纳秒脉冲电压下绝缘油中流注放电的演化特性与分叉机理研究

Insulating oil is widely employed in pulsed power devices due to its superior performance in dielectric liquid. The electric discharge events subjected by nanosecond pulsed voltage in insulating oil have become one of the crucial issues that hinder the performance of pulsed power devices. This project focuses on the spatiotemporal evolution dynamics, mode transient and branching micro mechanism of the streamer in oil. Firstly, the photo-electric phenomenon of streamer under nanosecond pulsed voltage in oil would be observed and the electric field dependency of streamer developing and branching behaviors investigated, and further, evolutionary characteristics and typical streamer modes could be derived. Subsequently, the key parameters indicating streamer branching based on image identification techniques are to be obtained and the correlation between macro parameters and micro properties proposed to unveil the streamer transient criteria. At last, the influences of the determined causes (electric field dependent) and stochastic causes (local turbulence) on streamer branching mechanism are to be studied. The predominate ionization mechanism and their applied conditions under high electric field are expected to be confirmed. By performing this project, better understanding of micro process of discharge and breakdown theory under fast pulsed voltage in liquid dielectric could be approached and scientific basis be provided for the insulation design, miniaturization and reliability assessment of pulsed power devices.

绝缘油是一种优良的液体介质，广泛应用于各类脉冲功率装置中。目前，纳秒脉冲电压下绝缘油中的放电是一个影响脉冲功率装备性能的关键问题。本项目针对纳秒脉冲下油中流注放电的时空演化过程、模式转换及放电通道分叉的微观机制等基础问题开展研究。首先实验观测纳秒脉冲下油中流注的光电现象，考察电场因素对流注发展特性及分叉现象的影响，获得不同条件下流注演化规律和典型放电模式；进而采用图像识别方法获得表征流注通道分叉行为的关键参数，通过光-电信号分析建立放电的宏观参量与微观特征的关系，探索放电模式的转换条件与演变规律；最后，借助三维建模仿真，研究确定性因素（电场变化）和随机性因素（局部扰动）对油中流注放电分叉现象的诱导机制，明确高场下的主导电离机制及其适用条件。通过本项目研究，可以深化理解快脉冲电压下液体绝缘放电的微观过程与击穿机理，为脉冲功率器件的绝缘设计、小型化及运行可靠性提供科学基础。

流注放电是液体介质中形成贯穿性击穿放电前的预放电现象，研究流注放电过程物理机制可进一步加深对液体放电现象的认知水平，对于高压设备的绝缘设计和安全稳定运行具有重要意义。本课题针对快脉冲电压下油中流注放电时空演化过程、模式转换及放电通道分叉的微观机制等基础问题开展研究。研究获取了快脉冲电压下油中流注发展过程的发光特性与电学参数，观测了快脉冲激励下油中不同模式放电起始—发展—击穿的时空发展过程；采用统计学方法对不同模式随电压幅值的转化规律进行了统计分析，得到了不同油中放电模式转换的条件与演变规律；通过仿真计算研究了杂质和介质不均匀区对流注发展过程中的分叉现象的影响，探索了杂质与介质不均匀性影响流注发展分叉特性的内在机制；最后，探索了纳秒脉冲下液体介质放电起始的新机制，考虑液体静压强的变化对空腔半径的时间演化进行了计算，提出了纳秒脉冲电压作用下电致伸缩效应导致的电子倍增电离模型。通过本项目研究，可以深化理解快脉冲电压下液体绝缘放电的微观过程与击穿机理，可为脉冲功率器件的绝缘设计、小型化及运行可靠性提供科学基础，并为评估杂质含量及种类对油纸系统绝缘性能的影响提供理论支撑。