共查询到20条相似文献,搜索用时 15 毫秒
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实际运行中的局放特高频传感器受诸如振动、温度、湿度、设备内外部的冲击信号等因素影响,很容易损坏,如何科学有效的校验运行中的传感器、检测系统的灵敏度,对于保证设备安全可靠运行有着至关重要的作用。目前常规方法均不适合现场校验,对此,采用基于等效注入场强的方式实现传感器的现场校验,并对某500kV气体绝缘金属封闭开关设备(gas insulated metal enelose switchgear,GIS)内置特高频传感器进行了实验室部分的测试。测试结果表明,该传感器能检测到1 pC放电,等效注入场强的方式用于现场校验是可行的,且注入信号的频谱与局放频谱相似。 相似文献
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Ding W. Hayashi R. Suehiro J. Zhou G. Imasaka K. Hara M. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2006,13(2):353-361
The authors proposed a new type of gas sensor for high sensitive detection of decomposition products generated by partial discharge (PD) in SF/sub 6/ gas. The sensor employed carbon nanotubes (CNTs) as gas sensing transducer and was fabricated by electrokinetic manipulation of CNTs using dielectrophoresis. Due to complicated gas decomposition process of SF/sub 6/ gas, calibration of the CNT gas sensor is an essential and challenging subject in order to realize reliable and stable detection of PD under practical conditions. In this paper, two methods for the CNT gas sensor calibration were proposed and tested. The first method was based on initial conductance dependence of the CNT gas sensor response. The CNT gas sensor response to PD increased almost linearly with the amount of CNT trapped onto the sensor electrode, which could be quantified by the initial conductance of the sensor. However, the calibration accuracy of this method was about 50 % and was not high enough for practical use. The second method employed NO/sub 2/ (nitrogen dioxide) as calibration gas because of the similarity in the CNT sensor response to PD decomposition products and NO2. It was found that the accuracy of the NO/sub 2/ calibration was about 10 % and far better than the first method. Finally, effectiveness of the NO/sub 2/ calibration was demonstrated by a PD monitoring test in which two CNT sensors were simultaneously exposed to SF/sub 6/ decomposition products with identical concentration. 相似文献
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A phenomenological approach to the operation of metal oxide gas sensors, the Integrated Reaction Conduction (IRC) model, is proposed which integrates the gas-surface reactions with the electrical conduction process in a weakly sintered, porous metal oxide. An effective medium approximation is employed to relate the mesoscopic microstructure and the carrier depletion at the granular surface to the macroscopic electrical conduction. For a given ambient gas concentration and temperature, the electron concentration in the depletion layer is calculated from the gas-surface reaction kinetics. The adsorption and oxidation reaction energies of the gas sensing reactions are extracted for a TiO2-x CO sensor by comparing experimental data with three-dimensional plots of IRC model resistance as a function of the ambient [CO(g)] and temperature. The IRC model predicts novel properties of the gas sensor, including the sensitivity and the response range, which depend on the doping of the sensor material, the temperature, the grain size, and the geometry of the necks between grains. 相似文献
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为减少气体绝缘金属封闭式开关设备(GIS)产品运行期间的成本,必须改变维护方式,即从设备的定期维护改变到状态维护.文章介绍了GIS气体监视(如温度,压力,密度及含水量)、局部放电监测、断路器机械及电气性能监测等状态检测项目.这些监测的共用技术都是以传感器信息为基础的技术,应充分重视传感器技术. 相似文献
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非本征法布里-帕罗干涉(EFPI)光纤超声传感器可用于气体绝缘全封闭组合电器(GIS)内部的局部放电超声信号检测及模式识别研究,相较于传统的压电式传感器,具有灵敏度高、抗干扰能力强等优点。基于此,文中在充有0.4 MPa SF6气体的GIS腔体内设置尖端、金属颗粒、悬浮和沿面4种典型的局部放电模型,创新性地利用EFPI传感器对放电超声信号进行检测,提取单次超声脉冲信号波形特征形成特征参数数据库,分别应用概率神经网络(PNN)算法和支持向量机(SVM)算法进行模式识别并比较分析。EFPI传感器检测到的超声信号特征突出,在提取特征参数的基础上,2种模式识别算法均能达到85%以上的平均识别率,且SVM的识别效果要优于PNN。 相似文献
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如何校核已投运的传感器性能是保障气体绝缘金属封闭开关设备(gas-insulated metal-enclosed switchgear, GIS)局部放电监测可靠性的重要课题。基于网络分析仪,采用扫频方法测试安装在实体 GIS 上的传感器的响应特性,并研究其与特高频传感器平均有效高度的关系。通过比较分析发现,实体 GIS 上传感器的等效频率响应特性与其吉赫兹横电磁波(gigahertz transverse electromagnetic,GTEM)小室内的等效高度曲线具有相似的频谱特征,实体 GIS上传感器的平均等效响应幅值与 GTEM小室内的平均有效高度具有相同的变化规律;结论认为,通过利用网络分析仪进行频响特性测试,可以有效反映特定型号 GIS 结构下的特高频传感器性能。基于该结果,提出了基于网络分析仪的 GIS局部放电监测特高频传感器现场校核方法。 相似文献
