【作者】 向彬；

【导师】 廖瑞金；

【作者基本信息】 重庆大学 ， 电气工程， 2008， 硕士

【摘要】 油纸绝缘是大型电力变压器内绝缘的主要组成形式,在温度、电场、氧气、水分等复杂环境的长期作用下逐渐老化,绝缘性能下降,绝缘寿命缩短,引发绝缘事故的可能性增加,降低电网安全运行可靠性。变压器油纸绝缘老化机理研究是绝缘老化状态评估、寿命预测和制定抗老化措施的前提和基础。传统的电气和老化生成物特性的研究很难从机理上对油纸绝缘的老化过程进行解释。油纸绝缘老化不仅与绝缘材料分子结构、聚态结构有关,还与热应力作用下的物理和化学性质有关,因此油纸绝缘老化的微观机理及热特性研究具有重要工程价值和学术意义。温度是油纸绝缘老化的主要因素,本文主要设计了油浸式电力变压器常用的普通牛皮纸和环烷基矿物油复合绝缘在90℃下长达370天的热单因子老化试验。利用FTIR(傅立叶红外光谱)、UV-Vis(紫外-可见光谱)、XRD(X射线衍射)定期测量了不同老化状态的绝缘样品,对比分析了油纸绝缘的官能团和绝缘纸的聚态结构的变化情况,并深入讨论了绝缘纸聚合度下降的动力学过程;最后利用DSC(差示扫描量热)和TG(热重)研究了绝缘纸分子热运动特点和裂解动力学过程并分析了不同老化程度绝缘纸热裂解动力学参数的变化。研究结果表明:①变压器油纸绝缘老化会产生溶解于油中的含C = C共轭基团和C = O生色基团的老化生成物,老化特征基团随老化时间的增加而增加。②绝缘纸在老化过程中,纤维素氢键和糖苷键发生断裂,引起聚合度下降,结晶区遭受破坏,晶粒尺寸减小,导致纤维素分子间作用力减弱,热裂解活化能降低。③老化过程中,绝缘纸纤维素晶体类型不变,聚合度的下降规律符合二阶动力学模型,相对结晶度的变化规律能很好的解释了聚合度的变化规律。④绝缘纸不定形区域中分子链在程序升温过程中出现“玻璃化转变”,但结晶区的氢键没有断裂,不定形区域分子链的热反应活性高于结晶区。⑤绝缘纸的热裂解过程中主裂解阶段在230～380℃,裂解活化能为65～96 kJ /mol。主裂解阶段中,当温度升至330℃时裂解机理发生改变,且低温降解阶段(230～330℃)的活化能小于高温阶段(330～380℃)的活化能。因此利用实验室恒温加速老化试验来模拟变压器绝缘纸的正常老化试验时,试验温度不宜过高。更多还原

【Abstract】 Oil-paper is mainly used as electrical insulation in large electrical power transformers. It is gradual aging under the long-term combined effects of temperature, electrical field, oxygen and water etc, which deteriorate the insulation performance, shorten the insulation life, increase the possibility of insulation accident and reduce the reliability of power grid security. Aging mechanism of oil-paper is the precondition and basis to assessment of the aging condition of paper, predicted insulation life and establishment of anti-aging measures for transformers. It is difficult to explain the detailed chemical mechanisms by characteristic of traditional electrical parameters or aging products. Oil-paper aging relates to not only the molecular structure and supramolecular structure, but also the physical and chemical property under the thermal stress effects, therefore, it is very important for engineering and learning field to understand the aging micro-mechanism and thermal characteristic of oil-paper in power transformers.The thermal aging plays the main role in oil-paper degradation. In order to study oil-paper aging mechanism, accelerated thermal aging experiments in laboratory is performed in the thesis. Kraft paper and naphthenic mineral oil is thermally aged for 370 days at 90℃. The FTIR,UV-Vis and XRD under different aging condition of insulation samples are periodically measured, functional group and supramolecular structure of oil-paper variation with different aging condition are investigated and the kinetic of paper degradation is also discussed in further. Finally, the thermal action of insulation paper molecular and kinetic of pyrolysis are investigated by DSC and TG respectively, kinetic parameters of pyrolysis variation with different aging condition are also analyzed.The results indicate that:①Aging products with C = C conjugated group and C = Ochromogenic group dissolved in oil are produced during oil-paper aging and the aging characteristic groups increase with increasing time.②The DP (degree of polymerization) of paper decreasing directly is caused by breakdown of hydrogen and glycoside bonds which results cellulose inter-or-innermolecular force weakening and the activation energy of pyrolysis decreasing. At the same time, the areas of crystallinity is destroyed and the crystal grain size decreasing during aging.③Crystal type hardly change during the paper aging, the decreasing of DP accord with second-order kinetic model and the decreasing law of DP can be well explained by relative degree of crystallinity.④The molecular chain in amorphous regions of paper occurs“glass transition”with the increasing temperature controlled by programme, but the hygrogen bond without fracture in areas of crystallinity , which explain that thermal reaction activity of molecular in amorphous regions is more higher than that in areas of crystallinity.⑤The temperature of main stage is between 230 and 380℃in insulation paper pyrolysis process and the activation energy is 65～96 kJ /mol . The pyrolysis mechanism change until 330℃and the activation energy of low temperature stage(230～330℃) is less than that of high temperature stage(330～380℃) in main pyrolysis process. So the test temperature can’t be set to more higher when normal oil-paper aging process in field is simulated by accelerated aging test carried out in laboratory.更多还原