【作者】 陈霄；

【导师】 隋青美；

【作者基本信息】 山东大学 ， 检测技术与自动化装置， 2012， 博士

【摘要】 近些年来,随着国内电力需求和电网规模的扩大,电力变压器等级和容量不断提高,变压器故障率和修复时间也随之不断增大。长期研究表明,变压器内部热状态以及绝缘油中气体组分和浓度很大程度地反映了变压器的热电故障程度和使用寿命,研究和发展变压器内部温度和绝缘油气体状态在线检测技术具有重要的理论和现实意义。变压器内部环境具有电压高、电磁干扰强、空间狭小、腐蚀性强等特点,变压器状态稳定、准确和快速检测及故障精确预测已经成为亟待解决和突破的关键技术难题。光纤半导体传感技术和半导体激光器技术的不断发展为解决该难题提供了可行的途径,但目前变压器内部状态检测中仍存在测量参数单一、抗干扰能力差、灵敏度有限、响应慢、多气体测量交叉影响等问题,尚不能满足变压器内部状态实时准确监测和故障精确预测的需要。针对以上问题,利用光纤半导体传感技术、气体光谱测量技术和变压器故障分析技术相结合,在研究半导体温度传感理论、气体直接吸收光谱理论和光声光谱理论基础上,建立了基于CCD衍射波长解调技术的光纤半导体温度和基于超窄线宽激光特性的光纤气体传感模型,通过设计高耦合率、小体积GaAs探头和高灵敏度检测气室,搭建了适用于变压器内部主要部件温度和绝缘油中气体检测的新型传感系统,可实现变压器内部多参数(温度和绝缘油中气体)的高精度、高灵敏度、快速在线测量,有效提高电力变压器状态在线检测和故障预测的技术水平。本文主要研究内容如下：(1)从油浸式变压器内部结构出发,研究变压器内部发热(损耗)、散热原理及温升特性,分析变压器主要过热故障原因及其温度特性,列出了主要部件的温升限值；详解变压器正常运行和电热性故障时油中气体的产生原理及气体在油中溶解和扩散过程,得出了变压器内主要部件故障类型与油中气体组分和含量的关系,为油浸式电力变压器运行状态在线检测的实现奠定了一定的理论基础。(2)针对以往变压器内部温度在线测量中响应速度慢、抗干扰能力差、匹配性不好等问题,在详细分析半导体材料光学性质(光学常数和本征吸收)基础上,深入研究半导体材料温度传感原理,揭示了GaAs晶体吸收光波长随温度变化的关系,建立了GaAs晶体温度-波长传感模型,通过设计新型反射式GaAs传感探头和基于CCD衍射技术的波长解调系统,搭建了新型光纤半导体温度传感系统。新型GaAs探头具有体积小、耦合率高、电绝缘性好、抗腐蚀能力强,匹配性好等特点；基于CCD衍射技术的新型波长解调系统有效克服了半导体温度传感光强解调易受光源抖动和光路扰动影响的缺点。通过不同温度下GaAs反射光谱测量实验,验证了GaAs温度-波长传感特性,温度传感实验表明：0℃～235℃测量精度为±0.5℃,分辨率为0.1℃,响应时间小于6s；长时间实验温度最大波动为±0.3℃；强磁场环境下15℃～175℃测量精度仍为±0.5℃。此系统测量范围广、精确度高、响应时间快、稳定性好、抗电磁干扰能力强,非常适合用于油浸式电力变压器内部热状态在线检测,可实现变压器内主要部件温度的实时在线测量和及时预警。(3)针对变压器油中气体在线检测存在测量参数单一、抗干扰能力差、多气体测量交叉影响等问题,深入分析气体分子选择吸收理论、气体吸收谱线线型和线宽理论、气体吸收谱线强度分布理论,以气体吸收光谱理论和Beer-Lambert定律为基础建立了开放式差分检测、单光源多气体检测和多参数直接检测传感模型,搭建了适用于变压器油中气体检测的新型传感系统并进行了实验分析。首先,通过设计低噪声反射式结构长光程气室,利用超窄线宽外腔式半导体激光器特性(输出激光精确锁定气体吸收和非吸收峰且线宽远小于单条气体吸收谱线宽)、改进的差分检测模型以及光学时分、空分复用技术相结合,精确测量并分析不同压强下1572.66nm附近CO2吸收谱线,实现了CO2气体的多点高精度快速测量,其结构简单,易于实现,可消除变压器油中其它气体成分和灰尘颗粒的干扰,非常适合开放式环境的变压器气体检测,测量精度(相对误差<3%)和响应时间(<8s)均达到波长调制型系统检测效果；其次,基于光谱调制和谐波探测技术,利用单一高频三角信号调制激光光谱,通过设计具有横向空间小、长光程特点的串联结构气室,结合超窄线宽激光和光源波长高精度调节特性,实现了单光源多组分气体(CO、CO2、CH4)高精度多点测量,CO、CO2、CH4多组分气体浓度测量最大相对误差小于2%,动态响应时间均小于10s,长时间实验最大相对波动均小于1%,可有效解决变压器油中多气体测量交叉影响的问题；最后,基于超窄线宽激光特性和激光器波长扫描技术,通过对不同温度下CO气体在6354.179cm-1和6383.09cm-1附近吸收谱线对的精确测量和分析,利用谱线对积分面积比与温度关系(直接测温法)并结合浓度差分检测模型实现了CO气体多参数(温度和浓度)同时在线检测,其结构简单,便于操作,温度测量最大相对误差小于4%,长时间实验最大相对波动小于3.5%；浓度测量最大相对误差小于5%,最小检测限为0.05%。甲烷、一氧化碳、二氧化碳等气体是变压器故障气体主要组成部分,其开放式、单光源多组分、直接式多参数高精度多点快速在线检测的实现可有效提高电力变压器油中溶解气体在线分析和故障预测水平。(4)针对变压器油中微量气体检测存在测量精度有限、多气体测量交叉影响等问题,以光声效应原理和腔内增强吸收光谱理论为基础,利用超窄线宽半导体激光器特性建立了光声光谱式单光源多组分气体高灵敏度谐波检测模型和腔内激光衰荡时间与气体高灵敏度检测模型,搭建了适用于变压器油中微量气体检测的新型传感系统并进行了实验分析。研究光声池工作方式和结构特性,分析光声系统噪声的来源及特点,建立光声池设计优化基础理论,设计了新型结构一阶纵向多光程共振光声池,实现池内光声信号低噪声、高灵敏度检测；剖析谐振腔内激光传输特性及激光频率与谐振腔模式匹配方式,依据激光腔内耦合理论设计了由两块高反射率平凹透镜组成的低损耗调谐式光学衰荡腔,实现了激光频率和腔长的共同调谐。基于光谱调制技术和谐波检测技术,利用高频正弦信号调制激光光谱,并结合超窄线宽激光和光源波长高精度调节特性,设计了光声光谱式单光源多组分微量气体高精度实时在线检测系统,有效消除吸收池内背景噪声和光源抖动的影响,实验验证了系统调制幅度与二次谐波信号形状(峰值大小与半峰全宽比值)的关系,并确定了系统检测最佳调制幅度；C2H2、CO、CO2多组分气体浓度测量最大相对误差小于2%,最大相对波动小于1.5%,极限检测灵敏度可达10-6数量级,可有效解决变压器油中多组分微量气体测量灵敏度有限和交叉影响的问题。通过扫描衰荡腔长使入射激光频率与谐振腔模式相匹配并利用激光失谐技术快速切断腔内入射激光,精确测量衰荡时间值并根据衰荡时间—气体检测模型设计了腔增强吸收光谱式气体高灵敏度和高精度检测系统,利用新型衰荡腔超长光程吸收特点,精确测定并分析6518.824cm-1附近C2H2弱吸收谱线以及C2H2气体浓度与衰荡时间的关系；C2H2气体浓度测量最大相对误差小于2.5%,动态响应时间均小于10s,极限检测灵敏度为2x10-6,可有效解决变压器油中微量气体检测误差较大的问题。光声光谱式单光源多组分和腔增强吸收式高灵敏度气体检测系统实现了10-6数量级单一或多组分气体高精度快速在线测量,十分适合用于变压器油中微量气体高灵敏度在线检测,及时预报早期内部故障形成和发展情况。更多还原

