Analysis of SF₆ decomposed products by fibre-enhanced Raman spectroscopy for gas-insulated switchgear diagnosis

Sulphur hexafluoride (SF6) decomposed products analysis is highly critical in the early-stage fault diagnosis of gas-insulated switchgear (GIS). Spectrum technology outperforms traditional methods on non-invasiveness, no sample preparation, and no consumption. Here, the authors present an improved fibre-enhanced Raman spectroscopy (FERS) as a comprehensive analytical tool to detect a suite of SF6 decomposed products (SO2F2, SOF2, SO2, H2S, CF4, OCS, CO2, and CO). The FERS approach is combined with two iris diaphragms for spatial filtering and a rear-end reflector for additional Raman signal enhancement. Limits of detection down to 1x10(-6)-8 x 10(-6) are achieved for different SF6 decompositions, and quantification of an undefined multigas, sampled from an 800 kV GIS in service, is realised utilising SF6 as the internal standard gas and with a maximum error of 5.5 %. The GIS is diagnosed according to the results and confirmed by an on-site check. The authors foresee that this technique will provide a route for trace gas analysis in the power industry.