The application of C4F7N and its gas mixtures as mainstream eco-friendly insulating media in electrical equipment is rapidly developing in recent years. It is critically important to research the arc-extinguishing performance and high-capacity interruption technologies. In this paper

the arc and its decomposition characteristics of C4F7N/CO2/O2 gas mixture were investigated by the simulation tests

with SF6 gas as a reference. Tests were conducted on a 126 kV circuit breaker to analyze the gas decomposition during arc discharge and the influences of test currents

the concentrations of C4F7N

and O2 on the arc behavior. Key parameters

including circuit currents

arc voltage waveforms

and travel curves

were measured. Results indicate that the arc-extinguishing voltage peak increases with the C4F7N concentration

while the O2 content exhibits minimal influence on the arc voltage and conductance. Significant amounts of CO and CF4 were generated during interruption

and higher O2 concentrations effectively suppress the formation of decomposed gases. Based on the existing structure of SF6 high-voltage circuit breakers

an optimal molar volume ratio of 6% C4F7N and 10% O2 is proposed. The research results on arc characteristics provide a useful reference for the design and development of eco-friendly gas circuit breakers

demonstrating significant practical relevance for advancing sustainable power grid technologies.