3D imaging of lightning channel and leader progression velocity

Three‐dimensional imaging of lightning channels by means of UHF interferometers is performed. To realize this, a field campaign was conducted with two observation sites in Darwin, Australia. The distance between the two sites is about 14 km, and the triangulation scheme is applied to estimate locations of UHF radiation sources. Since the UHF radiation is more likely during the leader progression than in the return stroke phase, imaging of lightning channels is obtained mainly for downward leaders. Velocities of downward leaders are estimated and statistics are presented for first and subsequent strokes. The result is consistent with those of former investigations obtained by optical observations. The statistics for the velocity of leader propagation inside thunderclouds are presented herein. Using optical measurement, velocity estimation of leader progressions inside thunderclouds is impossible, and the presented results are concluded to be the first results of their kind. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 22–28, 2001     

Lightning activity during winter thunderstorm and leader progression in thundercloud

We have been studying lightning discharges by means of a UHF interferometer, and we show a comparison between lightning during winter thunderstorms are those during summer. The main objective of the comparison is further understanding of features of lightning during winter storms, especially of positive cloud to ground flashes. For this purpose we compare negative and positive flashes on UHF radiation and pulse density, and perform two‐dimensional mappings of UHF radiation sources. Moreover we show the three‐dimensional imaging for a cloud flash, and discuss the relationship between the altitude of leader progressions and atmospheric temperature profiles as a function of height. We also show the estimated velocity of leader progressions and find no discrepancy with the earlier results obtained by Proctor. © 2000 Scripta Technica, Electr Eng Jpn, 133(4): 71–78, 2000     

人工引发闪电和自然闪电回击电流波形的对比分析

对2005年夏季在山东引雷实验中获得的一次传统人工引发闪电1μs时间分辨率的电流资料进行了分析。整个电流持续时间约1120ms,包含10次回击过程,时间间隔为18~210ms,平均为87ms;回击电流峰值的几何平均值为11.9kA,变化范围为6.6~21.0kA。通过人工引发闪电和自然闪电的对比分析,发现传统人工引发闪电的回击电流峰值(10~17kA)与自然闪电的继后回击(12~18kA)基本一致;空中人工引发闪电的首次回击(也有作者称为"小回击过程")电流峰值(24~37kA)略小于自然闪电的首次回击(30~45kA);不同地区下行自然闪电回击电流峰值存在最大约50%的差异;上行自然闪电回击电流峰值(8~10kA)小于其他类型的回击。     

地闪回击辐射场的局地等效H?lder指数特征

利用2002年夏季青海的慢天线电场变化仪野外观测资料，应用基于小波变换的局地等效H?lder指数计算方法，对122例负地闪首次回击辐射场波形及精细结构的标度特征进行了检测统计分析，结果表明，回击处标度指数具有突降性，初始峰值处最低，平均值约为-0.1，而后相对缓慢上升，上升时间基本上与回击脉冲持续时间对应，平均值约为117ms；标度指数标准差在回击前达最大，呈现明显的尖峰，峰值位置与回击的间歇平均约为23ms；分析表明，标度指数方法可以有效地应用于地闪回击各种特征的自动检测和分析。     

Winter lightning on Japan Sea coast-development of measuring systemon progressing feature of lightning discharge

With the aid of recent optoelectronic techniques, the authors have developed a measuring instrument named ALPS (Automatic Lightning Discharge Progressing Feature Observation System) to determine the progress of lightning flashes. The progress velocities of stepped leaders for lightning in winter seasons were observed using the ALPS in the coastal area of the Japan Sea. The progress velocity of an individual step of a stepped leader can be expressed by a lognormal distribution and its mean value is 1.6×10⁶ m/s for upward leaders and 4.0×10⁶ m/s for downward leaders. The mean progress velocity of a total leader process is given as 0.8~2.7×10⁵ m/s for upward leaders and 2.9×10⁵ m/s for downward leaders     

Performance of MOV arresters during very close, direct lightningstrikes to a power distribution system

