【作者】 冯运；

【导师】 廖瑞金；

【作者基本信息】 重庆大学 ， 电气工程， 2007， 硕士

【摘要】 变压器是电力系统中的核心设备,在电力系统中处于极其重要的地位,保障大型电力变压器运行的可靠性对整个电网的安全可靠运行具有重要意义。油纸绝缘是变压器寿命的决定因素,其在运行过程中逐渐老化,承受短路电流电动力的能力缓慢降低,成为威胁设备及电网稳定运行的重大隐患。因此,通过实验室加速老化试验并结合现场实际,对油纸绝缘的老化特性和机理进行研究,从而为变压器绝缘状态评估和寿命预测提供依据和参考,具有重要的学术和实际意义。本文在总结国内外油纸绝缘老化研究成果的基础上,分析了影响变压器油纸绝缘老化主要因素的作用机理以及老化过程中常见化学特征量的变化原理。通过对变压器油纸绝缘模型的加速热老化试验,研究了油纸绝缘老化过程中特征量随老化时间的变化关系以及特征量之间的相互关系,讨论了油纸绝缘的老化机理及其动力学原理,并对老化特征产物的生成速率进行了分析,在本文试验条件下,得到的主要结论有:1、与普通硫酸盐木浆纸相比较,Munksjo热稳定纸具有良好的热稳定性,其老化过程中糠醛产量较低。在利用油中糠醛含量对油纸绝缘老化程度进行估算时,必须考虑油、纸类型对糠醛含量的影响。变压器油中糠醛含量的注意值应根据其对应的油纸绝缘类型制订相应的标准。2、与25号变压器油相比,BIOTEMP油具有较高的饱和水分含量,这导致了其快速的老化,对应于较高的油酸值,可能会对变压器内部金属部件造成严重的腐蚀;BIOTEMP油与常规硫酸盐木浆纸组合时可以有效抑制油纸绝缘的老化,但与Munksjo热稳定纸组合时无明显效果。3、油纸绝缘老化过程中,绝缘纸纤维素长链的断裂并不严格遵守随机断链的机理,绝缘纸的降解速率随老化时间增加成指数递减关系;而基于随机断链的动力学模型对降解速率在老化后期的减小趋势考虑不够,使用该模型对油纸绝缘剩余寿命进行预测会出现偏小的数据。4、处于老化中后期的油纸绝缘,初始老化程度低的油纸绝缘在进一步老化中有相对较高的特征产物生成速率,而该生成速率随油纸绝缘初始老化时间的增加呈近似指数下降趋势,与纤维素绝缘纸降解过程中降解速率的变化相一致。更多还原

【Abstract】 Power transformer is the key equipment in power system and stands an extremely important position. It is of great significance to guarantee transformer operation reliably. The life of transformer is limited to the life of its oil-paper insulation. It degrades as the time goes by, and eventulally its capacity of exposure to short-circuit current has been significantly lowered and becomes a hidden threaten to system security. Therefore, studying the aging characteristics and mechanisms of oil-paper insulation, through accelerated aging experiments and onsite experiences, can provide information and references for transformer insulation condition-based assessment and also lifetime forecasting.On the basis of summarizing the domestic and international oil-paper insulation aging research results, the mechanisms that how the main factors affecting oil-paper insulation aging function and how the main chemical characteristic parameters change are analyzed. Through thermal accelerated aging experiments, the correlations of main chemical characteristic parameters and the relation of such parameters with aging time are studied, the aging mechanisms and dynamics are discussed, the generation rate of those characteristic products are also analyzed. The main conclusions are:1. Compared to ordinary Kraft paper, Munksjo paper has good thermal stability and lower furfural output. The types of oil and paper are needs to be considered when using furfural for oil-paper insulation aging estimating. The attention value of furfural in oil should be formulated based on its corresponding oilpaper insulation types.2. Compared to 25# transformer oil, BIOTEMP oil has higher saturated moisture content. This leads to its rapid aging and correspond to higher value of acid number, it may cause serious corrosion to transformer internal metal components. BIOTEMP oil can effectively inhibit oil-paper insulation aging when using with ordinary Kraft paper but without tangible results when using with Munksjo paper.3. In the process of oil-paper aging, cellulose bond scission rate is not strictly random, the degradation rate decreased exponentially with aging time. The remaining life will be shorten when using the random-scission model for lifetime prediction, due to it ignores the decline trend of degradation rate in the latter part of aging.4. Generation rates of characteristic products are consistent with the change of bond scission rate of cellulose, when samples were in mid-end life and aged further, the generation rate decreases almost exponentially.更多还原