纳米改性液体电介质绝缘特性及其内部空间电荷的测量研究

发布时间：2018-01-12 10:29

本文关键词：纳米改性液体电介质绝缘特性及其内部空间电荷的测量研究　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：液体电介质的击穿特性是影响并制约电力设备及电力系统发展的重要因素，，在电力设备运行过程中，液体电介质内部的电场对其绝缘性能有着极大的影响，而空间电荷的出现及分布又对电场的改变起着重大的作用。为了提高变压器油绝缘性能，本文研究了添加不同导电性能的纳米材料改性对液体电介质宏观击穿性能的影响。选取铁磁性导电纳米粒子Fe3O4、半导体纳米粒子TiO2和非导电纳米粒子Al2O3，经不同的表面改性剂处理后，分散于变压器油中，制得纳米改性变压器油，并通过测量透射系数证实了三种纳米改性变压器油的稳定性。通过工频击穿试验、操作冲击击穿试验，对比研究了不同浓度纳米改性变压器油的宏观击穿特性，得出三种纳米改性变压器油能够提高其击穿特性的最佳浓度分别为0.03g/L、0.01g/L和0.02g/L。在纳米改性变压器油的最佳浓度下再对比工频电压和正、负极性下的操作、雷电冲击电压下不同纳米改性变压器油的击穿特性。结果表明，除负极性雷电冲击情况外，三种纳米改性变压器油的冲击击穿特性较之纯净变压器油均有较大程度的提高。其中在最佳浓度下三种纳米改性变压器油的操作正极性击穿电压提高幅度较大，提高幅度分别为44.1%、33.3%和35.5%。试验研究结果显示，经三种纳米粒子改性后变压器油的综合击穿特性较纯净变压器油均有不同程度的改善。基于纳米粒子对电子的捕获理论，从空间电荷分布角度理论上分析了冲击电压下和交流电压下纳米改性变压器油高绝缘特性的机理，同时结合极化理论分析出三种纳米改性变压器油击穿特性差异性的原因。考虑到空间电荷对击穿过程的重要意义，为了进一步试验探究纳米粒子对液体电介质击穿特性提高的机理，本文完成了高Kerr常数液体电介质中空间电场及空间电荷测量平台的搭建及优化；同时在此基础上，考虑了低Kerr常数变压器油的特性，使用灵敏度更高的光电探测器替代高速CCD、增加空间滤波装置，完成了对工程常用液体电介质变压器油中空间电场及电荷测量平台的优化改进，为后续试验奠定了基础。为了较好的观察分析纳米粒子对液体电介质内空间电荷的影响，本文利用测量精度较高的高Kerr常数液体电介质中空间电场及空间电荷的测量平台对平行极板间同一电压下同一时刻纯净和添加纳米改性后碳酸丙烯酯中的空间电场及空间电荷分布情况进行测量比较，结果表明：在添加不同类型的纳米粒子改性后，由于纳米粒子对空间电荷的阻挡作用，纳米改性液体电介质中空间电荷较纯净液体电介质更集中在两极板附近，从而使得添加纳米粒子后平行极板间的电场分布更加均匀，因而纳米改性有助于液体电介质击穿电压的提高。
[Abstract]:The breakdown characteristic of liquid dielectric is an important factor that affects and restricts the development of power equipment and power system. During the operation of power equipment, the electric field inside liquid dielectric has a great influence on its insulation performance. The appearance and distribution of space charge play an important role in the change of electric field in order to improve the insulation performance of transformer oil. In this paper, the effects of nano-materials modified with different conductive properties on the macroscopic breakdown properties of liquid dielectric were studied. The ferromagnetic conductive nano-particle Fe3O4 was selected. The nanometer modified transformer oil was prepared by TiO2 and Al _ 2O _ 3, which were treated with different surface modifiers and dispersed in transformer oil. The stability of three kinds of nano-modified transformer oil was confirmed by measuring transmission coefficient. The macroscopic breakdown characteristics of different concentrations of nano-modified transformer oil were compared by power frequency breakdown test and operation impact breakdown test. The results show that the optimum concentration of three kinds of nano-modified transformer oils can improve their breakdown characteristics is 0.03g / L, respectively. 0.01g / L and 0.02g / L. at the best concentration of nano-modified transformer oil, the power frequency voltage and the operation under positive and negative polarity are compared. The breakdown characteristics of different nano-modified transformer oils under lightning impulse voltage. Compared with pure transformer oil, the impact breakdown characteristics of the three kinds of nano-modified transformer oil are improved to a greater extent, and the operating positive breakdown voltage of the three nano-modified transformer oils is greatly improved under the optimum concentration. The increase ranges were 44.1% and 35.3%, respectively. The comprehensive breakdown characteristics of transformer oil modified by three kinds of nanoparticles were improved to some extent compared with pure transformer oil. Based on the electron trapping theory of nanoparticles. The mechanism of high insulation properties of nanometer modified transformer oil under impulse voltage and AC voltage is analyzed theoretically from the angle of space charge distribution. At the same time, the reason of the difference of breakdown characteristics of three kinds of nanometer modified transformer oil is analyzed by polarization theory. Considering the importance of space charge on the breakdown process, the mechanism of the improvement of breakdown characteristics of liquid dielectric by nanoparticles was investigated in order to further study the mechanism. In this paper, the measurement platform of space electric field and space charge in liquid dielectric with high Kerr constant is built and optimized. At the same time, considering the characteristics of low Kerr constant transformer oil, the photoelectric detector with higher sensitivity is used to replace the high-speed Kerr, and the spatial filter device is added. The optimization and improvement of the measuring platform of space electric field and charge in liquid dielectric transformer oil are completed. In order to better observe and analyze the effect of nanoparticles on space charge in liquid dielectric. In this paper, the measurement platform of space electric field and space charge in liquid dielectric with high Kerr constant is used to measure the pure and nano-modified propylene carbonate at the same time and at the same voltage between parallel plates. The distribution of space electric field and space charge were measured and compared. The results show that the space charge in the nano-modified liquid dielectric is more concentrated near the two polar plates than in the pure liquid dielectric due to the blocking effect of nano-particles on the space charge after the addition of different types of nano-particles. Therefore, the electric field distribution between parallel plates is more uniform after the addition of nano-particles, so nano-modification is helpful to increase the breakdown voltage of liquid dielectric.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM214

【参考文献】