Study On SF₆ Decomposition Characteristic Gas Detection Method Based On Laser Raman Spectroscopy

SF₆ decomposition product analysis is one of the most convenient and efficient methods to diagnose potential faults of SF₆ insulation power equipment.It is of great practical significance to study the on-line monitoring method of SF₆ insulation power equipment based on SF₆ decomposition characteristic gas analysis,which can improve the maintenance level of medium and high voltage power equipment and ensure the reliable operation of power network.Compared with traditional SF₆ decomposition characteristic gas monitoring techniques,including chromatography,chromatography-mass spectrometry,infrared spectroscopy,photoacoustic spectroscopy and electrochemical sensor,etc.Laser Raman spectroscopy is a molecular identification method based on scattering effect.Because it can detect gas without destroying and the mixed gas does not need be separated,it is very suitable for on-line monitoring of SF₆ decomposition products in power equipment.The new method of laser Raman spectroscopy of SF₆ decomposing characteristic gases plays an important role in the on-line monitoring and fault warning,which can improve the monitoring technology of medium and high voltage power equipment.In this context,the method of SF₆ decomposition characteristic gas detection based on laser Raman spectroscopy is studied.This paper mainly includes the following points:?1?According to the development of SF₆ decomposition characteristic gas in power equipment and Raman spectrum,based on the theory of Raman scattering,the quantum chemical explanation of Raman scattering was analyzed.The basic principle of the hybrid functional B3LYP for the calculation of molecular Raman spectra in density functional theory?DFT?was studied.Based on this theory,the Raman characteristics of SF₆ and its decomposition gas,SO₂,H₂S,CO,CO₂ and CF₄,were calculated.Then Raman scattering of six gases and the corresponding Raman frequency,Raman activity and relative intensity were obtained.?2?Analysis of the basic characteristics of the DIS-Raman,and the principle which is suitable for low concentration gas enhanced detection of Raman spectrum.The construction scheme of DIS-Raman and surface enhanced Raman spectrum of SF₆ gas decomposition characteristics as the leading was determined.A special platform of SF₆decomposition characteristics gas in power equipment was built based on the method of DIS-Raman and surface enhanced Raman spectroscopy.?3?The single and mixed components of SF₆ and its decomposing characteristic gas,SO₂,H₂S,CO,CO₂ and CF₄,have been measured by the spectrometric method.The original spectrum obtained from the test is processed in order to improve the signal-to-noise ratio of the experimental results,by using polynomial fitting baseline correction,Savitzky-Golay smoothing,wavelet threshold de-noising and other signal preprocessing techniques.Finally,based on matlab R2015a,the preprocessing software of Raman spectrum of SF₆ decomposition characteristic gas was developed.?4?Based on the simulation analysis and experimental results,the Raman characteristic spectra of SF₆ and its decomposition gas,SO₂,H₂S,CO,CO₂ and CF₄,have been determined.The order is:775.18cm^-1,1150.83cm^-1,2607.40cm^-1,2140.62cm^-1,1388.29cm^-1,912.44cm^-1.The vibration ascription of these characteristic peaks has been simulated and analyzed,which meets the requirements of qualitatively identified SF₆and its decomposition gas,SO₂,H₂S,CO,CO₂ and CF₄,by Raman spectra.The results show that it is feasible to apply Raman spectroscopy to detect SF₆ decomposition characteristic gases in power equipment.Finally,a Raman spectral quantitative model for the decomposition of characteristic gas CF₄ in SF₆ insulation power equipment was established,based on the PLS theory.This paper lays a foundation for monitoring the operation and maintenance,and early warning of faults of SF₆ insulated power equipment,based on laser Raman spectroscopy of SF₆ decomposition characteristic gases.