Purpose
The detection of SF₆ decomposition products is an important factor in the state evaluation of SF6 insulated electrical equipment. Electrochemical technology has been widely used in the field detection of decomposition products. However, due to its cross interference and short life of the electrochemical sensor, the detection of SF₆ decomposition products has become a research hotspot. H₂S concentration in SF₆ gas insulation can be used to characterize the severe discharge of epoxy resin solid medium. Here, two important on-site detection technologies of H₂S in SF₆, semiconductor gas sensor and absorption spectroscopy gas sensor, were reviewed, and the future of on-line detection technology of H₂S in SF₆ is prospected.
Semiconductor gas sensor
Semiconductor gas sensor also includes metal oxide semiconductor gas sensor and organic semiconductor gas sensor. For the detection of H₂S, the metal oxides such as Fe₂O₃, WO₃, SnO₂ and TiO₂, and organic semiconductors mainly used polymers and carbon group materials were used. However, the semiconductor gas sensor is still at the laboratory stage. On the one hand, the semiconductor gas sensor's nature defects limit its commercial application; On the other hand, the existence of other sulfur-containing compounds in SF₆ decomposition product will affect the selectivity of the semiconductor gas sensor for H₂S, and further research in this area needs to be carried out.
Absorption spectroscopy gas sensor
 At present, the commonly used spectral absorption H₂S gas sensors mainly include ultraviolet absorption (UV) and infrared absorption (IR) mode. UV absorption spectroscopy and tunable Diode Laser Absorption Spectroscopy (TDLAS) methods cannot detect the concentration of H₂S in ppb-level SF6, and cannot meet the needs of hydrogen sulfide detection in SF6 gas-insulated equipment. Cavity ring-down spectroscopy (CRDS) and Photoacoustic spectroscopy have received more attention from researchers in the recent years, both of which can detect H₂S in SF₆ with a volume concentration as low as 100 ppb. However, spectroscopy still faces the problem of absorption line interference, especially for CO₂ and CO. The anti-interference characteristics of CRDS and Photoacoustic spectroscopy need to be further studied.
 

H2S,characteristic decomposition components of SF6,semiconductor gas sensor,absorption spectroscopy gas sensor