电晕空间电荷作用下雷电上行先导起始条件的实验与理论研究

Lightning protection is essential for the security concern of power system and other infrastructures. To investigate the discharge mechanism of lightning upward leader is a hot topic in the research area of protection against direct lightning strokes. The main objective of this project is to study the influence mechanism of glow space charge on the inception of lightning upward leader and establish a revised upward leader inception criterion. In order to improve the equivalence of upward leader simulation experiment, a power electronics controllable charging based impulse generator is adopted. By developing the IGBT switching strategy and electrode optimization, the spatiotemporal characteristics of electric field near ground during the lightning attachment process can be reproduced. Using quantitative schlieren method and other observation techniques, the characteristics of upward leader is observed by measuring the optical, electrical and thermal parameters. Combined with numerical simulation works, quantitative study on the charged particles transport property of streamer discharge and energy convection process of upward leader inception in the presence of glow corona discharge is carried out. The electric field shielding effect and energy inhibit effect of glow corona space charge on the initiation of upward leader is revealed, and a revised upward leader inception criterion is proposed. It is of great theoretical and practical significance for the deeply understanding of lightning attachment process and improvement of existing leader progression models.

直击雷防护是电力系统和其它地面基础设施安全关注的重点，雷电上行先导放电机理是直击雷防护研究领域关注的前沿课题。针对电晕空间电荷对雷电上行先导起始过程的影响机制不明晰、缺乏考虑电晕空间电荷影响的上行先导起始判据问题，项目拟采用一种基于电力电子可控充电原理的冲击电压发生器，通过研究IGBT开关控制策略，优化放电结构，实现雷电近区电场时空分布的等效模拟，以解决雷电上行先导放电模拟实验等价性不足问题。通过引入激光定标纹影等多种测量手段，系统获取雷电上行先导起始放电阶段的光学、电学和热学参量。结合数值仿真，深入研究电晕放电对流注放电粒子输运特性以及先导起始能量转化过程的影响规律，揭示电晕空间电荷对上行先导起始的电场屏蔽效应和能量抑制效应，提出电晕空间电荷作用下的雷电上行先导起始判据，对深入认识雷击接闪放电物理过程、完善雷电先导发展模型具有重要的理论和应用价值。

面向提升电力系统和其它地面基础设施直击雷防护水平的迫切需求，针对雷电上行先导模拟实验等效性不足、电晕空间电荷对雷电上行先导起始过程的影响机理不明晰问题，项目取得的研究进展如下: ① 实验获得了3.3kV级IGBT器件高频开关过程和反激变压器电磁暂态特性，建立了考虑IGBT开关损耗和反激变压器损耗的雷击放电近区电场模拟装置的宽频电磁暂态模型，实验和仿真的输出电压峰值误差小于4.6%、回路能量传递效率误差小于4%。据此提出了装置开环控制IGBT触发脉冲的计算方法。② 建立了电晕向流注放电实验观测平台，采用带通量限制器的二阶精度有限体积法建立了电晕空间电荷分布的时域计算模型，实测获得了棒形电极和导线电极的伏安特性曲线和电晕-流注转化的临界电压上升率，以典型的±800kV和±1100kV特高压直流线路为研究对象，仿真分析了雷云和下行先导电场作用下，线路附近电晕空间电荷的分布规律及其向流注转化对应的下行先导临界高度。③ 研究建立了空间分辨率为48.7μm/pixel、时间分辨率为1.25μs高速定量纹影成像系统，发现了因注入空间电荷量的降低，暗区时间内放电通道中心温度随时间的变化趋势由下降趋势逆转为上升趋势的现象，并实验获得了不同电极形状下导致两类变化趋势发生转变所对应的临界注入空间电荷量。建立了考虑包括电子、正负离子、中性和激发态粒子在内共14种组分的N2/O2体系气体加热瞬态过程一维径向热流体数值仿真模型，实测和仿真结果表明，当注入空间电荷量降低时，暗区时间内离子电流的加热作用是保持先导通道气体温度的原因。最终建立了考虑电晕空间电荷电场屏蔽作用和热电离抑制作用的雷电上行先导起始判据，以典型±1100kV特高压直流输电线路导线为研究对象，仿真分析了考虑电晕空间电荷对导线上行先导的起始和发展过程以及导线雷电击距的影响规律。