Zhiwai compares four SF₆-free RMU ranges for utility buyers

Zhiwai has released a document-based comparison of four SF₆-free ring main unit ranges for secondary distribution up to 24 kV, focusing on switching design, retrofit needs, utility references and environmental declarations. The guide is aimed at helping network owners compare products on the same technical and procurement criteria as EU rules tighten around fluorinated gases.

Why it matters: - Utilities and network owners are being pushed to compare SF₆-free medium-voltage gear on more than just emissions claims. - The comparison highlights that product fit still depends on switching function, installation requirements and product-specific evidence. - EU rules now prohibit putting into operation certain medium-voltage switchgear up to 24 kV that relies on fluorinated gases for insulation or interruption, subject to derogations. - SF₆ has a 100-year global warming potential of 24,300 relative to CO₂ under Regulation (EU) 2024/573.

What happened: - Zhiwai published a comparison of SF₆-free ring main unit ranges for secondary distribution up to 24 kV. - The review covers Schneider Electric's RM AirSeT, ABB's SafeRing Air and SafePlus Air, Siemens' 8DJH 24 blue GIS and Eaton's Xiria. - The guide draws on manufacturer documents, regulatory texts and project announcements. - The comparison did not include independent product testing.

The details: - 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 of zero. - Siemens specifies a global warming potential 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. - RM AirSeT uses Shunt Vacuum Interruption for load-break switching. - In RM AirSeT, a vacuum interrupter sits 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. - RM AirSeT completes breaking and disconnection in one operation and keeps 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 functional unit, switching duty and endurance should be checked against type-test evidence. - Maintenance intervals should be checked against the manufacturer's operation and maintenance instructions. - ABB says SafeRing and SafePlus Air retain the interface, footprint and operation of the corresponding SF₆ products. - Siemens says 8DJH 24 blue GIS retains the compact dimensions of its SF₆ counterpart. - 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.

Between the lines: - The guide treats utility adoption records as evidence of deployment, not proof of superior reliability. - Schneider Electric and E.ON's 2025 framework covers GM AirSeT primary panels and RM AirSeT secondary panels. - The earlier Westnetz pilot involved primary gas-insulated switchgear. - ABB announced a separate E.ON agreement in 2025 for SafeRing and SafePlus Air 24 kV secondary switchgear. - Siemens documented an 8DJH 24 installation with Netze BW in 2020. - Eaton describes Xiria deployment by Vores Elnet on a 10 kV grid. - Environmental labels also vary in scope and verification. - Schneider Electric's RM AirSeT IEC 12 kV Product Environmental Profile is a Type II declaration under ISO 14021 with internal verification. - Schneider Electric's 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 says 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 and check validity, verification status, calculation rules, system boundaries and reference service life before comparing results.

What's next: - Buyers are expected to use the guide as a short list filter, not a final compliance check. - Tender specifications should define rated voltage and current, functional-unit configuration, short-time withstand current and duration, internal arc classification, accessibility type, protected sides, loss of service continuity category, partition class, monitoring and communication requirements, and environmental documents. - Offers can then be compared against the same requirements and installation conditions. - Zhiwai said SF₆-free status alone does not distinguish the ranges or establish compliance with a complete tender. - Zhiwai described its work as document-based and said it does not perform independent laboratory testing.

The bottom line: - SF₆-free is only the starting point. Utility buyers still need to verify switching design, footprint, retrofits, environmental paperwork and exact test evidence before choosing an RMU.