雷云下空间电荷对直流输电线路上行先导起始特性的影响  

Influence of Space Charge on the Upward Leader Characteristics Emerging from the DC Transmission Lines Under Lightning

作　　者：李志钊[1] 曾嵘[1] 庄池杰[1] 廖永利 高超 

机构地区：[1]清华大学电机工程与应用电子技术系电力系统及发电设备控制和仿真国家重点实验室,北京100084 [2]南方电网科学研究院有限责任公司,广州510080

出　　处：《高电压技术》2014年第5期1358-1364,共7页High Voltage Engineering

基　　金：国家重点基础研究发展计划(973计划)(2011CB209403);中国南方电网有限责任公司重点科技项目(K201014)~~

摘　　要：以往在分析直流输电线路上行先导的起始过程时,一般只考虑了雷云、下行先导以及直流运行电压对输电线路附近电场的影响,而未充分考虑输电线路周围早已存在的空间电荷对原来电场所带来的畸变。为此,对上行先导起始前的一系列放电过程进行了研究,包括雷云所导致的地表空间电荷层、直流运行电压所引起的离子流电荷层等,并比较了这些过程对上行先导起始特性的影响。分析发现,上行先导起始前线路周围空间电荷的分布主要决定于运行电压及雷云,2者在输电线路周围所产生的空间电荷密度可超过10 nC/m3;相对来说,因雷云所导致的空间电荷层的电荷密度只有约1 nC/m3,故雷云对上行先导起始的影响可以忽略不计;另外,因下行先导只有在发展至较低高度时,才能产生与运行电压、雷云相当的影响,故下行先导对空间电荷分布的作用甚微。基于上述分析,建立了考虑离子流影响后的上行先导起始模型,并对实际的上行先导起始过程进行了仿真。与传统模型比较发现,考虑离子流影响后,下行先导必须发展至更低的高度才能使导线周围电场强度满足上行先导起始条件,导致上行先导的起始时间延后,这说明了直流输电线路的离子流有碍上行先导的起始。Traditionally, in the process of analyzing the initiation process of upward leader from DC transmission lines, only the surface electric field of conductor produced by thundercloud, downward leader and DC operation voltage is considered, but the influence of space charge is not fully considered. Therefore, we studied the discharge processes before the initiation of upward leader, including the space charge layer induced by thundercloud and the ion flow due to DC operation voltage, etc. We also compared the effects of these discharges on the initiation of upward leaders. It is concluded that the space charge distribution around conductors before upward leader initiation is mainly determined by operation voltage and thundercloud： the charge density from these two sources can exceed 10 nC/m3. Comparatively speaking, the space charge layer induced thundercloud has charge density of only about 1 nC/m3, hence its influence on upward leader initiation can be neglected. In addition, the influence of downward leader on the distribution of space charge is comparable to that of operation voltage and thundercloud only if a downward leader has developed to a height low enough. This means that the influence of downward leader is small and can be neglected. Finally, after establishing a model of upward leader initiation that takes ion flow into consideration, we simulated actual upward leader initiation with the model. Comparison with previous researches using traditional models indicates that, considering ion flow, a downward leader has to develop to a lower position to induce the electric field around conductors intense enough for upward leader inception, which is certainly delayed. This suggests, that in DC transmission lines, the existence of ion flow obstructs inception of upward leader.

关 键 词：屏蔽失效 上行先导 直流运行电压 离子流 地表空间电荷层 起始时间 

分 类 号：TM863[电气工程—高电压与绝缘技术]