Xiangyang power grid applies hybrid gas technology, cutting SF₆ use by 70 percent

As the 57th World Earth Day approaches, State Grid Xiangyang Power Supply Company is taking concrete steps to fulfill its environmental responsibilities.

On April 17, operation and maintenance personnel from the Dongtai Substation team conducted inspections at the 220 kV Mizhuang Substation, focusing on key indicators such as gas pressure in the hybrid gas-insulated switchgear (HGIS) at the Mi07 and Mi08 bays, and overall equipment performance, to ensure safe and stable operation while promoting greener power practices.

The Mi07 and Mi08 bays are part of the first 220 kV hybrid gas HGIS system put into operation in Hubei Province. As a core component of the power grid, HGIS plays a critical role in electricity transmission and switching, while the insulating and arc-extinguishing gases used inside directly affect both operational safety and environmental impact.

Traditional HGIS equipment typically uses sulfur hexafluoride (SF₆), which ensures stable performance but is also a potent greenhouse gas regulated under the Kyoto Protocol. With a global warming potential 23,500 times that of carbon dioxide and an atmospheric lifetime of up to 3,200 years, any leakage can pose a significant environmental risk.

To address this challenge and support China's "dual carbon" goals, the company is leading in piloting hybrid gas HGIS technology. The system installed at Mizhuang Substation has operated safely for two years, using a gas mixture of 30 percent SF₆ and 70 percent nitrogen (N₂) to replace pure SF₆, reducing greenhouse gas emissions at the source.

"Over the past two years, we have recorded more than 1,000 sets of operational data and established a dedicated monitoring system to track equipment performance and ensure stable, fault-free operation," said Xiao Feng, head of the Dongtai Substation team. The technology reduces SF₆usage by 70 percent while maintaining insulation and arc-extinguishing performance, achieving a balance between grid reliability and environmental protection.

The adoption of hybrid gas technology provides a replicable pathway for greener power grid upgrades. By the end of 2025, all equipment at the 220 kV Yitianqiao transmission and transformation project had adopted this technology, fully replacing conventional SF₆ insulation. The station is expected to cut carbon emissions by about 5,000 kilograms annually, setting a new benchmark for green power grid development in Xiangyang.

Building on the Mizhuang Substation project, the company is expanding the use of hybrid gas technology to new facilities such as Yitianqiao Substation. At the same time, it is implementing a closed-loop management system for SF₆ in line with State Grid Hubei Electric Power requirements, strengthening greenhouse gas control across the province.

Through digital tracking, each SF₆ gas cylinder is assigned a QR code to ensure full traceability throughout procurement, storage, use and recycling. During maintenance, specialized equipment is used to achieve a gas recovery rate of over 98 percent, preventing any uncontrolled release. Recovered gas is sent to processing centers in Wuhan and other cities, where it is purified to 99.99 percent for reuse.

Data show that in 2023, about 10.9 tons of SF₆ were recovered across Hubei Province, equivalent to reducing carbon dioxide emissions by approximately 274,700 tons. These results reflect both meticulous on-site management and continued technological innovation.

Protecting the environment remains an ongoing task, and the transition toward greener power systems continues. Hybrid gas technology is currently a transitional solution, while the long-term goal is the complete replacement of SF₆ to eliminate its environmental impact at the source.

"We will continue to explore the application of environmentally friendly insulating gases such as fluoroketones and fluoronitriles, as well as technologies like vacuum and solid insulation, to further advance low-carbon development of the power grid," said Ren Xiang, head of the technical office of the substation operation and maintenance branch.

Going forward, State Grid Xiangyang Power Supply Company will continue to support the green transformation of the power grid through refined operations and maintenance, implementing China's dual carbon strategy across all aspects of its work. By ensuring both grid safety and environmental protection, the company aims to contribute to sustainable development and global climate efforts, in line with the World Earth Day theme of "Cherish the Earth, harmonious coexistence between humans and nature."