SM6 Modular Air Insulated Medium Voltage Ring Main Unit (RMU)

The SM6 medium voltage ring main unit is designed for indoor installation in power distribution rooms and container substations, with front cable wiring. Its dimension range: width 375–750mm, height 1600–2050mm, fixed depth 840mm. All control components are centralized on the front operation panel for easy operation, compatible with relays, coils, instrument transformers and other accessories. Rated for 12kV/24kV/36kV, it features E3 class making-breaking capacity, 630A-1250A rated load breaking current and reliable short-circuit withstand performance. It works stably within defined temperature, altitude, humidity and pollution limits without direct sunlight exposure.

product details

Normal Operating Conditions

Ambient Temperature: Max 40°C, 24h average ≤35°C, min -25°C
Altitude: 12kV model: ≤2000m; 24kV model: ≤1000m. Derating needed for higher altitudes, contact us.
Sunlight: No direct sunlight exposure.
Environment: No heavy dust, smoke, corrosives, flammable gas, vapor or salt mist.
Humidity:

1. 24h average RH ≤95%, monthly RH ≤90%;
2. 24h vapor pressure ≤2.2kPa, monthly ≤1.8kPa.

Condensation seldom happens here, but may occur with high humidity & sharp temperature shifts. Follow civil engineering standards and equip proper ventilation to prevent insulation damage.

product Display

SM6 medium voltage ring main unit inside

Technical Parameters

Main Electrical Characteristics

Specification Item	12 kV	24 kV	36 kV
Rated Voltage (kV)	12	24	36
Insulation Level
50Hz / 1min (kV rms) – Earth	42	65*	70
50Hz / 1min (kV rms) – Interrupt Gap	48	79*	80
1.2/50μs Lightning Impulse (kV peak) – Earth	95	125	170
1.2/50μs Lightning Impulse (kV peak) – Interrupt Gap	110	145	195
Breaking Capacity
No-load Transformer Breaking Current (A)	16	16	16
No-load Cable Breaking Current (A)	25	25	50
Short-time Withstand Current & Duration	25kA 1s 20kA 3s 20kA 4s*	20kA 1s	16kA/1s (630–1250A) 20kA/1s (630–1250A) 25kA/1s (1250A)
5% Rated Load Breaking Current (A)	31.5	31.5	31.5
Making & Breaking Class	E3	E3	E3
Rated Active Load Breaking Current (A)	630	630	630–1250
Rated Closed-loop Breaking Current (A)	630	630	630–1250
Rated Short-circuit Making Current (kA)	50, 63	50	50
Internal Arc Withstand Capacity	12.5kA/1s or 20kA/1s*	12.5kA/1s or 20kA/1s*	20kA/1s

*Note: Parameters marked with * are optional configurations, fully compliant with IEC medium voltage switchgear standards.

General Specifications (12kV / 24kV / 36kV full series)

Cubicle Model	Rated Current / Short-circuit Rating	Applicable Voltage
IM, IMC, IMB, NSM-C	630A	12kV / 24kV / 36kV
QM, QMC, PM	31.5kA (12kV); 20kA (24kV/36kV)	12kV / 24kV / 36kV
DM1-A, DM1-D, DM2	25kA (12kV); 20~25kA (36kV)	12kV / 24kV / 36kV

● Service continuity category: LSC2A
● Partition class: PI
● Transfer breaking current: 3 times in accordance with IEC60420 & GB16926

- 1750A @12kV
- 1400A @24kV

Core Structure Zones Introduction

1. Switch Compartment: 3-position epoxy encapsulated load switch sealed in SF6 gas tank (sealed pressure system standard). Observation window built-in, gas pressure gauge optional.
2. Busbar Compartment: All busbars are arranged on the same horizontal plane. The cabinet can be extended laterally to both sides with simple interconnection between units.
3. Cable Compartment: Cables are connected from the front for easy wiring to switch and earthing switch terminals. For transformer protection configuration, an extra earthing switch is installed below fuses inside this compartment.
4. Operating Mechanism Compartment: Houses manual operating mechanism to perform closing, opening and earthing operations with clear position indication; electric operating mechanism is optional.
5. Low Voltage Compartment: Installed with low-voltage fuses, relay protection devices and terminal blocks. An extended low voltage compartment can be added on cabinet top if internal space is insufficient.
Key Product Feature Summary

1. Fully sealed SF6 gas tank insulation, stable insulation performance and safe operation
2. Modular expandable busbar design, flexible for multi-unit ring network configuration
3. Front cable access layout, convenient on-site wiring and maintenance
4. Independent compartment layout, mechanical isolation improves operation safety
5. Customizable accessories: pressure gauge, electric operating device, extended low voltage cabinet

SF6 Circuit Breaker Cabinet Structure

1. Switch Compartment: 3-position epoxy cast switch sealed in SF6 gas tank (sealed pressure system). Observation hole built-in; pressure gauge optional.
2. Busbar Compartment: Horizontal busbar layout, lateral expandable for easy cabinet connection.
3. Cable Compartment: Front access for breaker wiring, CT/VT mountable. Two breaker types available:

- SFset: Self-powered protection with dedicated sensors
- SF1: Comprehensive relay with standard sensors (auxiliary power required)

4. Mechanism Compartment: Holds operating unit with position indicator; electric actuator optional.
5. Low Voltage Compartment: Fits fuses, relays and terminal blocks. Extended low-voltage compartment can be added on top for extra space.