Power distribution system equipment overvoltage protection

Application of surge overvoltage protection devices in general is based upon rule of thumb without the benefit of understanding basic parameters, system components and configuration, and energy content of the surge. This may result in the selection of an inadequate device. Selection of surge protective devices should be based on the magnitude of surge overvoltage, and also upon the expected energy associated with the surge. Characteristics of surge arresters are reviewed from the application point of view. Fundamentals of surge energy are presented. The MOV surge arrester selection parameters are discussed. The need for industry standards for the application of DC surge arresters is contemplated     

Protecting load devices from the effects of low-side surges

Wherever lightning and poor utility power system grounds exist, distribution secondary systems are subjected to high-voltage surges due to lightning current seeking ground through low-voltage circuits. Utilities are becoming aware of this low-side surge phenomena and are taking measures to protect their distribution transformers' secondary windings. These measures can increase the voltage stress at the customer service entrance. If any ground paths exist on the customer side of the service entrance, surges can penetrate further into the customer's system and damage loads. Damage caused by low-side surges can be avoided if properly coordinated arresters are installed at the transformer secondary, at the service entrance, and at load devices. This work describes the secondary surge phenomena and the importance of protecting the service entrance and critical load devices effectively, especially when the transformer secondary is protected. A properly coordinated and effective protection scheme is described and recommended     

Device for diagnostic monitoring of surge arresters

Basic reasons for the failure of nonlinear surge arresters are considered; most widely spread methods and devices for diagnostic monitoring of nonlinear surge arresters in the course of their operation are analyzed, and a new monitoring device registering discharge current pulses caused by lightning and switching voltage surges is proposed.     

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.     

Lightning and Power Surge Damage to Appliances

Lightning rarely damages appliances by direct stroke to the appliance. Damage is usually caused by direct strokes to the power lines or by induced surges. Induced surges are caused by the release of bound charges on the line when overhead clouds lose charge because of a strike to objects other than the line. The direct stroke produces a large voltage, while induced surges usually have a lower magnitude voltage. Lightning usually damages appliance electrical insulation which leads to a continuation of the damage by the 60-Hz power that has the appearance of a non- lightning-related failure. Lightning or power surge damage can probably be ruled out if the equipment has failed because of certain problems such as an open conductor or a bad bearing. Electric lamps can provide a clue as to whether a high-voltage surge occurred in the electrical system because the filaments often open when subjected to such surges. Equipment can be protected by a design to withstand the highest normal voltage spikes expected. Proper grounding and bonding also is important. For critical components or equipment, surge arresters may be required.     

Diagnostic methods in revealing internal moisture in polymer housed metal oxide surge arresters

Diagnostic measurements performed for surge arresters are normally studied by evaluating their suitability to detect aging and degradation of metal oxide material. The suitability of different methods for revealing internal moisture in arresters has not been studied much. This aspect is considered in the paper based on measurement results obtained during a 1.5-yr laboratory test series conducted for six different types of polymer-housed distribution class arresters. AC power losses, third-harmonic content of resistive leakage current, DC leakage current, and partial discharge measurement results over the test period are given and discussed. Details of the measurement procedures suitable for measuring polymeric arresters with internal moisture are also studied. AC power loss and DC leakage current measurements were found to be good methods, whereas the other two can only be used as additional methods when diagnosing internal moisture in polymer-housed arresters.     

全碳化硅大功率直流电源关键技术研究

碳化硅SiC(silicon carbide)功率器件的耐压、频率和损耗等特性均优于硅(Si)器件,然而SiC器件抗冲击能力差、电磁干扰大,且SiC器件对整个功率变换系统的贡献尚缺乏分析验证,因此,采用全SiC器件研制高性能的大功率直流电源具有一定挑战.首先针对SiC器件抗冲击能力差的问题,引入嵌入式保护策略,应对直流...     

Laboratory and analytical studies of the effects of multipulselightning current on metal oxide arresters

Multiple stroke lightning ground flashes can impose surges of exceptional severity on the arresters used to protect exposed distribution system equipment. This paper reports laboratory and analytical studies of the effects of representative multiple impulse currents on zinc-oxide surge arresters of distribution class. The results indicate that sextuple 8/20 μs currents can cause damage to arresters not evident with standard lightning current tests and so are worthy of inclusion in testing Standards     

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.     

一种氧化锌避雷器阻性电流的提取方法

氧化锌避雷器作为电力输变电系统的一个核心保护设备,必须进行在线状态监测。文章在研究氧化锌避雷器常用的在线监测方法的基础上,提出了一种基于谐波分析法的新的氧化锌避雷器阻性电流提取方法。该方法采用准同步DFT谐波分析线性修正算法来实现氧化锌避雷器的阻性电流的测量。仿真实验和现场实验表明,该方法可行、有效,有极高的应用价值。     

Evaluation of polymer-housed distribution arresters for use onrural electric power systems

Users have converted to polymer-housed distribution surge arresters because of concerns over violent porcelain arrester failure. There is a false perception in the industry that polymer arresters are intrinsically fail-safe. It is proposed that there is a lack of understanding of the differences in failure mechanisms between porcelain and polymer arresters. Polymer arresters have unique design requirements to provide the desired reliability improvements. This paper suggests criteria for rural electric power system user evaluation of polymer arrester design and performance. Users are encouraged to participate in the standards writing process to facilitate changes beneficial to the industry     

Impact of shunt capacitor banks on substation surge environment andsurge arrester applications

