介质高频特性对GIS绝缘子绝缘性能影响研究

发布时间：2018-10-24 08:15

【摘要】：全封闭组合电器(GIS)中绝缘介质除具有绝缘性能和灭弧性能优异的SF6气体外,还有大量以环氧树脂为绝缘介质的盆式绝缘子。因为绝缘介质的介电常数会改变电场强度,当在电场中放入高介电常数的材料时,电场强度会有一定量的下降,反之亦然。而介电常数除了与材料有关外,还与温度和频率有关。本文以1100kVGIS中的盆式绝缘子为例,分析其介电常数受频率变化的影响,以及在雷电和快速暂态过电压(VFTO)高频作用下绝缘子的电气性能,提高GIS运行的可靠性。雷电冲击电压作用下GIS中会产生一个时变场,必须考虑电介质中因极化引起的极化电流。本文给出了暂态电场时域计算模型,考虑了静态介电常数、光频介电常数和松弛时间对电场分布的影响,以及高频下介质的物理特性。在雷电冲击作用下,计算得出不同时刻绝缘子内部的电场分布和绝缘子上、下表面的电场分布,为提高绝缘子的可靠性和降低沿面放电发生机率提供依据。此外,隔离开关分合母线时引起的VFTO过电压,具有幅值高、上升快的特点,波形中包含从几兆赫兹到几十兆赫兹的频率成分。本文给出了GIS中隔离开关开断母线充电电流的等值电路并进行了数值模拟。针对VFTO电压波的特点,将快速暂态过电压进行离散的傅里叶变换,得到波形中主要含有的不同频谱分量。分析不同频率分量作用在绝缘介质中时,绝缘介质的相对介电常数的变化情况;考虑高频下绝缘材料的复介电常数,计算不同频率分量作用下绝缘子电场,并得出在VFTO作用下的绝缘子内部电场分布规律以及在绝缘子上几个具体位置的沿面电场分布规律,找出绝缘子绝缘相对薄弱的环节。为了进一步探究绝缘子的介质特性,考虑在雷电冲击电压作用下,当绝缘子介电常数不同时和各向异性时,对绝缘子电场分布的影响。计算结果表明,当介电常数不同时盆式绝缘子电场分布的趋势大致相同,其最大电场强度随介电常数的增大而减小;考虑介质各向异性时,盆式绝缘子的电场分布与各向同性时相比有很大区别,所以介质的各向异性也应是盆式绝缘子绝缘性能的考虑因素之一。
[Abstract]:In (GIS), the insulating dielectric is not only the SF6 gas with excellent insulation and arc extinguishing performance, but also a large number of basin insulators with epoxy resin as the insulating medium. Because the dielectric constant of the insulating medium will change the electric field intensity, when the material with high dielectric constant is added in the electric field, the electric field intensity will decrease by a certain amount, and vice versa. The dielectric constant is not only related to material, but also to temperature and frequency. In this paper, taking the basin insulator in 1100kVGIS as an example, the influence of frequency on the dielectric constant of the insulator is analyzed, and the electrical performance of the insulator under the high frequency action of lightning and fast transient overvoltage (VFTO) is analyzed to improve the reliability of GIS operation. There is a time-varying field in GIS under the action of lightning impulse voltage. The polarization current caused by polarization in dielectric must be considered. In this paper, the time-domain calculation model of transient electric field is presented. The influence of static dielectric constant, optical dielectric constant and relaxation time on the electric field distribution and the physical characteristics of the medium at high frequency are considered. The electric field distribution in the insulator and the electric field distribution on the upper and lower surface of the insulator at different times are calculated under the action of lightning shock, which provides the basis for improving the reliability of the insulator and reducing the probability of the discharge along the surface. In addition, the VFTO overvoltage caused by the separation of the bus bar by the isolator has the characteristics of high amplitude and fast rise, and the waveform contains frequency components ranging from several megahertz to tens of megahertz. In this paper, the equivalent circuit of on-off busbar charging current in GIS is given and the numerical simulation is carried out. According to the characteristics of VFTO voltage wave, the discrete Fourier transform of fast transient overvoltage is carried out, and the main spectral components in the waveform are obtained. This paper analyzes the variation of relative dielectric constant of insulating dielectric when different frequency components act on the dielectric, and calculates the insulator electric field under the action of different frequency components considering the complex dielectric constant of insulating material at high frequency. The internal electric field distribution law of insulator under the action of VFTO and the distribution law of electric field along the surface of several specific positions on insulator are obtained, and the relative weak link of insulator insulation is found out. In order to further explore the dielectric characteristics of insulators, the influence of the dielectric constant and anisotropy of insulators on the electric field distribution of insulators is considered under the action of lightning impulse voltage. The results show that the maximum electric field intensity decreases with the increase of dielectric constant when the dielectric constant is different, and the maximum electric field intensity decreases with the increase of dielectric constant, and when the dielectric anisotropy is considered, the electric field distribution of the basin insulator is approximately the same. The electric field distribution of the basin insulator is different from that of isotropic insulator, so the anisotropy of the dielectric should be one of the factors to consider the insulation performance of the basin insulator.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM216;TM595

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