基于油中甲醇含量的油纸绝缘老化状态评估方法研究

发布时间：2018-04-10 06:13

  本文选题：纤维素裂解　切入点：油中甲醇含量　出处：《西南交通大学》2017年硕士论文

【摘要】：变压器油纸绝缘系统中,绝缘纸的机械强度取决于纤维素链的平均长度,聚合度DP作为反映纤维素分子B-D-吡喃葡萄糖环数量的参数是评估绝缘纸老化程度最直接的测量手段。而在变压器实际运行中,聚合度不具备直接测量的条件,一般通过分析研究绝缘纸组分老化降解的油溶性特征产物来间接反映变压器内绝缘的老化状态。因为传统的基于油中气体含量和油中糠醛含量的绝缘状态评估方法或多或少的存在一些缺陷,且随着检测技术和仪器的不断进步与成熟,寻找更为准确有效的老化产物作为油纸绝缘状态评估的参数指标更具实际意义。本文研究了油纸绝缘老化产物甲醇与绝缘纸纤维素裂解之间的特性关系,在实验室中设计了不同温度和初始水分含量下的油纸绝缘系统老化试验,引入了化学分析中先进的顶空进样气相色谱-质谱联用法对老化后的油中甲醇含量进行测量。以绝缘纸聚合度为参量建立老化动力学模型,引入Mark-Houwink方程,得到不同老化条件下纤维素的裂解速率,分别提取纤维素裂解及甲醇生成过程中相应的特征参数,进行Arrhenius参数拟合分析。结果表明:老化温度的升高可以提高甲醇的生成速率与纤维素分子链的裂解速率,但对老化产物向生成甲醇方向发展的影响无明显规律可循;水分和氧气的存在催化了纤维素裂解产物向生成甲醇的方向转变,纤维素水解的中间产物产生甲醇的几率较小,甲醇主要来自于纤维素氧解的中间产物,且氧解中间产物进一步反应生成甲醇需要水的协同作用,在此基础上,设计中间产物的老化试验,对该结论提供了一定的证明。在纤维素裂解产生甲醇特性研究的基础上,通过建立甲醇与聚合度的关系模型,对实验室条件下的油纸绝缘系统进行寿命预测,结果表明绝缘纸中水分含量每增加0.5%,绝缘的寿命减半;老化温度每上升8-10℃,绝缘纸寿命减半;与众多研究相吻合。试验研究了甲醇在油纸系统中的稳态分布情况,结果显示正常的老化温度下,纤维素裂解产生的甲醇很大一部分存在于绝缘纸中。研究为基于油中甲醇含量的变压器状态评估体系的建立提供了 一定的参考。
[Abstract]:In transformer oil-paper insulation system, the mechanical strength of insulator paper depends on the average length of cellulose chain. The degree of polymerization DP is the most direct measurement method to evaluate the aging degree of insulator paper as the parameter reflecting the number of cellulose molecule B-D- glucose ring.However, in the actual operation of transformer, polymerization degree does not have the condition of direct measurement. Generally, the aging state of insulation in transformer is indirectly reflected by analyzing and studying the oil-soluble characteristic products of aging degradation of insulator paper components.Because the traditional methods based on gas content in oil and furfural content in oil have some defects, and with the development and maturity of detection technology and instruments,It is of practical significance to find more accurate and effective aging products as parameter indexes for evaluation of oil-paper insulation status.In this paper, the characteristic relationship between methanol, the aging product of oil-paper insulation, and cellulose cracking of insulator paper was studied. The aging test of oil-paper insulation system was designed at different temperature and initial moisture content in laboratory.The advanced headspace injection gas chromatography-mass spectrometry (GC / MS) method was used to determine the methanol content in aged oil.The aging kinetic model was established with the polymerization degree of insulator paper as a parameter. The Mark-Houwink equation was introduced to obtain the decomposition rate of cellulose under different aging conditions, and the corresponding characteristic parameters in the process of cellulose cracking and methanol generation were extracted respectively.Arrhenius parameter fitting analysis was carried out.The results show that the increase of aging temperature can increase the rate of methanol formation and the cleavage rate of cellulose molecular chain, but the effect of aging products on the direction of methanol formation is not obvious.The presence of water and oxygen catalyzes the conversion of cellulose pyrolysis products to methanol. The probability of methanol production from the intermediate products of cellulose hydrolysis is relatively small, and methanol is mainly derived from the intermediate products of cellulose oxylysis.On the basis of this, the aging test of the intermediate product was designed to prove this conclusion.On the basis of the study on the characteristics of methanol produced by cellulose cracking, the life of oil-paper insulation system under laboratory conditions was predicted by establishing the relationship model between methanol and polymerization degree.The results show that with the increase of moisture content in insulator paper, the insulation life is halved, and the aging temperature increases from 8 鈩，

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