Decomposition Characteristics of C₄F₇N Environmental Mixed Gas at High Current Breaking

In recent years, perfluoro-isobutyronitrile <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{C}_{\mathbf{4}} \mathbf{F}_{7} \mathbf{N}$</tex>, proposed by 3 M company of the United States, has gained more and more attention in the industry as an alternative gas to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{S F}_{\mathbf{6}}$</tex> due to its excellent insulation and environmental performance. However, there is still a lack of research on the decomposition characteristics of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{4} ~\mathrm{F}_{7} ~\mathrm{N}$</tex> mixed gas under high current conditions. This paper investigates the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{4} ~\mathrm{F}_{7} ~\mathrm{N}-\text{CO}_{2}-\mathrm{O}_{2}$</tex> eco-friendly mixed gas as an arc-extinguishing medium, conducting short-circuit current interruption experiments in actual high-voltage self-powered circuit breakers. The study found that under the arc discharge with a current of 25 kA, the decomposition products of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{4} ~\mathrm{F}_{7} ~\mathrm{N}$</tex> mixed gas include <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{CO}, \mathrm{C}_{3} \text{HF}_{7}, \text{CF}_{4}, \mathrm{C}_{3} ~\mathrm{F}_{8}, \mathrm{C}_{3} ~\mathrm{F}_{6}$</tex> and other fluorocarbon compounds, as well as cyanide compounds such as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{2} ~\mathrm{F}_{3} ~\mathrm{N}, \mathrm{C}_{3} ~\mathrm{F}_{5} ~\mathrm{N}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{3} ~\mathrm{F}_{3} ~\mathrm{N}$</tex>. Among these, CO and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{CF}_{4}$</tex> are the most abundant, serving as the main decomposition products of the mixed gas discharge. The results provide important references for the engineering application of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{C}_{4} ~\mathrm{F}_{7} ~\mathrm{N}$</tex> mixed gas.