1. What Is SF6 Gas Insulated Ring Main Unit (RMU)?
SF6 Ring Main Unit, also widely known as Gas Insulated Ring Main Unit (Gas Insulated RMU), is a compact fully sealed medium voltage (MV) switching device designed for urban ring distribution networks, compact secondary substations and new energy power collection systems.
Unlike air-insulated ring main units (AIS RMU), all live components including load switches, vacuum circuit breakers, disconnectors and earthing switches are hermetically locked inside a stainless steel metal tank filled with high-insulation SF6 sulfur hexafluoride gas. SF6 acts as both arc-quenching medium and insulating medium, with dielectric strength 3 times higher than air under equal pressure, greatly shrinking cabinet volume while improving operational safety.
The whole gas tank adopts fully sealed welding technology with annual gas leakage rate ≤0.01%, so internal switching components are completely isolated from external dust, coastal salt fog, high humidity and small animal intrusion. This maintenance-free design makes gas insulated RMUs the mainstream MV distribution equipment for space-limited and harsh-environment projects worldwide, complying strictly with IEC 62271 international medium voltage switchgear standards.
Standard rated voltage grades of our factory SF6 RMU cover 12kV, 24kV and 36kV; rated current ranges from 630A to 1250A, supporting short-circuit withstand current 20kA, 25kA and 31.5kA to match global grid standards of Europe, Southeast Asia, Middle East and Australia.
2. Core Advantages of SF6 Gas Insulated Ring Main Unit
2.1 Ultra-Compact Footprint, Save Civil Construction Cost
The sealed gas tank structure eliminates large air insulation gaps between live parts. A single SF6 RMU panel only occupies 300–400mm width, reducing total installation space by over 60% compared with traditional air insulated ring main units. It can be installed in underground cable tunnels, narrow urban sidewalk kiosks and small integrated box substations, cutting building area investment and civil engineering construction cycles significantly.
2.2 Fully Sealed & Maintenance-Free Operation
All switching cores are isolated inside the SF6 tank. There is no regular cleaning, insulation test or dust removal work required within the 30-year service life. Only periodic simple gas pressure inspection is needed, suitable for unattended remote sites such as mountain wind farms, rural power grids and highway service stations. For property owners and engineering contractors, long-term operation and maintenance labor costs are reduced by more than 70%.
2.3 Strong Environmental Adaptability
SF6 gas insulated RMUs perform stably under extreme working conditions:
- Coastal areas with heavy salt fog;
- High-altitude plateau zones over 3000m;
- Underground damp cable tunnels;
- Chemical industrial parks with corrosive gas;
- Cold regions with minus 40℃ low temperature.
The external cabinet reaches IP4X protection grade, and the internal gas tank achieves IP67 sealing grade, completely avoiding short-circuit failures caused by environmental pollution.
2.4 Modular Combination & Flexible Expansion
Our SF6 ring main unit supports fully modular assembly, with interchangeable functional modules including incoming cabinet, outgoing cabinet, metering PT cabinet, vacuum breaker cabinet and bus coupling cabinet. Customers can freely combine two-in two-out, two-in four-out and multi-feeder schemes according to project ring network layout. Extended shielded busbars realize seamless splicing without extra insulation treatment, convenient for later grid capacity expansion.
2.5 High Safety for Operators
Three-position interlock mechanism (switch on, switch off, earthing) prevents misoperation; internal arc-proof design meets AFLR internal arc resistance standard. Even short-circuit faults occur inside the gas tank, high-temperature arc will be limited within the sealed metal cavity without splashing out to hurt field staff, widely recognized for public buildings with dense pedestrian flow.
3. Main Application Scenarios of SF6 Gas Insulated RMU
3.1 Urban Municipal Power Distribution
City underground cable ring networks, community compact kiosk substations, central business district underground power rooms and residential district secondary distribution stations are the largest application markets for SF6 ring main units. Dense urban construction restricts equipment floor area, and maintenance-free feature reduces frequent road excavation maintenance work, fitting city management requirements perfectly.
