大气离子迁移率是直流输电线路周围的电磁环境参数计算中的重要参数，它是大气中多种载荷粒子共同作用的结果，比起实验室单纯环境下测得的单载荷粒子迁移率，其影响因子更多，变化规律也有所不同。输电线路沿线大气环境复杂多变，气压、温度等环境参数都会改变大气离子迁移率。为了预测不同大气条件下离子迁移率，为更准确地仿真输电线路电磁环境提供支持，测量大气离子迁移率、探索其变化规律、并研究其影响因子十分必要。本文首先对目前国内外关于离子迁移率的影响因子的理论研究做出较全面的综述，总结了离子迁移率的宏观与微观影响因子的种类，选择温度、气压、湿度三个环境参数作为起主要作用的离子迁移率宏观影响因子进行研究。同时结合前人的实验数据，初步了解这些影响因子对离子迁移率的影响。然后就目前的离子迁移率测量方法及其理论进行调研，选取了其中适合测量大气离子迁移率的平行平板离子场产生与测量方法，并用电晕U-I曲线外推法作为辅助。制造平行平板离子流发生器并对其进行调试，深入理解其理论基础和校正方法，并调整发生器到最适合测量的参数设置。选择所要研究的环境参数范围和取点间隔，建造气候实验箱，控制其中的环境参数，用平行平板离子流发生器与电晕发生器分别测量得到不同环境参数下的大气离子迁移率。在气压、相对湿度、温度三维坐标图和修正后的分子密度、绝对湿度、温度三维坐标图中分别研究大气离子迁移率的变化特征与性质。相同条件下正离子迁移率小于负离子迁移率，正负离子迁移率均随着气压和湿度的增加单调减小；而温度对离子迁移率的影响形式十分复杂，并不单调。运用多种拟合方式，在前人的理论研究基础上，初次同时结合三种影响因子，提出将湿度因子引入气压与温度对离子迁移率的影响规律中，最终得到了一个大气离子迁移率的经验公式。将所得的大气离子迁移率规律带入直流输电线路周围电磁环境计算程序中，得到大气离子迁移率对地面电场和地面离子流密度这两个重要电参数的影响规律：地面电场基本不受离子迁移率的影响，但是地面离子流密度在可能的离子迁移率变化范围内已经能产生可观的变化。正离子迁移率增加，地面正离子流密度增加；负离子迁移率增加，地面负离子流密度增加。
In the calculation of the electro-magnetic parameters of the surrounding of the HVDC lines and the parallel DC and AC lines, parameter-air ion mobility is widely used. It’s the average of ion mobilities of all sorts of charge carrier. As it’s in a much more complicated environment than in Lab, the influence factors of it are multiple and their influence rules are different. The complex environment the transmission lines passing by changes air ion mobility obviously. It’s necessary to estimate air ion mobility at different value of factors for simulating the electro-magnetic environment precisely.In our research, firstly we surveyed present theories of ion mobility comprehensively and concluded the microscopic and macroscopic influence factors of air ion mobility. Temperature, pressure and humidity are chosen as the main macroscopic studied factors. In present theories, air ion mobility decreases with pressure, humidity and increases with temperature.Secondly we surveyed the measurement methods for ion mobility and chose parallel plate ion current-generation and measurement method as the main means to measure the air ion mobility, corona VA character curve extrapolation method as the contrast method.We built a parallel plate ion current-generated apparatus. Adjusting its structural parameters made us a better understanding of the theory of the apparatus and the mechanism of every part. We adjusted the parameters to the status for precise measurement.An environment test chamber was built and an environmental influence factors-controlled experiment was taken. In the experiment we controlled pressure, temperature and humidity at certain value and measured the air ion mobility by parallel plate ion current-generated apparatus and corona generator respectively. Positive air ion mobility is generally lower than negative ion mobility in same condition. The data was analyzed in (pressure, temperature, relative humidity) coordinate axis. Air ion mobility decreases with the three factors and the extents of decrease of ion mobility by three factors are nearly the same. Then the data was analyzed in transformed (number density, temperature, absolute humidity) coordinate axis and finded that air ion mobility decreases with AH and number density, but the influence of temperature is complex. Combining the existing theory, we raise a fitting formula of air ion mobility which takes humidity, pressure and temperature into account at the same time.Finally we put the air ion mobility into the use of electro-magnetic environment of HVDC lines calculation. We changed the ion mobility in the simulation program, and finded ion mobility influences the value of ground electric field and ground ion current density. Ground electric field varies with the ion mobility randomly in a scope of 20%, and ground ion current density varies significantly with both ion mobilies, especially ion mobility with same polarity.
