Detection of Transient Decomposition Products of CF3SO2F and C4F7N via OES Under Spark and Glow Discharges

The optical emission spectra (OES) reflect the presence of excited states in the gaseous discharge, which are directly linked to the decomposition characteristics of insulating gases. In this study, a pin/rod–plate discharge reactor driven by either a high-voltage direct current (DC) generator or a pulsed generator was developed to establish an effective platform for generating decomposition products of ${\text{CF}}_3{\text{SO}}_2\mathrm{F}$ and ${\mathrm{C}}_4{\mathrm{F}}_7\mathrm{N}$. The experimental setup involved separate mixtures of ${\text{CF}}_3{\text{SO}}_2$F and ${\mathrm{C}}_4{\mathrm{F}}_7$N with different buffer gases (${\mathrm{N}}_2$, ${\text{CO}}_2$) under optimised operating conditions (maximum current) with varying mixture ratios. Through systematic investigation of emission spectrum characteristics under different gas mixing ratios, energy transitions of transient species induced by electrical excitation were captured using a high-resolution optical emission spectrometer. Under spark discharge conditions, transient decomposition products such as F-atoms, C-atoms and CN radicals were detected from ${\text{CF}}_3{\text{SO}}_2\mathrm{F}$ and ${\mathrm{C}}_4{\mathrm{F}}_7\mathrm{N}$ mixed with ${\mathrm{N}}_2$ or ${\text{CO}}_2$, indicating that discharges induced the cleavage of C–S, C–F and C–C bonds, and revealing the decomposition characteristics of the two eco-friendly insulating gases in different buffer atmospheres. This work advances the understanding of decomposition mechanisms, providing valuable insights for fault diagnosis in gas-insulated electrical equipment.