The world's first 550 kV perfluoroisobutyronitrile (C4F7N) eco-friendly gas-insulated transmission line has been successfully commissioned.

Recently, the world’s first 550 kV perfluoroisobutyronitrile (C4F7N)-based eco-friendly gas-insulated transmission line, developed by a Chinese manufacturer specializing in environmentally friendly gas-insulated power transmission equipment, was officially commissioned at the 500 kV Rongsheng Substation in Anqing, Anhui Province. This milestone marks another major breakthrough for China in the field of eco-friendly power equipment.

For decades, sulfur hexafluoride (SF₆) has been widely used in the power industry due to its excellent insulation and arc-quenching properties. However, SF₆ has a global warming potential (GWP) 24,300 times greater than that of carbon dioxide, posing significant environmental concerns. As a result, policies restricting or phasing out SF₆ emissions have been introduced both domestically and internationally. 

Against this backdrop, finding an environmentally sustainable alternative to SF₆ has become a critical task in building a green, low-carbon next-generation power system. Perfluoroisobutyronitrile (C4F7N) has emerged as the leading SF₆ replacement gas globally, demonstrating outstanding performance in terms of low global warming potential, low-temperature operability, high dielectric strength, chemical stability, and non-flammability.

In active response to China’s national “Dual Carbon” goals (carbon peak and carbon neutrality) and to accelerate the green transformation of power equipment, the Chinese manufacturer launched the scientific and technological project “Key Technologies and Application of Ultra-High-Voltage Eco-Friendly Gas-Insulated Transmission Lines.” The project successfully overcame core technical challenges related to insulation design and temperature rise in transmission line equipment using C4F7N-based eco-friendly gas, resulting in the successful development of the 550 kV C4F7N gas-insulated transmission line. 

Compared to conventional SF₆-based systems, this new solution reduces greenhouse gas impact by 97%. Moreover, it achieves “identical dimensions, identical structure, and identical parameters” compared to standard 550 kV SF₆ gas-insulated transmission lines and remains compatible with both pure SF₆ and SF₆/N₂ gas mixtures. This provides a practical green upgrade path for both retrofitting existing substations and constructing new ones, significantly advancing the eco-friendly transformation of China’s power transmission and transformation infrastructure.

The world-first commissioning of this 550 kV C4F7N eco-friendly gas-insulated transmission line holds profound significance. It offers the power industry a replicable and scalable green alternative, delivers strong technical support for building a new-type power system, and makes a meaningful contribution toward achieving China’s “Dual Carbon” targets.