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Ring Main Unit (RMU)

The Ring Main Unit (RMU) is a compact switchgear for medium voltage distribution systems, widely used in urban distribution networks, industrial parks, commercial buildings, and new energy projects. It is a core equipment in ring network power supply systems.
This series adopts gas-insulated or air-insulated structure, featuring compact structure, safe operation, maintenance-free design, and high reliability. It provides functions such as cable incoming, outgoing, bus-tie, and transformer protection.


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Technical Parameters

Electrical Performance Parameters

Parameter	Specification
Rated Voltage	12kV / 24kV / 36kV
Rated Frequency	50Hz / 60Hz
Rated Current	630A / 1250A
Rated Short-Time Withstand Current	20kA / 25kA / 31.5kA (3 Seconds)
Rated Peak Withstand Current	50kA / 63kA / 80kA
Rated Insulation Level	Power Frequency Withstand: 42kV / 65kV
Rated Insulation Level	Lightning Impulse Withstand: 75kV / 125kV
Protection Class	Enclosure: IP4X
Protection Class	Gas Tank: IP67
Insulation Medium	SF6 Gas / Eco-Friendly Gas / Air
Gas Tank Pressure	0.02 ~ 0.04 MPa（Relative Pressure）

RMU Main Functional Units

Unit Type	Function	Typical Configuration
Incoming Unit	Cable incoming, power input	Load Switch / Circuit Breaker
Outgoing Unit	Cable outgoing, load power supply	Load Switch + Fuse / Circuit Breaker
Bus-Tie Unit	Bus connection, ring network connection	Load Switch
Metering Unit	Energy metering	PT + CT
PT Unit	Voltage measurement, operating power supply	Potential Transformer

RMU Complete Parameter Table

No.	Rated Voltage (kV)	Rated Current (A)	Short-Time Withstand Current (kA/3s)	Functional Unit	Dimensions L×W×H (mm)	Weight (kg)
1	12	630	20	Incoming	500×900×1800	150
2	12	630	20	Outgoing	500×900×1800	160
3	12	630	20	Bus-Tie	500×900×1800	140
4	12	630	25	Incoming	500×900×1800	160
5	12	630	25	Outgoing	500×900×1800	170
6	12	1250	31.5	Incoming	600×1000×2000	220
7	12	1250	31.5	Outgoing	600×1000×2000	240
8	24	630	20	Incoming	600×1000×2000	200
9	24	630	20	Outgoing	600×1000×2000	210
10	36	630	20	Incoming	800×1200×2200	300
11	36	630	20	Outgoing	800×1200×2200	320

Note: The dimensions above are for reference only. Specific dimensions can be customized according to customer requirements.

Combined Configuration Reference Table

Configuration	Combination	Dimensions L×W×H (mm)	Weight (kg)
2 Units	Incoming + Outgoing	1000×900×1800	300
3 Units	Incoming + Outgoing + Outgoing	1500×900×1800	450
4 Units	Incoming + Outgoing + Outgoing + Bus-Tie	2000×900×1800	600
5 Units	Incoming + Outgoing + Outgoing + Outgoing + PT	2500×900×1800	750
6 Units	Incoming + Outgoing + Outgoing + Outgoing + Outgoing + Bus-Tie	3000×900×1800	900

Product Features

Feature	Description
Fully Insulated & Sealed	High voltage live parts are fully sealed in stainless steel gas tank, unaffected by environment, suitable for harsh outdoor conditions.
Compact Structure	Small size, small footprint, suitable for space-constrained distribution locations.
Safe Operation	Complete five-protection interlock devices prevent misoperation and ensure personnel safety.
Maintenance-Free	Gas tank uses SF6 or eco-friendly gas insulation, fully sealed structure, no regular maintenance required.*
Flexible Combination	Modular design allows flexible combination of incoming, outgoing, bus-tie, metering, and other functional units.
Smart Monitoring	Optional smart monitoring system enables remote operation, status monitoring, and fault alarm.

Applications

Application	Recommended Configuration	Key Advantages
Urban Distribution Networks	Incoming + Outgoing + Bus-Tie	Ring network power supply, high reliability
Commercial Complexes	Incoming + Multiple Outgoing	Compact structure, space saving
Industrial Parks	Incoming + Outgoing + Metering	Modular design, flexible configuration
Residential Communities	Incoming + Outgoing	Maintenance-free, stable operation
PV Power Plants	Incoming + Outgoing + PT	Adapts to new energy grid connection
Wind Power	Incoming + Outgoing + Metering	High reliability, suitable for harsh environments

Selection Guide

Voltage Level Selection

Rated Voltage	Applicable Scenario
12kV	Urban Distribution, Industrial & Commercial Distribution
24kV	Industrial Parks, New Energy Projects
36kV	Large Industries, Substations

Functional Unit Selection

Functional Unit	Application Scenario
Incoming Unit	Cable incoming, power input
Outgoing Unit	Cable outgoing, load power supply
Bus-Tie Unit	Bus connection, ring network connection
Metering Unit	Energy metering
PT Unit	Voltage measurement, operating power supply

Fuse Configuration Selection

Transformer Capacity (kVA)	Recommended Fuse Current (A)
100	10
200	20
315	31.5
400	40
500	50
630	63
800	80
1000	100
1250	125

Customization Services

Sline provides comprehensive customization services for Ring Main Units based on your project requirements:

Customization Option	Description
Voltage Level	12kV / 24kV / 36kV / Optional
Rated Current	630A / 1250A / Optional
Functional Unit Combination	Free combination of incoming, outgoing, bus-tie, metering, PT, etc.
Smart Monitoring	Optional smart monitoring system
Special Environment	High altitude, coastal salt fog, etc.

For detailed technical drawings or customized solutions, please contact the Sline technical team. We will provide one-on-one engineer-led service throughout the process.