3.2 Commercial & Public Infrastructure
Shopping malls, hospitals, airports, metro transit stations, schools and data centers all adopt gas insulated RMUs. These projects demand uninterrupted power supply and strict fire safety standards; compact SF6 RMUs can be placed inside basement power rooms without independent fire isolation space. For data centers, stable ring network switching ensures zero power outage during equipment maintenance.
3.3 New Energy Power Plants
Ground photovoltaic power stations, distributed rooftop solar systems and onshore wind farms widely match SF6 ring main units as medium voltage collection switching equipment. The sealed anti-corrosion structure adapts outdoor open-air installation, modular design matches multi-group PV string parallel access, and optional DTU intelligent communication modules support remote SCADA monitoring of power generation data.
3.4 Industrial & Mining Projects
Manufacturing factories, chemical plants, oil & gas stations and mining sites choose SF6 gas insulated RMUs to cope with dust, corrosive gas and unstable load fluctuations. Short-circuit breaking capacity can bear instantaneous impact current from large industrial motors, effectively protecting distribution transformers and production equipment.
3.5 Highway & Remote Infrastructure
Highway toll stations, mountain water conservancy projects and remote communication base stations rely on maintenance-free SF6 RMUs. Remote unattended sites lack professional electrical maintenance personnel, and long-term stable operation reduces on-site inspection frequency.
4. SF6 Gas Insulated RMU VS Air Insulated Ring Main Unit Comparison
Many overseas purchasers confuse gas insulated and air insulated RMUs during project tendering. The core differences are sorted below for quick selection:
- Space occupation: Gas insulated RMU ultra-compact; air insulated RMU large cabinet, requiring spacious power room.
- Maintenance: SF6 RMU maintenance-free; air insulated RMU needs annual dust cleaning and insulation detection.
- Environment tolerance: Gas insulated type fits underground, coastal, corrosive workshops; air insulated only suitable for dry indoor factory power rooms.
- Project cost: Single gas insulated RMU unit price higher, but saves civil construction space cost; air insulated equipment low procurement price with higher later operation cost.
- Service life: SF6 RMU over 30 years; air insulated RMU 15–20 years affected by environmental aging.
Selection suggestion: Choose SF6 gas insulated ring main unit if your project is underground, urban, new energy or coastal; select air insulated RMU only for spacious dry factory indoor distribution with tight budget.
5. Standard Technical Parameters of Our SF6 Ring Main Unit
As a power equipment manufacturer with 15 years of production experience, all gas insulated RMUs pass full type tests and comply with IEC 62271 international standards, supporting global grid customization:
- Rated voltage: 12kV / 24kV / 36kV
- Rated current: 630A, 1250A
- Short-time withstand current: 20kA/3s, 25kA/3s, 31.5kA/3s
- Gas tank leakage rate: ≤0.01% per year
- Protection grade: Gas tank IP67, outer cabinet IP4X
- Mechanical operation life: Load switch ≥10,000 times, vacuum breaker ≥20,000 times
- Optional functions: Intelligent DTU remote monitoring, temperature sensor, voltage metering PT, arc protection
We support customized cabinet color, brand logo, internal wiring scheme and communication protocol to meet tender requirements of European, Southeast Asian and Middle Eastern engineering companies. All finished RMUs complete gas tightness, temperature rise and short-circuit withstand tests before delivery, with full test reports provided for third-party inspection.
6. Why Source SF6 Gas Insulated RMUs From Our Factory?
- Strict raw material control: Imported stainless steel gas tank plate, high-purity copper contact and imported SF6 insulating gas guarantee stable long-term performance.
- Independent mold R&D: Complete series of modular molds for standard and non-standard RMU schemes, fast delivery for bulk orders (7–15 working days for standard models).
- One-stop supporting matching: We can supply supporting dry type transformers, oil immersed transformers, low voltage distribution cabinets and DC EV charging stations together with SF6 RMUs to form complete compact substation solutions.
- Global OEM & ODM service: Accept private label customization, parameter adjustment and packaging optimization for overseas distributors and electrical engineering contractors.
- Professional overseas after-sales: Provide remote installation guidance, operation training and long-term supply of spare parts such as gas pressure gauges and interlock components, supporting multi-language technical documents.
