交、直流输电线路雷电先导发展模型及其应用

Lightning is the primary threat to the security and stability of power system. Shielding failure is the main form of the lightning accidents for UHV and EHV transmission line, making the lightning shielding performance evaluation is an important issues during the design and operation of transmission lines. As the voltage increases, the line upward leader cannot be ignored. The EGM, which is used to assess the performance of shielding failure in the past, fails to work because it ignores the existence of the upward leader and the difference between the evaluation results and operational experience becomes bigger. Thus it is urgent to establish a model considering the impact of the upward leader. Leader progression model (LPM) which is studied in this project is such a model. In previous study on LPM, there were several aspects that needs improving: The line upward leader inception and development characteristics has not been measured through 1:1 ratio experiment model; The difference between line upward leader inception and development characteristics under AC and DC pre-applied voltage is not distinguished; The influence of the space charge like the ion flow, is not consider. In response to these problems, the project plans to do research on test method, simulation experiment and theoretical models. A great number of discharge experiments under joint applied voltage of both AC and impulse will be taken and a LPM considering the impact of space charge will be established. Finally, a software base on the proposed LPM will be developed and used for the lightning shielding performance evaluation of AC/DC transmission lines.

雷电是电力系统安全稳定运行的首要威胁。绕击是特（超）高压输电线路雷击故障的主要形式，雷电绕击屏蔽性能评估是线路设计与运行中的重要问题。随着电压等级提高，线路上行先导的影响不能再忽略，以往评估绕击屏蔽性能的电气几何模型因忽略线路上行先导的存在，评估结果与运行经验差异越来越大。亟需建立考虑上行先导影响的新模型。本项目研究的雷电先导发展模型考虑上行先导与运行电压的影响，更贴近真实雷电发展机制。以往先导发展模型研究未在等比模型上实测过线路上行先导的起始与发展特性；未区分交流与直流预电压下线路上行先导起始与发展特性的差异；未考虑离子流等空间电荷对线路上行先导起始与发展的影响。针对上述问题，本项目拟从试验方法、模拟试验、理论模型三个方面，研究交流、冲击联合加压放电试验技术，系统开展交流、冲击联合加压放电试验，研究考虑空间电荷影响的先导发展模型，开发计算软件，并用于交、直流输电线路雷电绕击屏蔽性能评估。

项目以110-1000kV四种电压等级的交流输电线路绕击模型试验为基础，建立考虑运行电压的影响、适用于较高电压等级线路的先导发展分析方法。采用两台不同角度的高速摄像机对6m长间隙中先导发展过程进行观测，经过图形处理对两张相机拍到的二维先导通道进行三维重构，比较三维和二维的先导长度和发展速度，通过统计分析研究先导发展路径的分散特性。搭建雷电绕击线路模拟试验系统，以110kV、220kV、500kV和1000kV电压等级的模拟导线为研究对象，在棒-板电极上施加200/2000μs负极性操作波的冲击电压，当模拟导线上交流瞬时电压分别达到不同相位角时触发冲击发生器，统计出流注起始时间、不连续及连续先导起始时间等先导起始特性，先导发展速度和单位电荷密度等先导发展特性，并研究导线分裂数、对地高度对先导特性的影响。对110kV、220kV、500kV和1000kV不同电压等级交流线路地线和导线同时存在的情况进行模拟，通过电流测量及高速摄像机拍照，在地线保护角为0°时，将导、地线双根实验的结果和其他条件不变、仅有导线存在时的结果相对比，研究地线的存在对导线上先导特性的影响。随着地线保护角的减小，由+5°到0°到-5°，研究导线、地线上的先导起始和发展特性。研究相同幅值的交、直流预电压对先导起始和发展特性的不同影响，探讨同一电压等级不同触发相位角带来的影响，究竟是由电压幅值还是电压相位角的作用造成的。进而结合自洽先导起始判据和自洽先导发展模型，将前文实验中得到的平均先导发展速度和电荷密度应用到模型中，建立考虑运行电压的适用于超特高压线路雷电屏蔽失效性能评估的数值计算模型，并应用于特高压与500kV交流同塔四回线路中计算线路绕击跳闸率。