Dynamic propagation velocity of a positive streamer in a 3 m air gap under lightning impulse voltage

Streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% U50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.

Estimation of Lightning-Generated NO_(x) in the Mainland of China Based on Cloud-to-Ground Lightning Location Data

Lightning-generated nitrogen oxides(LNO_(x))have a major influence on the atmosphere and global climate change.Therefore,it is of great importance to obtain a more accurate estimation of LNO_(x).The aim of this study is to provide a reference for the accurate estimation of the total LNO_(x) in the mainland of China based on cloud-to-ground lightning(CG)location data from 2014 to 2018.The energy of each CG flash was based on the number of return strokes per CG flash,the peak current of each return stroke,and the assumed CG breakdown voltage.The energy of intracloud lightning(IC)was based on the estimated frequencies of IC and the assumed energy of each IC flash.Combining the energy of lightning and the number of nitric oxide(NO)molecules produced by unit energy(ρno),the total LNO_(x) production in the mainland of China was determined.The LNO_(x) in the mainland of China estimated in this study is in the range(0.157-0.321)×10^(9) kg per year[Tg(N)yr-1],which is on the high end of other scholars’works.Negative cloud-to-ground lightning(NCG)flashes produce the most moles of NO_(x),while positive cloud-to-ground lightning(PCG)flashes produce the least total moles of NO_(x).The breakdown voltage of PCG is greater than that of IC or NCG,while the latter has a greater output of LNO_(x).

Observation and study on the whole process of cloud-to-ground lightning using narrowband radio interferometer

A narrowband radio interferometer has been developed and used to locate the entire sources of VHF radiations from a negative cloud-to-ground (CG) lightning discharge which contains 19 strokes. This system uses five antennas to form an array consisting of short- and long-baselines along two or- thogonal directions. The system error which comes from frequency conversion is reduced by phase detection through direct high frequency amplifying. An interactive graphic analysis procedure is used to remove the fringe ambiguities which exist inherently in interferometry and to determine the direction of lightning radiation sources in two dimensions (azimuth and elevation) as a function of time at a time resolution of microsecond orders. With the developed system, the whole progression process in time and space of a lightning flash can be reconstructed. In this paper, combining the synchronous data of electric filed change and VHF radiation, the whole processes of an example negative CG flash have been studied in detail. It is found that the preliminary breakdown event of the CG flash started from negative charge region and exhibited firstly a downward pregression and then an upward propagation. There were very intense and continuous radiations during stepped leaders which became much stronger when the first return stroke began. In contrast, there were less and only discrete radiations during dart leaders. Stepped leader and dart leader may transform to each other depending on the state of the ionization of the path. The progression speed of initial stepped leaders was about 105 ms?1, while that was about 4.1×106 and 6.0×106 ms?1 for dart leaders and dart-stepped leaders, respectively. M events produced hook-shaped field changes accompanied by active burst of radiations at their begin- nings. Followed these active radiation processes, M events appeared to contact finally into conducting main discharge channels. The mean progression speed of M events was about 7×107 ms?1, greater than that of the dart leaders and dart-step leaders. K events and attempted leaders were essentially the same as dart leaders except that they could not reach the ground and initiate return strokes.

Characteristics of Cloud-to-ground Lightning during a Squall Line Process outside of the Subtropical High

Based on the monitoring data of cloud-to-ground( CG) lightning positioning network and Doppler weather radar as well as MICAPS1°× 1° objective analysis field,a squall line process outside of the subtropical high in low-latitude plateau on May 7,2010 was analyzed. The results showed that wind direction shear between low and high levels and low-level convergence zones provided favorable circulation background for the strong thunderstorm process,while high energy and high humidity,strong thermal instability and ascending motion at low and middle levels offered beneficial environmental conditions for the formation of the thunderstorm. 9 620 return strokes of cloud-to-ground lightning were monitored by the lightning positioning network,and cloud-to-ground lightning was distributed like bands between 584 and 586 hP a. The occurrence of cloud-to-ground lightning was mainly related to echo top and echo intensity at-10 ℃ stratification height,and it mainly appeared in zones where echo top height was larger than 13 km and echo intensity at-10 ℃ stratification height was 35-40 dB Z. Wind convergence and maintaining of high radial velocity were favorable for the development of convective echoes and occurrence of cloud-to-ground lightning.

