Scope of Application
The DFWK-12 series outdoor ring main unit (RMU) is a gas-filled outdoor RMU developed and produced by our company with foreign professional technology, in line with the characteristics of regional distribution networks in China and the actual situation of urban distribution cable-ization projects, reaching international professional standards.
The DFWK-12 series outdoor RMU adopts the HRM16-12/24 series SF6 fully-sealed fully-insulated ring-main switchgear, which is modular, extensible, fully insulated, fully sealed, safe, reliable and maintenance-free, suitable for any harsh environment, and is widely used in industrial parks, residential areas, streets, airports, various buildings, busy commercial centers and other places.
The DFWK-12 series outdoor RMU has standard voltage classes of 12 kV and 24 kV, and can be extended with distribution automation functions to make the RMU intelligent and the grid stronger and smarter. The DFWK-12 series outdoor RMU has a rated voltage of 12 kV/24 kV and a rated frequency of 50 Hz; the gas tank protection class reaches IP67, enabling ring-main supply and distribution automation.
Type Designation
Service Conditions
- Ambient temperature: maximum +50℃, minimum -40℃, maximum daily average not exceeding 35℃;
- Relative humidity: daily average not exceeding 95%, monthly average not exceeding 90%;
- Wind speed: not exceeding 35 m/s;
- Pollution degree: Class III;
- Seismic intensity: degree 8;
- Ground inclination: not more than 3 degrees;
- Installation site: install in places free from fire, explosion or violent vibration, well ventilated and free from corrosive gases.
Special conditions
- When the equipment is installed at an altitude above 1000 m, please specify specially so that the company can adjust the SF6 pressure during manufacturing.
- For special severe conditions, please be sure to consult the company.
Product Features
High safety
- All live parts are enclosed in the SF6 gas tank, achieving full sealing and full insulation;
- Mechanical interlocks meeting the five-prevention requirements prevent misoperation;
- Incoming/outgoing cables use fully insulated, fully sealed touchable connections, ensuring personal safety to the greatest extent;
- The tank is fitted with a gas-pressure monitoring device for real-time pressure monitoring during operation;
- An explosion-venting pressure-relief device is arranged at the rear lower part of the gas tank, and the internal arc test has been passed by an authoritative institution.
Flexible schemes
- Flexible incoming/outgoing modes: left, right and bottom incoming (outgoing) cables;
- Flexible combination: any combination between all units with unlimited extension;
- Built-in busbar extension fully meets usability, economy and aesthetic requirements;
- Flexible design schemes can meet the site requirements of users.
Compact & rational structure
All unit modules have identical dimensions (except the metering module); the compact size does not affect construction convenience.
Economy
Maintenance-free; small footprint, high cost performance; service life over 30 years.
Wide application
The stainless-steel plates of the gas tank are automatically TIG-welded by robots, with protection class up to IP67; it can be installed in humid, dusty, saline, mining and any air-polluted places without special precautions.
Intelligence
Motorized operating devices and distribution automation terminal equipment can be provided to realize intelligent switchgear with "four-remote" functions, meeting all requirements of the smart grid for such equipment.
Applicable Standards
- GB 1984-2003 High-voltage AC circuit breakers
- GB 1985-2005 High-voltage AC disconnectors and earthing switches
- GB 3804-2004 3.6 kV-40.5 kV high-voltage AC load switches (IEC 60265)
- GB 16926-2009 AC high-voltage load switch-fuse combinations (IEC 60420)
- GB 3906-2006 3.6 kV-40.5 kV AC metal-enclosed switchgear and controlgear (IEC 62271)
- GB/T11022-2011 Common technical requirements for high-voltage switchgear and controlgear standards (IEC 60694)
- GB/T11023 SF6 gas sealing test methods for high-voltage switchgear
- GB 4208-2008 Degrees of protection provided by enclosures (IEC 60529)
- DL/T404 3.6 kV-40.5 kV AC metal-enclosed switchgear and controlgear
- DL/T 728-2000 Guide to the ordering of gas-insulated metal-enclosed switchgear
- Q/CSG 10012 Technical guidelines for urban distribution networks of China Southern Power Grid
- State Grid Corporation material procurement standard - General technical specification for 12 kV and 24 kV ring main units
Main Technical Parameters
| Item | Unit | C load-switch panel | C load-switch panel / F combination unit | V circuit-breaker panel |
|---|---|---|---|---|
| Rated voltage | kV | 12/24 | 12/24 | 12/24 |
| Rated frequency | Hz | 50 | 50 | 50 |
| Rated current | A | 630 | 125 | 630 |
| Rated transfer current | A | - | 1750 | - |
| Rated insulation level | 1-min power-frequency withstand voltage (phase-to-earth) kV | 42/65 | 42/65 | 42/65 |
| 48/79 | 48/79 | 48/79 | ||
| Lightning impulse voltage kV | 75/125 | 75/125 | 75/125 | |
| 85/145 | 85/145 | 85/145 | ||
| Rated short-circuit breaking current | kA | 20 | 315 | 20 |
| Rated short-circuit making current | kA | 50 | 80 | 50 |
| Rated short-circuit making current (earthing switch) | kA | 50 | 50 | 50 |