【Abstract】 In recent years, the level and capacity of power transformer improve continuously, with the increase in domestic demand for electricity and the grid size. However, at the same time transformer failure rate and repair time are also increasing. Long-term researches show that concentration and composition of oil-gas and internal temperature are related to the degree of faults and life of transformer. For this reason, the study of novel on-line inspection technology of internal temperature and gas in transformer has great significance both in theory and practical. However, the internal environment of transformer has features of high voltage, powerful electromagnetic influence, small space and strong Corrosion. It has become a key technology problem to be solved that detecting transformer condition and forecasting transformer faults at high accuracy and timely. The development of technologies of fiber and semiconductor sensing and semiconductor laser provide of feasible approach to solve this problem. Unfortunately, for now, the detecting technology of transformer internal condition still has disadvantages of single parameter, low anti-interference capacity, sensibility and accuracy, slow response and multi-gas interference, which can not well satisfied with the needs of real-time monitoring transformer and forecasting transformer at high accuracy currently.In response to above problems, combining fiber semiconductor sensing technology with gas spectrum measurement technology and transformer fault analysis technology, optic-fiber semiconductor temperature and optic-fiber gas sensing models are established based on researches of theoies of semiconductor temperature sensing, gas absorption spectrum and photoacoustic spectroscopy. Meanwhile, a novel GaAs probe with high coupling coefficient and a novel gas cells with high sensitivity are designed. Further temperature and gas inspection systems in transformer are also presented, which can be used in the measurement of multi-parameter at high accuracy, good sensibility and quick response in real time. As a result, the research effectively improves the level of transformer condition detection and fault prediction. The main research contents are as follows:(1) Based on the structure of oil-Immerse transformer, the characteristics of temperature increase and principle of fever and cooling are discussed. The reason of transformer overheating fault and its characteristics are also analyzed. Meanwhile, the limit of transformer temperature rise is provided. Furthermore, a detailed explanation of the principle of transformer gas at normal or non-normal work state and the dissolve and diffusion process about gas in transformer oil are introduced. Then the relationship between the types of transformer internal failures and concentration and composition of oil-gas is disclosed. Finally this part research lays possibility and a theory foundation for study of on-line inspection technology for oil-immersed transformer condition.(2) For the problem that the technology of on-line detection of transformer temperature has some disadvantages of slow response and poor anti-interference capability and matching, the relationship between temperature and the absorption wavelength of GaAs is revealed because of in-depth analysis of GaAs optical properties and research of temperature sensing principle of semiconductor. On the basis of above this relation, the GaAs temperature sensing model is established and the temperature sensing system is constructed in which a novel reflective sensing probe and wavelength demodulating system based on CCD and diffraction technology are