Relationship between Creeping Discharge along Aerial Insulated Cable and Duration of Wave Front of Inductive Lightning Surge

We report the results obtained on the developing characteristics of creeping discharges along the insulated cable surface under inductive lightning surge voltages with various durations of wave front. The aerial insulated cables, usually, are supported by the post insulator and the binding wire at the reinforced concrete pole. When a lightning strikes near by the aerial insulated cables, the overvoltage due to the inductive lightning surge invades to the central line of the cable. The creeping discharge can develop along the cable surface from the free end of the binding wire just after a flashover of the post insulator at the cable supporting point. This creeping discharge may give rise to the accidents such as a melting or snapping of the cable. An important subject to prevent these accidents is to clarify the characteristics of creeping discharge along the cable surface and the developing mechanism of discharges. In this study, the impulse voltages with various durations of wave front are applied to the central line of the wire as the inductive lightning surge. The length and aspect of positive and negative creeping discharges developing along the cable surface are measured using a still camera with an image intensifier, and the developing mechanisms of creeping discharges are discussed on the basis of the models which are proposed taking into account the obtained results.     

Development of a positive creeping discharge along an aerial insulated wire

In high‐voltage aerial distribution systems, the insulated cables are supported by the binding wire with the post insulator at the utility pole. When a lightning strike occurs in the neighborhood of the insulated cable in an aerial power distribution system, inductive lightning surges invade the central line of the cable. Then, creeping discharges develop along the cable surface from the binding wire tip at the same time as flashover of the post insulator at a supporting point of the cable. If the cable insulator has weak points such as pinholes, a malfunction near the cable supporting point may occur, with melting of the wire due to punch‐through breakdown. To prevent such accidents, it is important to clarify the mechanism of the creeping discharge along the insulated cable caused by the lightning strike. The polarity of creeping discharges depends on the polarity of the inductive lightning surges, and the extension length and aspect of the discharge differ greatly depending on the discharge polarity. The development of these creeping discharges is attributed to complicated behavior of the positive and negative electric charges. In the present study, we examined in detail the development of a positive creeping discharge along a wire surface by using a high‐speed image converter camera. This paper describes the mechanism of development of a positive creeping discharge based on the experimental results. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(3): 20–29, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20997     

Characteristics of creeping discharge along aerial insulated wire under impulse voltages with various wave front durations

When lightning occurs in the neighborhood of outdoor high‐voltage distribution lines, creeping discharges propagate along the wire surface from the binding wire tip just after insulator flashover. These discharges give rise to various faults on distribution lines, for instance, disconnection and melting of wire, punch‐through breakdown, and so on. We must clarify the creeping discharge characteristics associated with various inductive lightning surges from the viewpoint of safety in high‐voltage distribution systems. In our previous paper, it was reported that the lengths and aspects of the negative creeping discharges were influenced by the wave front durations of impulse voltages applied to the central line with a grounded binding wire. The present study was performed to obtain more information on such creeping discharges. This paper describes the distinctive characteristics of a creeping discharge along the insulated wire surface when impulse voltages with various wave front durations are applied to the binding wire. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 29–37, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20430     

The influence of wave front duration of impulse voltage on creeping discharges along aerial insulated wire

In high‐voltage aerial distribution systems, creeping discharges progress along the cable surface from the free end of the binding wire when overvoltages caused by a lightning surge have invaded the central line of an insulated cable. Consequently, various accidents such as punch‐through breakdown, melting, or snapping of a cable, often occur at these systems. In our previous studies, it has been clarified that the lengths and aspects of creeping discharges under a 1.2/50 µ s impulse voltage condition can be markedly affected by changes in the electric field strength on the cable surface. However, lightning impulse surges which may invade the central line of a cable have various wave front durations. This will further complicate creeping discharge phenomena due to lightning. In this paper, we report the influence of the wave front duration on both the lengths and the aspects of the creeping discharges which progress on the cable on application of lightning impulse voltages. It has been shown that the behavior of negative creeping discharges reveals pronounced changes in response to the duration of the wave front of the applied voltage. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(2): 30–38, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10263     

Study concerning production of lightning overvoltages on low‐voltage power distribution lines

In order to study lightning problems of low‐voltage power distribution lines, lightning overvoltage waveforms were observed inside the homes of customers. The cause of lightning overvoltages was examined from observation of striking points by still cameras. Lightning overvoltages of 62 waveforms were recorded by observation over a period of about 3 1/2 years. Observed waveforms can be classified into three types of single polarity (positive or negative), both polarities (which change from positive to negative or negative to positive), and pulsive waveform. The causes of these lightning overvoltages which were estimated from striking points are shown as follows: (1) Induced lightning overvoltages on low‐voltage distribution lines. (2)   Electric potential rise due to discharge of surge arresters or current of overhead ground wire. (3)   Shift of lightning overvoltages from high‐voltage side of transformer to low‐voltage side, which is due to electromagnetic induction. © 2000 Scripta Technica, Electr Eng Jpn, 130(4): 66–75, 2000     

Observation of lightning at 500‐kV transmission lines (part 1)

