有机酸对变压器油纸绝缘热老化特性的影响研究
发布时间：2018-07-24 19:43
【摘要】：油浸式电力变压器是电力系统输变电环节的核心设备,其内部的油纸复合绝缘系统决定了变压器的安全运行和电力的可靠供应。有机酸和水分是油纸绝缘系统最重要的两种老化产物,但目前不同种类有机酸的性质、有机酸对油纸绝缘热老化的影响特性、有机酸与不同检测方法特征参数之间的关系以及不同老化阶段油纸绝缘中的水分分布情况还有待深入研究。根据五种不同有机酸的性质,选取甲酸和硬脂酸作为研究对象。对比分析了甲酸和硬脂酸在油纸绝缘系统中的溶解分布特性,并通过不同试样绝缘纸聚合度随热老化的变化规律研究了甲酸和硬脂酸对绝缘纸降解速率的影响。基于零阶动力学模型得到了甲酸和硬脂酸初始酸值与绝缘纸平均降解速率的关系。研究结果表明：甲酸大部分被绝缘纸吸附,硬脂酸大部分溶解在绝缘油中；绝缘纸平均降解速率随酸值增加呈线性形式增长；甲酸对绝缘纸的平均降解速率是硬脂酸的8倍左右,甲酸酸值达到0.1mgKOH/g就会对油纸绝缘热老化起到明显的加速作用,因此在实际案例的研究分析中,需要特别考虑甲酸等低分子强极性酸对油纸绝缘热老化的加速作用。根据电介质响应原理推导了极化／去极化电流的通用表达式,研究了油纸绝缘在甲酸和硬脂酸作用下热老化的极化去极化电流特性,并与相应试样的绝缘电阻和吸收比进行了对比分析。研究结果表明：PDC曲线可以反映油纸绝缘的热老化情况,甲酸对油纸绝缘热老化反应的催化作用比硬脂酸显著,表现在极化电流末端平稳部分和去极化电流起始部分；去极化电流衰减速率随初始酸值的升高而加快,且含甲酸试样的去极化电流衰减速率大于含硬脂酸的试样。相比于绝缘电阻和吸收比,极化去极化电流能够更全面、有效地反映油纸绝缘不同老化阶段的绝缘状态。根据油纸绝缘热老化后的水分分布情况,提出将绝缘油中酸值作为表征油纸绝缘热老化程度的特征参数,用以定量描述老化对水分分布的影响。研究了绝缘油中水分的饱和溶解度随着老化程度的变化规律。引入随绝缘油中酸值变化的平移因子m,推导了油中水分饱和溶解度与油中酸值、环境温度的定量关系；基于Freundlich等温吸附方程,推导了绝缘纸中水分含量与绝缘油中水分含量、油中酸值、温度的定量关系,并研究了吸附平衡常数c和系数n与温度的对应关系。应用以上研究成果可以更准确有效地评估不同老化程度的绝缘纸中水分含量,对实际运行中的变压器具有重要的工程应用价值。
[Abstract]:Oil-immersed power transformer is the core equipment of transmission and transformation in power system. Its internal oil-paper composite insulation system determines the safe operation of transformer and the reliable supply of power. Organic acid and moisture are the two most important aging products of oil-paper insulation system, but at present, the properties of different kinds of organic acids and the influence of organic acids on thermal aging of oil-paper insulation are discussed. The relationship between organic acids and characteristic parameters of different testing methods and the distribution of moisture in oil-paper insulation at different aging stages need to be further studied. According to the properties of five different organic acids, formic acid and stearic acid were selected as research objects. The dissolution and distribution characteristics of formic acid and stearic acid in oil-paper insulation system were compared and analyzed. The effects of formic acid and stearic acid on the degradation rate of insulator paper were studied by the change of polymerization degree of different samples with thermal aging. Based on the zero order kinetic model, the relationship between the initial acid values of formic acid and stearic acid and the average degradation rate of insulator paper was obtained. The results show that most of formic acid is adsorbed by insulator paper, and stearic acid is dissolved in insulating oil, and the average degradation rate of insulator paper increases linearly with the increase of acid value. The average degradation rate of formic acid to insulator paper is about 8 times that of stearic acid. When the acid value of formic acid reaches 0.1mgKOH/g, it will obviously accelerate the thermal aging of oil paper insulation. Special consideration should be given to the acceleration of thermal aging of oil paper insulation by low molecular strong polar acids such as formic acid. According to the principle of dielectric response, the general expression of polarization / depolarization current is derived, and the characteristics of polarization depolarization current of oil-paper insulation under the action of formic acid and stearic acid are studied. The insulation resistance and absorption ratio of the sample are compared and analyzed. The results show that the ratio PDC curve can reflect the thermal aging of oil-paper insulation. The catalytic effect of formic acid on thermal aging reaction of oil-paper insulation is more significant than that of stearic acid, which is shown in the stationary part of polarization current end and the initial part of depolarization current. The depolarization current decay rate increases with the increase of initial acid value, and the depolarization current decay rate of formic acid sample is higher than that of stearic acid sample. Compared with the insulation resistance and absorption ratio, the polarization depolarization current can reflect the insulation state of different aging stages of oil-paper insulation more comprehensively and effectively. According to the moisture distribution of oil-paper insulation after thermal aging, the acid value in insulating oil is taken as the characteristic parameter to characterize the thermal aging degree of oil-paper insulation, which is used to describe quantitatively the effect of aging on moisture distribution. The variation of water saturation solubility with aging degree in insulating oil was studied. Based on the Freundlich isothermal adsorption equation, the water content in insulating paper and the moisture content in insulating oil are derived by introducing the translation factor m, which varies with acid value in insulating oil, and the quantitative relationship between water saturation solubility in oil and acid value and ambient temperature in oil is derived. The quantitative relationship between acid value and temperature in oil was studied, and the relationship between temperature and adsorption equilibrium constant c and coefficient n was studied. The application of the above research results can more accurately and effectively evaluate the moisture content in the insulator paper with different aging degree, which has important engineering application value to the transformer in actual operation.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM411
