Perfluoroisobutyronitrile (C4F7N) has the potential to replace SF6 due to its excellent environmentally friendly dielectric properties, and has received extensive attention at home and abroad. C4F7N has a low liquefaction temperature, so it is necessary to mix it with low-boiling gas during application. Among them, the C4F7N/CO2 mixed gas has excellent performance, but the insulation capacity is closely related to the C4F7N content. Therefore, the preparation of high-precision C4F7N/CO2 mixed gas is conducive to scientific demonstration of C4F7N and minimizes the hidden dangers of industrial applications. Through the Fourier infrared detection platform, the infrared absorption information of C4F7N gas in the 500~4500cm-1 band was obtained, and the 1200~1300cm-1 band was determined as the key research object. A portable detection system for C4F7N/CO2 mixed gas is designed based on NDIR technology. As for the C4F7N gas sensor module, the low-power EMIRS50-AT06V standard blackbody light source with rugged MEMS design and the dual-channel detector with InfraTec LRM-202 narrow bandpass filter, combined with the gold-plated gas chamber structure of the reentrant light path, can effectively improve the detection accuracy of the system.Determine the inversion algorithm of the difference principle, and finally realize the fast detection of the C4F7N gas content. The experimental results show that the non-linear correlation between SB/SA (the ratio of the amplitude of the reference signal and the signal amplitude of the measurement channel) and the volume concentration fitting nonlinearity R2 is 0.99797. Within the range of the sensor, the maximum indication error is 1.05%, and the RSD of the sensor repeatability experiment is 0.47%, 0.36%, 0.31%, 0.34%, all of which do not exceed 0.5%, indicating that the sensor has good accuracy and consistency.The high integration and portability of the system can provide a novel method for the rapid online detection of the C4F7N/CO2 mixed gas mixture ratio of high-voltage electrical equipment.
H2S and moisture content are important indicators to evaluate the potential faults and insulation performance of H2S electrical appliances. Currently, there is no report on the simultaneous detection of H2S gas and moisture content. In order to realize the accurate detection of H2S gas and H2O at the same time, Lorentz simulation analysis was performed on the absorption spectra of H2S gas and H2O molecules. The absorption was strongest near 2684nm, and there was no cross interference of SF6 other decomposition products. H2S and moisture content at different concentrations were measured by TDLAS technology in a customized CW-DFB laser with a central wavelength of 2.68μm combined with a small-volume Herriott long-range cell with multiple reflections. In order to verify the detection ability of selected spectral lines to H2S gas and H2O molecules at low concentration, trace H2S and H2O vapor with SF6 as background were detected by direct absorption technology and wavelength modulation technology respectively. In the second harmonic absorption, the minimum detection lower limit of H2S and H2O is 9.01×10-6 and 4.54×10-6, respectively. The maximum harmonic signal amplitude has a good linear correlation with concentration, and the linear fitting degree R2 is 0.978 and 0.997, respectively. SF6 gas displacement experiments with different flow rates showed that the equilibrium time of H2S and moisture content at 708mL/min was 90s and 100s, respectively. The response time of H2S and H2O at the same concentration and injection velocity is 30s and 45s, respectively. Wavelength modulation technology can provide a reliable experimental basis for the simultaneous detection of trace H2S and H2O in high voltage combination electrical appliances.