【作者】 严家明；

【导师】 廖瑞金；

【作者基本信息】 重庆大学 ， 电气工程， 2011， 博士

【摘要】 一直以来局部放电都被认为是引起绝缘材料劣化的主要原因之一。油纸绝缘是电力变压器内绝缘的主要形式,其在生产、运输、装配和运行过程中不可避免地产生各种潜伏性缺陷,导致运行中产生局部放电,对绝缘材料造成损伤甚至引发击穿事故,严重威胁变压器安全、可靠运行；随着电压等级提高,局部放电对绝缘材料的损伤将变得愈加突出。因此,深入研究局部放电对油浸绝缘纸材料的损伤特性,对于丰富固体绝缘材料击穿理论,开发新型耐局部放电绝缘材料,提高基于局部放电的绝缘故障诊断能力,从而从根本上抑制或减缓局部放电对绝缘材料的损伤,无疑具有重要理论意义和实际应用前景。本文根据CIGRE MethodⅡ标准设计了油浸绝缘纸内部扁平气隙模型,在实验室中展开了几百小时的局部放电损伤试验,并由局部放电相位分布模式(Phase-resolved Partial Discharge, PRPD)划分损伤阶段；采用光学显微镜、扫描电子显微镜、原子力显微镜、X射线衍射仪、X射线光电子能谱仪、傅里叶变换红外光谱仪、气-质联动仪和气体测量模型等材料分析手段,分析了不同损伤阶段油浸绝缘纸的表面形貌、表面产物、微观结构等材料特征以及气隙气体；采用高阻仪、宽带介电谱测试系统、柱-柱电极系统以及空间电荷测试仪等电气分析手段,分析了不同损伤阶段油浸绝缘纸的极化、电导、损耗、击穿及空间电荷密度等电气性能；同时采用材料分析和电气分析相结合的方式,探讨了油浸绝缘纸损伤与电学性能之间的有机关联性。论文取得的创新性研究成果主要有：研究获得了油浸绝缘纸损伤过程中局部放电灰度图像、二维相位分布图及其特征量的变化规律,为提取局部放电新特征信息奠定了基础。首次研究了局部放电对油浸绝缘纸表面损伤的微观形貌,得到了局部放电损伤过程中油浸绝缘纸表面形貌和表面粗糙度的变化规律和发展趋势,分析了在局部放电作用下绝缘纸微区结构中晶区和无定形区分子链结构变化的差异以及表面损伤对缺陷电场的畸变。首次研究了局部放电对油浸绝缘纸表面损伤的产物,确定了损伤过程中油浸绝缘纸表面“液滴”和晶状“固体”的主要成分；得到了局部放电损伤过程中气隙气体体积、组分的变化规律；分析了表面产物的形成过程以及气体变化对局部放电形式转换的影响。首次研究了局部放电对油浸绝缘纸损伤的体相性能,得到了局部放电损伤过程中油浸绝缘纸的结晶度、取向度、晶粒尺寸等聚集态结构特征变化以及其极化、电导、损耗、击穿等电气性能变化趋势,分析了微观结构和电气性能之间的关联性。在对局部放电信号和油浸绝缘纸损伤研究基础上,进一步分析了局部放电与绝缘损伤之间的关联性,得到局部放电灰度图像、二维相位分布图及其特征量分别与绝缘材料表面损伤和气隙气体之间所具有的相关性；得出表面电导率、表面粗糙度对放电模式形状特征的影响。为判断油浸绝缘纸表面损伤状况及气隙缺陷发展状况提供了参考信息。更多还原

【Abstract】 Partial discharge (PD) has been considered one of the major causes of the deterioration of insulation materials. The internal insulation of a power transformer mainly consists of oil-paper insulation, in which all kinds of flaws are inevitably formed and generated during manufacture, transportation, assembly, and operation. In a running transformer, these flaws may cause partial discharge. PD may damage insulation and cause potential malfunction or breakdown, seriously threatening the safe operation of the transformer. Furthermore, the higher the voltage level is, the more serious PD damage to insulation materials may be. A thorough investigation of characteristics of PD damage to oil-impregnated insulation paper will encourage further studies on damage and breakdown mechanism, help improve PD resistance of insulation materials, develop an effective PD-based assessment model for insulation aging states, and then will eventually suppress or reduce PD damage to insulation materials. Therefore, the research work is of theoretical and practical importance.In this thesis, according to CIGRE MethodⅡ, an experimental model was devised to stimulate the flat cavity inside oil-impregnated insulation paper, and PD damage experiments were performed in laboratory for hundreds of hours. According to phase-resolved partial discharge (PRPD) patterns, PD damage process could be divided into several stages. On the one hand, material analysis techniques, such as optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometry (GC-MS) and Gas-measuring Model, were utilized to analyze surface topography, surface products and surface microstructure of oil-impregnated insulation paper at different damage stages as well as gas within cavity; on the other hand, electrical analysis techniques, such as high resistance meter, broadband dielectric spectra testing system and space charge measurement, were employed to analyze electrical properties of oil-impregnated insulation paper at different damage stages, including polarization, conductance, loss, breakdown and space charge density etc. Meanwhile, combined with material analysis techniques and electrical analysis techniques, the relationship between damage of oil-impregnated insulation paper and its electrical properties was also studied. The creative achievements which this thesis acquired can be summarized as follows: In-depth studies were conducted on the variation laws of gray intensity images, 2-deminsional phase distributions and its features, which has laid the solid foundations for the extraction of new PD features.For the first time, this thesis studied the surface morphology of oil-impregnated insulation paper after PD damage, revealed evolution laws and development tendencies of surface topography, surface roughness and surface conductivity during PD damage process. Meanwhile, after exposure to PD, the difference between the molecular structure variations in crystal regions and the molecular structure variation in amorphous regions was also studied. Furthermore, the distribution of the electric field within the cavity with surface solid was simulated and analyzed.For the first time, this thesis studied the surface products of oil-impregnated insulation paper after PD damage, specified the main constituents of "droplets" and crystalline "solids" generated on insulation surfaces, and revealed the generation mechanism of surface products under the condition of PD. Meanwhile, this thesis obtained the variations on volume and constituents of the gases within the cavity during the PD damage process. The generation mechanism of surface products and gas variation’s influence on the transition of discharge types were also analyzed.For the first time, this thesis studied the bulk properties of oil-impregnated insulation paper after PD damage, analyzed the structure features of aggregation state of oil-impregnated insulation paper such as crystallinity, orientation degree and crystal grain size, as well as electrical properties such as polarization, conductance, loss and breakdown etc.; meanwhile, explored the intrinsic relationship between microstructure and electrical property.Based on the analysis of PD signals and PD damage to oil-impregnated insulation paper, this thesis further analyzed the intrinsic relationship between PD and insulation damage, revealed the correlations between gray intensity images,2-dimensional phase distributions and surface damage, gas within the cavity, respectively; revealed the mechanism on how surface conductivity, surface roughness and surface trap density influenced PRPD patterns; provided reference information for assessment of the surface damage of oil-impregnated insulation paper and the evolution of cavity flaws.更多还原