【作者】 董典帅；

【导师】 杜伯学；

【作者基本信息】 天津大学 ， 高电压与绝缘技术， 2008， 博士

【摘要】 聚合物绝缘材料有着特殊的电气破坏现象:其表面在特定条件(潮湿与污秽)下会发生电痕劣化现象,并在周围产生更多的碳化物,形成碳化导电通路,甚至导致整个绝缘击穿。采用比漏电痕指数(CTI)方法评定材料的耐电痕性有很大的分散性,试验条件的略微改变都会对其产生较大影响,因此有必要对电痕劣化现象进行深入研究。耐电痕试验中采集的放电电流对分析聚合物材料的耐电性有重要作用,已有的文献主要通过计算放电量、进行频谱和功率谱分析等方法研究放电电流的内在特性。由于耐电痕劣化试验放电是一个非常复杂的过程,若仅考虑上述指标是不够科学的。研究放电电流的非线性特征量有助于理解放电过程的内在机理,这是由于:1)放电过程是一个非周期、非随机和非确定的复杂过程;2)经过小波变换去除工频信号的放电电流波形,其轮廓具有Mandelbrot所描述的分形体特征。本文运用递归图技术、递归定量分析方法、重构混沌吸引子、庞加莱截面法和计算分形维数、最大李雅谱诺夫指数等非线性指标,提供可视化(如混沌吸引子、递归图、庞加莱截面)或定量(如递归定量指标等)方法,揭示放电电流在m维相空间中的动力学特性。混沌状态被认为是局部放电和电树枝的最终形态,而电痕与混沌的关系并未有报道,本文对于耐电痕试验放电过程是否可以进入混沌状态,进行了不同层面的讨论,所得结果为:放电电流的最大李雅谱诺夫指数为正;放电电流的分形维数随着嵌入维数的增加逐渐达到饱和值;放电电流的递归图具有典型混沌信号的拓扑和细纹理结构;放电电流吸引子的庞加莱截面有大量成片的、有分形特征的不动点。由此可知耐电痕试验最终将进入混沌状态。聚合物绝缘材料越来越多的应用在各种辐射环境中,在强辐射线的照射下聚合物绝缘会发生一系列的化学变化,其中最主要的变化是分子链交联和降解反应,有必要对辐射条件下材料的耐电痕性能进行评定。辐射线对聚合物耐电痕性能的影响非常复杂,本文主要基于IEC60112耐电痕试验,运用递归图技术和递归定量分析等方法,对交联型和降解型聚合物进行耐电痕性评定。所得结果表明递归图方法可以将辐射剂量的影响,定性的展现在二维可视化图像中,而递归定量分析方法则量化了这种影响。尽管阻燃剂可以延迟材料的起始闪络电压和火的传播速度,但同样会影响材料的电气特性。关于阻燃剂对材料耐电痕性能影响的文献较少,本文主要讨论不同溴族阻燃剂剂量对聚合物材料耐电痕性能的影响。主要方法为分析放电电流的非线性特征,并测量材料的比漏电痕指数等。所得结果表明,递归图和分形维数等非线性指标评定阻燃剂剂量的影响同样有效。递归图等非线性方法对评定聚合电痕劣化不同阶段也是非常有效的,混沌吸引子的演化轨道、递归图的拓扑结构和分形维数的变化规律等,都和耐电痕试验的放电阶段有较好匹配。另外,本文同时对不同电压波形,如交、直流时,材料耐电痕性能进行非线性分析,所得结果表明非线性方法同样有效。更多还原

【Abstract】 Tracking failure is a dielectric breakdown phenomena occurring on polymer surfaces comprising carbonized conductive path, resulting in a permanent loss of the surface dielectric performance. Because the resulting comparative tracking index (CTI) has wide variation, an attempt has been made to evaluate the resistance to tracking more consistently. Numerous studies have been conducted to characterize the properties of discharge currents by calculating the discharge quantity or analyzing the power spectrum. However, discharge is a complicated process and reproducible results of the indices mentioned above are difficult to obtain. Studying the non-linear characteristics of the discharge current can assist in understanding the underlying mechanism of the process because: 1)the surface discharge process is complex and irregular; 2) after the power frequency is filtered, the platform outlines of the discharge waveform as first discussed by Mandelbrot. In this paper, recurrence plots (RPs), recurrence quantification analysis (RQA), fractal dimensions, largest Lyapunov exponent, chaos attractors and Poincarémaps, which can provide quantitative, qualitative, visualization description of statistics characteristic of the discharge current in m-phase space, are reconstructed or calculated to extract information from the discharge currents.It is found that the largest Lyapunov exponent of the discharge is positive, the fractal dimensions as a function of embedding dimension will saturate at a value, the recurrence plots shows the chaotic frame-work patterns, and the he Poincarémaps will have the chaotic characteristics. The results show that the discharge currents of the tracking test do exhibit chaotic behavior.Due to the widespread use of polymeric insulating materials in radiation environments, there is an increasing demand to evaluate the radiation effects on the surface dielectric characteristics of polymeric insulating materials. The resistance to tracking of polymer materials can be changed by gamma-ray radiation through altering the molecular structure. Because the radiation has complex effect on the molecular structure of polymer materials through mechanism like chain scission, cross-linking and oxidation, it is hard to demonstrate the effect on resistance to tracking. This paper presents the recurrence plot (RP) and recurrence quantification analysis (RQA) approaches to analyze the surface discharge of gamma-ray irradiated polymeric insulating materials based on the tracking test described in IEC60112. Recurrence plots of the discharge currents are derived. It is found that the resistance to tracking could be projected on a map as a function of the dosage of irradiation. The recurrence plots and recurrence quantification analysis are sensitive and give visual and quantitative methods for identification of the dosage of irradiation effects on the resistance to tracking.In order to satisfy the safety of fireproofing, the flame retardants are used in almost all polymer insulating materials. Although the flame retardant can hinder the fire from spreading, it may have negative influence on the electrical insulation. However, the research about the effect of flame retardant on the electrical insulation is very few. Consequently it is important to investigate the influence of the flame retardant on the dielectric strength. In order to assess the performance of the insulation degradation, the non-linear analysis methods are adopted in this research. The recurrence plot topological structures and fractal dimensions are studied. It has been shown that the methods are valid. For varied discharging stages, the attractors of discharge current show different characteristics in evolutionary tracks, the topological structure and grain direction of recurrence plots show significant differences, and the fractal dimensions of discharge current change obviously.更多还原