China, Hubei, Wuhan: State Grid Corporation of China has connected the world’s first operational 550 kV SF₆-free gas-insulated switchgear to the grid at the Yuxian substation in Wuhan.
The installation, energised on 29 May 2026, uses Hitachi Energy’s EconiQ® 550 kV GIS. The technology was first presented as a prototype at the CIGRE Session in Paris in 2024, before a memorandum of understanding was signed with State Grid in 2025.
The project is significant because SF₆ has long been used in high-voltage switchgear for its strong insulating and arc-quenching properties. However, it also has a very high global warming potential, making its replacement an important step in reducing emissions from grid infrastructure.
At 550 kV, removing SF₆ is especially challenging because equipment must meet demanding performance and reliability requirements in EHV transmission systems. Hitachi Energy’s solution uses a gas mixture of CO₂, O₂ and C4-FN to provide the required dielectric and switching performance with a much lower climate impact.
According to Hitachi Energy, over a 40-year service life, a conventional SF₆ GIS bay can generate insulation gas emissions equivalent to around 1,674 t of CO₂, while the EconiQ alternative reduces this to 12.6 t, a reduction of 99.2 %.
The Wuhan Yuxian substation is a key transmission node where reliability is critical. The successful energisation gives utilities and grid operators a real-world reference for SF₆-free technology at extra-high voltage.
The project supports State Grid’s decarbonisation efforts and China’s wider carbon goals, while showing that sustainable high-voltage equipment can operate in a live transmission network.
Source: Hitachi Energy
