纳米粒子对变压器油纸绝缘中电荷传输的影响机理

In recent years, it was found that the electrical strength at AC, DC and positive impulse breakdown voltage of transformer oils can be significantly enhanced by proper modification of nanoparticles. Some people try to explain phenomenon observed in conductive particles modified oil with the theory of nanoparticles capture fast electrons, whereas some others use trap theory to explain the phenomenon observed in semiconductive particles modified oil. However, it is difficult to clearly explicate the effect of nanoparticles on space charge transport behavior of transformer oil with both theories as both of the theories have no universality. In this project, improved Zeta potential and Faraday Cup measurement method will be used to study the influence of well-dispersed nanoparticles on charge trapping in transformer oil. Moreover, effect of nanoparticles on space charge distribution in modified oil and charge accumulation at oil-paper interface will also be tested by using Kerr effect optical measurement method. In addition, in order to help understanding the inhibition mechanism of nanoparticles’ microscopic characteristics on streamer development, high-speed photoelectric measuring system will be applied to measure the streamer development (length, velocity and shape) in transformer oil and oil-paper system with and without modification of nanoparticles. Finally, based on the measurements results, this project aims to propose a mechanism of charge transport in nanoparticles modified oil and oil-paper system, and to lay the theoretical foundation for developing nanoparticles modified oil-paper insulating system.

近年来人们发现，添加在油中的纳米粒子显著提高了变压器油的工频、直流和正极性冲击击穿电压。有人用纳米粒子捕捉快电子的理论来解释导电粒子的改性现象，有人用陷阱理论来解释半导电粒子的改性现象，但这些理论都没有普适性，难以说明纳米粒子对油中电荷传输的影响机理。.本项目采用改进的Zeta电位和法拉第杯测量技术，研究具有良好分散稳定性纳米粒子对变压器油中电荷的捕捉现象和规律。采用Kerr效应光学测量技术，研究纳米粒子特性对油中空间电荷分布以及纸板界面电荷积累的影响。采用热刺激电流和脉冲电声测量技术，研究纳米粒子特性对变压器油和油浸纸复合绝缘的陷阱分布、电荷积累与输运特性影响规律。采用高速光电测量系统，研究改性前后油中和油纸复合介质流注发展的现象（长度、速度和形态），揭示纳米粒子微观特性对流注发展的抑制机理。在此基础上，提出纳米粒子对油和油纸绝缘中电荷输运的作用机制，为开发纳米油纸绝缘系统奠定理论基础

本项目针对现有纳米粒子对变压器油改性理论缺乏普适性，难以说明纳米粒子对油中电荷传输的影响机制这一问题，以不同形貌、尺寸和表面修饰状态纳米粒子改性变压器油（简称：纳米油）为研究对象，实验验证了纳米粒子对油中电子的捕获作用，研究了纳米粒子微观特性对变压器油和油纸复合介质绝缘强度的改性作用，分析了纳米粒子微观特性对油中和油纸界面流注发展特性的影响规律，结合纳米粒子表面陷阱态、纳米油陷阱特性和电荷输运特性，提出了纳米油中电荷捕捉与浅陷阱传输协同作用的电荷输运机理，建立了基于电荷捕捉和浅陷阱跃迁机制的协同电荷输运模型。.主要研究成果包括：1. 首次试验验证了不同导电类型纳米粒子对电子的捕获作用，发现纳米粒子对电子的捕捉作用与陷阱跃迁迁移共存，纳米粒子极化速度越快，极化强度越大，对电子的捕捉作用就越显著，而纳米粒子向油中引入的浅陷阱越多，越利于油中电子的跳跃传输。2. 制备出了不同形貌、尺寸和表面修饰状态的二氧化钛纳米粒子及其纳米变压器油，实现了纳米粒子在变压器油中的长期均匀稳定分散。3. 揭示了纳米粒子对变压器油中流注发展特性的影响规律，正流注分支增多、长度变短，负流注分支减少，长度增加，这是由于纳米变压器油中电子迁移率增大影响了低密度区电荷的分布，进而引起了流注发展特性的变化，极大的提高了正冲击击穿强度。4.揭示了纳米粒子对油纸沿面闪络特性和界面流注发展特性的影响规律，提出了纳米粒子对变压器油纸复合介质绝缘强度的改性机制。5.基于纳米变压器油中电荷传输的微观特性与宏观绝缘特性和流注发展特性的关系，提出了纳米油中电荷捕捉与浅陷阱传输协同作用的电荷输运机理和模型。.本项目研究成果已发表SCI论文23篇，EI期刊和会议论文16篇；获得和申请国家发明专利共4项，培养博士后1名、博士研究生3名、硕士研究生9名。