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Microhotplates are micromachined platforms with integrated heaters and contact electrodes that can be used as miniature substrates for metal oxide film growth. Fabricated as arrays, they enable efficient combinatorial studies to be performed on a single chip. A variety of growth methods are compatible with their use, including evaporation, sputtering, chemical vapor deposition, and deposition from pastes or sol gels using screen printing, drop deposition, or spin-coating. The microheater on each element may be used to control the temperature during deposition or for a post-annealing step such as sintering, while the film contact electrodes serve as a built-in monitor of the fabrication process. In chemical vapor deposition using arrays, the elements with heaters set above the lowest nucleation temperature for a given precursor are the only ones that will have film deposited on them, resulting in a kind of self-lithography. This review gives examples of different methods of film growth that have been employed on microhotplates with applications for chemical sensing, with an emphasis on the chemical vapor deposition method. 相似文献
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V. A. Dvoinishnikov D. A. Khokhlov V. P. Knyaz’kov A. Yu. Ershov 《Thermal Engineering》2017,64(5):364-371
How the points at which the flue gas was injected into the swirl burner and the design of the burner outlet influence the formation and development of the flame in the submerged space, as well as the formation of nitrogen oxides in the combustion products, have been studied. The object under numerical investigation is the flame of the GMVI combined (oil/gas) burner swirl burner fitted with a convergent, biconical, cylindrical, or divergent throat at the burner outlet with individual supply of the air and injection of the gaseous fuel through tubing. The burners of two designs were investigated; they differ by the absence or presence of an inlet for individual injection of the flue gas. A technique for numerical simulation of the flame based on the CFD methods widely used in research of this kind underlies the study. Based on the summarized results of the numerical simulation of the processes that occur in jet flows, the specific features of the aerodynamic pattern of the flame have been established. It is shown that the flame can be conventionally divided into several sections over its length in all investigations. The lengths of each of the sections, as well as the form of the fields of axial velocity, temperatures, concentrations of the fuel, oxygen, and carbon and nitrogen oxides, are different and determined by the design features of the burner, the flow rates of the agent, and the compositions of the latter in the burner ducts as well as the configuration of the burner throat and the temperature of the environment. To what degree the burner throat configuration and the techniques for injection of the flue gas at different ambient temperatures influence the formation of nitrogen oxides has been established. It is shown that the supply of the recirculation of flue gas into the fuel injection zone enables a considerable reduction in the formation of nitrogen oxides in the flame combustion products. It has been established that the locations of the zones of intensive fuel burnout and generation of nitrogen oxides do not coincide over the flame length, and the ambient temperature has a significant impact on the combustion stability at low values and on the concentration of nitrogen oxides in the combustion products at high values. 相似文献
