【作者】 樊利国；

【导师】 荆洪阳；

【作者基本信息】 天津大学 ， 材料加工工程， 2005， 硕士

【摘要】 电的发明与使用,是人类历史上一场伟大的革命,不但大大方便了人民的日常生活,而且促进了其他领域连锁式的飞跃发展,推动着人类向更深领域探索与进军。电力绝缘子是变电站和传输线路的重要组成部分,主要作用是将导线连接在支架上,起绝缘、机械连接和支撑作用。输电线路可靠性运行的关键是悬式绝缘子的质量。我国70年代初大量投入使用的绝缘子,距今已有30多年的历史,由于近年来频繁发生的断裂事故,给国民经济生产带来无法估量的损失,成为电力部门最大的隐患。电力瓷绝缘子一般由铸铁法兰、胶装水泥和瓷体胶装而成,水泥夹在法兰和瓷体之间,膨胀受到约束,在瓷绝缘子中产生应力。统计表明,法兰口附近是瓷绝缘子引发裂纹并最终导致断裂的多发部位。为了降低水泥膨胀所引起的膨胀应力,延长瓷绝缘子的使用寿命,在胶装时一般在瓷体和水泥之间涂一层沥青缓冲层。电瓷材料属于典型的脆性材料,裂纹扩展的速度相当快,因此需定期对其进行无损检测,防止破坏。无损检测的目的是及时将内部的微观缺陷检测出来,特别是微观裂纹,以便预测其使用寿命或及时更换不良绝缘子,消除事故隐患。但由于胶装部位结构的复杂性,采用常规检测方法很难达到满意的检测效果。本文首先从陶瓷材料的性能特点和对绝缘子的性能要求入手,对电力瓷绝缘子的劣化原因进行了深入的分析:瓷绝缘子的断裂是多种因素相互作用的综合结果,除了制造加工过程中引入的缺陷以及运行过程中承受的自身重力和机械载荷外,环境因素也是不可忽略的一个因素。而胶装时缓冲层的厚度不够或者在以后的运行过程中缓冲层的弹性失效老化,使胶装剂产生的膨胀应力无处释放是导致瓷绝缘子断裂的主要原因。采用有限元法ANSYS分析软件对该部位的温度结构应力进行了分析,分析结果表明沥青缓冲层显著降低了胶装部位的应力大小,改变了该部位的应力分布。然后通过分析找出承受最大应力的部位,采用断裂力学计算出了该应力下的最小临界裂纹尺寸,为瓷绝缘子无损检测提供了一定的理论指导。对超声爬波检测绝缘子进行了理论分析与试验研究,分析了爬波探头检测瓷绝缘子的可行性,加工制作了爬波检测专用试块,通过试验对比了单晶爬波探头与双晶爬波探头检测瓷绝缘子的优缺点,为棒形瓷绝缘子胶装部位的无损检测提供了一种新的方法。更多还原

【Abstract】 The invention and application of electricity are a great revolution in human’s history, which not only create more facilities for human’s daily life, but also promote a chain of development in other fields, impel human being to explore further. Electrical insulator is one of the important parts in transformer substation and transmission line, plays a role in connecting the lead with the bracket, as a kind of electrical insulator, mechanical connection and support. The key to safe operation of electrical transmission line is the quality of suspension insulator. Frequent fracture accidents have already happened to a great deal of insulators used in our country from the beginning of 1970’s, with about 30 years history from then on, which brought our country economy and production out a great deal of loss, being a great hidden trouble to electrical department. Electrical porcelain insulator (EPI) is mostly made up of cast-iron flange, electrical porcelain and cement, the cement is gripped between the cast-iron flange and electrical porcelain, restrained when expansion, then produces stress on electrical porcelain insulator. It is numerical stated that the site near the flange oral part is the main position where the crack initiate and EPI rupture ultimately. In order to reduce the expansion stress resulting from cement’s expansion and prolong the life-span of porcelain insulator, a thin asphalt buffer layer is coated between the porcelain and the cement. Electrical porcelain is a kind of classical brittle materials; the velocity of crack’s growth is quite rapid so it’s very important to prosecute non-destructive testing termly to avoid damage. The main aim of non-destructive testing about EPI is to detect inner micro-flaws as soon as possible, especially micro-crack, in order to forecast the length of life or replace the bad insulator, and eliminate hidden trouble resulting in accident. But because of structural complexity, the common examining measurement can’t be used to get satisfying result. In this paper, the porcelain material’s features are discussed first, and then the cause of EPI’s deterioration is discussed: the failure of EPI is resulted from multiform factors which interact, except flaws which are taken in the process of manufacture, machining and self gravitation,mechanical load which are endured in the course of operation, environmental factor can’t be ignored. It is the prime reason that the buffer layer’s thickness isn’t thick enough in the process of cementing or the buffer layer loses its elasticity in the course of operation, which results in nowhere does swelling stress’s release produced by the cement. FEM analysis software-ANSYS is used to analyze temperature-structural stress in this location, and the analysis shows that the stress is reduced and changed by the asphalt buffer layer, and then the maximum stress is found, the minimum critical crack size is computed in the help of fracture mechanics, which offers guidance for non-destructive testing about the EPI. The examination about the EPI with the help of creeping wave probe is discussed not only in theory but also in experiment. The feasibility of examining EPI with the help of creeping wave is analyzed, and then the special test block is made, through experiment the advantage and disadvantage between the single crystal creeping wave probe and the twin crystal creeping wave probe with examining EPI are compared, which provide a kind of new means for non-destructive testing about the EPI.更多还原