【作者】 刘勇；

【导师】 杜伯学；

【作者基本信息】 天津大学 ， 高电压与绝缘技术， 2009， 博士

【摘要】 绝缘子闪络严重危害电力系统及其输变电设备的安全运行,因此积极开展绝缘子运行状态的检测研究,对预防闪络事故,提高电网运行可靠性具有重要意义。本文基于泄漏电流检测绝缘子运行状态的研究现状,在人工污秽试验方法的基础上,将混沌理论的递归分析技术应用于泄漏电流的特征分析,结合绝缘子表面动态变化和闪络过程,旨在研究及时有效的绝缘子状态检测与闪络预测方法。首先针对绝缘子在灾害性浓雾天气下容易发生的闪络事故,通过观察闪络现象与过程,对闪络发展各个阶段的泄漏电流进行时间序列的混沌特征判别,计算和分析了Lyapunov指数、分形维数、功率谱密度、吸引子相图以及Poincare截面,论证了泄漏电流具有混沌特征,阐明了泄漏电流递归分析方法应用于绝缘子泄漏电流非线性特征分析的可行性。在建立浓雾环境下泄漏电流与绝缘子闪络过程对应关系的基础上,运用小波变换方法提取闪络发展各个阶段泄漏电流的频率分布与特征,通过相空间重构技术将频率分量的时间序列拓展至m维空间,根据递归分析技术得到各个频率分量发展变化的递归图及递归定量指标,提出了泄漏电流高频分量可以有效反映绝缘子表面放电的非线性特征,提高了检测与预测的准确性。为了研究大气环境因素对绝缘子运行状态的影响,在人工污秽试验基础上开展了污秽程度、环境温度和相对湿度等诸多因素下绝缘子的状态检测研究,提取与绝缘子表面动态变化密切相关的泄漏电流特征量,在论证当前特征分析方法局限性的基础上,根据泄漏电流递归图拓扑结构及其定量指标有效揭示了环境参数对外绝缘状态的影响程度与机理,建立了基于泄漏电流递归分析的绝缘子运行状态检测方法。最后,基于绝缘子雾凇闪络现象的观察与泄漏电流的递归分析,检测并研究了绝缘子在雾凇环境下的闪络过程与机理,提出泄漏电流递归图能够定性表征绝缘子雾凇闪络过程中表面放电特征,并且递归定量分析法进一步增强对闪络过程的监测分析。泄漏电流递归分析法为绝缘子运行状态提供了一种可视化的检测方法,递归图拓扑结构及其定量指标有效反映了绝缘子表面状态,揭示了表面放电的非线性特征及发展过程,提高了绝缘子状态检测的有效性和准确性。更多还原

【Abstract】 Generally, the flashover accidents of outdoor insulators can cause serious influence on the operation stability of power system and its equipments. Therefore, it is significant to evaluate and monitor the insulator performance for the prevention of the flashover accidents and the improvement of the power system reliability. In this paper, based on the present investigation of leakage current for evaluating and monitoring outdoor insulators, the recurrent plot technique is proposed to analyze the characteristics of leakage current through the artificial contamination experiments. In accordance with dynamic behaviors and flashover process on the insulator surface, the results obtained aim to investigate the effective methods for performance evaluation and flashover protection of outdoor insulators.In order to determine whether the leakage current during the flashover process has chaotic characteristics, the experiments simulating the insulator flashover in heavy fog were carried out and the chaotic analysis method of time series was selected to analyze the non-linear properties of leakage current in accordance with the flashover process. Lyapunov exponent, fractal dimension, power spectral density, chaos attractor, as well as Poincare map were calculated to reveal that the variation of leakage current during the flashover process has chaotic characteristics. The results demonstrate the feasibility of using the recurrent plot technique for the non-linear characteristic analysis of leakage current.Based on the corresponding relationship between the leakage current and the flashover process in heavy-fog conditions, the wavelet transform technique was applied to decompose the leakage current into different frequency components. The temporal series of the extracted components are extended to m-dimensional phase space by using a phase-space reconstructed method. The recurrent plot is obtained to show that the topological structure of the high-frequency components is prominent to identify non-linear properties of discharge activities. The dynamic behaviors on the insulator surface are graphically illustrated on the rectangular block structures with higher density of points. Based on the analysis of the high-frequency components, the quantitative indicators of recurrent plot are obtained to reflect the underlying mechanism of flashover process. The results obtained indicate that the recurrent plot technique is helpful to improve the accuracy of insulator evaluation. Considering the effect of wet-contaminated environment on the insulator performance, the artificial contamination experiments were conducted to investigate the performance evaluation in multi-environmental factors including contamination degree, ambient temperature and relative humidity. The characteristics of leakage current were extracted to reflect dynamic behaviors on the insulator surface. Based on the limitation of the present analysis method, the topological structure and quantitative indicator of recurrent plot of the leakage current were obtained to reflect the influence mechanism of environmental factors on the outdoor insulation. The recurrent plot method was established for the relationship between the leakage current and the insulator performance.Finally, the phenomena of the rime flashover were observed and the non-linear characteristics of leakage current were analyzed. The experiments are helpful to monitor and reveal the process and mechanism of insulator flashover in rime conditions. The results show that the recurrent plot of leakage current can qualitatively reveal the discharge characteristics during the rime flashover process, and the further quantitative analysis enhances the monitoring and the understanding of the flashover mechanism.In conclusion, the recurrent plot technique gives a visible monitoring method for outdoor insulators to monitor the flashover process and evaluate the operating performance. The topological structure of recurrent plot and its quantification indicators can effectively represent the surface performance and further reveal the characteristics and state transition of surface discharges during the flashover process. Therefore, the recurrent plot analysis of leakage current is an effective method for the insulator monitoring system.更多还原