冲击发电机系统的过电压防护研究

为了设计冲击发电机系统的金属氧化物避雷器MOA保护系统,计算了开断时间极快,产生过电压较断路器操作过电压高的限流熔断器过电压;采用有限元方法分析限流熔断器熔体的熔化、汽化过程,得到熔体的热电耦合模型,该模型可求出熔断器开断过程的电阻-时间特性;在EMTP/ATP中建立熔断器开断试验系统模型,并分析接入不同类型MOA时,发电机端、熔断器端的过电压幅值;建立MOA的有限元模型,研究MOA的热特性和使用寿命。在冲击发电机系统中进行的不同型号限流熔断器开断试验验证了计算结果,该MOA保护方案能有效的保护发电机。     

Coordination of surge arresters with medium-voltagecurrent-limiting fuses

Current-limiting fuses (CLFs) are commonly used for unit substation primary protection. Simultaneously, surge arresters are also provided on the primary side of the transformers, more so for the dry-type transformers. The arc voltages generated by CLFs will store energy in the inductive elements of a distribution system. This stored energy divides between the CLF and surge arrester, and the surge arrester may operate. This paper outlines a procedure to calculate the energy diverted to the surge arresters and shows that, in some cases, surge arresters may fail on operation of the CLFs. Guidelines are developed for selection and application of the surge arresters at 13.8-, 4.16-, and 2.4-kV voltage levels     

Detection of Damaged Distribution Surge Arresters Using an Impulse Generator

Distribution surge arresters with an internal series gap have been installed on Japanese distribution lines at high density to reduce lightning‐related overvoltages. In contrast, surge arresters are sometimes damaged by direct lightning strokes, particularly in winter. Measurement of the insulation resistance between the terminals of the surge arrester and measurement of the dc discharge voltage of the surge arrester are generally adopted to detect damaged arresters. However, if metal‐oxide (MO) varistors are damaged and the internal series gap is not damaged, it is difficult to detect damaged arresters by the two conventional methods. Therefore, this paper presents a proposed detection method that can accurately detect damaged arresters. In the proposed method, first, the voltage between the terminals of the surge arrester is measured when the output of an impulse generator is applied to the surge arrester. Second, the damaged arrester is detected by comparison between its voltage waveform and the voltage waveform of the nondamaged arrester. The detection rate of damaged arresters by the proposed method is markedly higher than the rates of detection by the two conventional methods.     

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.     

复合外套避雷器在昌房500kV紧凑型线路的防雷效果分析

５００ ｋＶ昌房紧凑型线路采用线路避雷器后,能较大地提高线路的耐雷水平。紧凑型线路避雷器本体的荷电率取０．９,完全能承受雷击杆塔时的放电电流和放电能量。     

Rocket-triggered lightning experiments on zinc oxide arresters and their applications to power transmission lines

In measurements of rocket-triggered lightning current and voltage performed between 1986 and 1995 on the mountain top of Okushishiku in the Kanazawa area, the authors succeeded in artificially inducing winter lightning to arresters. Using the data obtained from those measurements, we analyzed the energy absorption characteristics of surge arresters, such as are installed on every transmission line tower for three phrases, by EMTP. The energy withstand capability of an individual arrester was verified to be approximately the same as the expected value. The analysis results for the energy share of each arrester connected in parallel showed that the usual light duty arresters installed on every tower have the possibility to be able to absorb extreme winter lightning energy even if the lightning hits the power line directly. © 1998 Scripta Technica. Electr Eng Jpn, 122(4): 25–33, 1998     

Assessment of surge arrester failure rate and application studies in Hellenic high voltage transmission lines

The use of transmission line surge arresters to improve the lightning performance of transmission lines is becoming more common. Especially in areas with high soil resistivity and ground flash density, surge arresters constitute the most effective protection mean. In this paper a methodology for assessing the surge arrester failure rate based on the electrogeometrical model is presented. Critical currents that exceed arresters rated energy stress were estimated by the use of a simulation tool. The methodology is applied on operating Hellenic transmission lines of 150 kV. Several case studies are analyzed by installing surge arresters on different intervals, in relation to the region's tower footing resistance and the ground flash density. The obtained results are compared with real records of outage rate showing the effectiveness of the surge arresters in the reduction of the recorded failure rate. The presented methodology can be proved valuable to the studies of electric power systems designers intending in a more effective lightning protection, reducing the operational costs and providing continuity of service.     

