空间电荷对硅橡胶复合绝缘子材料沿面闪络影响的研究

发布时间：2018-07-06 10:40

本文选题：沿面闪络 + 电晕老化　；参考：《华北电力大学》2017年硕士论文

【摘要】：沿面闪络电压的研究一直是个热点课题,发展了各种理论,基于实验的研究,提出了很多提高沿面闪络电压的方法。在各种研究因素中,空间电荷对沿面闪络电压的影响研究较少,随着材料老化程度的增加,材料内陷阱密度变大,空间电荷入陷形成空间电荷层,一方面形成了材料内附加电场,另一方面蕴藏了大量的极化能量,空间电荷对沿面闪络电压影响不能被忽略。对沿面闪络电压的影响研究,能够为材料改性方面提供指导意义,进一步提高绝缘材料沿面闪络电压,探索空间电荷对沿面闪络过程的作用关系,有助于拓展绝缘材料沿面闪络的相关机理。本文通过人工电晕老化的方法,老化了不同时长的硅橡胶试样,随着老化时间的增加,材料内部陷阱密度变大,通过电极注入电荷被陷阱俘获,形成蕴含空间电荷数由少到多的试样,在指状电极下进行沿面闪络电压测试,探究空间电荷对沿面闪络电压的影响。首先搭建了人工电晕老化试验装置,获取具有不同陷阱数目的老化试样。并且搭建了沿面闪络电压测试平台,编写了恒定升压速率的升压控制软件,基于单片机控制的高压直流电源能够以均匀的升压速率输出电压,减小了电压波形对沿面闪络电压的影响,大大降低了实验数据的分散性,是实验成功进行的保障。其次利用电导电流曲线粗略的反映老化材料内陷阱密度。电导电流对数坐标系下曲线的斜率代表空间电荷入陷速率。电导电流测试受多种因素影响,重复性较差,对升压梯度和升压间隔较敏感。为此开发了基于单片机平台的等梯度、等间隔升压系统,通过读取采样电阻上的电压值,经集成运放放大后,自动将运算后的电导电流值发送至电脑端。最后通过曲线拟合得到电老化阈值,估算材料内陷阱密度情况。研究结果表明,空间电荷对沿面闪络流柱发展存在重要影响,一方面空间电荷层形成的空间电场,对表面流柱内电荷有力的作用,加速了流柱内正负粒子的分离速度,正负粒子形成的空间电场对电极间的电场有削弱的作用;另一方面空间电荷层使电极间的电场向材料表面弯曲,使流柱沿着材料表面前进,受材料表面形貌的影响变大,沿面闪络电压在一度程度内会升高。大量积聚的空间电荷蕴含了大量的极化能量,空间电荷释放时大量能量参与到沿面闪络中,同时表面电荷受空间电荷引力的作用,表面电荷消散相对较难。使沿面闪络电压急剧下降。提高沿面闪络电压需要抑制表面电荷的积累,也要兼顾空间电荷的分布与空间电荷量蕴含的极化能量。
[Abstract]:The study of flashover voltage along the surface has been a hot topic. Various theories have been developed. Based on the experimental research, many methods to improve the flashover voltage along the surface have been proposed. Among all the factors studied, the influence of space charge on flashover voltage along the surface is less studied. With the increase of aging degree of materials, the density of traps in materials becomes larger, and space charges sink in to form space charge layers. On the one hand, the additional electric field in the material is formed, on the other hand, there is a large amount of polarization energy, so the influence of space charge on the flashover voltage can not be ignored. The study on the effect of flashover voltage can provide guidance for material modification, improve the flashover voltage of insulating material, and explore the relationship between space charge and flashover process. It is helpful to expand the mechanism of insulator flashover along the surface. By means of artificial corona aging, the samples of silicone rubber with different ages were aged. With the increase of aging time, the trap density of the material increased, and the charge injected into the electrode was captured by the trap. The flashover voltage was measured under the finger electrode to investigate the influence of space charge on the flashover voltage. First, artificial corona aging test device was built to obtain aging samples with different number of traps. A flashover voltage test platform is built, and a constant boost control software is developed. The voltage output of HVDC power supply based on single-chip microcomputer can be uniform at the booster rate. The influence of voltage waveform on flashover voltage along the surface is reduced, and the dispersion of experimental data is greatly reduced, which is the guarantee of successful experiment. Secondly, the conductance current curve is used to roughly reflect the trap density in aging materials. The slope of the curve in logarithmic coordinate system of conductance current represents the rate of entrapment of space charge. The measurement of conductance current is affected by many factors, and its repeatability is poor, and it is sensitive to the voltage gradient and the booster interval. In this paper, an equal-gradient, equal-interval voltage booster system based on single-chip microcomputer is developed. By reading the voltage value on the sample resistor and amplifying by integrated operational amplifier, the calculated conductance current value is automatically transmitted to the computer. Finally, the electrical aging threshold was obtained by curve fitting, and the trap density in the material was estimated. The results show that space charge has an important influence on the development of flashover flow column along the surface. On the one hand, the space electric field formed by the space charge layer has a force on the charge in the surface flow column, which accelerates the separation speed of positive and negative particles in the flow column. The space electric field formed by the positive and negative particles weakens the electric field between the electrodes; on the other hand, the space charge layer bends the electric field between the electrodes towards the surface of the material, making the flow column advance along the surface of the material, which is greatly affected by the surface morphology of the material. The flashover voltage along the surface increases at one degree. A large amount of accumulated space charge contains a lot of polarized energy. When the space charge is released, a large amount of energy is involved in the flashover along the surface. At the same time, the surface charge is affected by the space charge gravity, so it is relatively difficult to dissipate the surface charge. A sharp drop in flashover voltage along the surface. To increase the flashover voltage along the surface, the accumulation of surface charge should be restrained, and the distribution of space charge and the polarization energy contained in the amount of space charge should be taken into account.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM216

【参考文献】