Development of a suitcase time-of-flight mass spectrometer for in situ fault diagnosis of SF sub(6)-insulated switchgear by detection of decomposition products

Rationale Sulfur hexafluoride (SF sub(6)) gas-insulated switchgear (GIS) is an essential piece of electrical equipment in a substation, and the concentration of the SF sub(6) decomposition products are directly relevant to the security and reliability of the substation. The detection of SF sub(6) decomposition products can be used to diagnosis the condition of the GIS. Methods The decomposition products of SO sub(2), SO sub(2)F sub(2), and SOF sub(2) were selected as indicators for the diagnosis. A suitcase time-of-flight mass spectrometer (TOFMS) was designed to perform online GIS failure analysis. An RF VUV lamp was used as the photoelectron ion source; the sampling inlet, ion einzel lens, and vacuum system were well designed to improve the performance. Results The limit of detection (LOD) of SO sub(2) and SO sub(2)F sub(2) within 200 s was 1 ppm, and the sensitivity was estimated to be at least 10-fold more sensitive than the previous design. The high linearity of SO sub(2), SO sub(2)F sub(2) in the range of 5-100 ppm has excellent linear correlation coefficient R super(2) at 0.9951 and 0.9889, respectively. Conclusions The suitcase TOFMS using orthogonal acceleration and reflecting mass analyzer was developed. It has the size of 663 496 338 mm and a weight of 34 kg including the battery and consumes only 70 W. The suitcase TOFMS was applied to analyze real decomposition products of SF sub(6) inside a GIS and succeeded in finding out the hidden dangers. The suitcase TOFMS has wide application prospects for establishing an early-warning for the failure of the GIS.