KEY POINTS
- Toshiba validates 300kV GIS and GCB using only natural-origin gases, fully eliminating SF6
- CO2-oxygen mixed gas with proprietary arc-quenching chamber meets applicable standard specifications for interruption and insulation
- Prototype design to start immediately, targeting commercial product launch within fiscal year 2028
Toshiba Energy Systems & Solutions Corp. said it has confirmed the fundamental performance of 300kV gas-insulated switchgear (GIS) and gas circuit breakers (GCB) that use only naturally occurring gases — entirely eliminating sulfur hexafluoride (SF6) — marking a significant step in efforts to decarbonize high-voltage power infrastructure.
Laboratory validation tests conducted at Toshiba's Energy Systems R&D Center in Kawasaki, Kanagawa Prefecture, demonstrated that full-scale test models using a carbon dioxide-oxygen mixed gas met design targets based on applicable standard specifications for both current interruption and electrical insulation performance, the company said.
The GCB's interruption chamber adopts a proprietary puffer-type arc-quenching structure — a design that forces pressurized gas across the arc formed when contacts separate — with internal geometry optimized for the physical properties of the natural-gas mixture, Toshiba said. The company also validated performance of key GIS subcomponents including disconnectors, which isolate circuits during maintenance under no-load conditions, and earthing switches, which ground circuits to protect personnel and equipment. Toshiba said the results indicated that equipment using naturally occurring gases can be made practical at a reasonable size.
SF6 has been the insulating medium of choice in high-voltage switchgear for decades due to its exceptional dielectric strength and arc-quenching capability, enabling compact equipment design at transmission-level voltages. However, the gas carries a global warming potential (GWP) approximately 25,000 times that of carbon dioxide — the company cites a figure of approximately 25,200 times — making it one of the most potent greenhouse gases regulated under international climate frameworks. SF6 was designated a reduction-target gas at COP3 in Kyoto in 1997, and pressure on utilities and manufacturers to phase it out has intensified as net-zero commitments spread globally.
Japan presents a particularly acute challenge: the country accounts for roughly 20% of all SF6 gas used in the power-sector GIS market worldwide, according to the company, underscoring the scale of the opportunity for domestic manufacturers that can deliver credible alternatives.
Toshiba has positioned its SF6-free effort under a proprietary brand called AEROXIA, which covers transmission and substation equipment using nitrogen, CO2, and oxygen mixtures — gases with a GWP below 1 and zero ozone depletion potential. The AEROXIA platform is designed to remain liquid-free at temperatures as low as approximately minus 50 degrees Celsius even at elevated pressures, making it suitable for outdoor installations in cold climates, the company said. Because the gases contain no fluorine, they carry no future regulatory risk and can be sourced reliably from existing industrial supply chains. Toshiba said it plans to further expand the AEROXIA product lineup beyond the initial 300kV class equipment.
Having completed full-scale test-model validation, Toshiba said it will now begin designing a commercial prototype, subject it to a series of formal type tests, and target product launch within fiscal year 2028 — the Japanese fiscal year ending March 2029.
Demand for SF6-free transmission equipment is growing from both conventional power utilities and renewable energy developers seeking to reduce the carbon footprint of grid infrastructure. European regulators have already moved to restrict SF6 use in new equipment, and similar pressure is building in other major markets, creating an opening for manufacturers that can demonstrate grid-scale performance without the gas.
Toshiba, which separated its energy and infrastructure businesses into independently operating units following a prolonged corporate restructuring, has identified transmission and substation equipment as a core growth segment. The 300kV class is critical: it sits at the heart of backbone transmission networks, where the ability to interrupt large fault currents reliably is essential to grid stability. Confirming that natural-gas alternatives can meet the same performance benchmarks at this voltage level removes a key technical barrier that has until now limited SF6 substitution to lower-voltage applications.
Originally published on ibtimes.co.jp