本文编号：2142454
[Abstract]:Oil-immersed power transformer is the core equipment of transmission and transformation in power system. Its internal oil-paper composite insulation system determines the safe operation of transformer and the reliable supply of power. Organic acid and moisture are the two most important aging products of oil-paper insulation system, but at present, the properties of different kinds of organic acids and the influence of organic acids on thermal aging of oil-paper insulation are discussed. The relationship between organic acids and characteristic parameters of different testing methods and the distribution of moisture in oil-paper insulation at different aging stages need to be further studied. According to the properties of five different organic acids, formic acid and stearic acid were selected as research objects. The dissolution and distribution characteristics of formic acid and stearic acid in oil-paper insulation system were compared and analyzed. The effects of formic acid and stearic acid on the degradation rate of insulator paper were studied by the change of polymerization degree of different samples with thermal aging. Based on the zero order kinetic model, the relationship between the initial acid values of formic acid and stearic acid and the average degradation rate of insulator paper was obtained. The results show that most of formic acid is adsorbed by insulator paper, and stearic acid is dissolved in insulating oil, and the average degradation rate of insulator paper increases linearly with the increase of acid value. The average degradation rate of formic acid to insulator paper is about 8 times that of stearic acid. When the acid value of formic acid reaches 0.1mgKOH/g, it will obviously accelerate the thermal aging of oil paper insulation. Special consideration should be given to the acceleration of thermal aging of oil paper insulation by low molecular strong polar acids such as formic acid. According to the principle of dielectric response, the general expression of polarization / depolarization current is derived, and the characteristics of polarization depolarization current of oil-paper insulation under the action of formic acid and stearic acid are studied. The insulation resistance and absorption ratio of the sample are compared and analyzed. The results show that the ratio PDC curve can reflect the thermal aging of oil-paper insulation. The catalytic effect of formic acid on thermal aging reaction of oil-paper insulation is more significant than that of stearic acid, which is shown in the stationary part of polarization current end and the initial part of depolarization current. The depolarization current decay rate increases with the increase of initial acid value, and the depolarization current decay rate of formic acid sample is higher than that of stearic acid sample. Compared with the insulation resistance and absorption ratio, the polarization depolarization current can reflect the insulation state of different aging stages of oil-paper insulation more comprehensively and effectively. According to the moisture distribution of oil-paper insulation after thermal aging, the acid value in insulating oil is taken as the characteristic parameter to characterize the thermal aging degree of oil-paper insulation, which is used to describe quantitatively the effect of aging on moisture distribution. The variation of water saturation solubility with aging degree in insulating oil was studied. Based on the Freundlich isothermal adsorption equation, the water content in insulating paper and the moisture content in insulating oil are derived by introducing the translation factor m, which varies with acid value in insulating oil, and the quantitative relationship between water saturation solubility in oil and acid value and ambient temperature in oil is derived. The quantitative relationship between acid value and temperature in oil was studied, and the relationship between temperature and adsorption equilibrium constant c and coefficient n was studied. The application of the above research results can more accurately and effectively evaluate the moisture content in the insulator paper with different aging degree, which has important engineering application value to the transformer in actual operation.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM411
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