In 1996, at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida, the responses of MOV arresters in an unenergized test distribution system, composed of an overhead line, underground cable, and padmount transformer with a resistive load, were measured during very close, direct lightning strikes to the overhead line. Arresters were installed on the overhead line at two locations 50 m apart (on either side of the strike point) and at the primary of the padmount transformer which was connected to the line via the underground cable. We obtained arrester data for this test configuration from two lightning flashes (containing a total of five strokes) which were artificially initiated from a natural thunderstorm, using the rocket-and-wire technique. We present the simultaneously-recorded arrester discharge current and voltage waveforms from one lightning stroke for one of the two arresters on the line and for the arrester at the transformer primary. Additionally, we estimate the energy absorbed by the arrester on the line as a function of time for the first 4 ms of the lightning event. The records presented are representative of those for all five strokes     

云闪定位算法及误差分析

为了降低云闪对空间飞行器的危害,同时能够更全面地研究雷暴活动,并为地闪的探测预警提供技术支持,开展云闪定位方法的研究具有重要的价值。本文根据现场云闪探测仪采集到的VHF辐射源入射方向信息和达到探测站的时间差信息,结合无线电测向时差定位技术,研究了VHF云闪的四站定位算法及其误差精度分析。在对该算法和误差精度进行matlab仿真的基础上,得到了不同布站方式和基线距离情况下定位误差分布图,为探测站的布站选址提供了理论支撑。     

基于高速数字电路的PD UHF信号纳秒级陡脉冲源研制

超高频法是目前电力设备局部放电在线监测广泛使用的监测方法,超高频电磁信号的定量、定位研究需要稳定可靠的UHF信号模拟发生装置,针对这一现实需求,文章设计了一种基于数字电路的纳秒级脉冲源,用于产生PD UHF模拟信号。文章详细分析了利用数字电路产生陡脉冲的原理,选用简单的高速逻辑器件构建了脉冲发生电路,并采用虚拟仪器产生频率可变的方波信号作为脉冲源的触发信号。用Pspice仿真分析了门电路的脉冲响应特性,并搭建了试验电路进行性能测试。实验结果表明,该脉冲源产生的陡脉冲信号幅值可达2 V,脉冲重复率为50 k Hz-20 MHz,上升陡度为1 ns,脉宽为3 ns,能有效模拟PD UHF信号,并进行相关的局部放电实验。     

Experiments on lightning protection for automatic weather stations using artificially triggered lightning

This paper focuses on the voltages electromagnetically induced by the multiple return strokes involved in a triggered lightning on an overhead power line and a vertical signal line of an automatic weather station (AWS), and the backflow currents and residual voltages in a surge protection device (SPD) embedded in the power line. Pulses of voltage on the overhead power line corresponding to the return strokes with the peak currents ranging from −6.67 to −26.47 kA showed bipolar features. Subpeaks and main peaks ranged from 0.99 to 4.47 kV and from −4.98 to −10.31 kV, respectively. The voltage waveforms corresponding to the return strokes on the vertical signal line of wind speed were of two types: with and without a subpeak after the main peak. All the main peaks, with the peak value from −0.41 to −3.10 kV, were ‘V’ shaped. A significant relationship exists between the peak currents of the return strokes and the 10–90% average gradients of the voltages. The peaks of currents through the SPD ranged from −0.22 to −1.64 kA. The durations of residual voltages ranged from 0.6 to 5.9 ms, average value being 2.1 ms. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High‐current lightning discharges in winter

Lightning electric‐field waveforms related to power line faults in winter have been identified. Most of those waveforms appear to be associated with upward lightning discharges with absolute peak currents of over 100 kA. They are quite different from common return‐stroke waveforms, and the lightning discharges which produce these characteristic waveforms are called GC (Ground to Cloud) flashes. These high‐current lightning discharges are distributed around the coastline in different ways depending on their polarities. The spatial distributions of high‐current lightning discharges around Japan are also investigated. It is revealed that the region of Honshu Island along the coastline of the Sea of Japan belongs to the area in which the density of high‐current lightning flashes is the highest in Japan through the year. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 8–15, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20874     

Statistical analysis of lightning performance of distribution lines based on observation in fields

