【作者】 李进；

【导师】 蔡力；

【作者基本信息】 武汉大学 ， 电气工程， 2021， 硕士

【摘要】 雷电具有长距离、大电流、强电磁辐射的特征,会严重威胁输电线路和电力系统及控制系统的运行,甚至影响到人类生命安全。研究雷电的放电过程,可指导防雷工作的开展。本文采用火箭引雷技术,连续两年在广州从化开展人工触发闪电实验,积累了丰富的与雷电相关的光、电、磁多参量观测资料。通过同步测量的电流和电场变化,人工触发闪电有无回击的初始阶段的放电参数具有明显的差异。在没有回击过程的初始阶段,初始电流变化存在明显的静默期,静默期之后的重建电流脉冲具有相对较大的幅度（1237A）和快速的上升时间（0.7μs）,类似于回击电流。而对于具有回击的初始阶段的初始电流变化,没有电流静默期的产生,等离子通道重建过程的电流脉冲类似于M分量,具有较小的幅度（172.8A）,以及缓慢的上升时间（57.0μs）。初始阶段放电越强,通常会伴随着回击。人工触发闪电平均回击数为5.6。与自然雷电的后续回击相比,本文中的回击表现出更短的上升时间（0.6μs）和更大的峰值电流（16.4k A）,且第一次回击通常比随后的回击具有更大的雷电流幅度和较慢的上升沿。回击的峰值电流与1ms电荷转移量和1ms作用积分均表现出很强的幂函数相关性,与回击电场的初始电场峰值和回击幅度之间均表现出一定的线性相关性,与先导磁场、回击磁场和总磁场峰值均呈现线性关系。随着距离的增加,磁场峰值减小,对不同距离的所有磁场峰值的分析表明与r^-0.90呈线性关系。磁场的上升时间10-90%随距离的增加而增加,并且与ln（r）呈线性关系。连续电流是发生在回击之后的电流过程,其放电通道含有几十到几百安培、甚至k A量级的电流,持续时间约为几十到几百毫秒。根据连续电流的持续时间,可分为小于10ms和大于10ms连续电流两类,并呈现出各种不同的波形。发生在连续电流过程中的脉冲扰动称为M分量。M分量的电流幅值小于回击电流脉冲,其几何平均值为401.5A,10-90%上升时间和半峰值宽度大于回击电流脉冲,其几何平均值分别为120.8μs和204.2μs,与初始连续电流脉冲非常类似。空中引雷与传统引雷相比,主要区别在于小火箭尾部的金属线不直接与引雷针相连接。在双向先导-小回击过程,电场正向且缓慢变化,主要上行正先导的影响。当光脉冲（或反冲流光）进入弱化的放电通道并使其重新发光时,会产生初始电流脉冲或M分量。在先导-回击阶段,先导电场变化波形的类型是不同分支共同作用的结果。慢前沿的形成机制可能与附着过程有关,在此阶段,上、下先导的延伸等离子体通道相互接触,而多个放电通道可能会影响回击慢前沿的电场变化。更多还原

【Abstract】 Lightning has the characteristics of long distances,large currents,and strong electromagnetic radiation,which will seriously threaten the operation of transmission lines,power systems and control systems,and even affect the safety of human life.Studying the discharge process of lightning can guide the development of lightning protection.Rocket-triggered lightning technology has been used in Conghua,Guangzhou for two consecutive years to carry out triggered lightning experiments,and we have accumulated a wealth of optical,electrical,and magnetic observational data related to lightning.Through the synchronous measurement of current and electric field changes,there are obvious differences in the parameters of the initial discharge stage of triggered lightning with or without return strokes.In the initial stage of lightning without return stroke,there is an obvious silent period in the initial current variation,and the reconnection current pulse after the silent period has a relatively large amplitude（1237A）and rapid rise time（0.7μs）,similar to the return stroke current.For the initial current variation of lightning with return strokes,there is no current silent period.The current pulse in the plasma channel reconstruction process is similar to the M component,with a smaller amplitude（172.8A）and a slow rise time（57.0μs）.It is indicated that stronger initial stage discharge is usually accompanied by return strokes.The average number of triggered lightning flashes is 5.6.Compared with the subsequent return strokes of natural lightning,the return strokes in this article show a shorter rise time（0.6μs）and larger peak current（16.4k A）,and the first return stroke usually has a larger lightning current amplitude and a slower rise time than the subsequent return strokes.The peak current of the return stroke has a strong power function correlation with the charge transfer within 1 ms and action integral within 1 ms.It has a certain linear correlation with the initial electric field peak value and the electric field amplitude of the return stroke.It also has a certain linear correlation with the leader magnetic field and the return stroke magnetic field.As the distance increases,the peak value of the magnetic field decreases.The analysis of all peak values of the magnetic field at different distances shows a linear relationship with r^-0.90.The 10-90%rise time of the magnetic field has a linear relationship with ln（r）.The continuous current occurs after the return stroke,and there is still a current process of tens to hundreds of amperes or even k A in the return stroke channel,with a duration ranging from tens to hundreds of milliseconds.According to the continuous current duration,it can be divided into two types of continuous current less than 10 ms and greater than 10 ms,and present a variety of different waveforms.In the continuous current process,the existing pulse disturbance is called the M component.The current amplitude of the M component is smaller than the return stroke current pulse,and its geometric mean value is 401.5A.The 10-90%rise time and half-peak width are greater than the return stroke current pulse.The geometric average values are 120.8μs and 204.2μs,respectively,which are very similar to the initial continuous current pulse.Compared with traditional triggered lightning,the main difference of altitude triggered lightning is that the metal wire at the tail of the small rocket is not directly connected with the lightning rod.The initial positive change of electric field in the stage of bidirectional leader process is mainly affected by the upward positive leader.The light pulse（or recoil streamer）entered weakened discharge channel and made it re-emit.Then the ICCP or M-component was produced and corresponding electric field changed.With using the optical information,it is possible to assign certain pulses to certain branches.In the stage of leader-return stroke,the presented types of dart leader electric field waveforms are the result of processes in different branches.The formation mechanism of the slow front may be related to the breakthrough stage of the attachment process,through which the extended plasma channels of the upper and lower leader contact each other.Multiple discharge channel could influence electric field change of the slow front of the return stroke.更多还原