Characteristics of mesospheric sprites in the Hokuriku area and their causative lightning discharges

Mesospheric optical phenomena (including sprites) are becoming an interesting subject from the standpoint of atmosphere–ionosphere coupling. This paper deals with our observation of sprites associated with winter thunderstorms in the Hokuriku area and we show the characteristics of those sprites and their parent lightning discharges. Although the scale of Japanese lightning in winter is very small compared with the MCS (Mesoscale Convective System) for the summer continental lightning, the essential quantities (polarity, charge transfer, and so on) are found to be nearly the same as those for the MCS. However, an additional factor might be required, such as the self‐organization of the lightning. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 9–17, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20178     

Achievements of recent research on electrical discharges and theirpractical applications in Japan

In recent years, many of the researchers in the field of the discharge-aided environment improvement technology have been published, and it is expected that such a tendency will be continued for a considerable length of time in the future, and many fruitful outcomes are anticipated. It has conventionally been believed that that the understanding of the uses of discharge phenomena has mostly been due to experimental discovery, but in the future there will be accumulation of knowledge by the study of the collision process of electrons, atoms, and molecules. This latter approach has been vigorously promoted in Japan with practical use in mind     

雷击建筑物时的雷电流分布研究

建立了雷电流、雷电防护系统、配电变压器等配电网络的模型，利用国际通用的电磁暂态分析程序EMTP研究了TT系统（一种典型的低压与电系统）在遭受雷击时，雷电流在TT系统中的分布。并研究了单相和三相供电、不同波形的雷电流、传输线的线路阻抗对雷电流分布的影响。     

Study on the effectiveness of lightning rod tips in capturing lightning leaders

This paper addresses the performance of various lightning rod tips: pointed, concave, blunt, flat and conical for lightning air terminal (LAT). To observe the behaviour of the various lightning rod tips, laboratory examination was conducted under two conditions, i.e. corona emission pattern under quasi-static electric field and lightning impulse testing—with and without pre-ionization. The data obtained from the corona emissions were correlated to the surface sharpness area of the tip. Using dimensional analysis, it can be concluded there is strong evidence that increased surface sharpness can lead to an increase in the corona discharge current. In addition, an impulse test was conducted to determine the performance of the LATs with different tip types and sizes. Using the individual and competitive test, it was found that the blunt LAT is the most recommended receptor.     

A theoretical study on the consequence of a direct lightning strike to electrified railway system in Sweden

Direct lightning strike to a single-track electrified railway system in Sweden is modeled in this paper. Using this model, the induced voltages in each of the nine conductors at heights varying from 0.5 m (tracks) to 10 m above the ground are estimated. The effect of the finitely conducting ground is included using a time domain expression for the transient ground impedance that has better early time and late time behavior. The main interconnection between the conductors and the flashover strength of the supporting insulators is included in the simulations. A simple model for the arc channel during flashover of the insulators and the ionization of the soil around the pole foundations is also included in the model to assess the possible realistic surge voltage distribution in the system. It is shown in the paper that finite ground conductivity, interconnections between the conductors, arcing phenomena of insulation flashover and grounding of the poles decide the voltage/current distribution in the conductors. Simulations have been also carried out to determine the voltages on the lines and across the rails as function of distance from the point of strike as it could be a necessary data for deciding the possible future protection schemes. It was found that for a lightning stroke of 31 kA peak, large common mode and differential mode surges exist on the lines which could create excessive voltages between the line and neutral of the transformer and might pose a threat to the various low voltage equipments used for telecommunication, signaling and control.     

Quantification of the probability of lightning strikes to structures using a fractal approach

Recently fractal theory has been used to model the observed paths of lightning discharges. This paper extends previous work by using a fractal approach to describe the effects of tortuosity and branching of the lightning channel. In particular, we use the model to make predictions of the probability of lightning strikes to practical structures. Some of the specific estimates include the probability of strikes as a function of interception angle, predictions of the strike points on structures, and the probability of "side strikes" to tall structures. Significant polarity and geometric effects are shown. The shielding effects of nearby taller structures, shielding failure or "breakthrough" probabilities of so-called protected objects, and the effects of ground topography are also examined. The results are discussed in terms of the implications for the protection of structures against lightning.     

