空气间隙放电是高压输变电系统外绝缘安全的主要威胁，也是雷电放电的物理基础。湿度和气压是影响空气间隙放电特性的两大主要环境因素，但以往研究较少且不深入。本论文通过试验观测和仿真计算的方法研究了湿度和气压对空气间隙放电过程的影响规律，并建立了考虑环境条件影响的先导放电模型。既为高海拔、高湿地区的高压输变电系统外绝缘的优化配置提供分析依据，也为高空雷电放电的研究奠定了理论基础。首先，研制了放电试验用人工气候罐，实现了对间隙长度、环境气压、空气湿度和气体组分比例四种参数的精确调控。建立了空气间隙放电特性综合观测平台。该平台可同步测量到放电电压波形、放电电流波形、纳秒级流注起始发展光学图像、微秒级放电通道发展全过程光学图像和表征放电通道热力学特性的干涉条纹演化图像。提出了一种精确获取流注起始时延的方法和利用阿贝尔逆变换分析放电通道气体温度、气体密度的方法，并对先导通道热直径进行了界定。其次，研究了不同绝对湿度对流注和先导放电特性的影响规律与机理。分析了水分子浓度对流注起始特性的影响。测量了不同湿度下流注的发展速度、直径及二维分支角度，研究了水分子浓度对流注发展特性的影响规律，并估算了不同湿度下流注头部的最大场强。观测了不同湿度下先导的放电形态、发展速度、通道热直径及内部气体温度、气体密度，研究了水分子浓度对先导发展特性的影响。第三，研究了气压对先导放电特性的影响规律和机理。通过试验获得了约化电场恒定和电场恒定两种情况下不同气压下先导的通道直径、发展速度、通道气体温度和气体密度等重要参数。通过计算并分析先导发展各个阶段的注入电荷量和注入能量分配，分别研究了两种情况下气压对先导放电特性的影响。最后，建立了考虑空气密度和湿度影响的一维径向先导放电模型。该模型能够考虑先导起始及发展阶段放电通道内电、热等物理参数的一维径向分布。基于该模型，仿真研究了不同空气密度与水分子浓度下放电通道演化的物理过程及其关键参数。利用该模型计算分析了不同试验环境条件下放电通道的热力学参数，仿真与试验结果的趋势吻合较好。

Air gap discharge is the main research object of the external insulation configuration theory of high voltage power transmission system, and it is also one of the important physical processes of lightning discharge. As the main body of discharge, the main factors in the gas phase state parameters affect the electrical insulation properties are humidity and air pressure. In this dissertation, experimental observations and simulations are used to study the effects of humidity and air pressure on the air gap discharge process and provide models for the optimal configuration of external insulation in high-voltage power transmission and transformation systems in different atmospheric environments (such as high-altitude areas). The theoretical basis also laid the foundation for the study of the mechanism of lightning discharge.First, an artificial climate tank was developed as a discharge test vessel, and precise control of the gap length, ambient air pressure, air humidity, and gas composition ratio was achieved. Based on artificial weather tanks, an integrated observation platform for air gap discharge characteristics was established. Through the comprehensive test platform, the discharge voltage waveform, the discharge current waveform, the nanosecond streamer initiation optical image, the optical image of the whole process of development of the microsecond discharge channel, and the thermodynamic characteristics of the discharge channel can be measured synchronously during one discharge. Interference fringe evolution image. Then, a method for accurately obtaining the initial delay of the streamer and a method for analyzing the gas temperature and gas density of the discharge channel by using Abelian inverse transform are proposed, and the thermal diameter of the leader channel is defined.Secondly, the effects of different absolute humidity on the flow injection and the leader discharge characteristics were studied. The influence of the concentration of water molecules on the initial flow characteristics was analyzed from both experimental and theoretical perspectives. Based on the development speed, diameter and two-dimension branch angle of streamer measured under different humidity, the influence of water molecule concentration on streamer development characteristics was studied, and the maximum field strength of the streamer head under different humidity was estimated. Through the development of the leader discharge observed under different humidity conditions, the differences in the shape of the leader discharge between different absolute humidity levels are summarized. According to the obtained development speed of the leader under different humidity, the diameter of the channel heat and the internal gas temperature, gas density, the influence of the concentration of water molecules on the development characteristics of the leader was studied.Thirdly, the law and mechanism of the influence of atmospheric pressure on the discharge characteristics of the leader were developed. The important parameters, such as channel diameter, development speed, channel gas temperature and gas density, were obtained under different gas pressures under constant and reduced electric field conditions. The injection charge distribution and injection energy distribution at each stage of the development of the leader were calculated and analyzed, and the influence mechanism of the atmospheric pressure on the leader discharge characteristics under two conditions was explained.Finally, a one-dimensional radial leader discharge model considering the influence of air density and humidity was established. One-dimensional radial distribution of electrical parameters, such as electrical and thermal parameters, in the discharge channel from the flow injection to the leader conversion stage can be considered. The key physical parameters of the discharge channel under density and humidity are in good agreement with the trend of simulation results.