We investigated the phenomenon of lightning strokes on 500‐kV transmission lines from 1984 to 1993. The investigation covered the recording of lightning paths by still cameras and measurements of lightning current at the lower part of transmission tower on 31 towers, over a 12.7‐km‐long section of the transmission line. We also observed lightning on an isolated tower at a nuclear power station. In the course of lightning observations spanning a 10‐year period, we have confirmed the suitability of the lightning protection design on transmission lines. The distribution of lightning incidence angle (θ) expressed in terms of (cos^mθ) was characterized by exponent m = 2 for the three‐dimensional observations and m = 3.5 for the two‐dimensional observations. No cases of shielding failure on 500‐kV transmission lines were observed. The ratio of lightning current at the top of the isolated tower to the lower part was about 11 to 1. In addition, the lightning current waveform at the top of the isolated tower was similar to that at the lower part. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 59–67, 2000     

两起多重雷击引起的220 kV断路器断口瓷套外闪的分析

介绍了两起因线路多重雷击引起的220 kV断路器断口瓷套外闪的事故发生的过程和原因分析,据此,建议在变电所线路的出线安装线路避雷器限制开断状态的断路器断口的过电压.     

UHV MOA设定30kA级标称放电电流的必要性

为提高变电站过电压保护及避雷器运行的可靠性,从标称放电电流如何影响1000kV避雷器的保护特性、运行特性,以及特高压变电站的雷电侵入波保护可靠性等方面出发,对1000kV变电站雷电侵入波及通过避雷器雷电流进行了EMTP仿真分析,并按1000kV变电站雷电侵入波平均无故障时间>1500a的要求,根据IEC60071-2、IEC60099-5的基本原则,讨论和分析了1000kV特高压交流系统用无间隙金属氧化物避雷器(MOA)标准,认为设定30kA标称放电电流等级是必要和可行的。     

Relationship between the energy distribution of electrostatic field change and lightning activity

A lightning strength parameter α (denoted as LSP or LAIDO), which is used for characterizing the phenomena of lightning activity, has been proposed, where α is defined by the characteristic energy obtained from the energy distribution of a radiated field component E in the electrostatic field changes produced by lightning discharge. Here, it is observed that the energy distribution of E_γ components is Maxwellian type. To prove more clearly the forementioned assumption from another viewpoint, changes of the amplitudes of the electrostatic field component E_S were measured and their distribution functions constructed. In the cloud-to-ground lightning discharges, the E_S components have a positive sign in the changes. However, those changes in the intercloud discharges are observed with either a negative or positive change depending on the distance between the striking point and the observation site. Therefore it is necessary to sum the numbers of occurrences of both positive and negative components for constructing an energy distribution of the E_S component. A fieldmill and a pair of doughnut-shaped electrostatic antennas are used in measuring the changes of the E_S component. As a result it is found that the changes of the amplitudes of the E_S components have a Maxwelliantype energy distribution. A characteristic energy β is defined which is obtained from the component of the electrostatic fields as a measure of LSP. Based on comparison of α and β it is clarified that β has the same characteristic nature with α. The lightning activity could be estimated from β.     

云广±800 kV特高压直流输电线路耐雷性能研究

国内外运行经验表明,雷击是造成输电线路跳闸的主要原因。基于杆塔的多波阻抗模型和基于先导发展的雷电屏蔽模型,分析了云广±800 kV特高压直流输电线路的反击、绕击耐雷性能及其影响因素。结果表明：随着杆塔高度的降低,冲击接地电阻的减小,线路反击性能增强;随着保护角的减小,地面倾角的减小,海拔的降低,线路雷电屏蔽性能增强;引起特高压输电线路雷击故障的主要因素是雷电绕击,建议特高压输电线路采用负保护角运行。     

输电线路雷害分析及防雷措施

基于对黄冈电网220kV及以上输电线路历年雷击闪络故障的分析,以及找到的故障原因,提出了降低杆塔接地电阻、加装线路避雷器和安装可控放电避雷针等多种防雷措施,并进行了实施,经过实际运行验证,采取的这些防雷措施有效地降低了线路雷击跳闸率。     

国外对特高压输电线路雷击跳闸原因的一个新观点

介绍了国外在分析特高压输电线路雷击跳闸原因时提出的一个新观点,即雷电击中档距中间部位的避雷线会引起避雷线相导线间隙击穿放电,进而引起线路跳闸。采用避雷线负保护角并不能避免这种放电发生。提高避雷线保护匠有效性可以通过减小避雷线一相导线间隙击穿概率来达到。     

针对某35kV配电线路防雷问题的探讨

雷击是导致35 kV配电线路故障的重要原因之一。丘陵地区雷电活动频繁,对35 kV架空线路的安全运行危害极大。衡量线路防雷性能优劣的重要指标有两个:一是线路雷击跳闸率;二是线路耐雷水平。分析了河南某35 kV线路防雷现状,认为线路耐雷水平不高、运行维护不到位、防雷措施不够完善是导致35 kV配电线路雷击跳闸率高的重要原因。结果表明:采取全面检测绝缘子,更换劣质绝缘子、加装带间隙的线路避雷器、提高线路的绝缘水平、采用输电线路绝缘子并联间隙技术保护改造方案、架设避雷线等多种措施进行综合治理,可以大幅度减少雷害事故。     