Temporal and Spatial Distribution of Lightning Activity in Ulanqab City

From January 2020 to December 2021,Ulanqab Meteorological Bureau of Inner Mongolia used VLF/LF lightning locator to carry out three-dimensional lightning monitoring in Ulanqab City,and compared with ADTD lightning location data in the same period.The results show that both VLF/LF lightning locator and ADTD lightning locator had excellent monitoring ability for lightning during flood season in Ulanqab.VLF/LF lightning locator was slightly superior to ADTD lightning locator in observation accuracy,the observation ability of low-current cloud-to-ground lightning,intracloud lightning observation and so on.There were obvious temporal and spatial characteristics of cloud-to-ground lightning during flood season in Ulanqab,and there was a certain correlation between the areas where lightning appeared frequently and surface water.Intracloud lightning was mainly concentrated at a height of 1-7 km.Negative cloud-to-ground lightning accounted for about 75%of total cloud-to-ground lightning,and negative intracloud lightning accounted for 39%of total intracloud lightning.

Study on the Scope of Small Amplitude of Cloud-to-ground Lightning in Lightning Weather Monitoring

Based on lightning location data in Chongqing region during 1999-2008,the frequency of lightning in various amplitude ranges and its annual variations were analyzed firstly.Afterwards,with the aid of matlab mathematical software,the distribution of the lightning location data was fitted using logarithmic normal distribution function.The results showed that after data of cloud-to-ground lightning with current amplitude from-5 to5 kA were deleted from lightning location data,the statistical characteristics of cloud-to-ground lightning could be reflected well.Meanwhile,lightning with current amplitude from-5 to 5 kA accounted for 1.05%（less than 2%）,which accorded with the detection principle of lightning position indicator（there existed error detection）.Therefore,cloud-to-ground lightning with current amplitude of-5-5 kA in lightning location data of Chongqing region was defined as small amplitude of cloud-to-ground lightning,which could provide scientific references for the processing of lightning location data in Chongqing region as well as analysis and quality control of lightning location data in other regions.

Studies on the Distribution Characteristics of the Cloud-to-Ground Lightning and Its Disasters Prevention in Xinjiang, China in 2017

Xinjiang, China is affected by geographical terrain and other factors, and is prone to lightning disasters. In order to effectively carry out lightning protection and disaster reduction work and improve defense capabilities, based on the data of lightning location monitoring in Xinjiang in 2017 and the statistics reports of the lightning disasters from 2015 to 2017, the characteristics of the cloud-to-ground (CG) lightning activities and disasters in Xinjiang were statistically analyzed. The results show that the CG lightning in Xinjiang is mainly the negative one, accounting for 79.7% of the total lightning. In 2017, the distribution of positive, negative and total the CG lightning months mainly focuses on June to August, and the main occurrence period is from 14 to 23 hours. The intensity of total the CG lightning and negative the CG lightning mainly distributes from 20 to 40 kA, and the peak value appears in 30 kA. The CG lightning intensity is mainly distributed in 30 - 70 kA. The distribution of the CG lightning density in Xinjiang is larger in the north than in the south and larger in the west than in the east. Lightning disasters mainly occur from May to August, accounting for 93.2 percent of the total, with the largest number in June. From 2005 to 2017, 44.6% of lightning accidents occurred in farming and pastoral areas, followed by civil electronic equipment damage. In addition, electrical equipment, buildings and factory equipment are damaged by lightning strikes to varying degrees.

Characteristics of Cloud-to-ground Lightning during a Local Rainstorm in Meizhou City

Based on cloud-to-ground lightning data of lightning location system,Doppler radar data,and precipitation data of regional automatic weather stations,the characteristics of cloud-to-ground lightning during a local rainstorm on June 4,2016 in Meizhou City were analyzed. The results showed that the spatial distribution of cloud-to-ground lightning from 14： 00 to 20： 00 on June 4,2016 in Meizhou City had obvious local characteristics,and the proportion of negative lightning was larger than that of positive lightning（ only 16. 8%）. The concentration period of positive lightning coincided with that of cloud-to-ground lightning. The peak of proportion of positive lightning lagged behind the peak of cloud-to-ground lightning,and appeared in the late period of thunderstorm disappearance. The dense area of cloud-to-ground lightning and the area with heavy rainfall coincided with the area with strong radar echoes. Doppler weather radar data had the feature of the headwind zone,strong combined reflectivity,vertical height of strong echoes,high echo top,and fast radial movement. The peak of cloud-to-ground lightning appeared one hour earlier than that of precipitation. There was no significant correlation between the frequency of cloud-to-ground lightning and precipitation. The peak of negative lightning corresponded to that of positive lightning,and cloud-to-ground lightning ended earlier than rainfall. After the peak of precipitation,convective system rapidly weakened and disappeared. Precipitation and the frequency of cloud-to-ground lightning fluctuated frequently during the whole process. The jumps and peaks of negative lightning were indicative of rainfall changes.