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Determining the composition of combustion products is important in terms of both control of emissions into the atmosphere from thermal power plants and optimization of fuel combustion processes in electric power plants. For this purpose, the concentration of oxygen, carbon monoxide, nitrogen, and sulfur oxides in flue gases is monitored; in case of solid fuel combustion, fly ash concentration is monitored as well. According to the new nature conservation law in Russia, all large TPPs shall be equipped with continuous emission monitoring and measurement systems (CEMMS) into the atmosphere. In order to ensure the continuous monitoring of pollutant emissions, direct round-the-clock measurements are conducted with the use of either domestically produced or imported gas analyzers and analysis systems, the operation of which is based on various physicochemical methods and which can be generally used when introducing CEMMS. Depending on the type and purposes of measurement, various kinds of instruments having different features may be used. This article represents a comparative study of gas-analysis systems for measuring the content of polluting substances in exhaust gases based on various physical and physicochemical analysis methods. It lists basic characteristics of the methods commonly applied in the area of gas analysis. It is proven that, considering the necessity of the long-term, continuous operation of gas analyzers for monitoring and measurement of pollutant emissions into the atmosphere, as well as the requirements for reliability and independence from aggressive components and temperature of the gas flow, it is preferable to use optical gas analyzers for the aforementioned purposes. In order to reduce the costs of equipment comprising a CEMMS at a TPP and optimize the combustion processes, electrochemical and thermomagnetic gas analyzers may also be used. 相似文献
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在气体绝缘组合电器(gas insulated switchgear,GIS)实体模型内部模拟了高压导体表面突起、悬浮金属颗粒和绝缘子表面固定金属颗粒三种绝缘缺陷,其中用针-板放电模型模拟高压导体表面突起缺陷。GIS模型内部充入0.4MPa的SF6气体,当加压到60kV时,三种模型均有稳定的放电。用超声波传感器分别测得其响应的放电波形100组,取相邻两个半波的信号幅值差的绝对值Udif和一个周波内的信号值的绝对值之和Utal作为特征量,用BP神经网络进行识别,识别率在80%左右,最后用最小距离分类器与BP神经网络的分类结果做对比,证明了BP神经网络的优越性。 相似文献
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Takeki Nogami Yoshihide Yokoi Hideo Ichiba Yoshihiro Atsumi 《Electrical Engineering in Japan》1995,115(1):93-103
This paper describes a method available for early detection of abnormality in an oil-filled transformer. In this method, four gas sensors having different characteristics and neural network are used to identify gas species (H2, CH4, C2H4, C2H2 and mixture of two species). To improve the selectivity of gas sensors, the time response patterns induced by changing sensor temperature and the stationary sensor output are identified by neural network. Furthermore, the mixture ratio of gases is derived by using the stationary sensor output in response to the changing sensor temperature. Gas species are well discriminated, and the mixture ratio derived from the sensor output agrees well with the measurement by gas chromatography. Therefore, it is confirmed that our method is applicable to the transformer diagnostic technology. 相似文献
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针对锅炉受热面初始沉积层的热泳沉积机理建立了模型,采用文献中的实验结果及模型研究结果检验了模型的合理性,并通过考虑沉积层外表面温度随沉积层生长的动态变化改善了模型预测的准确性。结果表明:烟气温度和碱金属质量浓度高对热泳沉积表现为促进作用,烟气流速高对热泳沉积仅表现出微弱的促进作用;较高的管壁温度对热泳沉积表现为抑制作用;在相同的条件下,K2SO4的热泳沉积过程与Na2SO4具有高度的相似性,热泳沉积与气溶胶颗粒的组成成分无关;当气溶胶颗粒粒径小于1μm时,初始沉积层厚度与颗粒粒径的分布无关。 相似文献
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基于计算机视觉的金属板带材表面缺陷检测是冶金工业领域的研究热点,金属板带材制造行业对其表面质量的高标准要求自动化视觉检测系统及其算法性能不断提升。通过回顾关于钢板钢带、铝板铝带和铜板铜带等典型金属板带材产品的110余篇文献,对基于二维和三维机器视觉的表面检测技术进行了系统综述。根据算法性质和图像特征,将现有二维缺陷检测技术分为基于统计、谱、模型和机器学习的4类方法,根据三维数据获取方式,将三维缺陷检测技术分为立体视觉测量、激光扫描仪测量法和结构光测量方法。对经典算法和新近方法进行了介绍、分析和比较。最后,对缺陷视觉检测仍存在的挑战和未来研究趋势进行了讨论与展望。 相似文献
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用于绝缘油中气体监测的半导体气敏传感器模型 总被引:1,自引:1,他引:0
利用塔板理论建立混合气体色谱柱分离的数学模型;分析了半导体气敏传感器的稳态、暂态响应与恢复特性,提出了关于传感器响应与恢复特性的3个假设:传感器稳态输出电阻的对数与气体浓度的对数服从正切关系,暂态响应特性取决于传感器当前的阻值状态和当前时刻的气体浓度,恢复特性取决于传感器当前阻值状态和下一时刻的气体浓度。采用实验与数值逼近等数学方法确定所需参数。最后设计了验证实验,结果表明将3个假设用于油中气体监测系统的半导体传感器能够满足要求。 相似文献