基于灰色关联分析的变压器油纸绝缘状态评估研究

发布时间：2018-03-20 14:11

本文选题：油纸绝缘　切入点：聚合度　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：电力系统的安全、稳定离不开各种高压设备的可靠运行,其中,油浸式电力变压器是最为重要的高压设备之一。油浸式变压器的整体寿命主要取决于其内部油纸绝缘的老化状况。变压器在运行过程中会受到电、热、机械等应力,致使油纸绝缘发生老化。油纸绝缘在老化过程中的介电响应结果变化不一,关于其老化程度和水分含量的时域介电特征量虽已有很多,但是这些特征量只能表征油纸绝缘整体的绝缘状态,且无法区分老化程度和水分含量的影响。得到能分别表征绝缘纸和绝缘油状态的特征量,并结合算法对油纸绝缘进行状态评估是亟须解决的重要问题。本文对老化不同天数的油纸绝缘试样进行了极化/去极化电流法试验,提出以稳态油老化电量和稳态油纸界面极化电量作为变压器绝缘油与油纸界面极化的老化特征量,并提取绝缘纸时域介电谱峰值和峰值时间作为绝缘纸老化特征量,最后通过现场试验验证了以上述特征量分别表征油纸绝缘老化状态的可行性。稳态油老化电量随老化时间的增加而增大,两者间存在线性拟合关系,稳态油老化电量可以表征油中偶极子转向极化强度;绝缘纸时域介电谱峰值及对应时间分别代表了其内部因纤维素裂解引起的界面极化强度和响应速度,其中时域介电谱峰值和聚合度之间具有指数负相关关系;稳态油纸界面极化电量随老化时间增加而增大,两者间存在线性拟合关系,稳态油纸界面极化电量可以表征油纸界面极化强度。本文通过热老化和吸潮试验,得到了老化程度、水分含量各不相同的若干油纸绝缘试样,然后在分析极化/去极化电流曲线变化规律的基础上,提出油纸绝缘最大时间常数支路系统极点作为油纸绝缘状态特征量。水分含量对于油纸绝缘时域介电检测结果影响规律与老化类似,含水量上升会导致试样的极化/去极化电流电流往左上方平移,极化电流的初值和稳定值都增大,且达到稳定的时间缩短。系统极点对水分含量和老化程度都很敏感,可作为油纸绝缘状态特征量,但其无法区分两者的影响。介绍了灰色关联分析理论的诞生、发展与现状,选择最为合适的邓氏关联度分析作为油纸绝缘状态量的整合算法。介绍了现场变压器介电检测试验注意事项,整合油纸绝缘时域介电特征量得到其参考向量和规范化后的参考向量。最后计算并对比关联度来对变压器油纸绝缘状态进行诊断,得到的诊断结果基本和实际运行经验符合。下一步可丰富试验条件,在参考状态中加入测试温度的影响或减小水分含量与老化程度的变化梯度,消除测试电极、纸板类型可能带来的误差,建立完备的状态参量数据库,内置在评估软件中,使评估结果更加精确。
[Abstract]:The security and stability of power systems can not be separated from the reliable operation of various high-voltage equipment, among which, Oil-immersed power transformer is one of the most important high-voltage equipments. The whole life of oil-immersed transformer mainly depends on the aging condition of oil-paper insulation inside it. The transformer will be subjected to electric, thermal, mechanical and other stresses during operation. The results of dielectric response of oil-paper insulation vary with each other during aging. Although there are a lot of time domain dielectric characteristics about the aging degree and moisture content of oil-paper insulation, However, these characteristics can only represent the insulation state of oil-paper insulation as a whole, and can not distinguish the influence of aging degree and moisture content. It is an important problem that must be solved to evaluate the state of oil-paper insulation with the algorithm. The polarization / depolarization current test of oil-paper insulation samples with different aging days has been carried out in this paper. In this paper, the aging characteristic of transformer insulation oil and oil-paper interface is proposed, and the peak value and time of time domain dielectric spectrum of insulator paper are extracted as the aging characteristic quantity of insulator paper. Finally, the feasibility of characterizing the aging state of oil-paper insulation with the above characteristic quantities is verified by field tests. The steady state aging power of oil increases with the aging time, and there is a linear fitting relationship between the two. The steady-state oil aging can characterize the polarization intensity of dipoles in oil, the peak value of dielectric spectrum in time domain and the corresponding time of insulator paper represent the interfacial polarization intensity and response speed caused by cellulose cracking, respectively. Among them, there is an exponential negative correlation between the peak value of time domain dielectric spectrum and degree of polymerization, and the polarization charge of steady state oil-paper interface increases with aging time, and there is a linear fitting relationship between them. The polarization intensity of oil-paper interface can be characterized by the polarization quantity of steady state oil-paper interface. In this paper, some oil-paper insulation samples with different aging degree and moisture content are obtained by means of thermal aging and moisture absorption tests. Then, on the basis of analyzing the variation law of polarization / depolarization current curve, The maximum time constant branch system pole of oil-paper insulation is proposed as the characteristic quantity of oil-paper insulation state. The effect of moisture content on the time domain dielectric detection results of oil-paper insulation is similar to that of aging. The increase of water content will cause the polarization / depolarization current to be shifted to the upper left, the initial value and the stable value of the polarization current will increase, and the time to reach the stabilization will be shortened. The system poles are sensitive to the moisture content and the degree of aging. It can be used as the characteristic quantity of oil-paper insulation state, but it can not distinguish the influence of the two. The birth, development and present situation of grey relational analysis theory are introduced. The most suitable Dunn correlation analysis is selected as the integration algorithm of oil-paper insulation state quantity. The matters needing attention in the field transformer dielectric testing test are introduced. The reference vector and the normalized reference vector are obtained by integrating the time domain dielectric characteristic of oil-paper insulation. Finally, the correlation degree is calculated and compared to diagnose the oil-paper insulation state of transformer. The diagnostic results obtained are basically consistent with the actual operation experience. The next step is to enrich the test conditions, add the influence of test temperature to the reference state or reduce the gradient of water content and aging degree, and eliminate the test electrode. The possible errors caused by paperboard type, the establishment of a complete database of state parameters, built into the evaluation software, to make the evaluation results more accurate.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM855

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