發(fā)布時間：2018-07-24 19:43

【摘要】：油浸式電力變壓器是電力系統(tǒng)輸變電環(huán)節(jié)的核心設(shè)備,其內(nèi)部的油紙復(fù)合絕緣系統(tǒng)決定了變壓器的安全運(yùn)行和電力的可靠供應(yīng)。有機(jī)酸和水分是油紙絕緣系統(tǒng)最重要的兩種老化產(chǎn)物,但目前不同種類有機(jī)酸的性質(zhì)、有機(jī)酸對油紙絕緣熱老化的影響特性、有機(jī)酸與不同檢測方法特征參數(shù)之間的關(guān)系以及不同老化階段油紙絕緣中的水分分布情況還有待深入研究。根據(jù)五種不同有機(jī)酸的性質(zhì),選取甲酸和硬脂酸作為研究對象。對比分析了甲酸和硬脂酸在油紙絕緣系統(tǒng)中的溶解分布特性,并通過不同試樣絕緣紙聚合度隨熱老化的變化規(guī)律研究了甲酸和硬脂酸對絕緣紙降解速率的影響。基于零階動力學(xué)模型得到了甲酸和硬脂酸初始酸值與絕緣紙平均降解速率的關(guān)系。研究結(jié)果表明：甲酸大部分被絕緣紙吸附,硬脂酸大部分溶解在絕緣油中；絕緣紙平均降解速率隨酸值增加呈線性形式增長；甲酸對絕緣紙的平均降解速率是硬脂酸的8倍左右,甲酸酸值達(dá)到0.1mgKOH/g就會對油紙絕緣熱老化起到明顯的加速作用,因此在實(shí)際案例的研究分析中,需要特別考慮甲酸等低分子強(qiáng)極性酸對油紙絕緣熱老化的加速作用。根據(jù)電介質(zhì)響應(yīng)原理推導(dǎo)了極化／去極化電流的通用表達(dá)式,研究了油紙絕緣在甲酸和硬脂酸作用下熱老化的極化去極化電流特性,并與相應(yīng)試樣的絕緣電阻和吸收比進(jìn)行了對比分析。研究結(jié)果表明：PDC曲線可以反映油紙絕緣的熱老化情況,甲酸對油紙絕緣熱老化反應(yīng)的催化作用比硬脂酸顯著,表現(xiàn)在極化電流末端平穩(wěn)部分和去極化電流起始部分；去極化電流衰減速率隨初始酸值的升高而加快,且含甲酸試樣的去極化電流衰減速率大于含硬脂酸的試樣。相比于絕緣電阻和吸收比,極化去極化電流能夠更全面、有效地反映油紙絕緣不同老化階段的絕緣狀態(tài)。根據(jù)油紙絕緣熱老化后的水分分布情況,提出將絕緣油中酸值作為表征油紙絕緣熱老化程度的特征參數(shù),用以定量描述老化對水分分布的影響。研究了絕緣油中水分的飽和溶解度隨著老化程度的變化規(guī)律。引入隨絕緣油中酸值變化的平移因子m,推導(dǎo)了油中水分飽和溶解度與油中酸值、環(huán)境溫度的定量關(guān)系；基于Freundlich等溫吸附方程,推導(dǎo)了絕緣紙中水分含量與絕緣油中水分含量、油中酸值、溫度的定量關(guān)系,并研究了吸附平衡常數(shù)c和系數(shù)n與溫度的對應(yīng)關(guān)系。應(yīng)用以上研究成果可以更準(zhǔn)確有效地評估不同老化程度的絕緣紙中水分含量,對實(shí)際運(yùn)行中的變壓器具有重要的工程應(yīng)用價值。
[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.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TM411

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