两次仅有连续电流的负极性人工引发雷电特征分析

对2006年8月28日在广州从化人工引发的两次雷电(F184626和F185503)的特征进行了分析。这两次触发闪电都是经典负极性慢型放电过程,整个放电过程仅有连续电流没有回击,但连续电流过程中包含有多个M分量。两次过程触发时地面电场分别为-6.1 kV/m和-8.2 kV/m,触发高度分别约336 m和244 m。资料分析表明,两次人工引发雷电形成稳定上行正先导之前,出现多次明显的双极性脉冲,脉冲间隔平均值分别为18.12 ms和16.64 ms;在上行正先导产生初始阶段出现明显的阶梯特性,梯级先导脉冲的平均间隔分别为20 ms和24 ms,总持续时间都约为250 ms,脉冲的宽度约1 ms。8月28日的两次触发闪电与以往北方正极性的慢型放电过程相比有连续电流持续时间较长等特征。     

Experimental and analytical studies on lightning surge characteristics of a buried bare wire

Lightning surge analysis is very important from the viewpoint of insulation design of transmission lines and substations. Lightning surge analysis has many parameters, which include lightning surge characteristics of transmission towers, back flashover phenomena at an arcing horn, characteristics of footing resistance, effects of corona wave deformation, characteristics of electromagnetic fields caused by lightning, and other parameters. This paper describes experimental and analytical studies on lightning surge characteristics of a buried bare wire. The measurement of the lightning surge characteristics of the buried bare wire is carried out under various experimental conditions. The experimental parameters controlled in these experiments include earth resistance, length of the buried bare wire, and waveform of the injected current. The measured results are compared with analytical results based on the theoretical study by Sunde. A comparison of the measured results with the analytical results shows good agreement. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(3): 35– 41, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20532     

Simulation of Lightning Overvoltage Distribution on Stator Windings of Wind Turbine GeneratorsEI北大核心CSCD

This paper analyzes lightning surge on the stator windings of wind turbine generators. The path of lightning in the wind turbines was analyzed. An equivalent circuit model for megawatt direct-driven wi...     

化工储罐区防雷状况分析

雷电是自然界中普遍的现象,它是由于雷雨云中电荷放电而产生的复杂的自然现象,也是一种会造成严重灾难的自然现象。根据气候、卫星及闪电定位仪观资料估计表明,在任一秒,全球表面上连续发展着大约100个雷电。雷电放电过程同时出现三种物理现象：静电感应、电磁感应和辐射感应。对不同的场合会有不同程度的危害,仅依靠传统避雷针等直击雷防...     

电源类电涌保护器的安全性

针对低压电源感应雷电,采用电涌保护器进行防护已是目前普遍采用的方法。从低压电源系统故障、防雷器件特性、防雷标准、防雷产品、试验检测等方面,对电源类电涌保护器进行了相关论述。指出电涌保护器工作在低压电源系统中,在考虑雷电防护能力的同时,也必须关注产品的安全性。     

Quantitative evaluation of lightning surge range voltage–time characteristics in high‐pressure SF6 gas

Gas‐insulated switchgear (GIS) is subjected to very fast transient overvoltages such as lightning surges or disconnector switching surges. Therefore, the sparkover voltage and time (V?t) characteristics of SF₆ in a very short time range of less than are of great interest from the viewpoint of insulation design and coordination for a GIS. This paper describes the V?t characteristics of SF₆ at a gas pressure of 0.5 MPa using a steep‐front square impulse voltage under a quasi‐uniform field gap and presents a quantitative evaluation of the V?t characteristics for a nonstandard lightning impulse voltage. In the case of a square impulse, the V?t characteristics of positive polarity were observed to be almost flat over a long time range from 80 ns to , and rose steeply over a short time range from 80 ns down to 20 ns. For negative polarity, the V?t characteristics exhibit a gentle rise from 200 ns down to 40 ns. In the estimation of V?t characteristics, the equal‐area criterion parameters were quantitatively estimated using the square impulse. For a nonstandard lighting impulse, we found that application of the equal‐area criterion with these parameters for the nonoscillating impulse and oscillating impulse of up to 5.3 MHz as a model of lightning surge and disconnector switching surge is possible. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 8– 17, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20309     

750 kV输变电示范工程单相人工接地故障试验现场实测和计算分析

应用电磁暂态计算程序(electromagnetictransientprogram,EMTP)对安装金属氧化物避雷器的35kV配电线路的耐雷水平进行了分析计算。具体比较了雷击有、无避雷线的线路,采取不同避雷器安装方案时的耐雷水平;分析了杆塔冲击接地电阻、绕击导线位置对耐雷水平的影响。仿真计算结果表明,安装线路避雷器﹑减小杆塔的接地电阻可有效提高35kV配电线路的耐雷水平。对于35kV有避雷线配电线路,加装线路避雷器后可显著降低其发生绕击闪络的概率。