Manufacturer: Hitachi Energy
Original publication date: 10 July 2026
Topic: 550 kV GIS, SF₆-free transmission equipment and commercial grid operation
Hitachi Energy reports that its EconiQ 550 kV gas-insulated switchgear has entered commercial service at the Wuhan Yuxian substation in China. The installation was energized on 29 May 2026 and is described by the manufacturer as the world’s first commercial SF₆-free GIS at 550 kV operating in a live transmission network.
From prototype to an energized transmission asset
The system was first presented publicly in 2024, followed by collaboration with State Grid Corporation of China, factory acceptance testing, site installation and commissioning. Commercial energization is an important distinction: the equipment is no longer only a development platform or test object but a load-carrying part of an extra-high-voltage grid.
Hitachi Energy says the insulation system uses a mixture of 86.5 percent carbon dioxide, 10 percent oxygen and 3.5 percent C4-FN. According to the company’s lifecycle comparison, one conventional SF₆ GIS bay would account for insulation-gas emissions equivalent to about 1,674 tonnes of CO₂ over 40 years, while the EconiQ alternative is estimated at 12.6 tonnes—about a 99.2 percent reduction.
Key technical points
- Rated voltage class: 550 kV.
- Application: commercial gas-insulated switchgear in a live transmission substation.
- Site: Wuhan Yuxian substation, Hubei Province, China.
- Grid energization date reported by Hitachi Energy: 29 May 2026.
- Alternative gas mixture: CO₂, O₂ and C4-FN in the proportions published by the manufacturer.
Why it matters
Removing SF₆ at 550 kV is technically demanding because insulation coordination, switching performance, sealing, thermal behavior and long-term reliability must all be demonstrated at extra-high-voltage stress levels. A commercial reference gives utilities more concrete evidence for procurement decisions than a laboratory prototype alone. Long-term service data will now be especially valuable for assessing gas quality, leakage management, maintenance procedures, availability and lifecycle performance.
Source note: This is an independent editorial summary prepared by Learn Switchgear. It is not an official Hitachi Energy article and contains no sponsored content. Performance and lifecycle figures are attributed to the manufacturer. Read the original Hitachi Energy feature.