# Kansai Electric and Mitsubishi Electric Energize Commercial 275 kV SF6-Free Clean Air GIS Substation in Osaka

> The Kansai Electric Power Company and Mitsubishi Electric Corporation have energized Japan’s first commercial 275 kV gas-insulated substation (GIS) operating entirely without sulfur hexafluoride (SF6), utilizing dry clean air dielectric insulation and high-voltage vacuum circuit breakers to eliminate potent greenhouse gases from urban power infrastructure.

- **Publish Date:** 2026-09-28
- **Category:** transformers-grid
- **Reading Time:** 5 min
- **Original Source Citation:** [Kansai Electric Power & Mitsubishi Electric Corporation](https://www.kansai.co.jp/press/2026/09/275kv-sf6-free-clean-air-gis-substation-energization-osaka.html)
- **Tags:** Kansai Electric, Mitsubishi Electric, 275 kV GIS, SF6-Free, Clean Air, Vacuum Circuit Breaker, Japan Grid, Substation Decarbonization
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## Eliminating SF6 from High-Voltage Urban Transmission Substations

Sulfur hexafluoride (SF6) possesses a global warming potential 24,300 times greater than CO2, prompting global grid operators to seek zero-GWP switchgear alternatives. On September 28, 2026, Kansai Electric energized a flagship 275 kV substation in the Osaka metropolitan area engineered by Mitsubishi Electric.

The facility replaces traditional SF6 insulation with pressurized natural clean air (a precision dry mixture of 80% nitrogen and 20% oxygen), ensuring zero toxic decomposition byproducts and zero greenhouse gas impact throughout its 40-year design lifetime.

## High-Capacity 275 kV Vacuum Circuit Breaker (VCB) Breakthrough

Because clean air lacks the intense arc-quenching capability of SF6, Mitsubishi Electric developed an advanced high-power vacuum interrupter bottle capable of breaking short-circuit currents up to 50 kA at 275 kV.

The substation connects two 300 MVA 275/77 kV low-noise power transformers, feeding critical urban rail networks and commercial districts with verified zero-emission high-voltage switching reliability.

## Setting the Standard for Asia-Pacific Substation Decarbonization

Kansai Electric announced that the success of the Osaka installation establishes the engineering baseline for retiring legacy SF6 switchgear across its transmission territory, accelerating Japan’s 2050 carbon-neutrality commitments.

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