Rotating Differential Dual-Channel NDIR Technique: For the Environmentally Friendly Insulating Gas C4F7N Detection

Perfluoroisobutyronitrile (C4F7N) has the characteristics of stable physical and chemical properties, high dielectric strength, and low global warming potential. Gas-insulated equipment using C4F7N as the medium has been gradually promoted and used. To ensure the safe operation of equipment and monitor possible gas leakage failures in time, it is important to study the rapid detection method of trace C4F7N. In this article, based on the infrared spectrum analysis platform, the trace C4F7N detection band is selected, and the center wavelengths of the dual-channel filters are determined to be 7.9 and
$3.3~\mu \text{m}$
. A differential dual-channel C4F7N detection platform based on the nondispersion infrared (NDIR) with a rotary runner is built. The system demonstrates an ability to identify trace C4F7N within the range of 1–49.84 ppm. The linear fitting coefficient
${R}^{{2}}$
of C4F7N gas concentration and signal measurement value is 0.9915, and the maximum absolute error is 0.1110. The theoretical detection limit is
$0.32~\mu \text{L}$
/L, and its repeatability is 3.4%. The leakage of C4F7N gas is detected in an open environment, and the system can achieve rapid detection within 6 min at a distance within 2 m. The research results provide a feasible solution for the safe operation of C4F7N gas-insulated equipment.