Ring Main Unit（RMU）
Future-proof your power grid with our SIS RMU (Solid Insulated Switchgear), the ultimate climate-neutral solution for medium voltage secondary distribution. Unlike traditional GIS RMUs, this innovative unit uses zero greenhouse gases. Instead, all primary live parts—including vacuum interrupters and main busbars—are completely encapsulated in high-dielectric-strength epoxy resin using advanced APG (Automatic Pressure Gelation) technology.
Designedstrictly to meet IEC 62271-200 standards, our SIS RMU completely eliminates the risks of gas leakage, pressure drops, and phase-to-phase internal arcs. It combines the ultra-compact footprint of a gas-insulated unit with the absolute environmental safety of an air-insulated unit, making it the premium choice for eco-conscious projects, extreme climates, and high-altitude installations.
Core Engineering Advantages
• 100% Eco-Friendly (Zero F-Gas): Contains absolutely no SF6 or any other fluorinated gases. It fully complies with the strictest global environmental regulations (such as EU F-gas regulations), eliminating gas monitoring, reporting, and end-of-life recycling costs.
• Immune to Extreme Environments: Because it does not rely on gas pressure, the SIS RMU operates flawlessly in high-altitude regions (where gas pressure drops) and extreme cold environments (where gas can liquefy). Standard operation down to -45°C.
• Single-Phase Encapsulation: Each phase is cast independently in solid epoxy with an external grounded shielding layer. This design physically isolates the phases, effectively reducing the probability of phase-to-phase short circuits to zero.
• Ultra-Compact & Maintenance-Free: Offers a footprint comparable to GIS. The solid encapsulation protects the vacuum arc-extinguishing chamber and conductive parts from dust, moisture, and salt spray, ensuring a completely maintenance-free high-voltage compartment for its 30-year design life.
• Highly Modular Architecture: The solid insulated busbars allow for easy plug-and-play extension on-site. Modules can be swapped, added, or upgraded without any gas handling equipment, significantly reducing downtime.
Technical Specifications
Technical Parameter | Specification (12kV) | Specification (24kV) |
Applicable Standards | IEC 62271-200, IEC 62271-100, IEC 62271-103, IEC 62271-1 | |
Rated Voltage | 12kV | 24kV |
Rated Frequency | 50Hz / 60Hz | 50Hz / 60Hz |
Insulation Medium | Solid Cast Epoxy Resin | Solid Cast Epoxy Resin |
Switching/Arc-Quenching | Vacuum Interrupter | Vacuum Interrupter |
Power Frequency Withstand Voltage (1 min) | Phase to Earth/Phases: 28kV / Across Open Contacts: 32kV | Phase to Earth/Phases: 50kV / Across Open Contacts: 60kV |
Lightning Impulse Withstand Voltage (BIL) | Phase to Earth/Phases: 75kV / Across Open Contacts: 85kV | Phase to Earth/Phases: 125kV / Across Open Contacts: 145kV |
Rated Current (Main Busbar) | 630A / 1250A | 630A / 1250A |
Rated Current (T-off / Feeder) | 630A (LBS) / 630A or 1250A (VCB) | 630A (LBS) / 630A or 1250A (VCB) |
Short-Circuit Breaking Capacity (VCB) | 20kA / 25kA | 20kA / 25kA |
Short-Time Withstand Current (3s) | Up to 25kA | Up to 25kA |
Peak Withstand Current | 62.5kA (at 50Hz) / 65kA (at 60Hz) | 62.5kA (at 50Hz) / 65kA (at 60Hz) |
Internal Arc Classification (IAC) | IAC A-FLR 20kA / 1s or 25kA / 1s | IAC A-FLR 20kA / 1s or 25kA / 1s |
Degree of Protection | HV Compartment: IP67 / Enclosure: IP4X (Standard) | |
Standard Ambient Temperature | -45°C to +45°C | -45°C to +45°C |
Applicable Altitude | Up to 4000m (Standard, can be customized) | Up to 4000m (Standard, can be customized) |
Main Applications
• Eco-Sensitive Zones: National parks, water treatment plants, and urban residential areas enforcing strict zero-emission mandates.
• Extreme Conditions: High-altitude mining sites, offshore wind farms, and regions with severe cold (-45°C) or rapid temperature fluctuations.
• Modern Rail & Infrastructure: Underground transit systems and airport terminals prioritizing fire safety and toxic-gas-free equipment.
• Premium Commercial Assets: Data centers and luxury high-rises where absolute reliability and footprint reduction are critical.
Q1. What is Solid Insulated Switchgear (SIS) and how does it work?
A: SIS is a modern, eco-friendly medium-voltage switchgear where all high-voltage live parts are encapsulated in solid insulating materials (typically epoxy resin). This design replaces SF6 gas insulation, providing a fully shielded and sealed system that is immune to environmental factors.
Q2. What are the primary advantages of SIS RMU over SF6 Gas Insulated Switchgear (GIS)?
A: The main advantages include:
SF6-Free: Environmentally friendly with zero Greenhouse Gas (GHG) emissions.
No Gas Leakage Risk: Eliminates the need for gas pressure monitoring or refilling.
Explosion-Proof: The solid insulation prevents internal arcs from expanding, enhancing operator safety.
Compact Footprint: Similar or smaller size compared to GIS.
Q3. Is the SIS RMU suitable for high-altitude or coastal environments?
A: Yes. Because the high-voltage components are hermetically sealed in solid resin, the dielectric strength is not affected by air pressure or humidity. This makes SIS the ideal choice for high-altitude regions ($>3000$m), coastal areas with high salt spray, and damp underground mines.
Q4. What is the typical service life and maintenance requirement?
A: Our SIS RMU is designed for a service life of 30 years. Since there is no gas to monitor and the primary circuit is fully enclosed, the unit is virtually maintenance-free. You only need to perform periodic inspections of the secondary control circuits and mechanical linkages.
Q5. How does SIS handle "Internal Arc" safety?
A: Our SIS modules feature a fully shielded design with a grounded conductive layer on the surface of the solid insulation. This prevents phase-to-phase short circuits and ensures that even if a fault occurs, it is contained within the module, protecting both the equipment and the operator.
Q6. What are the rated voltage and current specifications for your SIS units?
A: Our standard SIS RMU supports a rated voltage of 12kV or 24kV, a rated current up to 630A or 1250A, and a rated short-time withstand current (Icw) of 20kA or 25kA (4s). These specs meet the requirements for most industrial and utility distribution networks.
Q7. What types of functional units (modules) are available?
A: We offer a modular "Plug-and-Play" design including:
V-Unit: Vacuum Circuit Breaker module.
C-Unit: Load Break Switch module.
F-Unit: Fuse-Switch combination module.
PT-Unit: Voltage Transformer module for metering.
Q8. Does the SIS RMU support "Smart Grid" automation?
A: Absolutely. Every SIS RMU can be equipped with a Feeder Terminal Unit (FTU) and motorized operating mechanisms. It supports communication protocols like IEC 61850 and Modbus-RTU, enabling remote signaling, measuring, and control via your SCADA system.
Q9. What Ingress Protection (IP) rating does the enclosure provide?
A: The outer metal enclosure is typically rated at IP4X, while the internal primary high-voltage modules are hermetically sealed, providing an equivalent protection of IP67 against dust, moisture, and temporary flooding.
Q10. What testing standards do your SIS units comply with?
A: All SIS RMUs from our Shanxi factory are manufactured and tested in accordance with IEC 62271-200. We provide a complete technical package, including Type Test Reports (Internal Arc, Temperature Rise, and Dielectric Tests) and a Factory Acceptance Test (FAT) report for every order.