Study of Lightning Damage Risk Assessment Method for Power Grid

Based on the idea of risk evaluation, the existing lightning damage risk assessment methods are reviewed and summarized in this paper. And the power grid lightning damage risk assessment system is established on the basis of lightning flashover risk evaluation methodology for transmission lines, and adopts the improved Analytic Hierarchy Process as the core algorithm. It can comprehensively evaluate the risk for transmission lines of regional grid, various sections of a line and each tower of the section, considering much more impact factors, including the running time of line, importance of grades, equipment damage, and the success rate of lightning stroke reclosing and so on. According to the calculation results of the risk assessment of the analytic hierarchy process and lightning flashover risk evaluation, the principles and methods of grade classification for power grid lightning damage risk map are studied, and give typical examples in the paper. It can describe the lightning withstanding ability much more scientifically and provide important references for the manage department of power system.

Ball Lightning as Source of High-Energy Particles When It Enters a Dense Medium

Experiments have been carried out to study the anomalous passage of laboratory-produced ball lightning through solid-state sheets. The passing of the ball lightning within the standard model can be explained by cascading generation of particles at entering of high-energetic protons of the ball lightning into a dense matter. The process of energy conversion of its own poloidal magnetic field of the ball lightning into the kinetic energy of its charged particles occurs in this case. The energy of protons becomes sufficient for the generation of charged pions and their subsequent cascade decay. The decay of pions leads to the appearance of negative and positive muons, as well as muon antineutrino and muon neutrino. This fact is confirmed by the presence of a passed ball lightning and a high potential of variable polarity in the region above the solid-state sheet after the ball lightning passing through it. The dark ball lightning also found was in the experiments. The laboratory ball lightning opens up new perspectives in many areas of research and applications and may have a positive impact on attempts to solve the energy problem based on muon-catalyzed nuclear fusion.

Current Lightning Risk Assessment in Yantai

The development situation and business processes of lightning risk assessment in Yantai were summarized and analyzed to provide references for the operation of lighting risk assessment. This study aimed to further improve lightning risk assessment and promote the development of lightning risk assessment through practice and discussion.

闪电通道状态变化参数化的建立及截断和再击穿的数值模拟

为提高数值模式对闪电精细化放电过程的仿真能力并与不断提高的闪电探测技术形成互补,探讨再击穿过程与雷暴电参数的关系,建立了一个能够再现先导截断及再击穿过程的自持电中性完整闪电参数化方案。考虑到正、负先导的极性不对称,分别设置了不同传播速度及起始和传播阈值。方案新增了通道电导率、平均电流、电荷等非线性电参数,并以这些参数的实时更新驱动闪电通道发展,通过设置不同通道状态变化阈值实现了先导通道衰退、截断以及重新激活的实时状态变化。基于通道平均电流、纵向电场以及电导率的实时变化,方案将电荷在空间重新分配,保证了通道的自持电中性。将新方案植入经典雷暴云三极电荷模型,模拟得到的云闪在通道结构、先导截断及再次激活、正负先导的极性不对称等方面与现有观测事实有较好的一致性。概念模型验证表明,新方案在保证自持电中性的前提下,在模拟包含截断和再击穿过程的完整闪电放电过程方面具有一定合理性和先进性。

基于AHP-模糊综合评价法的化工园区雷电灾害风险评估

为了评估化工园区的雷电灾害区域风险,选取包含园区等级、经济产值、区域防雷安全管理和防雷检查覆盖率等在内的19个评估指标,采用层次分析法和模糊综合评价法,建立化工园区雷电灾害区域风险评估模型,并对河北衡水高新区化工片区开展雷电灾害区域风险评估,以发现化工片区的雷灾隐患点和防雷措施薄弱环节,确定科学的防雷减灾策略,有效保障园区内生产安全和人员生命财产安全.

基于傅里叶变换算法的变电站母线避雷器泄露电流异常检测方法

为降低变电站安全风险为目的,提出基于傅里叶变换算法的变电站母线避雷器泄露电流异常检测方法。利用无线传感器采集变电站母线避雷器运行电流数据后,对变电站母线电流进行平滑处理;去除其内部所含的干扰噪声后,利用基于递推傅里叶变换方法分解得到变电站母线避雷器运行电流内存在的谐波,该谐波即为变电站母线避雷器泄露电流异常检测结果。试验结果表明:对变电站母线避雷器运行电流去噪预处理能力较强,且其检测变电站母线避雷器泄露电流异常能力较强,具备较佳的应用效果。

基于层次分析法的南宁市雷电灾害风险评估与区划

本文以南宁市为例,根据气象灾害风险评估与区划方法建立雷电灾害风险区划指标体系。利用南宁市的气象、地理、人口、经济等资料,采用数据统计、调查问卷、层次分析和加权综合评价等方法,确定雷电灾害风险的权重和评价指标,使用ArcGIS技术进行栅格计算和图层叠加,最终得到南宁市的雷电灾害风险区划图。结果表明,南宁市范围内发生雷电灾害风险最高的处于青秀区、邕宁区、兴宁区、良庆区以及宾阳县、横州市、上林县、马山县一带,整个南宁市范围内,从高风险到中风险所占的区域面积最大,反映了南宁市范围内的雷电灾害风险普遍较高。

