多接地点闪电的梯级先导与回击过程的研究

RESEARCH ON STEPPED-LEADER AND RETURN-STROKE OF THE CLOUD-TO-GROUND LIGHTNING WITH MULTIPLE-GROUNDING-POINT IN THE SAME RETURN STROKE

利用成像率为1000幅/s的高速数字化摄像系统和电场变化仪,对在一次回击过程中具有多个接地分支的闪电(MGPF)进行了研究.结果表明:MGPF回击前的梯级先导由包含2～4个脉冲的脉冲束组成,脉冲束间的时间间隔平均值约为26μs,脉冲间的时间间隔平均值约为5μs;广东MGPF回击过程中和的电荷量约为4.5C,青海的约为11C;广东MGPF发生比例为16.7%,青海的为17.6%;一次回击的多个接地分支多发生在首次回击.通过分析发现,MGPF的形成与闪电的梯级先导、连接过程等有重要关系.闪电在一次回击过程中具有多个接地分支对雷电防护方法和设计的改进提出了更高的要求.

The flashes with multiple-grounding-point （MGPF） in the same return stroke were studied by using high-speed image camera system and fast antenna and slow antenna. The results are summarized as following： The stepped-leader just before the return-stroke consists of the pulse-chain which comprise 2-4 pulses. The average time interval between the pulse-chains is about 26μs, while the time interval between the pulses is about 5μs. Neutralized charges during the return-stroke are respectively about 4.5C and IIC in Guangdong and Qinghai. In the CGs of Guangdong, 62 exhibited MGPFS, and the percentage is 16.7%. In Qinghai, there were 21 MGPE and the percentage of MGPF is 17.6%. The multiple-grounding-point in the same return stroke mostly occured in the first-return-stroke, The leader and attachment process have important effects on the formation of MGPE Because MGPFs have more than one grounding points, they maybe produce more serious damage to facilities on the ground and should not be neglected in the design of lightning protection.