Lightning overvoltage protection of AC railroad vehicles bypolymeric arresters

In order to improve the operational reliability of AC railroad vehicles, ZnO surge arresters are used to protect them against overvoltages. The most serious threat to arresters installed on the roof of an AC railroad vehicle is the lightning overvoltage. When lightning strikes the mast or conductors, the distribution system can be treated as a system of multiple conductors including feeders, messenger wires, contact wires, protective wires and two tracks. The lightning impulse discharge current through the arrester and the absorbed impulse discharging energy by arrester in the actual field operation and the protective effect of arrester were analyzed by EMTP and discussed when lightning strikes the mast or distribution lines. When the arrester Is installed on the roof of a railroad vehicle, the potential difference on the primary side of high voltage transformer inside the vehicle is suppressed below 150 kV under very serious condition     

Suppression of lightning-induced overvoltages by distribution line surge arresters

The primary aim of surge arresters in power distribution lines is to protect lines and equipment from the voltage induced by nearby lightning strokes. To further improve power systems, methods to protect distribution lines against direct lightning strokes are still needed. An effective measure against direct lightning strokes is to increase the number of arresters. However, if the surge current is too large, some surge arresters absorb energy in excess of their capability and may break; this leads to a line fault. To evaluate the protective effect of the surge arresters against direct lightning strokes to overhead ground wire, the authors measured both the voltage across the surge arresters and the energy absorbed by them using a full-scale model line and a 12 MV impulse generator. The results were compared with simulation results by EMTP. There have been no previous studies making a comparison of this kind.     

F＆G高效的防雷及浪涌保护器

分析了防雷三级保护的必要性。介绍F&G电源防雷用低压侧全范围三级浪涌保护器的用途、结构特点、性能、主要技术参数和功能附件。给出了在不同接地系统中的应用线路和后备保护熔断器的选择方法     

Distribution arrester outages caused by lightning backflow current flowing from customer's facility into power distribution lines

Direct lightning strokes are considered to be a main cause of damage to surge arresters on power distribution lines. Recently, lightning performance of distribution lines has been observed using still cameras, and lightning‐caused distribution outages on hilltop areas on the coast of the Sea of Japan have been investigated. This research has shown a possibility that lightning backflow current flowing from customer facilities into distribution lines causes damage to surge arresters on the distribution lines. We have investigated the lightning backflow current flowing from customer facilities into distribution lines as a cause of damage to surge arresters. The main results are as follows: (1) The electric charge of the backflow current flowing into distribution lines is more than 60% of that of the lightning stroke current. (2) If the grounding resistance of the customer's facility is not low, the failure rates of a surge arrester caused by backflow current due to winter lightning is more than 90% of that caused by direct lightning strokes. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 9–20, 1999     

Use of line surge arresters for the improvement of the lightningperformance of 63 kV and 90 kV shielded and unshielded transmissionlines

The lightning performance of 63 kV and 90 kV shielded and unshielded power transmission lines, protected by surge arresters are considered. A specialized software package is used for the computation of the line's fast front transients. A Monte Carlo statistical method, together with a three-dimensional electrogeometric model is used to determine the lightning stroke locations. Different arrester installation configurations are analyzed and compared. The energy duties of the transmission line surge arresters are computed statistically     

A Procedure for Estimating the Lifetime of Gapless Metal Oxide Surge Arresters for AC Application

The development of the gapless metal oxide (ZnO) surge arrester has presented the arrester engineer with new materials and an opportunity for new designs. This situation arises because the gapless surge arrester is electrically active throughout its lifetime whereas its predecessor, the silicon carbide arrester, was electrically passive being electrically isolated with gap structures. The prime consideration is one of reliably estimating the lifetime of a gapless ZnO surge arrester under continuous ac stress while maintaining the capability not only to limit surge voltages but also to absorb energy inputs resulting from lightning or switching surges and temporary overvoltages. In this paper we establish a procedure for reliably estimating the lifetime of gapless metal oxide surge arresters for ac application by incorporating the device characteristics into design requirements. This method is illustrated for metal oxide surge arrester elements that exhibit a predictable linear resistive current versus time1/2 behavior as a function of applied voltage and temperature.     