Because of the lower insulation level than for transmission lines, in this study on lightning protection design of distribution lines, not only direct lightning strokes but also induced voltages caused by nearby strokes must be taken into account. Thus, it is necessary to grasp the frequency of occurrence of lightning phenomena around distribution lines. For this aim, lightning phenomena on TEPCO's distribution lines in use were continuously observed for 6 years (1996 to 2001). Through this observation, new interesting statistical data that can be a useful basis for rationalization of lightning protection design of distribution lines were obtained. Two hundred and four lightning strokes were observed through the six‐year period. Probability of occurrence of a direct stroke was 22% (45 direct strokes were obtained). The fact that in 47% of direct strokes the electric outage did not occur is very interesting. Moreover, the value of surge discharge current of the arrester in the case of nearby stroke is the basis for conventional theory of grounding system. Therefore, statistical analysis of ZnO discharging current in the case of nearby strokes was carried out. As a result, in the case of nearby strokes, 5% value of cumulative frequency of discharging current is 0.5 kA. This value is half the conventional data. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(2): 8–16, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20180     

地闪参量特征的统计分析

通过对北京和兰州中川地区测到的地闪资料进行的计算和统计分析,总结了两地区正负地闪的电流幅值、电流梯度、回收数、峰值电流时间、回周间隔等一批在防雷工程中具有较大在参考价值的闪电参量的概率分布特征,以及北京地区的平均年落雷密度分布和平均年雷暴日分布。     

检测气体绝缘组合电器局部放电的四频段微带单极子特高频天线设计

针对用于气体绝缘组合电器(GIS)局部放电特高频(UHF)在线监测的天线传感器应具有宽频带、高增益和小尺寸等性能要求,设计了一种外置小型四频段微带单极子特高频天线传感器。采用多个辐射单元技术,展宽了特高频天线的检测频段,实现了传感器的多频信号传感特性,运用HFSS仿真软件对天线结构尺寸进行优化设计,选取一组最优参数进行特高频天线实物制作。理论计算和实验室天线特性实测表明,研制的外置四频段微带单极子特高频天线性能优异,在实验室GIS装置上,用已有的微带贴片特高频天线与所设计的特高频天线传感器对模拟缺陷产生的局放信号进行了对比检测,进一步证明了微带单极子特高频天线具有良好的检测灵敏度。     

油中局部放电检测脉冲电流法与超高频法比较

为了研究局部放电检测中超高频法参量与脉冲电流法参量之间的关系,比较分析了局部放电检测中超高频法和脉冲电流法在原理上的区别。利用脉冲电流法和超高频法对油纸绝缘的几种典型模型下的局部放电活动同时进行测量,比较分析同一模型下的局部放电中超高频法参量与脉冲电流法参量之间的关系并探讨了局部放电检测中脉冲电流法对超高频法的标定问题。研究表明,在反映放电活动强弱上,超高频法的参量和脉冲电流法的参量之间有着相同的变化趋势,但是二者之间不存在直接的线性关系。     

基于超高频和超声波相控接收原理的油中局部放电定位法仿真研究

提出一种基于超高频和超声波相控接收阵的局部放电定位法。该方法以分别检测局部放电产生的超高频和超声波信号的相控接收阵构成平面传感器,以超高频相控接收阵检测到的局部放电超高频电磁波信号作为时间基准,由此得出接收到的超声波信号的时延,进而计算出放电点与传感器间的距离;再根据相控阵扫描的方位角和仰角,与算出的距离一起就可得出局部放电源的几何位置。多个空间位置不同的局部放电,其产生的最大信号所处的对应于空间角度的波束阵列的位置不同,相对于同一采样起始点的时间基准不同,而且时间间隔也不同,因此还可实现多局放源的定位。对这一设想进行仿真研究,结果表明该方法能对油中局部放电进行较精确的定位,并可较好地解决多局放点定位问题。     

GIS中典型局放缺陷的UHF信号与放电量的相关分析

超高频(UHF)信号与放电量的关系是局部放电UHF检测研究的难点问题,为了解GIS局部放电UHF法的检测结果与脉冲电流法的参量之间的关系,通过4种典型缺陷的局部放电模型的实验研究,比较了UHF信号的能量、二次积分、峰值电压、峰峰值、波面积等参量与放电量及放电量平方之间的联系。研究表明,UHF信号能量与其放电量平方的线性关系均具有最高的可决系数,即UHF信号能量与放电量平方之间存在线性关系;得到了UHF信号能量与其放电量之间的最佳回归曲线。研究结果对用超高频法定量检测电力设备局部放电具有重要的参考价值和指导作用。     