also designed. The novel GaAs probe has advantages of small volume, high coupling coefficient, perfect insulation, strong resistance to corrosion and good matching and the novel wavelength demodulating system can eliminate the influence of intensity fluctuation of the light source and the disturbances of optical path. Reflectance spectra at different temperatures have verified the sensing characteristics of GaAs semiconductor in further. Finally the experimental results indicate that the system has accuracy of±0.5℃, resolution of0.1℃and response time of less than6s with the range of0-235℃, the maximum temperature fluctuations is±0.3℃and the accuracy of temperature measurement is also±0.5℃at strong magnetic field environment. In short, the system has advantages of wide measure range, high accuracy, strong anti-interference ability, good stability and quick response, which is very suitable for on-line monitoring of transformer internal temperature and pre-warning for transformer in time.(3) In view of the problems of single parameter and gas component, low anti-interference capacity and mutual interference of multi-component gas in transformer oil-gas inspection, the detection models of open-difference, multi-component gas with single laser and multi-parameters are established based on studies on the theories of gas absorption spectrum and Beer-Lambert Law. Simultaneously, the new gas detection systems according to the three models are developed and also verified by experiments.Firstly, CO2absorption spectra around1572.66nm at different temperatures are measured and the multi-point inspection of CO2at high accuracy are also achieved by means of combining the ECDL characteristic with SDM and TDM technologies, difference detection model and a low noise and long optical-path gas cell. The structure of the difference detection system is simple so this system can be accomplished easily. In addition, the system can eliminate the interference of other gas and dust and is so suitable for transformer oil-gas detection in open environment. Especially experimental results of the difference detection system is so similar to wavelength modulation system’s. Secondly, a series gas cell with small size is designed and the high precision measurement of multi-component gas with single laser is carried out as well based on characteristic of Ultra-Narrow-Linewidth laser, high precision adjustment of laser wavelength, taking the sawtooth signal to modulate the spectrum of laser and harmonic detection technology. Furthermore the experiments indicate that the measurement relative error is less than2%, the system dynamic response time is less than10s and the relative concentration fluctuation is less than1%.Therfore, the system can eliminate the mutual interference of multi-componet gas in transformer oil-gas detection. Lastly, by measuring and analyzing the infrared absorption spectra of CO around6354.179cm-1and6383.09cm-1at different temperatures, a kind of detection system is designed based on the characteristics of Ultra-Narrow-Linewidth laser, the spectrum scanning technology and difference detection model which is simple and easy for handing. The results of experiments reveal that the temperature measurement relative error is less than4%, the relative temperature fluctuation is less than3.5%, the concentration measurement relative error is less than5%and the minimum detectable carbon monoxide is0.05%. Consequently, CH4, CO and CO2are the major components of fault gas of power transformer which are measured simultaneously at multi-parameter and high accuracy. It can improve the level of on-line monitoring of oil-gas and forecasting faults of power transformer.