【作者】 李洋流；

【导师】 赵学增；

【作者基本信息】 哈尔滨工业大学 ， 机械电子工程， 2007， 硕士

【摘要】 DGA技术是目前对充油电力设备进行常规监测的重要手段。本文在综述现行各种变压器DGA技术的主要优缺点的基础上,分析了将气体光声光谱检测技术应用于变压器DGA系统的优势,并介绍了光声光谱技术的历史背景,发展现状以及光声光谱技术的特点。本文从分子结构和分子光谱理论入手,论述了光声光谱气体浓度检测原理,包括光的吸收、热功率密度源的产生、光声信号的激发。建立了光声信号与光源强度、气体分子浓度关系的对应关系,推导气体浓度与传声器输出电信号的对应关系,为光声光谱气体浓度检测方法应用于变压器DGA系统提供了理论基础。基于光声光谱气体浓度检测理论,本文建立了变压器DGA系统的理论模型。分析了六种故障气体的红外吸收谱线,讨论了故障气体的谱线交叉时为避免干扰所选择的检测波长,得到系统光源的工作波长范围;在对比非共振式光声池与共振式光声池的优缺点基础上,设计了一种适用于变压器DGA系统的非共振式的小体积光声池。本文通过对微弱信号检测理论以及噪声抑制的相关方法的研究,利用互相关检测技术设计锁相放大电路,以代替锁相放大仪实现传声器输出信号的检测及处理。设计电路采用模拟乘法器实现相敏检波的功能,并通过有源积分电路与低通滤波器的联用以减小输出信号的波动,仿真结果表明该电路能实现较高的信噪比。最后对设计系统进行了气体浓度检测的实验,实验数据验证了设计系统的部分可行性,并拟合出检测系统的响应曲线。更多还原

【Abstract】 DGA is important means of transformer maintenance. As summarizing advantages and disadvantages of current methods used in DGA system, this thesis analyzed main advantage of photoacoustic spectroscopy applied in DGA. Meanwhile, the paper introduces the historical developments of photoacoustic spectroscopy, the new achievements in recent years, and the main points of the technology.Based on the molecule’s structure and the molecule’s spectrum and infrared spectrum structure of fault gases, the theory of gas detection using photoacoustic effect is discussed, which included the equation of photons absorption, the generation of acoustic energy, prompting of acoustic wave, and the detection of acoustic wave. The relationship between gas concentration and voltage output of microphone is deduced. All this become the foundation of the design of transformer DGA system.A model of DGA system is constructed based on photoacoustic spectroscopy. The movement form and absorption spectrum of six kinds of fault gases molecule is analyzed in this paper in order to confirm work wavelength of the system, and then the lamp-house used in this system is confirmed. Aiming high sensitivity at fault gas detection requirement, after comparing advantages and disadvantages of non-resonant cell with resonant cell, a small volume, non-reasonable cell was constructed, which is adapt to transformer DGA system.After studying on the theory of weak signal detection and noise restraint methods, a lock-in amplify detecting circuit was designed, which utilized cross-correlation technology. The whole circuit contains analog multiplier which realized phase signal detection function, both integral and low pass filter are used to reduce fluctuation of signal. The simulation result shows this circuit can realize high SNIR.An experimental system was established at last. The experiment data proved the partial feasibility of DGA system, and the response curve was fit.更多还原