Discharge characteristic investigation on surface discharge initiated by metallic particles attached to gas‐insulated substation insulator

The ultrahigh frequency (UHF) method is used for detecting the three kinds of surface discharges started by metallic particles on the spacer insulators in gas‐insulated switchgear (GIS). Three different designs of the same surface defect are applied to ensure the consistency of the results. The present experiments are made on a 220‐kV GIS, which is close to the actual situations to study the surface discharge characteristic. A measuring system for this purpose consists of an oscilloscope connected to UHF sensors. Partial discharge (PD) data was captured by UHF detection using an oscilloscope and stored as phase‐resolved pulse sequence (PRPS) data. Since PRPS data contain the complete information of the PD, PRPS analysis (PRPSA) pattern and three‐dimensional ϕ − q − n (3D PRPD) pattern can be calculated from the recorded PRPS datasets. The PRPSA data also allows us to obtain the actual test voltage (rms) of every cycle, the number of measuring cycles, and phase information of all PD pulses, together with their peak values, so that a statistical analysis of these data can be discussed. Besides, this paper also focuses on the frequency analysis and time–frequency analysis of the single‐pulse time‐domain signal. It is shown that the characteristic parameters obtained from the PRPS data, frequency spectrum, and time–frequency spectrum have the potential to be used as PD characteristic interpretation and further research on PD pattern identification. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Observation of lightning by means of time-of-arrival type lightning location system

LPATS—a lightning location system of time-of-arrival type—was installed in the middle of the Japanese island of Honshu by Tokyo Electric Power Co. in 1990. This system is LPATS Version III (LPATS III), which is the most widely used version of LPATS in the world, although there have been few reports on its operating characteristics. In order to utilize the outputs of this system to investigate lightning parameters, it is indispensable to identify its operating characteristics. The system was calibrated, and the observed distributions of the lightning current amplitude were analyzed and compared with previous reports. The results reveal that this system identifies negative return strokes in summer largely correctly, but in summer, it misinterprets many electric field pulses, originating from cloud discharges, as small positive return strokes. This result also suggests the strong dependence of the number of electric field pulses, associated with cloud discharges, on the polarity of the pulses. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 9–15, 1997     

Estimation of shielding failure number of transmission lines for different trace configurations using leader progression analysis

The electrogeometric model (EGM) is a technique used for analyzing the termination of lightning flashes on transmission lines and masts, etc. When using the EGM for modeling the lightning stroke to transmission lines, the power line has normally been represented by a set of horizontal wire and both the sag of the wire, the existence of the towers and effect of uneven way have been ignored. This approach has serious short comings including inability to determine the percentage of the strokes terminating on the towers, failure to correctly predict the effect of height, and giving an approximate value for the number of collected strokes. This paper presents the development of a method for estimating the shielding failure number of power transmission lines in different trace configurations by using the charge simulation method. The effects of towers, sags of conductors, and a perfectly conducting ground are represented in 3-D computation. In addition, the stepwise descending nature of a downward negative leader–streamer systems taken into account by using an appropriate progression model. Upward leader inception and propagation is also modeled utilizing critical equivalent streamer-length criterion. The method is applied to compute the shielding failure of power transmission line for different trace configurations. In this paper the 3-D method is extended by modeling the effect of sloppy trace, trees on both and one side of the transmission line with extensive simulation results. Also, in this paper the effect of variation of tree height, its distance from transmission line and the number of trees on SFN are analyzed and results are shown in curves.     

组合电器局部放电特高频检测的气压影响分析

特高频检测法以其高灵敏度和抗干扰能力,广泛应用于组合电器绝缘状态的现场检测。为研究局部放电特高频信号与视在放电量之间的关系,文中建立了基于特高频和脉冲电流法的局部放电联合检测系统,分别采集0.3~0.5 MPa气压下金属突出物缺陷模型的放电数据,提取UHF信号累积能量,并与视在放电量进行了相关分析。研究结果表明,各个气压下的UHF信号累积能量与放电量平方始终呈现线性函数关系,其线性斜率与气体压力相对应,这为特高频信号标定研究奠定了基础。