is commonly designed around IP54/IP55 depending on the application.
| Item | Technical Data |
|---|---|
| Product Name | 11kV Ring Main Unit |
| Product Type | Medium Voltage Ring Main Unit |
| Rated Voltage | 11kV |
| Highest Voltage for Equipment | 12kV |
| Rated Frequency | 50Hz |
| Rated Current | 630A |
| Rated Busbar Current | 630A |
| Rated Short-Time Withstand Current | 20/21kA, 3s |
| Rated Short-Circuit Breaking Current | Up to 20/21kA |
| Rated Short-Circuit Making Current | Up to 50/52.5kA |
| Power Frequency Withstand Voltage | 28kV, 1 min |
| Lightning Impulse Withstand Voltage | 75kV |
| Insulation Medium | SF6 / Solid Insulation |
| Main Switching Device | Load Break Switch / Vacuum Circuit Breaker |
| Circuit Breaker Type | Vacuum Circuit Breaker |
| Earthing Switch | Integrated |
| Busbar | Copper |
| Degree of Protection | Up to IP67 for sealed tank |
| External Enclosure | IP54/IP55 |
| Internal Arc Classification | Optional, up to IAC AFLR |
| Installation | Indoor / Outdoor |
| Configuration | 2-way / 3-way / 4-way / Customized |
| Operation | Manual / Motorized |
| Remote Control | Optional |
| SCADA Integration | Optional |
| Standard | IEC 62271-200 |
| Application | Medium Voltage Power Distribution |
Typical 11kV RMU specifications use 11kV nominal voltage, 12kV equipment voltage, 50Hz frequency and 630A rated current. Depending on the design and project requirements, short-time withstand ratings can be 20kA or 31.5kA for 3 seconds, with 28kV power-frequency withstand and 75kV lightning impulse withstand levels.
A typical 2-way configuration consists of two load break switch units and is mainly used for ring network incoming and outgoing feeders.
Typical configuration:
LBS + LBS
This configuration is suitable for transformer substations and secondary distribution networks where ring network operation and load switching are required.
A 3-way RMU can combine two ring main switch units with one circuit breaker feeder.
Typical configuration:
LBS + LBS + VCB
The VCB feeder provides protection for a transformer or downstream electrical equipment.
A 4-way RMU provides additional outgoing or protection functions.
Typical configurations include:
LBS + LBS + VCB + VCB
or customized combinations according to the distribution network requirements.
Different manufacturers provide configurations such as two-way, three-way and four-way RMUs, with combinations of isolator/load-break switches and vacuum circuit breakers.
The Load Break Switch (LBS) is used for switching and isolation of medium-voltage distribution circuits. It is commonly used for incoming and outgoing ring feeders.
The Vacuum Circuit Breaker (VCB) provides protection against overload and short-circuit faults. It can be equipped with protection relays and current transformers according to the project requirements.
The integrated earthing switch provides a reliable grounding path during maintenance and inspection operations and is mechanically interlocked with the main switching devices.
The RMU uses a copper busbar system designed according to the rated current and short-circuit withstand requirements.
The cable compartment provides space for medium-voltage cable termination and connection. Cable connection solutions can be customized according to the cable type and cable termination system.
Optional components include:
The SF6 gas-insulated RMU uses a sealed gas tank to isolate the medium-voltage switching components from the external environment.
The compact design allows the switching components to be integrated into a small footprint, making the RMU suitable for substations and distribution installations where installation space is limited.
The sealed tank can also reduce exposure of high-voltage components to dust, humidity and other environmental factors. ABB's comparable RMU technology, for example, uses sealed-for-life gas systems designed for long service life with low maintenance requirements.
For projects requiring an SF6-free solution, CHNGS can also provide solid-insulated RMU configurations.
The solid-insulated design uses epoxy resin insulation to encapsulate the high-voltage components and vacuum switching technology for interruption.
Advantages include:
Solid-insulated RMU technology is increasingly used as an alternative to SF6-insulated medium-voltage switchgear.
The 11kV RMU can be equipped with intelligent automation functions for modern distribution networks.
Optional functions include:
These functions allow the RMU to be integrated into smart-grid and distribution automation systems. Current RMU specifications also commonly reserve interfaces or space for RTU, FPI and remote monitoring equipment.
The 11kV Ring Main Unit is widely used in:
Used in medium-voltage distribution networks to provide reliable ring network power supply and fault isolation.
Suitable for factories, manufacturing plants, mining facilities, cement plants, steel plants and other industrial power distribution systems.
Suitable for:
The RMU can be used in:
Used together with distribution transformers to provide medium-voltage incoming, outgoing and transformer protection functions.
Customized Configuration
CHNGS can configure different RMU combinations according to the customer's single-line diagram, protection requirements and installation conditions.
Reliable Medium-Voltage Design
The RMU is designed for medium-voltage distribution applications with appropriate insulation, switching and short-circuit withstand capabilities.
Compact Structure
The integrated design reduces installation space and is suitable for compact substations and distribution rooms.
Flexible Protection
VCB feeders can be equipped with CTs, protection relays and other protection components according to the customer's requirements.
Smart Grid Ready
Motorized operation, fault indicators, RTU and SCADA communication can be integrated for distribution automation applications.
International Standards
The RMU can be designed and tested according to applicable IEC standards, including IEC 62271-200 for AC metal-enclosed switchgear and controlgear.
The 11kV RMU can be designed according to the following standards:
IEC 62271-200 is widely referenced for medium-voltage metal-enclosed RMU designs and type-testing requirements.
CHNGS can provide customized 11kV RMU solutions including:
The exact configuration, rated short-circuit current, insulation level, protection scheme and enclosure design can be customized according to the customer's project requirements.
An 11kV Ring Main Unit is a medium-voltage switchgear assembly used for ring network and secondary power distribution. It provides switching, isolation, grounding and feeder protection functions.
The nominal system voltage is 11kV, while the commonly specified highest voltage for the equipment is 12kV.
A common rated current is 630A, although higher current ratings can be provided for specific applications.
It can be. SF6-insulated RMUs are widely used, but SF6-free solid-insulated alternatives are also available.
Yes. Motorized operating mechanisms can be installed for remote control and distribution automation applications.
Yes. The RMU can be configured with RTU, communication interfaces, fault indicators and other automation components for SCADA integration.
Yes. The number of ways, LBS/VCB configuration, protection relay, CT/VT, cable connection, operating mechanism, communication system and enclosure can be customized according to the project requirements.
CHNGS / Gongshun Electric Co., Ltd. provides medium-voltage electrical equipment and customized power distribution solutions for utility, industrial, commercial and renewable-energy applications.
For an 11kV RMU quotation, customers can provide the following information:
Our engineering team can then recommend a suitable 11kV RMU configuration and technical solution according to the project requirements.
