1000kV交流特高压瓷外套金属氧化物避雷器的结构分析

本文根据《1000kV交流特高压试验示范工程主设备技术条件书（第二版）》，并结合本公司的研发实际，分析了1000kV交流特高压瓷外套MOA的结构。虽然均压电容组件可使MOA的电位分布不均匀系数及荷电率降低一些，但却带来了外套管径变大、径向电场集中、性能难以检验及运行可靠性下降等诸多不安全因素，得不偿失。应用现代解析和测试手段，依靠均压环优化设计、MOR合理分布、MOR允许荷电率的明显提高。可使无均压电容结构的MOA满足技术条件书的要求。建议优先选用无均压电容结构的MOA。     

Diagnostics and monitoring of metal-oxide surge arresters inhigh-voltage networks-comparison of existing and newly developedprocedures

Various diagnostic methods-either on-line or off-line-for monitoring of metal-oxide surge arresters in power systems are known. In most cases they are based on the measurement of the leakage current. This paper describes the most important ones in detail, such as measuring of the V-I-characteristics or analysis of the third harmonic content of the leakage current. Their advantages and weak points, respectively, are discussed, based on the most recent investigation results on the change of the V-I-characteristics due to electrical and nonelectrical stresses. It turns out that almost none of these commonly applied methods really work satisfactorily under either technical or economical aspects. As an alternative the temperature of the MO-insert is proposed to be used for diagnostics purposes. This is made possible by newly developed passive temperature sensors, which can be remotely accessed without any hardware connection to the environment. It is shown how the temperature can be used for monitoring of all kinds of degradation, energy absorption, thermal stability or even pollution performance     

Potential distributions of metal oxide surge arresters undervarious environmental conditions

A semi-analytical approach is proposed for potential distribution of metal-oxide surge arresters under normal condition. Conventional approaches like the finite-element method are also applicable. The authors suggest that the proposed method is more appropriate for a general approach; an analysis in combination with lumped constants of R, L and C is possible. Environmental conditions like pollution of snow-covering on the surface of insulators may disturb the potential distribution at normal condition. Potential distributions were experimentally measured in an artificial pollution test, naturally polluted and snow-covering conditions, whose major characteristics are shown     

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.     

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     

An assessment of the reliability of in-service gappedsilicon-carbide distribution surge arresters

Although gapped silicon carbide arresters are no longer purchased by electricity authorities, they still form the majority of the very large number of distribution arresters in service in Australia and many other countries. Most of the arresters of this type are now over ten years old and many are much older. So the question must be asked-what is to be done with this ageing and outdated class of arresters? Extensive Australian studies in the 1960s had revealed that internal degradation resulting from inadequate seals was the predominant cause of failure of gapped silicon carbide arresters. This paper describes the results of a recent investigation. Electrical testing showed that after about 10 years of service, there is a marked upturn in the number of arresters with unsatisfactory insulation resistance, and after about 13 years of service, a marked upturn in the number of arresters with reduced power frequency sparkover level. Inspection of the internal components of dismantled arresters confirmed that the likelihood of significant degradation increased markedly with years of service, and was evident in almost 75% of arresters with 13 years or more of service. The authors therefore recommend that all gapped silicon carbide arresters with 13 or more years of service be progressively replaced by modern metal oxide arresters     

Performance of metal-oxide arresters exposed to ferroresonance inpadmount transformers

Ferroresonant overvoltages have been recognized as a threat to arresters installed on underground distribution systems. Extensive tests have been performed to evaluate the thermal and electrical performance of MOV arresters exposed to this duty. Arrester discharge currents were found to be small and arrester heating is slow. The eventual temperature rise and the potential for thermal instability depends greatly on the type of arrester. Arrester designs which promote better heat dissipation to the ambient are shown to reach an acceptable steady-state temperature when exposed to ferroresonance of indefinite duration     

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     

Failure of surge arresters on low-voltage mains

The use of a secondary arrester on low-voltage AC supply mains to prevent damage to electronic equipment is addressed. Some failure mechanisms of secondary arrester are described, and ways to minimize risks from possible failure of the arrester are suggested. Applications of secondary arresters and fuses are discussed     

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.     

