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Toshiba Corporation has announced that TEPCO Power Grid, Incorporated (tepco.co.jp) has selected Toshiba's 300 kV dead tank gas circuit breaker (DT-GCB) and three-phase gas-insulated bus (GIB) for integration into its power transmission and distribution network. The equipment is the first in its class to completely eliminate use of sulfur hexafluoride (SF6), an extremely potent greenhouse gas, as electrical insulation and to replace it with a mixture of carbon dioxide and oxygen, natural-origin gases found in nature. The equipment is the first 300 kV-class DT-GCB and GIB with natural-origin gas insulation to find commercial application.
Toshiba is developing 300 kV DT-GCB and GIB as core products in its “AEROXIA™”*2 brand lineup of transmission and distribution equipment using natural-origin gases. And will contribute to reducing greenhouse gases while ensuring performance equivalent to conventional SF6 gas-applied equipment. Toshiba plans to deliver the DT-GCB in fiscal year 2029 and the GIB in fiscal year 2030. Toshiba will showcase AEROXIA™, including the 300 kV DT-GCB and GIB, at its booth at CIGRE Paris 2026 Exhibition from August 23 to 28.
DT-GCBs interrupt current flows in the event of abnormalities in transmission lines, preventing impacts on other electrical equipment. GIBs use busbars, which are metal conductors, to transmit high-voltage power within substations. The busbars are enclosed in gas with high insulation performance, typically using SF6, to prevent shorting and failure. These connect the power route from switching equipment to external transmission lines and transformers.
Transmission and distribution equipment, including DT-GCBs and GIBs, carry high-voltage currents and must be electrically insulated from their metal tank to prevent shorting. SF6 gas provides excellent insulation and has long been used for this purpose. However, it also has a global warming potential (GWP) approximately 25,000 times that of CO2, and its release has a significant impact on atmospheric heat retention. Reducing its use is an important global challenge.
After fully considering human safety, the environment (including toxicity and decomposition products), ease of handling, and long-term operational reliability, Toshiba decided to explore natural-origin gases as insulators. These are gases that occur in nature and have a much lower GWP, such as oxygen and CO2, and they offer the only viable means for eliminating SF6 and other artificially synthesized fluorinated gases. With its AEROXIA lineup, Toshiba is advancing development of products that satisfy the “seven requirements”*3 for SF6 alternatives defined by Japan’s electric utilities, manufacturers, and research institutions.
Toshiba has already commercialized and delivered 72/84 kV gas-insulated switchgear (GIS)*4 using natural-origin gases, and has also commercialized 420/550 kV GIB. The company has also confirmed the fundamental performance of 300 kV GIS and DT-GCB, and will use that know-how to manufacture and commercialize the 300 kV DT-GCB and GIB selected by TEPCO Power Grid, Incorporated. This selection is an important milestone in the practical application of high-voltage equipment using natural-origin gases.
Transmission and distribution equipment insulated with natural-origin gases will play a key role in next-generation power networks by reducing the use of SF6 and delivering stable power supply. Grid operators and renewable energy companies in Japan and overseas are interested in its potential. Toshiba will continue to expand its business of SF6-free transmission and distribution equipment under the AEROXIA brand, contributing to the realization of a sustainable society in harmony with the environment.
1. As of August 21, 2026, according to Toshiba, for gas circuit breakers and three-phase gas-insulated bus at the 300 kV level using natural-origin gases.
2. For further details on AEROXIA™, please refer to: AEROXIA_Brandbook_ENG (PDF)(9.08MB)
3. See page 3 of Roadmap of Transition toward SF6 Alternative Technologies Rev. (PDF)(401KB)
4. Equipment comprising circuit breakers that interrupt current in the event of abnormalities in transmission lines to prevent impacts on other electric power equipment, as well as disconnect switches for switching transmission systems, surge arresters, and instrument transformers.
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