(4) For the problem that detection technology for transformer trace oil-gas has disadvantages of low accuracy and mutual interference of multi-component gas, the high sensitivity measurement models of multi-component gas with photoacoustic spectroscopy and ring-down time are built based on depth analysis of fundamentals of photoacoustic effect and theory of cavity enhanced absorption. Simultaneously, the new trace gas detection systems according to the two models are developed and also verified by experiments.According to operation-modes, structural characteristics of resonant photoacoustic cell and the source of photoacoustic system noise, an optimal design theory of resonant photoacoustic cell is built. Therewith, a novel first-longitudinal resonant photoacoustic cell with multi-optical path is designed which can effectively reduce the noise disturbance and improve sensitivity. Meanwhile, according to the theory of laser coupling and the characteristics of laser transmission and laser frequency overlaps with one of cavity modes in cavity, a low noise tunable optical cavity which is consisted of two mirrors with high reflectivity also is used as the absorption cell which can simultaneously tune operation between laser frequency and cavity length. As a result, by taking the sine signal to modulate the wavelength of laser and combining second harmonic signal detection technique with laser wavelength scanning technique and characteristics of Ultra-Narrow-Linewidth laser, the detection system of multi-component trace gas with single laser is achieved which is able to effectively eliminate the background noise and the influence of intensity fluctuation and the relationship between modulation depth and measured peak amplitude also is obtained. Multi-component gas detection experiments indicate that the measurement relative error is less than2%, maximum relative fluctuation is less than1.5%and the sensibility can reach the order of magnitude of10-6. So the system can eliminate the mutual interference of multi-component gas and improve sensitivity in trace oil-gas detection. Meanwhile, the input laser is switched off by using laser detuning technique then detection system of trace acetylene wih high sensibility and accuracy is constructed based on ring-down time measured at different concentrations. Therefore, the absorption spectra of CH4around6518.824cm-1and the relationship between concentration and ring-down time are measured and also analysed. Cavity enhanced absorption gas experiments indicate that the concentration measurement relative error is less than2.5%, the dynamic response time is less than10s, and the lowest detection limit is2×10-6. So the system can improve accuracy in trace oil-gas detection. In conclusion, the multi-component detection system with single laser and photoacoustic spectroscopy technology and cavity enhanced gas detection system can measure single or multi gas at magnitude of10-6. It is suitable for on-line detecting for trace oil-gas and forecasting the early internal faults of transformer in time.更多还原