【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， 2011， 博士

【摘要】 油中溶解气体在线分析技术（On-line Dissolved Gas Analysis）是对变压器等充油电力设备运行状态进行在线监测的重要手段,也是实现变压器等电力设备状态检修的必然要求。通过对变压器绝缘油中溶解的故障气体（CH₄,C₂H₂,C₂H₄,C₂H₆,CO,CO₂,H₂）进行油气分离和定量分析,可以得到其运行状态进而对其进行故障诊断。油气分离膜可以实现对故障气体的连续在线分离,光声光谱（Photoacoustic Spectroscopy）气体定量分析方法可以实现对故障气体组分高灵敏度的定量分析。本文结合变压器在线监测与状态检修的要求,对基于油气分离膜和非共振光声光谱的变压器绝缘油中溶解气体在线分析技术中存在的一些问题进行了研究。通过分析膜对故障气体的油气分离过程,对影响油气分离过程及结果的因素进行研究。针对原有油中溶解气体体积分数计算方法的缺陷,提出了一种计算油中溶解气体体积分数的新算法——动态算法。该算法利用等时间间隔点上气室中气体体积分数,在油气分离过程未达到平衡时,计算绝缘油中溶解气体体积分数;同时在该算法中引入了温度修正系数,理论上消除了温度变化对动态算法计算油中溶解气体体积分数结果的影响。在实验室进行油气分离膜性能的比较实验后,建立了油气分离膜作为脱气单元的油中溶解H₂及CO气体在线分析系统。以实验室离线气相色谱的测量结果为基准值,采用动态算法并进行温度修正后得到绝缘油中溶解H₂与CO气体体积分数,与未采用动态算法相比气体体积分数结果的准确性和实时性得到提高,验证了基于膜分离的动态算法和温度修正系数的有效性。结合IEC与CIGRE的调查结果,对油中溶解气体在线分析结果提出了准确性、重复性及再现性的要求。给出油中溶解气体在线分析结果的典型值、注意值与预警值的设定方法后,基于绝缘油中溶解气体体积分数与变压器发生故障概率的关系,提出了一种根据油中溶解气体体积分数在线分析结果计算下一次采样时间间隔的方法,并给出了计算实例。在研究气体分子振转能级及跃迁条件的基础上,对故障特征气体中CO、CO₂、CH₄、C₂H₂、C₂H₄及C₂H₆气体分子的吸收谱线的特点进行分析。分析了光声光谱气体定量分析理论及光声信号的激发过程,深入研究了非共振与共振光声信号的差异,分析光声池壁对光声信号的反射与透射,推导传声器输出与光声池中声压的对应关系,为非共振光声池的设计提供了理论基础。建立故障气体非共振光声光谱定量分析系统的模型,推导吸收谱线存在交叉干扰的情况下,光声信号幅值与故障气体中各组分体积分数之间的对应关系,为非共振光声光谱法应用于变压器绝缘油中溶解气体在线分析提供理论基础。建立基于非共振光声光谱理论的绝缘油中溶解气体定量分析实验系统。通过分析光源调制频率对光声信号的影响,提出将光源调制频率降至次声频段的方法,提高了光声信号输出的幅值。分析实验系统的噪声来源,设计了高信噪比的非共振式光声池。采用建立的非共振次声光声光谱实验系统对CO、CO₂、C₂H₂、C₂H₄、C₂H₆及CH₄气体进行了定量分析,计算得到系统对于单一气体测量的极限灵敏度,同时对测量结果的准确性与精度进行了评估,并与气相色谱得到的结果进行对比,结果表明该实验系统能有效地用于变压器绝缘油中溶解气体在线定量分析。更多还原

【Abstract】 On-line DGA （dissolved gas analysis） is an important means by which not only the running condition of oil-filled electrical equipment, such as transformers, can be monitored promptly, but also the state maintenance of the electrical quipment can be achieved. The condition and fault of transformers are diagnosed by the separation and quantification of fault gases（CH₄,C₂H₂,C₂H₄,C₂H₆,CO,CO₂,H₂） dissolved in insulation oil of transformers. The fault gases can be separated from insulation oil by membrane continuously and quantifid by PA （photoacoustic spectroscopy） with high resolution. Combining the requirement of on-line condition monitoring and state maintenance, this dissertation studied the issues existed in the on-line dissolved gas analysis systems which adopt membrane extraction technology and PA gas quantification technology.Through the analysis of the extraction process of gases dissolved in insulation oil through membranes; the factors that influence the gas-in-oil extraction processes and results are also studied. Aiming at the defection of original calculation method, a new algorithm - dynamic algorithm is proposed based on those analyses. The algorithm utilizes the concentrations of gases in the gas separation cell at the same time interval to calculate the concentrations of gases dissolved in insulation oil, when the equilibrium state of the extraction process is not reached; also the algorithm consists of a temperature modified coefficient, which can remove the temperature affection of gas concentrations calculation theoretically.After the expetiment for comparision of extraction abilities of membranes in the laboratory is done, an on-line dissolved gas analysis system which amounts membrane as gas extractor is constructed, detecting the