The introduction of high voltage shunt capacitor banks on a power system can result in a number of overvoltage problems that tend to be associated with capacitor switching. The paper describes how proper application of surge arresters near a shunt capacitor bank requires careful analysis of the power system, the switching devices and their arrangements, the insulation level of nearby equipment, the type of grounding and the arrester energy dissipation duty     

Investigation of effect of transmission line arresters verified by lightning surges at substations

In recent years, transmission line arresters have been installed to protect overhead power transmission lines from backflashovers caused by lightning. In addition, it has been expected that substation lightning surges incoming via transmission lines can be suppressed by them. However, the suppression effect by those with series gaps has not been investigated sufficiently. The author has measured lightning surges at two 77‐kV substations from 1990 to 1993. As the transmission line arresters have been mounted on the towers since 1992, the lightning surges due to the sparkover of the series gap of the transmission line arresters can be observed at the substations. In this paper, the lightning surge waveforms due to such sparkover have been analyzed in detail. Next, an accurate EMTP simulation method considering the induced lightning surge voltages has been proposed. Finally, their suppression effect has been investigated by simulation corresponding to each mounting method. © 1999 Scripta Technica, Electr Eng Jpn, 126(4): 30–39, 1999     

Metal oxide arresters on distribution systems: fundamentalconsiderations

The authors compare the reliability of metal oxide and silicon carbide distribution arresters by examining the likelihood of failure as a result of moisture leakage and contamination, overvoltages, and lightning surges of high magnitude and long duration. It is found that metal oxide distribution arresters should be highly reliable in most applications because the arresters are far less likely than silicon carbide arresters to fail as a result of moisture ingress and contamination. Metal oxide arresters are more likely to fail as a result of system overvoltages because they conduct current in response to the overvoltages, and for this reason somewhat more care must be exercised in application to match the magnitude and time duration of system overvoltages to the temporary overvoltage capability of the arresters. Comparison of published metal oxide arrester energy absorbing capability against the energy absorbed in lightning surges that have been shown to exist indicates that the probability of failure may be high in areas of high lightning intensity. The authors suggest changes in the ANSI/IEEE C62.11 standard for metal oxide arresters to improve arrester reliability on lightning surges     

天生桥—广州直流工程控制保护系统改造后的过电压分析

基于改造后的天生桥—广州±500 kV高压直流输电工程,计算分析了在换流变Y/Y线圈阀侧单相接地、交流相间操作冲击、逆变侧失交流电源和逆变侧闭锁而旁通对未解锁4种典型故障工况下的系统过电压,确保在改造后的控制保护系统下,系统各点过电压及避雷器能耗限制在合理范围内,各电气设备能安全运行。分析结果表明:换流变Y/Y线圈阀侧单相接地故障将在中性母线上产生较高过电压,中性母线避雷器能耗较大;交流相间操作冲击会在阀两端产生较大过电压,阀避雷器动作;逆变侧失交流电源会在逆变站交流母线产生较高过电压,交流母线避雷器动作。逆变侧闭锁而旁通对未解锁会在逆变侧直流极线产生很高的过电压,直流极线避雷器能耗较大。上述4种故障工况下,各避雷器能耗均未超过设计通流容量,避雷器能安全稳定运行。     

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     

Multipulse lightning currents and metal-oxide arresters

Multiple stroke lightning ground flashes can impose surges of exceptional severity on exposed distribution surge arresters. This paper describes a series of tests on metal-oxide (MO) arresters and varistors to study surface flashover mechanisms. The results show that the more likely causes of surface flashover were plasma generation, manufacturing defects of the varistor surface coating, dielectric properties of the surface coating and the electrode contact system. For multipulses, plasma enhancement and varistor surface coating were found to play a dominant role in surface flashover     

浪涌抑制与电磁兼容

浪涌是低压电源线中最频繁发生的过电压和电流波动现象.研究电源线中的浪涌时不仅要分析它的电压幅值高低,还要分析它的电流和能量.电源线中浪涌抑制需要从过电压保护和电磁兼容两方面考虑.作者通过计算标准测试浪涌的波形和频谱,指出浪涌危害的主要原因和保护低压电源线与其上电子设备电磁兼容性的措施.最后计算了在交流电源中用氧化锌压敏电阻对浪涌进行限幅和泻流的一个实例.     

Temporary overvoltage capability of surge arresters for 1000 kV power systems

Insulation level (LIWV 2250 kV) of 1000 kV gas insulated switchgear will be adopted by installing high performance 1000 kV surge arresters. But when temporary overvoltage (TOV) is generated in power systems at line faults and load rejection including Ferranti effects, high performance surge arresters flow discharge current according to the value of TOV. Therefore, it is important to check TOV discharge capability of surge arresters. This paper describes the screening of zinc oxide elements using thermography (thermal uniformity factor) obtained by an infrared radiation camera, with discharge capability of surge arresters for 1000 kV power system.     

Transmission line arrester energy, cost, and risk of failureanalysis for partially shielded transmission lines

Application of metal oxide surge arresters in power systems has been traditionally linked to electrical equipment protection. The industry has noted a very significant increase in the application of metal oxide arresters on transmission lines in an effort to reduce lightning initiated flashovers. This paper describes a cost-effective installation of surge arresters on a partially shielded transmission line. It compares several options with respect to cost and gains in terms of lightning performance improvement. This paper also presents a new approach to calculate risk of failure of transmission line surge arresters (TLSAs) due to lightning strokes to towers, shield/phase conductors, and illustrates the method with an example for a partially shielded line. Results show that the risk of failure is very small. The installation of TLSAs completed in 1997 demonstrated that it is possible to afford adequate lightning protection levels by selectively applying surge arresters only to the towers most sensitive to backflashover and shielding failures