Salt fog testing of polymer housed surge arresters

This paper deals with the evaluation of the insulation design of polymer housed surge arresters for distribution lines. Five commercial designs were tested in a salt fog chamber for 9 cycles using a cycle consisting of 120 hours of salt fog that was followed by a 48 hour rest period for a total of 1280 hours of salt fog. In these tests, the specification for the 1000-hour salt fog test in IEC 1109 for composite insulators was used as a guide. The results demonstrate that a comprehensive evaluation of the external and internal insulation design of polymer housed surge arresters can be obtained by performing a salt fog test, and as such, the test can be considered as a useful design test. Suggestions for improvements in the insulation design of all polymer housed surge arresters evaluated are given in the paper     

Multistress aging tests of polymer housed surge arresters

The combined stresses in multistress aging tests produce cumulative accelerated effects on polymer materials and surge arrester constructions that simulate typical service aging. The aging of polymer housed surge arresters is manifested by increased watts loss (internal, external or both), external flashover, or internal failure. Multistress testing is able to demonstrate deficiencies, with respect to aging, of surge arrester materials and designs, including the nature of interfaces in the insulation design. Therefore, multistress testing is believed to be a suitable test for evaluating the aging performance of surge arrester designs. Surge arrester housings made of materials other than silicone rubber are shown to age more rapidly and to require greater creepage distance than silicone rubber to maintain equivalent watts loss levels in multistress tests     

Insulation system protection with zinc oxide surge arresters

Surge protection continues to evolve, and today, zinc oxide-based arresters predominate, often with polymeric housings. The author provides an overview and summary of the issues related to arrester design and selection     

A simplified model for zinc oxide surge arresters

A model for metal-oxide surge arresters, derived from that one recommended from the IEEE W.G. 3.4.11, is presented. The main innovation introduced by the paper lies in the simplicity of the criteria proposed for the model's parameter identification. Such criteria allow calculation of the model parameters directly from the standard data reported in the arrester data-sheets with a simple and straightforward procedure. The effectiveness of the model was tested for several arresters of different manufacturer both for medium voltage and for high voltage application. The discharge test results obtained by the manufacturers were compared with the results of simulations performed with the Alternative Transient Program (ATP). Effectiveness and simplicity of use make the proposed model a useful tool for insulation coordination studies involving steep front transients     

新型热爆式避雷器用脱离器

对现用脱离器的结构原理及优缺点进行了分析比较根据我国电网的特点及避雷器故障损坏的机理．提出了脱离器应满足的技术性能要求。设计了一种具有新型结构原理的热爆式脱离器，并对其应用作了说明，该种脱离器结构原理合理，运行可靠性高，技术性能完善，可推广使用．     

Investigation of diagnostic techniques for metal oxide surge arresters

Gapless metal oxide surge arresters (MOSA) have been available in the market for many years since they were first introduced in the 1970's. The aim of this study is to investigate some reliable diagnostic techniques to assess the condition of a metal oxide surge arrester when subjected to severe lightning strikes in the field. A number of nondestructive and destructive diagnostic techniques for metal oxide surge arrester (MOSA) are discussed in this paper. The nondestructive techniques include the standard 1 mA reference voltage, lightning impulse discharge residual voltage and a number of modern diagnostics based on polarization methods: Return voltage and polarization/depolarization current measurements. In order to observe, analyze and correctly explain the degradation phenomena, a number of destructive techniques based on microstructure observation are also conducted. The techniques include optical microscopy, scanning electron microscopy, X-Ray diffraction and energy dispersive spectrometry. The single and multipulse currents of 8/20 mus wave shape were used to artificially degrade the MOSA. The before and after diagnostic results of the nondestructive and destructive techniques are presented and interpreted to understand the aging mechanism in MOSA. The importance of modern nondestructive electrical diagnostics based on polarization methods is validated by test results and is highlighted in detail in this paper. Finally the correlation of the results of different diagnostic techniques with each other and with the results of standard techniques is discussed     

Validation of ZnO surge arresters model for overvoltage studies

This paper presents an improvement of the procedure to determine the parameters of the simplified model for metal-oxide surge arresters, derived from the IEEE standard model. The main innovation introduced by the paper lays in the possibility to define an approximate dynamic model even if data about residual voltages for steep current pulse are not defined in the manufacturer's data sheets. This model has a wide rangeability and its effectiveness is good for both medium- and high-voltage arresters. The effectiveness of the model was tested for several arresters of different manufacturers. The residual voltages reported in the datasheets and obtained by the manufacturers through a discharge test are compared with the simulations performed with Matlab. The possibility of defining a dynamic model for surge arresters even with missing data makes the proposed model a useful tool for insulation coordination studies involving steep front transients.     

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     

Bibliography of metal oxide surge arresters, 1990-1992

This is the second and continuation of the metal oxide surge arresters bibliography first published in IEEE Transactions on Power Delivery, vol. 8, no. 3, p.1000-34, 1991. This listing covers publications from 1990-1992. Some changes were made in this compilation. Publications on basic disk chemistry are not included. The abstracts are edited and reduced to one to three sentences to shorten the length of the publication. Abstracts for papers published in IEEE Transactions on Power Delivery, and IEEE Transactions on Power Systems are not included. References relevant for application of surge arresters are included, but not all aspects of low voltage applications are covered. Language of publication is English, unless indicated otherwise