雷电定位监测预报技术研究

雷电潜势预报是雷电灾害预警预报的重要基础。通过构建雷电系统框架结构,从基础算法、数据采集模块建立、数据处理的角度,设计一套针对闪电雷电定位监测的系统结构。该技术对预防雷电灾害、保障煤矿电力安全有着重要价值。

Positive Charge Region in Lower Part of Thunderstorm and Preliminary Breakdown Process of Negative Cloud-to-Ground Lightning

A new lightning locating technology, called Lightning Mapping Array （LMA）, has been developed. The system takes advantage of GPS technology to measure the times of arrival （TOA） of lightning impulsive very high frequency （VHF） radiation events at each remote location. The spatiotemporal development processes of lightning are described in three-dimension by measurement of the system with high time resolution （50 ns） and space precision （50-100 m）. The charge structures in thunderstorm and their relationship with lightning discharge processes are revealed. The temporal and spatial characteristics of preliminary breakdown process involved in negative cloud-to-ground （CG） lightning discharges are analyzed based on the data of lightning VHF radiation events. The effect of positive charge region in lower part of thunderstorm on the occurrence of negative CG lightning discharge is discussed. The results indicate that the preliminary breakdown process with longer duration in negative CG lightning discharges is an intracloud discharge process. It occurs between negative and positive charge regions located in middle and lower parts of thunderstorm respectively. It initiates from the negative charge region and propagates downward. After propagating into the positive charge region, the lightning channel develops horizontally. The characteristics of the preliminary breakdown process are consistent with that of intracloud lightning discharges. The stepped leaders are initiated by the K type breakdown which occurs in the last stage of the preliminary breakdown process and develops downward through the positive charge region. The existence of positive charge region in lower part of thunderstorm results in the occurrence of preliminary breakdown process with longer duration before the return stroke of negative CG lightning discharges.

基于直击雷先导发展模型的舰船雷击附着点计算及试验验证

[目的]为设置并完善舰船防雷措施,对舰船关键设备的雷击风险和避雷针防护效果进行评估。[方法]首先,构建能模拟自然先导发展状况的先导发展模型,并引入舰船模型对舰船的雷电附着过程进行分析计算;然后,研究下行雷电先导发展至舰船四周不同区域时的舰船表面电场分布、各位置受到雷击的可能性,以及避雷针对雷击风险的防护效果;最后,在实验室中开展缩比模型放电试验并验证计算结果。[结果]结果显示,雷击附着点主要集中在舰船结构相对突出的位置,避雷针可改善舰船表面的电位分布,起到雷击防护作用,但最终雷击点的确定与下行先导的发展区域有关。[结论]结合计算结果与舰船缩比模型雷击附着试验结果,能够分析舰船直击雷防护薄弱环节,雷击附着点的最终位置与双向先导的连接情况关系紧密,所提先导发展模型能较好地对不同先导发展方位下受到雷击的舰船区域进行预测。

基于改进层次分析法的雷电防护能力模糊综合评价

为科学评价雷电防护措施的防护能力,分析国内外多种评价方法的优劣,结合雷电防护措施的特点提出基于改进层次分析法的模糊综合评价。依据雷电防护相关技术标准和规范,综合考虑雷电环境、承载体特征、自然因素的影响,建立雷电防护能力评价指标体系。利用改进层次分析法计算各级指标的权重,采用模糊综合评价法确定雷电防护能力评价等级。运用此方法对采取多种雷电防护措施的油气集输站进行雷电防护能力评价,评价等级与实际情况和有关文献案例相符,表明该方法适用于雷电防护能力的评价。

雷击降弓过程中机车受流动态特性研究

针对雷击环境下重载列车降弓燃弧导致的行车安全问题,以实际牵引系统为参考,仿真建立雷电流与降弓运动环境下牵引系统弓网电弧综合模型。基于机车运行与电弧特性两个方面,研究宏观层面功率与高压侧整流侧电流的变化规律,同时分析了弓网电弧动态特性变化,评估雷击下降弓过程对时速73 km/h重载机车受流动态特性的影响。通过仿真对比得出,雷击降弓中的电弧使受电弓电源电压对电缆的寄生电容充电,由于机车高压端设备和受电弓的电感,影响了等效电路的振荡波动和过电压峰值;雷击降弓电弧存在滞后性;输入的雷电电流会引起牵引系统电感电容变化,也会改变电弧形成的等离子体的电容,从而增加电弧的储电能力和电弧电容对电压的敏感性。通过仿真为正确评估雷击环境下牵引系统特性研究提供理论数据,为提高牵引供电系统的安全运行奠定一定的技术基础。