Study On Carbon Nanotubes Sensor And Detect SF₆ Decomposition Components Under Partial Discharge

Partial Discharge (PD) occurred within Gas Insulated Switchgear (GIS) is the insulation fault of the early main forms, which may cause SF₆ to decompose. According to detect and analyze SF₆ discharge decomposition components, PD development situation in GIS can be monitored and further diagnose the reason that will trigger PD. At present, although gas chromatography, infrared spectroscopy and other methods have been applied to the detection of SF₆ discharge decomposition components, and some good results were achieved, but still there are many weaknesses. In this paper, multi-wall carbon nanotubes (MWNTs) were appied to detect SF₆ discharge decomposition components for this reason. This is the first time in China.Carbon nanotube (CNT) is a new type of one-dimensional nanostructured material that was discovered in 1991, which has unique geometry structure and fantastic physical, chemical properties leading to many potential applications. The CNTs as gas sensing materials have broad application prospects. In this paper, SF₆ decomposition products was detected by MWNTs gas sensor based on the developed SF₆ decompose apparatus under PD of 24 hours and the designed needle-plate insulation defects, also the standard gas of SOF₂ and SO2F₂ with the concentration of 20μL/L were detectd. The main achievements are as follows:CNTs were treated by mixed acid (concentrated nitric acid and sulfuric acid), and the functionalization modification of CNTs were realized, both treated CNTs and untreated ones were analyzed by transmission electron microscope (TEM) and infrared spectrum; A kind of MWNTs gas sensor based on printed circuit board was developed; At the same time, gas components detector was developed consist of cylinder, vacuum air pump, vacuometer, pressure gauge, AC magnetic contactor, accommodometer, electric stove, thermal resistive sensors and impedance analyzer, etc.The SF₆ decompose test was conducted based on SF₆ decomposition test device under PD and the designed needle-plate defect, and SF₆ decomposition products were collected after 24 hours. The gas sensing properties of untreated and modified MWNTs were determined against SF₆ decomposition products, SOF₂ (20μL/L) and SO2F₂ (20μL/L), respectively. The adsorption characteristics were compared of these two kinds of MWNTs at she same. The experiments results show that MWNTs modified by mixed acid can increase the sensitivity to SF₆ discharge decomposition components. The relationship between gas sensitivity and temperature of MWNTs gas sensor was studied by experiment, and the sensor has the best adsorption capacity for SF₆ decomposition components at temperature 85℃.The effect of metal ion doping on gas sensitivity of MWNTs was discussed, and gas sensing properties for SF₆ gas discharge decomposition products was tested using the MWNTs sensor with nickelous chloride doped. It was found that doped nickelous chloride can further improve the sensitivity of MWNTs.