GHRM□-12 Series SF6 Fully Insulated Compact Ring Main Unit
GHRM□-12 SF6 gas insulated compact metal-enclosed switchgear adopts a modular design, with a perfect combination of fixed configuration and flexible expansion capability. It is suitable for end-user substations or network node applications, while simultaneously meeting the requirements of various distribution switchgear, box-type substations, and cable branch boxes. It features compact structure, safety and reliability, long service life, and maintenance-free operation.
The switchgear utilizes SF6 (sulfur hexafluoride) gas as the insulating medium for all live components — including the busbar, load break switch, and earthing switch — sealed within a stainless steel tank at a typical pressure of 0.15–0.4 bar. This fully insulated, fully sealed design eliminates exposure of live conductors to ambient air, making the unit completely immune to pollution, humidity, salt spray, and other environmental contaminants. The sealed-for-life SF6 tank requires no gas handling or refilling during its operational lifetime.
Technical Specifications
ItemSpecificationRated Voltage12kV / 24kVRated Frequency50Hz / 60HzRated Current (Main Busbar)630ARated Short-time Withstand Current (Icw)20kA / 25kA (4s)Rated Peak Withstand Current (Ipk)50kA / 63kARated Active Load Breaking Current630A (load switch)Rated Short-circuit Making Current50kA / 63kA (peak)Rated Short-circuit Breaking Current (Fuse Combination)Up to 31.5kA (via fuse)Insulating MediumSF6 gas, sealed for life at 0.15–0.4 barSF6 Gas Leakage Rate≤ 0.1% per yearDegree of ProtectionIP67 (tank) / IP3X–IP4X (enclosure)Internal Arc ClassificationIAC AFL up to 20kA 1sCable Types CompatibleSolid dielectric / XLPE / PILCCable TerminationDry-type plug-in connectors (up to 630A) or bushing-typeOperating MechanismSpring-operated, manual or motor-chargedMechanical Endurance≥ 5,000 operations (load switch)Maintenance IntervalSealed-for-life — no scheduled maintenance requiredStandardsIEC 62271-200, IEC 62271-103, GB 3804
Key Features
- SF6 Fully Insulated Design: All high-voltage components are enclosed within a sealed stainless steel tank filled with SF6 insulating gas at low pressure, providing complete isolation from ambient environmental conditions — immune to dust, humidity, salt fog, chemical pollution, and altitude effects
- Modular and Expandable Architecture: Each unit functions as an independent module (incoming, outgoing, metering, bus-riser) that can be combined via plug-in gas-busbar connections to form multi-function switchgear assemblies — supporting both fixed-configuration and future-expandable arrangements without service interruption to existing modules
- Maintenance-Free Sealed Tank: The SF6 gas tank is sealed for life with a leakage rate below 0.1% per year, eliminating the need for periodic gas refilling, cleaning of live parts, or replacement of insulation components — significantly reducing lifetime operational costs
- Compact Footprint: The gas-insulated design reduces the physical dimensions by up to 60% compared to conventional air-insulated switchgear of equivalent rating, making it ideal for space-constrained urban substations, underground vaults, and prefabricated substation integration
- Submersible Tank Protection: The IP67-rated sealed tank can withstand temporary submersion without internal damage, ensuring continued service in flood-prone areas or underground installations — a critical advantage over air-insulated alternatives
- Arc-Resistant Enclosure: Type-tested internal arc classification IAC AFL up to 20kA 1s, with pressure-relief design that safely directs arc gases away from operator access areas
- Dry-Type Plug-In Cable Termination: Standard dry-type separable connectors (650/1250A bushing interface per EN 50180/50181) enable quick, tool-free cable connection and disconnection for testing, maintenance, or circuit reconfiguration
- Optional Automation Ready: Supports motor-operated mechanisms with remote SCADA control, fault passage indicators, and partial discharge monitoring for distribution automation (DA) and smart grid integration
Applications
- Ring main units (RMU) for urban underground cable distribution networks
- Prefabricated box-type substations — HV control and protection
- Secondary distribution substations — end-user and network node supply
- Wind farm and solar farm auxiliary power distribution
- Industrial and commercial facility medium voltage distribution
- Underground power vaults and flood-prone installation sites
- Offshore platforms and marine power distribution
- Infrastructure — tunnels, airports, railway electrification