Zhiwai Publishes SF₆-Free RMU Comparison for Utility Buyers

Review compares four manufacturers’ RMU ranges, covering switching designs, retrofit requirements, utility records and environmental documentation.

SINGAPORE, SINGAPORE, October 28, 2026 /EINPresswire.com/ -- Zhiwai has released a comparison of SF₆-free ring main unit (RMU) ranges for secondary distribution up to 24 kV: Schneider Electric's RM AirSeT, ABB's SafeRing Air and SafePlus Air, Siemens' 8DJH 24 blue GIS and Eaton's Xiria. The review covers insulation, switching, retrofit requirements, utility records and environmental documentation. It draws on manufacturer documents, regulatory texts and project announcements, without independent product testing.

Insulation and regulation. Schneider Electric uses Pure Air, ABB specifies dry air and Siemens uses Clean Air in sealed gas-insulated enclosures. Schneider Electric and ABB describe their air media as having a global warming potential (GWP) of zero; Siemens specifies GWP below one for Clean Air. Xiria combines vacuum interrupters with air and solid insulation. The named ranges use no fluorinated gas for insulation or interruption. Article 13(9)(a) of Regulation (EU) 2024/573 prohibits putting into operation medium-voltage switchgear up to and including 24 kV that relies on fluorinated gases for insulation or interruption in the EU, subject to the regulation's derogations. It lists SF₆'s 100-year GWP as 24,300 relative to CO₂.

Switching design. RM AirSeT's load-break switching uses Shunt Vacuum Interruption (SVI). A vacuum interrupter is connected in a shunt path parallel to the main contacts. During opening, current is diverted through the interrupter and interrupted in vacuum, while an air gap provides isolation. Breaking and disconnection are completed in one operation, retaining the familiar closed, disconnected and earthed positions. Siemens' three-position blue switch uses vacuum interruption in an auxiliary current path. Eaton uses vacuum interrupters for Xiria load-break switches and circuit breakers. ABB specifies dry-air puffer interruption for load-break switches and vacuum interruption for its V-module circuit breakers. For each offered functional unit, switching duty and endurance should be checked against type-test evidence, and maintenance intervals against the manufacturer's operation and maintenance instructions.

Retrofit requirements. ABB states that SafeRing and SafePlus Air retain the interface, footprint and operation of the corresponding SF₆ products. Siemens states that 8DJH 24 blue GIS retains its SF₆ counterpart's compact dimensions. Schneider Electric describes RM AirSeT as a compact RMU suited to kiosk substations. Eaton offers compact block and extendable Xiria configurations. Site checks still need to cover dimensions, cable interfaces, foundations, access, protection and extension arrangements.

Utility records. Schneider Electric and E.ON's 2025 framework covers GM AirSeT primary panels and RM AirSeT secondary panels; the preceding Westnetz pilot concerned primary gas-insulated switchgear. ABB announced a separate E.ON agreement in 2025 for SafeRing and SafePlus Air 24 kV secondary switchgear. Siemens has documented an 8DJH 24 installation with Netze BW in 2020. Eaton describes Xiria deployment by Vores Elnet on a 10 kV grid. These framework agreements and deployment case studies document utility adoption without establishing comparative reliability.

Environmental documentation. Schneider Electric's RM AirSeT IEC 12 kV Product Environmental Profile is a Type II declaration under ISO 14021 with internal verification. Its separate SM AirSeT-DMVL-A profile is an externally verified Type III declaration under ISO 14025 and does not establish coverage of the RM AirSeT range. Siemens' EcoTech profile states that a Type II environmental product declaration is available for the 8DJH 24 RRT block. Buyers should request declarations for the exact voltage and configuration from each supplier, checking validity, verification status, calculation rules, system boundaries and reference service life before comparing results.

Specifying the comparison. SF₆-free status alone does not distinguish these ranges or establish compliance with a complete tender. A specification should define rated voltage and current, functional-unit configuration, short-time withstand current and duration, internal arc classification with current, duration, accessibility type and protected sides, loss of service continuity category, partition class, monitoring and communication requirements, and environmental documents. Offers can then be assessed against the same requirements and installation conditions.

The guide states: “SF₆-free is now a starting point for comparing these RMU ranges. A network owner still needs to check the switching function, installation requirements and product-specific evidence before selecting a configuration.”

About Zhiwai

Zhiwai is an electrical-industry research and assessment organization serving engineers, buyers and network operators in Asia. It publishes neutral, document-based product comparisons and procurement guides using manufacturer specifications, regulatory texts, environmental declarations, utility requirements and documented project announcements, without independent laboratory testing.

Selina Huang
Zhiwai
+1 6174703131