SRM□-12 Fully Enclosed Fully Insulated Gas-insulated RMU

SRM□-12 Series Ring Main Unit Product Introduction

Complete Product Introduction

1. Product Brief Introduction

The SRM□-12 series ring main unit is an SF₆ gas-insulated metal-enclosed switchgear. It consists of load switch units, load switch-fuse combination units, circuit breaker units, and other functional modules. The product adopts a series of advanced technologies, featuring excellent electrical performance, strong environmental adaptability, small size, easy installation, and maintenance-free operation. It supports flexible combination modes, with an intuitive design that ensures simple and direct operation, and a large outgoing capacity suitable for various wiring schemes.

2. Unit Definition

Unit Code	Description
C	Standard single-cable load switch unit
F	Load switch-fuse combination unit
D	Circuit breaker unit (without switch)
V	Cable incoming/outlet unit (without switch)
-	Busbar branch sleeve
SL	Busbar connection sleeve
M	Metering unit
PT	PT unit
K2(4)	Load switch unit with double-cable outgoing

3. Product Characteristics

Operational Safety: Integral three-position load switch replaces the disconnector, ensuring higher safety and reliability. Fully enclosed design prevents accidental contact, meeting the five-prevention mechanical interlock requirements. The live indicator ensures safe operation of incoming/outgoing lines under voltage. All 10kV switches and busbars are sealed in an SF₆ gas tank welded from 3mm stainless steel, protecting against dust, humidity, and small animal interference. The front panel uses a galvanized steel plate with electrostatic spraying, providing excellent corrosion resistance. A pressure gauge monitors the SF₆ gas pressure inside the tank.
Maintenance-Free & Durability: Service life up to 20 years.
Flexible Scheme: Multiple incoming modes (left, right, front, or top) and combination modes, allowing arbitrary combination of units. Insulated busbars enable front/back or left/right cabinet connection.
Wide Application: Large outgoing capacity, small footprint, suitable for various application scenarios.

4. Performance Indicators

Item	Parameter	Item	Parameter
SF₆ Gas Pressure (20℃)	1.4bar (absolute pressure)	Normal Operating Temperature	-40℃ ~ 40℃
Annual Gas Leakage Rate	≤0.2%/year	Maximum Average Humidity	≤95%
Protection Class	IP67	Maximum Altitude	≤2000m
Gas Tank Stainless Steel Thickness	3.0mm	Busbar (Inside Cabinet)	400mm² Cu
Earthing Busbar	150mm² Cu	Compliance Standards	GB/T11022, GB3906, GB1985, GB3309, GB38041, GB1984, IEC60056, IEC60129, IEC60265, IEC60298, IEC60420, IEC60694
Cabinet Front Panel Color	RAL7012	Side & Cable Room Panel Color	RAL7035

5. Main Technical Parameters

Item	Unit	C Module	F Module	V Module		CB Module
Item	Unit	Load Switch	Combination Electrical Appliance	Vacuum Switch	Isolation/Earth Switch	Vacuum Circuit Breaker	Isolation/Earth Switch
Rated Voltage	kV	12	12	12	12	12	12
Rated Frequency	Hz	50	50	50	50	50	50
Power Frequency Withstand Voltage (Phase-to-Phase / Port)	kV	42/48	42/48	42/48	42/48	42/48	42/48
Lightning Impulse Withstand Voltage	kV	75/85	75/85	75/85	75/85	75/85	75/85
Rated Current	A	630	Note	630		1250/630
Rated Closed-Loop Breaking Current	A	630
Rated Cable Charging Breaking Current	A	135/135
Rated Short-Circuit Making Current (Peak)	kA	50	80
Rated Peak Withstand Current	kA	50
Rated Short-Time Withstand Current	kA/3s	20
Rated Short-Circuit Breaking Current	kA		31.5	20		25	25
Rated Transfer Current	A		1750
Maximum Current of Equipped Fuse	A	-	125
Loop Resistance	μΩ	≤ 300	≤ 600
Mechanical Life	Times	5000	3000	5000	2000	5000	5000

Note: (1) Depends on the current rating of the fuse.

6. Switch Unit

The load switch adopts a coaxial rotating double-break structure, and its functional operation is realized through the cooperation of a single operation hole and a sliding plate. Therefore, the switch can only be in one of the three states of "closed, open, earthed" at any time, which completely prevents misoperation.

7. Pressure Relief Device

The pressure relief device is separated from the cable compartment by a metal plate. If the pressure inside the gas tank is excessively high, the explosion-proof diaphragm in the device will rupture to release the pressure.

8. Operating Mechanism

The operating mechanism of the switch is mounted on the front outside the gas tank. It is treated with a special process for corrosion resistance, facilitating manual operation and maintenance, and enabling easy realization of electric operation. The operating mechanism can adopt a spring mechanism or a permanent magnet operating mechanism.

9. Genuine Cable Compartment and Cable Connection Mode Meeting Actual Requirements

The cable connection compartment features a large space, and the bushings adopt a standard design to be compatible with all European standard cable connectors. Under normal circumstances, each load switch unit can connect 1~3 outgoing lines, and the specially designed type can connect 4~6 outgoing lines. Each vacuum circuit breaker unit can connect 1~2 outgoing lines.

Internationally standardized universal bushings (compliant with DIN 47636 or American standards) are adopted for easy selection of corresponding cable accessories by users. T-type front and rear cable connector connection is applied with an European-style bolt step-by-step fastening structure, and the connection between the front connector and the bushing uses M16 bolts. For the cable connection mode, the ordinary terminal block and heat-shrinkable sleeve mode is also an optional choice.

10. Arrester Connection

A T-type rear plug-in fully sealed metal oxide arrester with silicone rubber housing can be retrofitted to the load switch unit. A W-type rear plug-in arrester is an alternative when the number of cable circuits is large and the installation space is insufficient.

11.Fuses

The fuse replacement of SRM□-12 gas fully insulated and fully enclosed ring main unit is direct and simple. The fuses are placed in insulating tubes, which are located in the metal gas tank filled with SF6 gas. This design has the following advantages:

The fuse cover and sealing device are positioned at the part with the weakest electric field.
No conductive substances can adhere to the fuse assembly.
The parts inside the SF6 gas are fully protected.

No additional insulated spring energy storage operating mechanism or interlocking tripping device is required for the fuse cover, which ensures that the three phases of the load switch are automatically disconnected simultaneously when the fuse of any phase blows.

12.SRM□-12 Series Switch Panel Indicators

Live Indicator
Main Switch Operation Hole (Operation Sequence: Clockwise for Closing / Counterclockwise for Opening)
Earthing Switch Operation Hole (Operation Sequence: Clockwise for Closing / Counterclockwise for Opening)
Open/Close Position Indicator (Red for Closed / White for Opened)
Earthing Position Indicator
Load Switch Padlock Position
Earthing Switch Padlock Position

13.Unit C

14. Fuse Replacement Steps

Rotate the switch operating handle counterclockwise by half a turn, pull it outwards to replace the fuse, and align it with the hook position and rotate clockwise during installation.