World First: Hitachi Energy and Tennet Germany Successfully Test First SF6-Free 420 kV Switchgear

Hitachi Energy Ltd. and TenneT Germany have successfully completed on-site acceptance tests of an SF₆-free gas-insulated switchgear at the Erzhausen substation. This confirms the operational readiness of the new technology at the highest transmission voltage level under real-world grid conditions. Technology shift in grid infrastructure – transition to SF-free insulation systems at extra-high voltage level The successful validation marks a first confirmation of the transition from SF₆-based to alternative insulation systems at extra-high voltage level under real operating conditions. For grid operators, this opens up a pathway to expand transmission infrastructure with significantly reduced climate impact. However, a key factor for broader market penetration will be the speed at which SF₆-free technologies can move from pilot projects into large-scale grid deployment and establish themselves as a new technical standard. Grid modernisation: validation at 420 kV switchgear level The tested 420 kV GIS is part of Hitachi Energy’s EconiQ technology platform and was trialled in cooperation with TenneT Germany as part of ongoing grid modernisation efforts. 420 kV switchgear units represent critical nodes in the European transmission system and are essential for large-scale power transmission. “The successful completion of the on-site tests in Erzhausen is a major milestone for this project and for our grid expansion plans,” said Stefan Bönig of Tennet Germany. “It shows that SF₆-free technology can meet the technical requirements at the highest voltage level and supports our long-term goal of building a more sustainable transmission system.” About SF₆ in switchgear Sulphur hexafluoride (SF₆) is used in the power sector as an insulating and arc-quenching gas in gas-insulated switchgear, particularly in substations and grid connection points across transmission and distribution networks. Its use is part of grid infrastructure and not power generation itself. As a result, SF₆ relates equally to all generation technologies, since all power plants – regardless of technology such as gas-fired generation, wind or solar – are connected to the electricity system via grid and switchgear infrastructure. SF₆ is used in sealed, pressurised systems and remains largely contained during normal operation. Emissions, if any, occur over the lifecycle of the equipment, particularly through minor leakage, maintenance activities, and during decommissioning or disposal. Traditionally, gas-insulated switchgear has relied on SF₆, a highly potent greenhouse gas with a global warming potential (GWP) approximately 24,300 times higher than CO₂. Eliminating SF₆ therefore significantly reduces the potential environmental impact of switchgear systems.

Mannheim, Germany – The use of sulphur hexafluoride (SF₆) in gas-insulated switchgear for power grids has long been the industry standard in high- and extra-high-voltage applications. However, due to its high climate impact, the technology is facing increasing regulatory and environmental pressure. With the world’s first successful validation of an SF₆-free 420 kV switchgear under real grid operating conditions, a key grid infrastructure technology has now been tested at extra-high voltage level in live operation.

Source: IWR Online, Jun 06 2026