Phenomenon of skipping sparks in discharges on a dielectric surface

Gliding sparks are associated with channel breakdown in air near a corona precharged dielectric layer backed by ground. Characterized by high current, their bright channels usually end in sudden branching/dimming. Infrequently, there occur cases in which channel brightness is interrupted, with no evident local branching but a new leader continuing on propagating after momentary delay. This skipping-spark phenomenon has been studied in an experimental system intended for taking Kirlian photographs. Operated in a Lichtenberg-figure mode, the method yields evidence in some detail. The authors report on observations of spark-channel touchdown and subsequent rebounding. A model based on nonuniform surface charging is proposed for explanation     

海南强雷区典型配电线路差异化防雷措施研究

海南地处我国最南端,雷电活动极为强烈,绝缘水平较低的10kV配电线路极易因雷击跳闸,直接影响海南工农业生产生活用电.因此,有效提高10kV配电线路防雷性能评估水平与治理能力,对保证海南地区供电的稳定可靠十分重要.本文采用配电网差异化防雷技术开展海南强雷区10kV配电线路防雷综合治理研究,首先建立综合考虑雷电信息、线路结...     

Impact of surge arrester number and placement on reliability and lightning overvoltage level in high voltage substations

Surge arresters are the most critical equipment for protecting high voltage substations. They play an important role in substations for limiting switching and lightning surges and diverting these surges to ground. On the other hand, surge arrester number and placement for high voltage substations can be determined based on some evaluations in the designing process of substations. Surge arresters can be placed on the both ends of substations, transformers, circuit breakers, reactors, capacitors and also high long bus-bars and etc. Therefore, failure of arresters during overvoltage can put substations in risk condition. Moreover, surge arresters may be inclined to be short circuit during normal operation condition due to ageing process and/or improper quality. This paper attempts to assess reliability of three common substation configurations namely: (1) one breaker and a half; (2) double-bus double-breaker; and (3) ring bus-bar in different placement of surge arresters. At first, maximum voltages on equipment are calculated in different lightning stroke locations through simulation in EMTP-RV. Studies without surge arrester and the presence of surge arrester in different locations are analyzed and compared. Then surge arrester’s placement impacts on the substations reliability indices are calculated in normal operating condition and overvoltage condition by minimal cut set method and simulation results. Analytical studies reveal that surge arrester can increase substations reliability. But for low annual number of lightning stroke, substation reliability may decrease. Also increasing surge arrester number more than substation need reduces reliability.     

串联供气电池组性能研究

提高自增湿质子交换膜燃料电池水管理能力的关键在于电池组结构设计。采用反应气串联供给的电池组结构,且反应气经循环回路进入电池组进行再利用。实验结果表明:氢气循环对电池组内水分的均匀分布有一定的促进作用,氧气循环操作对电池组性能影响明显。     

Analysis of the response to a lightning strike of a towers cascade equipped with its grounding systems

This paper presents an analysis of the response to a direct and indirect lightning strike of a transmission line towers cascade using a direct time domain approach based on the corresponding transmission lines equations and finite difference time domain (FDTD) method. The proposed work deals with a real case of towers being connected by ground wires and equipped with grounding systems with different topologies (vertical or horizontal conductor buried in the ground). In particular, this work realistically represents the tower geometry and accounts for the propagation phenomena along the tower and between the towers. The analysis carried out in time domain deals with rather complex electrical devices (towers, ground wires and grounding systems), but at the same time requires very low computational cost and also provides relatively simple implementation. Some illustrative computational examples related to some engineering applications are given in the paper.     

220 kV同塔多回线路防雷措施探讨

介绍了上海地区历年来220 kV输电线路雷击跳闸情况,通过对同塔多回线路的雷击跳闸统计分析与防雷验算,探索了220 kV同塔多回线路防雷措施.     

