多场耦合作用硅橡胶电树枝产生机理研究

发布时间：2019-06-18 19:28

【摘要】：高压电力电缆输电线路运行的安全可靠性受很多因素的影响,硅橡胶附件的电树枝老化问题是影响因素之一。这是因为电缆的附件结构非常复杂,界面很多,在受热或挤压过程中易发生应力集中现象,且预制式的电缆附件在生产和运输的过程易造成缺陷,这些因素都将在一定程度上促进电树枝的生长。高压直流输电线路在倒闸操作、换流和雷击的情况下,易形成脉冲冲击,恶化电缆附件的工作环境。另外,在直流电缆的输电过程中,较强的电流导致导体周围存在磁场,将影响绝缘材料的电树枝老劣化情况。在严寒地区,电缆工作环境进一步恶化,硅橡胶的形态也将发生改变。电极结构将对电树枝的引发生长和击穿过程产生影响,本文采用的是针-板类型电极结构。在本文中将对不同的实验条件如:脉冲电压,磁场环境和低温环境等多场耦合条件下电树枝的生长特性进行研究,探讨其老化的规律。主要的研究内容和结论如下:1.脉冲电压下,典型的硅橡胶中电树枝结构分为三种,即:树枝状、丛林状和树枝-藤枝混合状类型的电树枝。本文分别讨论了不同脉冲幅值、脉冲频率、脉冲极性下,电树枝的引发、生长和击穿等方面的特性。通过分析电树枝的类型、生长长度、起始概率和击穿特性等参数,得到脉冲冲击电压对硅橡胶试样的电老化特性的影响规律。2.通过施加脉冲电压和磁场环境,研究了这两种相互作用的场条件下脉冲冲击电压对硅橡胶中电树枝结构的影响,在此特定的场条件下,得到的电树枝结构均为树枝状。分别讨论了磁场环境下不同脉冲幅值、脉冲极性对电树生长特性的影响,并进一步分析了不同磁通密度对其生长特性的影响。3.低温寒冷环境下,对硅橡胶材料中的电树枝的老化特性进行了研究,讨论了该环境对硅橡胶试样物理结构的影响。分析发现,在温度降低的过程中,硅橡胶试样经历不同的相态变化,即高弹态、结晶态、玻璃态。在硅橡胶结晶的变化过程中,存在结晶区和不定型区,结晶体内部比较纯净,分子链排列紧密;不均匀结晶的边缘容易形成微孔和应力集中。进入玻璃态这一特殊的相态类型以后,结晶体的结构呈现如下特点,即排列紧密、分子链的活动性进一步减少。低温寒冷这一严酷环境,将对电树枝的生长特性产生严重影响。
[Abstract]:The safety and reliability of transmission line operation of high voltage power cable is affected by many factors, and the aging of electrical branches of silicone rubber accessories is one of the influencing factors. This is because the attachment structure of the cable is very complex, there are many interfaces, the stress concentration phenomenon is easy to occur in the process of heating or extrusion, and the prefabricated cable accessories are easy to cause defects in the process of production and transportation, these factors will promote the growth of electrical branches to a certain extent. Under the condition of switching operation, converter and lightning strike, HVDC transmission line is easy to form pulse impact and deteriorate the working environment of cable accessories. In addition, in the transmission process of DC cable, the strong current leads to the existence of magnetic field around the conductor, which will affect the deterioration of the electrical branches of the insulation material. In the severe cold region, the working environment of the cable will deteriorate further, and the shape of silicone rubber will also be changed. The electrode structure will affect the growth and breakdown process of the electric branch. In this paper, the needle-plate electrode structure is used. In this paper, the growth characteristics of electric branches under different experimental conditions, such as pulse voltage, magnetic field environment and low temperature environment, will be studied, and the aging law will be discussed. The main research contents and conclusions are as follows: 1. Under pulse voltage, the typical electric branch structure in silicone rubber can be divided into three types: dendritic, jungle and branch-rattan branch mixed type. In this paper, the characteristics of electrical branch initiation, growth and breakdown under different pulse amplitude, pulse frequency and pulse polarity are discussed respectively. By analyzing the types of electrical branches, growth length, initial probability and breakdown characteristics, the effect of pulse impulse voltage on the electrical aging characteristics of silicone rubber samples was obtained. 2. By applying pulse voltage and magnetic field environment, the effect of pulse impulse voltage on the electric branch structure in silicone rubber under the condition of these two interaction fields is studied. Under this specific field condition, the obtained electrical branch structure is dendritic. The effects of different pulse amplitudes and pulse polarity on the growth characteristics of electric trees in magnetic field environment were discussed, and the effects of different flux densities on the growth characteristics were further analyzed. The aging characteristics of electrical branches in silicone rubber materials were studied in low temperature and cold environment, and the effect of the environment on the physical structure of silicone rubber samples was discussed. It is found that the silicone rubber samples undergo different phase changes in the process of temperature decrease, that is, high elastic state, crystal state and glass state. In the process of crystallization of silicone rubber, there are crystallization zone and amorphous region, the crystal is pure and the molecular chain is arranged closely, and the edge of uneven crystallization is easy to form micropores and stress concentration. After entering the special phase type of glass state, the structure of the crystal shows the following characteristics, that is, the arrangement is close and the activity of molecular chain is further reduced. The harsh environment of low temperature and cold will have a serious impact on the growth characteristics of electric branches.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM75

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