SF6 Ring Main Unit

The SF6 Ring Main Unit (RMU) is a factory-assembled, metal-enclosed medium-voltage switchgear system engineered for 12kV to 40.5kV secondary power distribution networks. Housed in a hermetically sealed stainless steel tank filled with SF6 gas, live parts and switching components are isolated from aggressive environmental factors such as humidity, industrial pollution, and coastal salt spray.
The modular architecture supports both extensible and non-extensible layouts, integrating load break switches, vacuum circuit breakers, and earth switches to manage ring circuits and transformer protection. Fully compliant with IEC 62271-200 standards, alternative eco-efficient gas-free (dry air/vacuum) options and IEEE/ANSI compliant builds are available for regional grid specifications. 

Hermetically Sealed Stainless Steel Tank: Laser-welded 304 stainless steel enclosure provides a sealed, pressure-tight system that eliminates maintenance for live parts inside the tank.

Compact Footprint: Minimized panel dimensions optimize space utilization in compact urban secondary substations and renewable energy skids.

Integrated Three-Position Switch: Load break, isolation, and earthing functions are combined into a single rotary mechanism with mechanical interlocking to prevent misoperation.

Flexible Combinations: Standard configurations allow modular combination of SF6 switch modules (C-modules) and vacuum circuit breaker modules (V-modules) to match custom substation schematics.

Visual Position Indication: Direct mechanical indicators linked to the main contact shaft provide unambiguous verification of contact status independent of auxiliary power sources.

Urban Secondary Distribution: Compact secondary substations supplying residential zones, commercial buildings, and municipal infrastructure.

Renewable Energy Installations: Wind turbine tower bases and solar farm collection arrays requiring high resistance to vibration and ambient temperature swings.

Industrial Plants: Medium-voltage power distribution for manufacturing facilities, data centers, and mining operations requiring high supply continuity.

Infrastructure Networks: Underground utility tunnels, railway electrification distribution grids, and airport lighting substations.

Schematic Configuration: Support for custom single-line diagrams (SLD), combining metering panels, utility interface units, and cable testing compartments.

Busbar Extensions: Left and right extensible busbar interfaces available for future substation expansion without gas handling on existing panels.

Motorized Operation & SCADA: Integrated motor operators, shunt trips, and auxiliary contacts configured for remote control and automated distribution management systems (DMS/SCADA).

Cable Compartment Layouts: Adjustable base heights and custom gland plates designed to accommodate single-core or three-core XLPE cables with surge arresters.

Production utilizes automated laser welding systems for the stainless steel gas tanks to maintain precise weld penetration depth and structural seam integrity. Every gas compartment undergoes automated helium mass spectrometer leak detection to verify seal integrity prior to gas processing.

Routine factory testing includes mechanical operation cycles, micro-ohm resistance measurement of main circuits, high-voltage power frequency withstand tests, and automated partial discharge measurement to ensure strict compliance with international utility specifications.

Type Test Reports: Full type tests performed at independent accredited laboratories according to IEC 62271-200, IEC 62271-103, and IEEE C37.20.9.
Quality Management: Manufactured under ISO 9001, ISO 14001, and ISO 45001 certified production systems.

Engineering Downloads & Documentation Package Supplied

• Instant access to CAD/DWG general arrangement drawings and BIM 3D models for station design integration
• Certified dimensional drawings and electrical schematic diagrams
• Factory Acceptance Test (FAT) individual test sheets
• Operation, maintenance, and safety manuals
• SF6 gas handling, recovery, and recycling guidelines 

Packaging: Units are bolted to heavy-duty fumigation-free wooden pallets, wrapped in moisture-barrier VCI foil, and enclosed in rugged wooden crates suitable for export ocean freight and multi-stage land transport.

Shipping Configurations: Units are shipped filled with nominal pressure SF6 gas or transported dry with low-pressure nitrogen holding charges based on destination transport regulations and utility mandates.

Lead Time: Standard configurations ship within 4 to 6 weeks; custom engineering schematics require 8 to 10 weeks subject to final drawing approval.