Lightning occurrence characteristics in Japan for 17 years: observation results with lightning location systems of electric power utilities from 1992 to 2008

We summarize the lightning data for 17 years from 1992 to 2008 obtained with lightning location systems of nine electric power utilities in Japan and analyze them. The observed annual number of lightning flashes of which the current is more than 10 kA is 400 000–800 000 and the 50% value of the cumulative distribution of lightning peak currents is about 23 kA in recent times. The variation of lightning occurrence characteristics by areas, seasons, and so on, is clarified. Comparison of the obtained data with those obtained by another lightning location system is also made. The relationship between lightning occurrence and climate is discussed. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

The effect of neutral earthing practices on lightning currentdispersion in a low-voltage installation

Computer modeling with the EMTP code has been applied to several configurations and earthing practices in use in various countries to show the effect of any differences in the dispersion (sharing) of a lightning stroke current among the available paths for the earth-seeking lightning current. Simplifying assumptions have been made to some details of the configurations to focus on the main difference-earthing practices. Identifying such differences provides the necessary perspective on their significance and the strong need to take them into consideration when developing international standards on surge-protective device applications     

Contribution of surface conductivity to the current forms of partial discharges in voids

The current form of partial discharge (PD) in a void was divided into fast and slow components, with short and long fall times, respectively. Comparing these with the current shape of PD in a void between two metal surfaces, in which the slow component was not observed, it was suggested that the formation of fast component in a usual void was due to the instantaneous discharge between the discharge areas of the PD, i.e. the region to which the carriers in a PD process can instantaneously propagate, and the slow one might be due to the low conductivity in the regions outside the discharge areas. An equivalent circuit was proposed to describe the effect and numerical simulations were carried out. It was suggested that the fall part of the first PD after polarity reversal might reflect the surface conductivity change in aging process.     

应用线路避雷器提高10 kV配电线路防雷性能的研究

配电网系统作为电力系统的重要组成部分,承担着直接向用户供电的任务,是连接电网和用户的纽带,其安全运行非常重要.10 kV配电线路由于绝缘水平低的特点,易发生雷击过电压而造成绝缘事故.因此,10 kV配电线路的防雷保护是保证配电网安全运行、提高供电可靠性的重要措施.结合广东高要配电网的工程实际,以10 kV大企线为例,计算配电线路的耐雷水平和雷击跳闸率,并建立相应的ATP仿真模型,通过对安装线路避雷器前后的线路过电压水平的仿真计算,验证其能够有效提高配电线路的防雷性能,为工程设计提供有价值的基本数据.     

应用线路避雷器提高10 kV配电线路防雷性能的研究

配电网系统作为电力系统的重要组成部分,承担着直接向用户供电的任务,是连接电网和用户的纽带,其安全运行非常重要。10 kV配电线路由于绝缘水平低的特点,易发生雷击过电压而造成绝缘事故。因此,10 kV配电线路的防雷保护是保证配电网安全运行、提高供电可靠性的重要措施。结合广东高要配电网的工程实际,以10 kV大企线为例,计算配电线路的耐雷水平和雷击跳闸率,并建立相应的ATP仿真模型,通过对安装线路避雷器前后的线路过电压水平的仿真计算,验证其能够有效提高配电线路的防雷性能,为工程设计提供有价值的基本数据。     

Effect of mechanical vibration on the behavior of partial discharges in generator windings

As mechanical vibration usually exists in HV motors and generators, its influence on the partial discharge (PD) needs to be studied so as to improve the reliability of on-line PD monitoring method. In this report, the mechanical vibration frequency was synchronized to the power frequency and the effects of vibration phase and frequency were investigated. Because the length of the discharge gap changed with the vibration, obvious variation in the slot-PD patterns was observed at different vibration lead phase and frequency. Moreover, when the vibration amplitude was large, it was also found that the PD behavior at low voltage just above the PD inception voltage was different from that at higher voltage. This was explained in terms of the effects of the field variation in the gap due to the vibration and the charges left on the insulating surface due to PD.