| Rated short-time withstand current | Main circuit kA | 20 | 20 | 20 |
| Earthing switch kA | 20 | 20 | 20 | |
| Rated short-time duration | Main circuit s | 4 | 4 | 4 |
| Earthing switch s | 4 | 4 | 4 | |
| Rated peak withstand current | Main circuit kA | 50 | 50 | 50 |
| Earthing switch kA | 50 | 50 | 50 | |
| Internal arc test (IAC) | A | 630 | 20kA/0.5s | 630 |
| Rated closed-loop breaking current | A | 630 | limited by the fuse | 630 |
| Rated active load breaking current | A | 10 | limited by the fuse | 25 |
| Rated cable-charging breaking current | operations | 5000 | 17.4 | 3000 |
| Mechanical endurance | Load switch/disconnector, operations | 3000 | 5000 | 3000 |
| Earthing switch, operations | 3000 | 3000 | 10000 | |
| Vacuum circuit breaker | Mpa | - | - | |
| SF6 gas pressure (absolute pressure at 20℃) | - | - | 0.035 | - |
| Annual leakage rate | - | - | ≤0.025% per year | - |
| Gas tank & fuse cylinder protection class | - | - | IP67 | - |
| Tank & enclosure protection class | - | - | IP4X | - |
Structural Features
① Enclosure of the outdoor RMU
The enclosure is made of stainless steel (≥2.0 mm), SMC, GRC etc., customizable per user requirements; the door opening mode is flexible and waterproof rubber strips are provided at the door gaps, bringing the overall protection class to IP4X to meet outdoor requirements.
② Pressure gauge
For real-time monitoring of the SF6 pressure in the gas tank; a dry contact can be configured to alarm when the pressure is too low or too high.
③ Gas tank of the switch units
The gas tank is made of 304 stainless steel (3.0 mm), fully welded by automatic manipulators; it withstands the SF6 pressure inside and reaches protection class IP67. The tank is leak-tested, dried and filled by helium mass-spectrometry vacuum leak-detection equipment, ensuring tightness.
④ Load-switch panel
A three-position load switch is used to reduce the panel volume; SF6 gas is used for arc extinction, improving operational reliability.
⑤ Communication & control cabinet
For installing communication equipment such as DTU switches and optical terminals.
⑥ Fault indicator
For detecting line short-circuit and earth faults, facilitating fault location and providing a basis for future distribution automation.
⑦ Earthing switch
For maintenance earthing.
⑧
For observing the operation inside the cable compartment, providing maximum convenience for operation and maintenance.
⑨ Live-line indicator
Indicates whether the circuit cable is live; a phasing hole is reserved for use with a special phaser.
⑩ PT & automation cabinet
For installing the PT and distribution automation terminal devices. Made of stainless steel and connected to the switch units via fully sealed, fully insulated plug-in connectors.
Main Accessories
Tank
The RMU enclosure is designed as an outdoor-type structure; the tank material can be stainless steel plate, SMC or GRC per customer requirements, with plastic-sprayed surface and sufficient mechanical strength;
No removable fasteners on the tank surface (good anti-theft performance); the roof is a double-layer structure with an air interlayer and vents, with natural convection ventilation, good heat insulation and dissipation;
Rain-proof door locks; a limit hook fixes the door when open; the tank has sealed bottom plates at the cable entries to prevent small animals and moisture from entering;
The appearance and color of the tank can be customized; it is elegant and in harmony with the surroundings.
Switch units
The switch units used in the DFWK series outdoor RMU are the HRM16 series fully-sealed fully-insulated ring-main switchgear produced by our company, featuring modularity, unlimited free extension, compact structure, small size and maintenance-free operation. The functional units and their descriptions:
C unit: load-switch panel, mainly used for connection, branching, sectioning and control of 12 kV/24 kV distribution network cable incoming/outgoing lines;
F unit: load switch + fuse combination unit, used for control and protection of terminal distribution transformers with capacity up to 1250 kVA in 12 kV/24 kV distribution networks.
V unit: vacuum circuit-breaker unit, which can be used not only for connection, branching, sectioning, control and protection of 12 kV/24 kV distribution network cable lines, but also for control and protection of larger-capacity distribution transformers.
This unit is equipped with a microprocessor-based relay protection device, providing over-current protection and other functions.
D unit: cable incoming panel without switch, used for connecting incoming/outgoing cables directly to the busbar.
SV unit: bus-tie panel for connecting sectionalized busbars.
M unit: metering panel for electric energy metering, can be conveniently combined with any other panel.
PT unit: voltage transformer panel for installing the PT, automation terminal device and backup power supply, etc.
Cable Branch Box Foundation Drawing
Ordering Information
- Product model; primary diagrams available for special user requirements;
- Standard cross-sections of incoming/outgoing and branch cables;
- Quantity of optional surge arresters and short-circuit fault indicators;
- Enclosure material and color.
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