concentrations of H₂ and CO in the insulation oil. The off-line GC results are set as reference values, and the dynamic algorithm has been used to calculate the concentration of H₂ and CO dissolved in transformer insulation oil. Compared with the original calculation metrod, the accuracy and the immediacy of the calculation of concentrations of H₂ and CO are both improved. The validity of the dynamic aolgorithm with modified temperature coefficient for on-line DGA has been approved. Based on the research report and survey results of IEC and CIGRE, accuracy, repeatability and reproducibility are set as the quality indicator of on-line DGA results. Typical value, caution value and pre-failure value and the approaches to the setting of those values are proposed to evaluate the on-line DGA resuls. Base on the relationship between the concentrations of gases dissolved in oil and the probability of failure-related events in service, a sampling interval calculation method utilizing the on-line DGA results for calculating the next on-line DGA sampling interval is proposed.Based on the study of the model of molecule’s structure and the molecule’s vibration and rotational spectrum, the charaticristic of CH4, C₂H₂, C₂H4, C₂H₆, CO and CO2 structure and spectrum are analyzed. The photoacoustic spectroscopy theory for gas quantification and the inspiration process of PA signal is analyzed. The difference between resonant PA signal and non-resonant PA signal is studied particularly. The reflection of the sound pressure and the transmission of the sound pressure are both studied. The releationship between photoacoustic signal and the output singal of microphone is deduced. Those researches can provide the theoretical foundation for the design of the non-resonant PA cell. A non-resonant PA gas analysis model is constructed, the influence of the crossover interference is investigated, and the crossover of spectrum of fault gases is disquisitived. The dependence of photoacoustic signal on the concentration of each kind of gas in a mixture is deduced, which can provide the foundation for the application of non-resonat PA in the transformer insulation oil on-line DGA.A non-resonant photoacoustic spectroscopy experimental system applied for on-line analysis of gases dissolved in insulation oil was established. The dependence of photoacoustic signal on the modulation frequency is analysied, and an infrasonic photoacoustic way, which is decreasing the modulation frenquency of light to produce a higher amplitude photoacoustic signal, is proposed. Then the noises in the system have been researched, and high SNR gas cell is designed and constructed. The measurements of the concentrations of the CO, CO₂, CH₄, C₂H₂, C₂H₄, and C₂H₆ in the fault gases are carried out, and the limited sensitivity of each kind of gas is calculated. The accuracy, repeatability and reproducibility of the detection results are evaluated. Comepared with the GC results, the experiment results demonstrate that the probability of the non-resonant photoacoustic spectroscopy experiment system and the experiment system’s feasibility of application in field test of the analysis of gases dissolved in transformer oil is approved.更多还原