Research on Laser Cavity Ring-down Spectroscopy Measurement for SF6 Decomposed Gases

The four species gases including H2S, CO, HF and SO2 in the decomposition gas of SF6 were monitored online, according to the power industry requirements. The calibration technology and the algorithm, the optical path of cavity and signal to noise ratio of detection circuit are the key steps in the development of decomposed gas monitoring device. This paper first introduces the calibration method and technology of multicomponent trace gas analysis instrument based on the photoacoustic spectroscopy. The existing problems in the calibration process of photo-acoustic spectroscopy are analyzed in combination with spectral analysis. In this paper, an on-line monitoring device for SF6 decomposition gas based on the laser absorption spectroscopy is developed. The calibration algorithm is proposed and verified by experiment. The experimental results indicates that this algorithm can solve the calibration problem in part, with high-purity sulfur hexafluoride as background gas. And the experimental results are consistent with the theory. Within the range of 0~200ppm, the stability is less than 2%. The concentration calibration method proposed in this paper can effectively monitor the concentration of H2S, CO, HF, SO2 typical characteristic gases, and provide theoretical and technical guidance for SF6 gas insulated high-voltage combined electrical apparatus.