Research on the detection of SF6 decomposition products based on non-resonant photoacoustic spectroscopy

Abstract

Under partial discharge (PD), a gas-insulated switchgear (GIS) will produce SF₆ decomposition products. If the concentrations of these products are higher than the standard values, this indicates that the GIS equipment is faulty. Photoacoustic spectroscopy techniques show a high sensitivity and good stability and, furthermore, they can enable on-line monitoring, making them widely used in the detection of SF₆ decomposition products in GIS equipment. The basic principles of photoacoustic spectroscopy were introduced and a set of devices for the online detection of SF₆ decomposition based on non-resonant photoacoustics was designed and realized. According to the infrared spectral characteristics of the target gases, the appropriate narrowband filters and infrared radiation light source were selected. This detection system is able to continuously detect CO, SO₂ and CF₄. Calibration experiments with different concentrations of CO, SO₂ and CF₄ were carried out and the results show that the photoacoustic signal and concentration have a perfect linear relationship and the detection limits for CO, SO₂ and CF₄ are 5.9116, 8.2824 and 5.5226 ppm. Relative errors of the single measurements of CO, SO₂ and CF₄ are all less than 10% and the system exhibits excellent stability in a continuous 12 hour measurement.