Sensitivity Characteristic Analysis Of Adsorbent-doped Carbon Nanotube Sensors For The Detection Of SF6Decomposition Products Under PD Conditions

Sulfur hexafluoride (SF6) is an extremely inert gas and chemically stable. It is noteasy to be broken down. In recent years, SF6, which almost becomes the only insulatingand arc-extinguishing medium, is widely used in gas insulated switchgear (GIS) in thepower system. During long time operation, the internal insulation defects in GIS lead topartial discharge (PD). A part of SF6is decomposed into different gas components underPD. SF6may undergo a decomposition reaction when it reacts with water and oxygen toproduce a series of compounds, such as SOF2、SO2F2、SO2and H2S. The detection andanalysis of these gas decomposition components is becoming a hot topic in thedevelopment conditions of PD and condition assessment of GIS. Due to high sensitivity,low performance temperature and small size, gas sensor based on carbon nanotubes isfit for online monitoring of SF6decomposition component.In this work, K molecular sieve-doped sensors and4A molecular sieve-dopedsensors were proposed based on the intrinsic MWNTs gas sensor. These differentsensors were used to detect some characteristic SF6decomposition products in GIS andstudy the gas responses of the different sensors to SO2、SOF2、SO2F2and H2S. Then, itwas focused on the analysis the effects of different ratios and the two kinds of molecularsieves to the various gases.The results show that compared with intrinsic MWNTs sensors, the gas sensorfeaturing K molecular sieve-doped MWNTs has improved responsiveness to SOF2andSO2F2. Compared with intrinsic MWNTs and K molecular sieve-doped MWNTs sensors,the gas sensor featuring4A molecular sieve-doped MWNTs has significantly highersensitivity and responsiveness to SO2and H2S. Moreover, the resistance-change rate andgas concentration satisfy a linear relationship.The various sensors show very different response characteristics to the fourdecomposition components. With the mass ratios of5:1,10:1, and20:1, theresistance-change values of the adsorbent-doped MWNT sensors to SOF2all increasedto about13%, which is approximately ten times the resistance-change rate of theintrinsic sensor. With the mass ratios of10:1, the resistance-change values of theadsorbent-doped MWNT sensors to SO2F2increased to about17.3%, which isapproximately nine times the resistance-change rate of the intrinsic sensor. With themass ratios of10:1, the resistance-change values of the adsorbent-doped MWNT sensors to SO2increased to about33.7%, which is approximately thirty-five times theresistance-change rate of the intrinsic sensor. And with the mass ratios of5:1,10:1, and20:1, the resistance-change values of the adsorbent-doped MWNT sensors to SOF2allincreased to about50%, which is approximately four times the resistance-change rate ofthe intrinsic sensor. Thus, sensors with different doped ratios are selected to determinethe selectivity of the four gases according to this feature.It changes the selectivity to different gases that the adsorbent is doped into theMWNTs. To SOF2and SO2F2, K molecular sieve-doped sensors with the mass ratios of20:1have good selectivity. And to SO2and H2S,4A molecular sieve-doped sensors withthe mass ratios of5:1have very good selectivity.