Ultraviolet differential optical absorption spectrometry: quantitative analysis of the CS₂ produced by SF₆ decomposition

The occurrence of partial discharge or partial overthermal fault in sulfur hexafluoride (SF₆)-insulated electrical equipment frequently causes SF₆ and solid insulation materials to decompose into various products. One of the most characteristic products of this process is carbon disulfide (CS₂). The internal fault type and severity of the fault in the insulation equipment can be detected through the accurate quantitative detection of CS₂. A device for simultaneously determining and quantifying gaseous CS₂ via ultraviolet differential optical absorption spectrometry is developed in this study. A Sym14 wavelet transform and fast Fourier transform (FFT) are applied to process the spectral data of the feature regions, namely 190 nm to 210 nm. The concentration of CS₂ is determined, and the detection limit of the developed device is identified. A good linear relationship is observed between the characteristic peaks of FFT and the concentration of CS₂ after the operational parameters are optimized. Along the light path at 600 mm, the average detection limit for CS₂ is 8.65 ppb based on three times the standard deviation of the system noises. The proposed device, which exhibits high sensitivity and effective cost, addresses the urgent demand for the monitoring and diagnosis of SF₆-insulated electrical equipment via online detection of trace CS₂. (paper)