【作者】 洪川；

【导师】 孙才新；

【作者基本信息】 重庆大学 ， 电气工程， 2007， 硕士

【摘要】 由于对气体放电理论的研究涉及多学科交叉以及受到测量气体放电过程中各种参数所需的先进仪器的制约,到目前为止,在气体放电理论很不完善的情况下,高电压与绝缘技术研究还是一门以试验为基础的学科。模拟试验和真型试验不仅都存在各自的不足,而且耗费巨大的人力和物力,特别是超特高压输变电系统外绝缘的选择涉及各种复杂环境下的长空气间隙和绝缘子长串的放电特性,如果仍依赖于全电压、全尺寸下各种复杂环境中的试验,不仅很不经济,而且很难找到放电过程的普遍规律。因此,借助有限的实验条件研究结果,采用仿真计算方法对超特高压输变电系统外绝缘放电开展研究,会推动以放电理论为基础的高电压与外绝缘学科从半物理到物理研究的方向发展,而且对超特高压外绝缘的设计提供可靠的理论依据。本文在国内外已有研究基础上,采用有限元数值计算方法对超-特高压输电系统中面临的空气间隙放电问题建立了仿真模型,并对整个放电物理过程进行了计算研究,其主要结果如下:①流注起始放电时空间中的各离子浓度达到108个.cm-3,当先导放电形成后,流注头的正离子和电子浓度达到1012个.cm-3,此时,各种空间电荷产生的电场与外加电压产生的电场对总体空间电场的影响作用相当。②空间电场影响空气电离率а,从而影响到电子和正离子在空间中的浓度分布,离子浓度变化又会影响到空间电场大小,而附着率η、结合率β和解离率γ对电场影响较小,γ过程可忽略。③在等离子体电晕云模型中,不同电晕云长度对空间电场分布的影响都具有相同规律,其电晕云发展条件是头部电场达到11kV.cm-1,内部最低电场达到3kV.cm-1。④在外加500kV、250/2500μs操作波时,先导通道内的正离子和电子浓度将达到1013～1015个.cm-3,电场约为1～2kV.cm-1,先导起始时间在400μs左右,并以3×104m.s-1速度从棒电极向板电极传播。间隙击穿时先导通道长度占整个空气间隙长度的3/5。本文建立的等离子体电晕云模型和先导发展模型都能较好的反映长空气间隙的放电过程。通过对先导放电过程的仿真计算分析,得出了先导起始条件和空气击穿条件。更多还原

【Abstract】 For the cross of multi-disciplinary and the lack of advanced apparatus to measure the parameters of air discharge, the research on high-voltage and insulation technology was mainly based on experiments. The simulation experiment and real experiment both have many deficiency and will take many human power and financial resources, especially for the external insulation research of the ultra-high voltage (UHV) and extra-high voltage (EHV) which will involve the discharge of long air gap and long insulator string under the complex environment, if the research was developed on the real voltage and real dimension it would cost much but found the rule of discharge. For the reasons above we take the method of emulation to research the external insulation of UHV (EHV) and this will accelerate the discipline of high-voltage and insulation from semi-physical research into physical research.In this article, the air gap discharge model was established in finite element method (FEM), the whole process of air discharge was calculated and analyzing, the results obtained as follows:①The space charge density of electrons and irons had to reach 108cm-3 to start the stream discharge and reached 1012cm-3 when the leader discharge starting, at this time the efforts of space charge and applied voltage to the space electric field were correspondence.②The space electric field influences the ionizing rateаand further influences the space charge density, at the same time the variation of space charge density could change the space electric field distribution in air gap. But the attachment rateη,the association rateβand dissociation constantγhave small influences on electric field distribution.③In the plasma-corona cloud model, the efforts of different length corona cloud to space electric field are regular just when the electric field in head of the corona reached 11kV.cm-1 and 3kV.cm-1 inner, the corona can develop forward. The humidity of air influences the breakdown voltage deeply and the lower humidness the lower breakdown voltage.④In the leader development model, when applied 500kV、250/2500μs switching over-voltage, the ion density in the leader channel can reach 1013～1015cm-3 and the electric field reach 1～2kV.cm-1, the time to start leader discharge is about 400μs and the velocity of the leader development is about 3×104m.s-1 from rod electrode to plane electrode. The leader channel takes 3/5 of the whole gap, it’s very approach to the tested value 2/3.Both of the plasma-corona model and the leader growth model in this article can describe the long air gap discharge process perfectly. By the emulation and calculation of the process of leader discharge, we gained the starting condition of the leader and the breakdown condition of the long air gap.更多还原