陕西地区配电线路新型防雷装置研究与应用

针对陕西地区配电线路避雷器防雷效果不理想这一现状,提出一种多腔室雷击闪络限制器。该装置防雷性能优异,采用吹弧原理,熄弧能力强。经过试验,确定其串联级数为26级,电极直径8 mm,电极间隙1 mm,主间隙距离取45 mm时能可靠动作。工频湿耐受电压、50%雷电冲击动作电压、雷电冲击伏秒特性以及工频续流遮断能力均满足标准要求。装置在陕西地区典型线路上运行良好,防雷效果优异。     

具有绝缘子性能避雷器的结构设计与试验分析

高压输电线路通常采用线路避雷器并联绝缘子的方式作为其防雷措施,从而保证绝缘子在雷电时免受过电压闪络损伤,而此方式却造成线路和铁塔的负荷增大,线路设施复杂化。针对上述问题设计了一种具有绝缘子性能的避雷器,结合绝缘子和避雷器的试验标准以及设备的结构特点进行了试验研究和测试,并给出明确的试验项目和测试结果。     

输电线路避雷器断串分析与防范

目前采用的线路型避雷器多为绝缘子间隙避雷器。运行单位在安装线路避雷器时主要考虑的是避雷器的电气性能,很少对避雷器的安装形式和运行状态下的受力情况进行分析,以至运行中出现掉串现象。例举了一起线路型避雷器断串缺陷,通过计算分析得出断串的原因,并提出了避雷器安装的防范措施。     

500 kV线路避雷器保护失效分析及改进措施研究

线路避雷器是防止输电线路雷击跳闸的有效手段,随着高电压等级线路避雷器的使用,出现了因安装方式导致的线路避雷器保护失效问题。针对某500 kV输电线路发生的线路避雷器在大幅值雷电流反击下对绝缘子串保护失效的问题,采用电磁暂态分析软件ATP-EMTP建立了仿真分析模型,分别对雷电流绕击和反击情况下绝缘子串和线路避雷器两端承受的电压进行了量化,得出了导致反击情况下线路避雷器保护失效的原因;提出了对现有500 kV线路避雷器安装方式的改进方案,并对改进方案下反击雷电流导致的绝缘子串和线路避雷器两端电压波形进行了比较,验证了改进措施的有效性。所研究成果对于500 kV及以上电压等级线路避雷器的使用具有重要参考价值。     

Rotating Machinery Protection Using Metal Oxide Arresters

Metal oxide arresters are ideal for the protection of rotating machines against overvoltages. The absence of gaps, required in older silicon carbide arresters, results in more consistent operation and improved protection for fast-front surges. Also, the absence of gaps permits tailoring lower voltage arrester ratings to match the application of rotating machinery. The application of arresters along with the use of surge capacitors is discussed, to limit both magnitude and rate of rise of surge voltages, for the protection of sensitive insulation systems on a variety of medium voltage systems.     

Effect of overhead ground wires on reduction of failure rates of surge arresters on power distribution lines

Surge arresters are sometimes damaged by lightning strokes with high energy, in spite of installation of conventional protection methods. In order to reduce the number of failures of surge arresters, we should consider another protection method, such as an increase in the withstand capability of surge arresters and installation of additional overhead ground wires. However, quantitative comparison of these methods for preventing damage to surge arresters against lightning strokes with high energy has never been performed. This paper describes the effects of additional overhead ground wires for preventing damage to surge arresters. The main results are: (1) The failure rate of surge arresters on a distribution line with two overhead ground wires is about one third of that with an overhead ground wire. (2) Installation of a second overhead ground wire six to eight spans from the end of a line reduces the failure rate of a surge arrester at the end as effectively as increasing the withstand capability by a factor of two. © 1998 Scripta Technica. Electr Eng Jpn, 122(2): 12–20, 1998     

基于K-Means高频局放10 kV避雷器快速带电检测方法 研究

针对视觉观察、红外测温、超声波成像、泄漏工频电流和直流分量等方法无法快速发现10 kV配网架空线路上的氧化锌避雷器内部受潮及绝缘缺陷问题,文中提出了基于K-Means智能识别缺陷类型的方法及原理,使用人为制作10 kV氧化锌避雷器内部受潮、阀片裂纹等缺陷样品,通过无局放源的升压装置,加压至10 kV额定电压,通过高频电流传感器(HFCT)、高速采集卡拾取局部放电数据,建立氧化锌缺陷类型数据库;通过在现场不同测点测得不同10 kV氧化锌避雷器亚稳态下的13组数据,结果表明该方法对10 kV避雷器内部绝缘缺陷、内部受潮缺陷识别准确率达到98%以上,验证了基于K-Means高频局放10 kV氧化锌避雷器快速带电检测方法正确性,具有较高的经济效应和社会使用价值。