【作者】 韩慧慧；

【导师】 杨道武；

【作者基本信息】 长沙理工大学 ， 应用化学， 2010， 硕士

【摘要】 电力变压器作为电网中最重要和最关键的设备之一,它运行的可靠性直接关系到电网能否安全、高效、经济的运行。导致变压器发生事故主要原因多数是绝缘性故障。油浸式变压器的油纸绝缘寿命决定了变压器的使用寿命。研究变压器油纸绝缘老化的特性及机理,建立绝缘老化模型,对于识别变压器的绝缘老化程度,预测设备寿命,减少电网事故,提高变压器运行的可靠性,具有重要的学术价值和生产应用价值。本文选用25号及45号纯油和油纸,设计了变压器油纸绝缘老化实验,按有关标准的要求完善了各老化特征参数的测量方法,并用这些方法测取了油和油纸在120℃、100℃和80℃三种温度下进行热老化过程中的特征参数,如酸值、体积电阻率、微水含量、粘度、聚合值等,讨论了各特征参数之间的相关性;用多元线性回归分析了聚合度与多个老化参数间的线性回归关系;用GC-900-SD气相色谱仪按DL/T722-2000标准分析了老化过程中油中溶解气体如CO2、CO、氢气、甲烷、乙烯等老化产物的含量,研究了CO2/CO值与绝缘纸的老化程度的关系;用Shimadzu LC-10AT高效液相色谱仪和Avatar360傅立叶红外光谱仪研究了绝缘纸的热老化;用Accelrys Materials Studio 4.0分子模拟软件建立了油纸纤维素的分子模型,用量子化学分子动力学模块DMol3 /Dynamics模拟了绝缘纸纤维素分子在120℃时热老化过程,并结合上述研究结果和有关化学知识,初步探讨了绝缘纸的老化机理。得出的主要结论如下:(1)油纸在老化过程中生成多种物质,其中CO、CO2主要是绝缘纸老化裂解产生的, CO2/CO比值和微水含量随老化时间的变化趋势与绝缘纸的老化阶段有密切的关系,可以考虑用CO2/CO、微水含量变化来评估变压器绝缘纸的老化程度。(2)一些常规老化特征参数与糠醛及聚合度之间的多元回归模型为:Y=B0+B1x1 + B2x2+B3x3+ B4x4+B5x5+B6x6。这一模型有助于通过常规实验判断变压器绝缘老化的趋势和程度,对绝缘老化注意值增长明显的设备应进行糠醛试验,以便及时掌握设备安全状况,并制定合理的追踪试验计划,避免可能出现的设备故障。(3)有关老化征参数之间的相关性为:体积电阻率随酸值呈负指数关系:ρv = ae ?cm+b;聚合度与酸值之间呈指数关系: DP = Aex /b+c;微水合量与聚合度之间的关系: DP = A+Bx+Cx2;CO2/CO比值与随着聚合度的关系:DP=A+Bx+Cx2。(4)油和油纸的老化与温度密切相关,温度越高,油和油纸的老化速率越快。相同条件下,油纸各项老化参数比油的变化快,说明油纸老化速率比油快,绝缘纸促进了变压器的绝缘老化。(5)老化后绝缘纸试样红外光谱显示,1720cm-1处有醛类吸收峰,2900cm-1处的C-H伸缩振动特征吸收峰,老化前后在3500~3300cm-1之间的吸收峰有明显的变化,可以得到老化过程中油纸纤维素的分子结构变化的信息,高效液相色谱分析和傅立叶红外光谱分析都说明油纸老化过程中纤维素发生裂解产生了糠醛等物质。(6)初步探讨绝缘纸的老化机理是:在老化初期纤维素分子的1、4-β-苷键发生断裂,生成大量的D-单葡萄糖单体和大量小分子自由基;老化后期,部分葡萄糖单体内的吡喃环开环断裂,接着呋喃环中的半缩醛羟基断裂,生成CO2、CO以及烃类物质和糠醛等。在一定温度下,水和氧的存在会加速绝缘纸纤维素的降解。更多还原

