流注到先导转化过程的实验观测与机理研究

The research on streamer to leader transformation process has important significance for insulating characteristic of ultra-high voltage transmission lines and equipment. Previous studies are lack of quantitative measurements of lead radius, temperature, particle density, and rarely focus on thermodynamic characteristics of the leader channels. This study will investigate the streamer to leader transformation process and mechanism deeply using experiment study, theoretical analysis and numerical simulation. The laser interference technology, high speed digital sampling and optical fiber transmission technology and high speed photography technology also will be introduced to quantitative measure the channel length, radius, temperature, particle density, discharge current and injected charge, analyze the effect of voltage kind, polarity and electrode conditions, summarize the evolution regulars of plasma parameters during streamer to leader transformation process. Moreover, this study will establish the model of streamer-leader energy transfer considering particle internal energy and leader channels’ energy dissipation at the same time. The model will simulate streamer to leader transformation processes and plasma parameters under different conditions. According to comparison and verification between measurement data and simulation results, this study will propose streamer to leader energy transfer mechanism, explain leader channel formation process and physical characteristics. The achievement of this study will promote air gap discharge theory,and obviously have scientific value and academic significance.

研究流注-先导转化过程对特高压输电线路与设备的外绝缘具有重要意义。以往研究缺乏对先导通道半径、温度、粒子密度的定量测量，对先导通道的热力学特性关注不足。本课题拟采取实验研究、理论分析与数值模拟相结合的技术路线，围绕流注-先导转化的物理过程与机理进行深入研究。拟采用激光干涉技术、高速摄像技术、高速数字采样与光纤传输技术对流注-先导转化过程中的先导半径、温度、粒子密度、发展长度、放电电流、注入电荷进行定量测量，分析电压种类、极性与电极条件的影响，总结流注-先导转化过程中等离子体参数演化规律。同时建立考虑流注根部粒子内能与先导通道热力学特性的流注-先导能量传递模型，模拟各种不同工况下流注-先导转化的过程与等离子体参数演化过程。通过对比验证，提出流注-先导体系的能量传递机制，揭示先导通道的物理本质与形成机理，从而促进长空气间隙放电理论的发展，具有重要的科学价值与学术意义。

流注-先导转换过程的特征参数与机理，对高压输电工程空气间隙绝缘设计、防雷绕击分析与雷电物理研究均具有重要意义。本课题以1m棒-板空气间隙先为主要研究对象，提出了流注-先导转化过程等离子体参数测量方法，通过试验获取了先导形成与发展过程中热特性的时空演化规律，建立了流注-先导放电的一维热力学自洽模型，对流注-先导放电的热-动力学现象进行解释。首先，本课题提出了采用激光干涉的方法测量流注-先导放电热特性，通过采用连续激光器为干涉仪光源、CMOS高速摄像仪为干涉图像接收装置，实现了对先导放电热特性的时间分辨观测。以Mach-Zehnder激光干涉平台为主体，建立了先导放电多物理参数同步观测系统，实现了对放电电压、电流、光学形态、先导通道热特性的同步观测。其次， 开展了1 m棒-板间隙在冲击电压下的放电试验，重点对流注-先导转化过程的气体动力学现象与热参数演化规律进行了试验观测与定量分析。由时间分辨干涉条纹图像观测到了流注-先导转化过程中的先导通道热直径扩张规律、先导通道内（包括负极性放电中的空间先导）气体密度与气体温度的时空演化规律等定量参数。第三， 在已有的流注-先导转换模型的基础上，考虑放电通道参数的径向分布，融合气体动力学过程与热传导过程、粒子输运过程、细化的能力转换与弛豫过程，建立了先导放电一维热力学自洽模型，可对流注-先导放电过程中的气压、气体密度、气体温度、流速、粒子组分、电场参数等多种物理量的演化规律进行仿真分析，深入阐释流注-先导转换的具体过程与物理机理。