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1、分类号 TM215.1 密级 UDC 学号 3104162008 聚合物水树枝化的试验方法及规律研究学位申请人： 王 乐 指导教师： 曹晓珑 教授 学科专业： 电气工程 学位类别： 工 学 2007年5月硕士学位论文聚合物水树枝化的试验方法及规律研究申请人：王乐学科（专业）：电气工程指导教师: 曹晓珑 教授2007年5月Study on Test Method and Behaviors of Water Trees in PolymerThesis Submitted toXian Jiaotong UniversityIn partial fulfillment of the requir
2、ementfor the degree ofMaster of Engineering ScienceByWang Le(Electrical Engineering)Supervisor: Prof. Cao XiaolongMay 2007目 录论文题目：聚合物水树枝化的试验方法及规律研究学科专业：电气工程申请人：王乐指导教师：曹晓珑 教授摘 要交联聚乙烯（XLPE）电缆以其优异的性能广泛应用于电网之中。但随着早期敷设的XLPE电缆绝缘出现水树枝老化，导致在运行中的XLPE电缆绝缘击穿事故不断发生。因此，研究聚合物水树枝老化现象和外界因素对水树枝生长的影响，无论是对聚合物老化机理的认识，或
3、是对电缆的安全运行都有着重要的意义。近年来，有关研究人员针对XLPE电缆绝缘层中水树枝引发的机理给出了多种理论模型，对水树枝发展的规律也有很多的报道。目前，在我国还没有统一的进行水树枝老化试验的国家标准，导致不同实验室的研究结果差异较大，不具有可比性。本文参考IEC TS61956标准“评定绝缘材料中水树枝化的试验方法”的征询意见稿设计了一种杯状电极装置，对低密度聚乙烯（LDPE）和聚甲基丙烯酸甲酯（PMMA）两种片状聚合物绝缘材料进行水树枝老化方法的验证性试验，为我国制定水树枝老化试验的国家标准提供了实验依据，并据此编写了水树枝试验方法的国家标准征询意见稿。按照建立的水树枝老化试验装置和方法
4、标准，本文对低密度聚乙烯和聚甲基丙烯酸甲酯两种固体片状材料进行了水树枝老化规律的试验研究，重点研究了低密度聚乙烯材料中水树枝引发和发展的影响因素和规律，包括盐溶液的浓度对低密度聚乙烯中水树枝形态的影响，老化时间、外施电压频率、盐溶液的电容率与水树枝生长速度的关系。同时，文章对水树枝的自愈现象进行了试验和讨论。本文还在同等条件下对聚甲基丙烯酸甲酯进行了水树枝老化试验，发现与低密度聚乙烯相比，聚甲基丙烯酸甲酯更难于生长水树枝，我们对这一现象产生的原因进行了分析。试验表明，水针尖曲率半径的微小差异会导致水树枝生长速度明显不同，这也是本文试验误差的主要来源。关 键 词：水树枝；低密度聚乙烯；试验方法；
5、规律研究论文类型：应用研究Title: Study on Test Method and Behaviors of Water Trees in PolymerSpeciality:Electrical EngineeringApplicant:Wang LeSupervisor:Prof. Cao XiaolongABSTRACTXLPE cable has been used in power grid in China for many years for its excellent performance. But with the water tree degradation occ
6、urring in the XLPE cables, which were put into use early, more and more cable insulation breakdown accidents happened. Consequently, study on the water treeing phenomenon in polymeric materials and the influence of external conditions is of great significance, either to understand the mechanism of p
7、olymer aging or to safely operate the power cable. In the recent years, researches in the relative research fields have raised many academic models to explain the mechanism of water treeing growth in the insulation layer of XLPE cable. Lots of papers have also been published, focusing on the growing
8、 behaves of water trees.Till now, the standard for the test of water treeing in insulating materials has not been established in our country. As a result, test results in different laboratories vary largely. In this paper, a new kind of electrode equipment was designed according to IEC TS61956 Stand
9、ard, Methods of Test for the Evaluation of Water Treeing in Insulating Material. With this equipment, proving test of this standard was carried out on two kinds of materials, low-density polyethylene (LDPE) and polymethyl methacrylate (PMMA). Our test provided experimental base for the establishment
10、 of water treeing test standard method in China, and helped us to compose the draft of the standard file.Based on the established standard and the recommended electrode equipment, water treeing test was carried out on LDPE and PMMA, in order to study the behaves of water trees propagation. The study
11、 emphasis was put on the influence factors on the water trees initiation and growth in LDPE. For example, we studied the influence of saline solution concentration on the forms of the water trees in LDPE. The relationship between water tree growth speed and its influence factors, such as aging time,
12、 frequency of electrical field, and relative permittivity, was studied in this paper. Meanwhile, the water tree self-healing phenomenon was also examined and discussed. We found that PMMA was harder to grow water trees when it was put in the same condition as LDPE and the reason was discussed. The t
13、est also showed that the tiny difference in the curvature radii of the needles would result in large difference in water trees growth speed. It is the main source of the test error.KEY WORDS: Water tree; Low-density polyethylene; Test method; Study of behaviorTYPE OF THESIS: Application Research 47目
14、 录1 绪论11.1 水树枝的危害及研究意义11.2 水树枝化研究的现状21.2.1 水树枝引发和生长的研究现状31.2.2 抗水树枝电缆料的研制现状31.2.3 电缆中水树枝老化程度检测技术发展状况41.3 本文的研究任务52 水树枝试验的依据72.1 水树枝的定义、分类及特征72.2 影响水树枝生长的因素92.3 水树枝的生长过程112.4 水树枝的生长机理122.4.1 水树枝的Maxwell应力引发模型及其长度计算132.4.2 水树枝的化学反应引发模型142.4.3 溶液中的杂质离子对水树枝生长的催化作用163 水树枝试验方法的确定193.1 电极装置的设计193.2 试验材料的选取
15、203.3 试验参数的确定203.3.1 试验条件的选取203.3.2 针尖处电场强度的计算213.4 试验步骤233.4.1 针的选取233.4.2 试样制备233.4.3 电气线路243.4.4 水树枝的观察243.5 本章小结244 试验结果与分析264.1 NaCl溶液浓度对材料树枝化的影响264.2 NaCl溶液的相对电容率与水树枝长度的关系274.2.1 工频下的试验结果274.2.2 200Hz的试验结果294.3 老化时间与水树枝长度的关系304.4 电场频率对水树枝生长的影响324.5 关于水树枝自愈现象的讨论334.6 材料的特性对水树枝生长的影响384.7 针尖的曲率半径对水树枝