【Abstract】 Power transformer is one of the most important equipments in power grid. Whether the transformer work normal is directly related to power grid can be safe, efficient and economical operation. Insulation fault is mostly the main reason of accidents occurred in transformer. The age of the oil-immersed transformers is depending on the life of insulation . Reseaching the aging characteristics and mechanisms of the insulating oil-papers of transformers and establing the aging models of insulators are valuable on academics and productions for the identification of the aging degree of the insulators, the prediction of the lifetime of equipments, the reduction of power accidents, the improvement of the reliability of transformers.In this paper No.25 and No.45 pure oils and their oil papers were used on aging tests of the insulator of the transformer, and according to some related standards measureing methods for aging characteristic parameters were improved. These methods were employed to measure the thermal aging characteristic parameters such as acid value, volume resistivity, micro-water content, viscosity, aggregating value and so on of these oils and oil-papers at 120℃, 100℃and 80℃respectively. The relationships witnin characteristic parameters had been discussed. The lnear regression of the degree of polymerization and multiple aging parameterswere analyzed by multiple linear regression analysis modle; Gases dissolved in transformer oil during aging process were analyzed through GC-900-SD gas chromatograph according to DL / T722- 2000 standard, such as the content of the aging product of carbon monoxide and hydrogen, methane and ethane, etc. The relationship between the aging degree of the insulator and CO2/CO were studied. The heat aging process were studied by Shimadzu LC-10AT high-performance liquid chromatography and Avatar360 Fourier infrared spectrometer. The cellulosic molecule model were established by Accelrys Materials Studio 4.0. The cellulosic molecule aging process at 120℃had been simulated by quantum chemistry molecular dynamics module(DMol3 /Dynamics). Combining the research results and relevant knowledge of chemistry, the the aging mechanism of oil-paper is discussed. And the main conclusions are as follows: (1) Many materials are produced during the aging process. As part of the products, carbon monoxide and carbon dioxide are mainly come from insulation paper cracking of aging.The experiment result shows that there is close relationship between insulation paper aging stage and the trend with the aging time of CO2/CO or micro water. So the aging parameters of CO2/CO and micro water can be used to evaluation the insulation paper aging degree.(2) The multiple regression model of the degree of polymerization and multiple aging parameters can be drawed as : Y=B0+B1x1+B2x2+B3x3+ B4x4+B5x5+B6x6. It is useful to judge the insulation aging degree and trend of the transformer. In order to findequipment safety conditions, furfural test should be carried for those equipments whoes insulation aging note values increase obviously. Then the rational track test plan is formulate to avoid transformer fault.(3) The correlation between the parameters as followed, there is a negative exponent relationship between volume resistivity and acid value,ρv = ae ?cm+b; there is index relationship between the degree of polymerization and acid value, DP = Aex /b+c; there is correlation between micro water content and degree of polymerization, DP = A+Bx+Cx2; there is correlation between CO2/CO and degree of polymerization, DP = A+Bx+Cx2.(4) The aging of oil and oil-paper is closely related with the temperature. The higher the temperature, the faster ageing rate of oil and oil-paper . At the same aging conditions, the aging rate of oil-paper is faster than theat of pure oil. The corresponding parameter of oil-paper also change faster. It is explained that the ageing rate of oil-paper is faster than that of the oil, and insulation aging is promoted by the oil-paper.(5) The infrared spectroscopy of the insulating samples shows that, The absorption peaks of the aldehyde is at 1720cm-1, and the characteristic absorption peaks of telescopic vibration is at 2900cm-1,and the absorption peaks between 3500 cm-1 and 3300cm-1 is significant changed. The structural changements of paper cellulose molecules during aging process can be found. That the furfural produced during the aging process is confirmed by HPLC and IRC.(6) The aging mechanisms of insulating paper as followed: the 1、4-β-nucleoside key ,which connect glucose forms cellulose chain, is the easiest fracture key during insulation aging process. Large amounts of D-single glucose monomers and lots of small molecules free radicals are generated due to the fracture key. Then during the aging later, part of the pyranoid ring within the glucose monomer open-loop fracture, and half acetal hydroxyl followed fracture. The carbon dioxide、carbon monoxide, hydrocarbons and furfural are generated with the key broking.At a certain temperature, water and oxygen will accelerate the degradation of insulating cellulose.更多还原