Partial discharge early-warning through ultraviolet spectroscopic detection of SO₂

Abstract

Surveillance of SF6 decomposition products is significant for detection of partial discharge (PD) in gas insulation switchgear (GIS). As a basis in on-site detection and diagnosis, PD early-warning aims to quickly find the abnormalities using a simple and cheap device. In this paper, SO2 is chosen as a feature product and detected through ultraviolet spectroscopy. The derivative method is employed for baseline correction and spectral enhancement. The standard gases of the main decomposition products are qualitatively and quantitatively detected. Then decomposition experiments with different defects are designed to further verify the feasibility. As a stable decomposition product under PD, SO2 is proved to be applicable for PD early-warning in the field. By selecting the appropriate wavelength range, namely 290–310 nm, ultraviolet derivative spectroscopy is sensitive enough to the trace SO2 in the decomposed gas and the interference of other products can be avoided. Fast Fourier transform could be used for feature extraction in qualitative detection. Concentrations of SO2 and other by-products increase with increasing discharge time and could be affected by the discharge energy and PD type. Ultraviolet detection based on SO2 is effective for PD early-warning but the threshold should still be carefully selected in practice.

Optical properties and decomposition mechanisms of SF6 at different partial discharge determined by infrared spectroscopy

“…These highly reactive chemical species further react with other substances present in the gas chamber, such as carbon atoms (from the stainless steel electrodes and/or polymer materials), trace O atoms or O 2 molecules, forming various chemically stable products. [3][4][5] For example, the SOF 2 and SO 2 F 2 molecules can be formed when the SF 2 molecules continue to react with O atoms or O 2 molecules. It has been suggested in previous research work that CF 4 , SOF 2 , and SO 2 F 2 are the main decomposition products in the case of metal protrusion defects or creeping discharge faults, and the concentration ratios between them may provide crucial information on detailed fault type.…”

“…The optimal number of component in PLS was determined by cross-validation. 3 The best-calibration procedure was chosen by optimizing simultaneously the comparison between the experimental and calculated spectra. The root mean square error (RMSE) is an error measure for how well the model and calibration procedure performs.…”

“…Despite its chemical inertness at room temperature, SF 6 can decompose into lower sulfur fluorides under discharge induced by insulation defects in GIS. 2 Further reactions of these compounds with electrode materials and gas impurities in GIS generate products of significantly higher chemical reactivity and lower dielectric strength, such as CF 4 , SO 2 F 2 , SOF 2 , and SO 2, and increase the risks of electrical breakdown [3][4][5] Thus, it is of great importance to detect the decomposition products of SF 6 and thoroughly investigate the underlying mechanisms from both scientific and practical points of views.…”

Effects of SF6 decomposition components and concentrations on the discharge faults and insulation defects in GIS equipment

“…On the other hand, owing to the subtle insulation defects in the manufacturing process, discharge faults will be caused during the operation of the GIS equipment. As a result, SF 6 will be decomposed into lower sulfur fluorides under discharge induced by insulation defects 1 , 2 . These products will threaten the safety of the entire power grid system.…”

Ultraviolet differential spectroscopy quantitative analysis of SF 6 decomposition component SO 2

“…This spectroscopic technique has good prospects for application owing to low cost of its detection system and small gas consumption. As one of the characteristic components in the decomposed component analysis, SO 2 has a great absorption cross section in the UV region of 190-230 nm and 290-310 nm [8], and SF 6 does not have narrow band absorption in this spectral band, which provides a theoretical basis for the use of UV absorption spectroscopy in quantitative detection of SO 2 . However, because the original absorption spectra also contain absorption information that does not reflect the tested gas, such as Rayleigh and Mie scattering [9,10], the detection precision and anti-interference ability of the traditional UV absorption spectroscopy method still needs to be improved.…”