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Decomposition Characteristics of SF6 under Partial Discharge and Sensitivity of Single-wall Carbon Nanotube to SF6 Decomposition Products

Author: TanZhiHong
Tutor: SunCaiXin
School: Chongqing University
Course: Electrical Engineering
Keywords: Sulfur hexafluoride Partial discharge Decomposition components Carbon nanotubes Gas Sensing Properties
CLC: TM855
Type: PhD thesis
Year: 2011
Downloads: 94
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Abstract


h Gas Insulated Switchgear (Gas Insulated Switchgear, GIS), good stability, small footprint and high reliability in the electric power industry has been widely used. However, GIS equipment installation, maintenance and long-running and other reasons inevitably there will be a variety of internal insulation defects, these insulation defects in the long run, some will gradually develop and expand, that could eventually lead to the failure of the insulation of the GIS equipment. A large number of studies have shown that different levels of insulation defects Metropolitan excitation partial discharge Partial Discharge (PD), the extent and characteristics of the detected PD available to determine the condition of the insulation of the equipment. Traditional detection of partial discharge pulse current, ultrasonic method and ultra-high frequency method, they have their own characteristics, varying degrees of application. Co-existence difficult to get rid of the site strong electromagnetic interference, making them for online detection accuracy has been questioned. Non-electric detection from electromagnetic interference, in recent years, domestic and foreign research lead to the SF 6 gas decomposed due to PD very concerned about the preliminary results show that different insulation defects PD SF 6 decomposition characteristics are quite different, and SF 6 decomposition there is a certain relationship between the components and the insulation defects, can be used to diagnose GIS insulation condition, to improve the stability of the GIS equipment has a high theoretical value and practical significance. Therefore, the detection SF 6 of decomposition characteristics to diagnose the GIS internal insulation defects has become a hot issue for the present study. In this paper, the research group has been based on the study, carried out the PD SF 6 Decomposition and carbon nanotube sensor for on-line detection of trace components gas research, initially proposed for the SF 6 component analysis of the characteristics of gas, the gas sensing properties of carbon nanotubes decomposition component of the SF 6 , and theoretical calculations and simulations the SF 6 < / sub> decomposition of the adsorption process of the component. Specific work as follows: (1) to build four typical insulation defect model to the electric field simulation. Designed PD decomposition gas chamber, to establish a the decomposed SF 6 effective separation of the vapor component chromatographic quantitative detection system, and based on this platform, the type of a typical insulation defects generated under the PD SF 6 decomposition gas experiment, measurement decomposition components SOF is 2 , the SO 2 F 2 , CF < sub> 4 and CO 2 of the content. Studies have shown that four typical defect model in a predetermined position and a certain voltage can produce PD, where PD is the most stable high voltage conductor projections defects, and discharge energy, the PD SF 6 production gas and decomposition rate; freedom conductive particle defects single PD discharge high strength, the SOF 2 , the SO 2 F 2 two gas components with higher levels; insulator surface metal contamination defect because PD occurs involving and solid insulating materials react, so the CF 4 content increased significantly; the Insulator outside air gap defects PD higher strength, but gas production is relatively small. (2) different insulation defects PD the SF 6 decomposition characteristics and gas production in the law there are significant differences, initially proposed the SOF 2 / the SO 2 F 2 , CO 2 / CF 4 , (SOF 2 SO 2 F 2 ) / (CO 2 CF 4 ) ratio of three sets of gas content as a statistical features for four typical insulation defects the type of analysis and judgment pointed out the Available SOF 2 / the SO 2 F 2 to characterize the the the PD intensity discharge development trend, CF is 4 < component / sub> content to a certain extent, can explain the state of deterioration of the insulating material within the GIS. (3) using interdigital electrode substrate, prepared SWNT-OH and the intrinsic SWNT carbon nano trace gas sensors, it SOF 2 , the SO 2 F 2 , SO 2 , CF 4 four decomposition component of the gas-sensitive experiments, compared to both the gas sensing properties, with a focus on research and analysis SWNT-OH sensor decomposition component of the gas sensing properties, stability and recovery characteristics. The results showed that the highest rate of resistance change for four decomposition component SWNT-OH fastest the the SO 2 response speed, sensitivity with the SO 2 of gas concentration to meet certain linear relationship, and in the air can be self-recovery, the recovery time is short, you can meet the initial detection stability requirements. ④ Materials Studio (MS) the established the SF 6 decomposition component (SOF is 2 , the So 2 F 2 SO -2 , CF 4 ) and single-walled carbon nanotube micro-adsorption model, and theoretical simulation and calculations based on density functional theory (DFT) on the adsorption process, hydroxy-modified micro-sensing mechanism of the single-walled carbon nanotubes (hydroxylation single-wall carbon nanobutes, SWNT-OH). First, based on the results of the SWNT-OH and four molecules of the adsorption capacity of the judgment; Secondly, according to the degree of difficulty of the SWNT-OH with four molecules adsorption frontier molecular orbital theory analysis; again, calculated according to the bandgap results of the gas molecules adsorbed on the SWNT-OH its surface carrier ability to transfer, combined with the density of states calculated results of SO 2 SWNT-OH adsorption process of atomic orbitals Miscellaneous of the situation; Finally, the SWNT-OH calculation of the intrinsic SWNT contrast, results showed that the four molecules, SWNT-OH SO 2 adsorption, the adsorption capacity of the strongest and adsorption SO 2 after the energy gap decreases, resulting in its electron transfer ability; addition, the study found that the partial track of both atoms in the adsorption process, tends to hybrid formation of the electron transport channel. conducive to the electron transfer between the adsorption capacity of the SWNT-OH adsorption capacity higher than the intrinsic SWNT four molecules.

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CLC: > Industrial Technology > Electrotechnical > High Voltage Engineering > High - voltage insulation technology > Insulation test and inspection
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