【作者】 武利会；

【导师】 司马文霞；

【作者基本信息】 重庆大学 ， 电气工程， 2003， 硕士

【摘要】 覆冰、低气压和污秽共存的复杂环境对电力系统的安全运行造成极大的威胁。到目前为止，对复杂环境中直流输电线路外绝缘特性的认识还远远不能满足电力工业发展的要求。随着水电资源的大规模开发，西部高寒、高湿及高海拔对输电线路外绝缘电气特性的影响将更加突出。因此，对复杂环境中绝缘子闪络特性的研究具有非常重要的工程应用价值和学术意义。为此，在国内外现有工作的基础上，通过大量的试验研究，本文主要研究了复杂环境中绝缘子的直流闪络特性及闪络机理。其结果有助于进一步了解低气压下覆冰绝缘子的闪络现象，并可为输电线路的设计和安全运行提供理论依据。本文的主要工作和结论如下：在人工气候室内，根据不同覆冰绝缘子正、负极性下的闪络试验结果，得出负极性电弧金属阴极的强电子发射能力造成了单片瓷、玻璃绝缘子及被冰凌桥接的合成绝缘子有较低负极性冰闪电压；正极性电弧金属阳极侧产生高电阻区所处位置的差异使得瓷和玻璃绝缘子串具有明显的极性效应；覆冰较少时，合成绝缘子表面出现数量较多的非极性电弧使合成绝缘子无极性效应。利用覆冰期内平均闪络电压的试验方法，对不同材质和结构的绝缘子在覆冰、低气压和污秽共存环境中的直流闪络特性进行了研究。试验结果表明，直流平均闪络电压随着海拔的升高、覆冰量的增加以及污秽度的增加而降低，且其特征指数与绝缘子结构、覆冰量、覆冰状态、污秽度等有关。通过对摄像机、数据采集系统及高压试验装置记录覆冰绝缘子表面闪络电弧的发展过程的试验结果进行理论分析得出：弧根周围空气的热电离导致了电弧的发展，静电场力对电弧的发展起到了加速作用，电击穿仅发生在闪络最终的跳跃阶段；通过测量闪络过程中的放电电压、泄漏电流、闪络时间、覆冰水电导率、电弧长度及电弧半径等参数，得到了不同阶段电弧（电弧起弧阶段、电弧发展阶段及完全闪络）的发展速度、临界电弧长度均随覆冰水电导率的增加而减小。进一步分析覆冰绝缘子的闪络过程可知：覆冰绝缘子存在二个不同的闪络路径，即沿冰层外部和内部，这是由于电弧热作用蒸发的Na原子进入弧柱的方式不同造成的。基于上面的试验结果和理论分析，本文最后提出了复杂环境中绝缘子的选择方法及绝缘子直流闪络电压的校正公式。更多还原

【Abstract】 The severe atmospheric environment of low atmospheric pressure at high altitude with pollution and icing has an important effect on the external insulation performance of transmission lines and threatens the reliability of a power system. But up to now, the study on DC transmission line’ external insulation in the severe atmospheric environment could not meet the requirement of electric power industry development. With the large-scale exploitation of hydroelectric resource in the West, the effects of severely cold, high humility and high altitude on the external insulation performance of overhead transmission line insulator will more and more server. Therefore, a systematic study of discharge performances of several kinds of insulators for the complex atmospheric environment has both a very important academic meaning and an engineering value. Upon existent theoretical and experimental results and based on a great of laboratory investigations carried out in Chongqing University, for the first time this paper studies systematically the insulators DC discharge performance and flashover mechanism of iced insulators in the complex atmospheric environment, which will contribute to the understanding of flashover phenomena observed on ice surface at low air pressure and provide the test and theoretical reference for HV and EHV transmission lines design and safety service. The main work and conclusion for this paper is as following:According to the flashover test results of several kinds of iced insulators under positive voltage and negative voltage, this paper obtained: for the single porcelain insulator, the single glass insulator and the composite insulator bridged completely by icicle, the metal cathode’s strong ability of emission electron is the primary reason that results in the lower negative flashover voltage; the position difference of the high resistance district in method anode side results in that porcelain insulator cluster and glass insulator cluster have an evident effect of polarity; when less ice and no icicle at the brim of the sheds, due to numerous non-polar arcs on the composite surface ,the effects of polarity of composite insulator was lost Using the test method of the average flashover voltage in the freezing period, DC flashover performances were investigated of several insulators with some typical structures and different material. Test results indicated: with the hoist of altitude, the increase of ice amount and the rise of pollutant, the average flashover voltage reduced. The character exponent generally depends on the insulator profile, ice amount, ice state and pollution severity etc. By means of a high-speed camera, a data acquisition system and high voltage test facilities, a series of the flashover processes on ice surfaces were record. The experimental results form this study and the subsequent theoretical analyses suggested: the thermal ionization of the air in front of an arc root resulted in arc movement; the electrostatic force had an auxiliary effect of impelling arc propagation; the electrical<WP=6>breakdown only occurred during the final jump period of the flashover. During flashover process, related parameters were recorded. These parameters include the applied voltage, the leakage current, the freezing water conductive, the flashover time, the arc length and the arc root radius. Arc speeds in various periods of arc development, such as the arc-starting period, the arc developing period, and the finial flashover period, were measured and the critical arc length decreased with an increase in freezing water conductivity. An analyses of arc propagation process suggested an arc could propagate in two different ways: inside or outside the ice. This resulted from the different manner of Na atom entering the arc body. Based on above test results and theoretical analyses, this paper put forward both a calculation expression for correcting insulators flashover voltage and a method for choosing insulator in the complex atmospheric environment.更多还原