China has successfully developed its first domestically produced 145kV Gas-Insulated Switchgear (GIS) using a perfluoroisobutyronitrile (C4-FN) gas mixture, marking another milestone in the transition toward environmentally friendly high-voltage equipment.
The project was jointly completed by Pinggao Electric, China Electric Power Research Institute, Anhui Electric Power Research Institute, Xi’an Jiaotong University and several research organizations. The new GIS has successfully passed technical acceptance, demonstrating China’s capability to independently develop next-generation eco-friendly GIS technology.
For decades, SF6 has been the preferred insulating and arc-quenching gas for GIS because of its outstanding dielectric strength.
However, SF6 also has one of the highest greenhouse effects among industrial gases, with a Global Warming Potential (GWP) approximately 24,300 times that of CO₂.
As utilities worldwide work toward carbon neutrality, alternative insulating gases have become a major research focus.
Among the available candidates, C4-FN (Perfluoroisobutyronitrile) mixed with CO₂ and O₂ has become one of the most promising alternatives because it provides:
- Excellent insulation performance
- Much lower environmental impact
- Compatibility with existing GIS structures
- Strong engineering feasibility
Industry Insight: Why Gas Analysis Matters for C4-FN GIS
Compared with conventional SF₆ equipment, C4-FN-based gas mixtures require more precise monitoring of gas composition and moisture levels. Accurate gas analysis is essential for verifying insulation performance, supporting condition-based maintenance, and ensuring long-term operational reliability.
To address these evolving requirements, KSTONE offers gas analysis solutions capable of measuring SF₆ concentration, mixed gas composition, dew point, and other key parameters, helping utilities manage both conventional SF₆ assets and the next generation of eco-friendly gas-insulated equipment.
The development team focused on three key technologies.
Researchers established a full-scale testing platform to study insulation behavior of C4-FN/CO₂/O₂ mixtures under different gas ratios and pressures, providing engineering criteria for practical GIS design.
The team built comprehensive plasma simulation models and arc measurement systems to understand arc extinction characteristics, enabling reliable interruption of 40kA short-circuit current.
Based on mature SF6 circuit breaker technology, engineers redesigned the interruption chamber and hot-gas flow management system specifically for the new gas mixture, successfully overcoming thermal and dielectric breakdown challenges.
The newly developed GIS offers several important benefits:
- 97.5% lower greenhouse impact compared with conventional SF6 GIS.
- Maintains performance equivalent to traditional 145kV GIS.
- Rated at 145kV, 3150A and 40kA interruption capacity.
- 100% domestically developed core technology and components.
- Already selected for multiple transmission projects in China.
The successful development of China’s first 145 kV C4-FN gas-insulated switchgear demonstrates that environmentally friendly insulating gases are moving from laboratory research to practical power grid applications. As more utilities begin adopting alternative gas technologies, maintenance practices and gas handling equipment will also need to evolve.
Unlike conventional SF₆ equipment, eco-friendly gas mixtures require more advanced testing and handling solutions to ensure gas composition, moisture content, and insulation performance remain within specified limits throughout the equipment lifecycle.
As a manufacturer specializing in SF₆ gas leak detection and gas handling equipment for the high-voltage power industry, KSTONE has been supporting GIS installation, commissioning, and maintenance for years.
In response to the global transition toward environmentally friendly insulating gases, KSTONE has also developed a complete range of solutions for C4-FN gas mixtures, helping utilities and service providers adapt to next-generation GIS technologies.
Our solutions include:
- Leak detectors for both SF₆ and C4-FN insulating gases.
- Gas handling and recovery equipment designed for the safe evacuation, filling, recycling, and purification of C4-FN gas mixtures.
- Gas analysis solutions for measuring gas composition, dew point, and other key parameters to ensure reliable insulation performance.
- Vacuum evacuation and gas filling equipment for GIS installation, commissioning, and maintenance.
As eco-friendly insulating gases become increasingly adopted across the power industry, KSTONE remains committed to providing reliable gas handling and leak detection solutions that support the safe, efficient, and sustainable operation of both conventional SF₆ equipment and next-generation C4-FN GIS.
With continuous investment in research and development, KSTONE is expanding its product portfolio from conventional SF₆ applications to comprehensive solutions for C4-FN gas mixtures, supporting the industry’s transition toward greener and more sustainable high-voltage technologies.