Applications of polymeric outdoor insulation in Japan

Intensive research and development concerning the application of polymeric outdoor insulations in Japan started about 10 years ago. Research on applying polymeric insulating materials to power systems covers various fields such as insulators and interphase spacers for overhead transmission lines, polymer housing of bushing and surge arresters for substation apparatus, insulators and interphase spacers for distribution lines and insulators for railways. Polymeric insulators and housings for electric power systems are being evaluated to extend their use, focusing on insulation characteristics such as withstand voltage against salt contamination and deterioration through prolonged use. For railways, trial uses of polymeric insulators have been started on commercial lines     

Test methods for polymeric insulating materials for outdoor HVinsulation

The paper describes an analysis of standardized and non-standardized test methods for polymeric insulating materials, either suitable or applied for, outdoor HV insulation. The analysis particularly considers the increasing use of silicone elastomers for composite insulators. In the first part, test methods covering erosion/tracking performance and hydrolysis phenomena are discussed. These are inclined plane test (IPT) and arc test (AT) for the evaluation of the tracking and erosion behavior as well as boiling water test (BWT) for the evaluation of the HV diffusion-breakdown-strength. These tests have a long tradition in the field of material research. Secondly, the resistance of hydrophobicity under accelerating aging conditions using simultaneous moisture and voltage stress is considered. Results from the rotating wheel dip test (RWDT) are presented and related to results from an equivalent salt-fog test. The third part of the paper deals with the regeneration of hydrophobicity after sample exposure to moisture and corona discharges. Recovery includes also the transfer of hydrophobicity into pollution layers, which is quantified by measurement of dynamic contact angle     

Aging in EPDM used for outdoor insulation

The effect of accelerated weather aging on ethylene-propylene-diene monomer (EPDM) rubber used for outdoor insulation was studied by surface roughness measurement and X-ray photoelectron spectroscopy (XPS). The surface roughness of EFDM rubber changed with aging time. The surface oxygen and aluminum content were found to increase and that of carbon, silicon and nitrogen to decrease with time. The detailed XPS analysis indicated that the concentration of carbon in C-C decreased and that of highly oxidized carbons in C-O, C=O and O=C-O increased with time, which was due to the oxidation of EPDM rubber polymer. The appearance of O=C-O on the surface of EPDM rubber was a signal that EPDM rubber became aged. The aging speed decreased with time. The aging mechanism is discussed also     

Aging in silicone rubber used for outdoor insulation

A hypothesis for aging produced by dry band arcing in silicone rubber material used for outdoor insulation is presented and experimentally proven. Aging is indicated by permanent changes. The analytical techniques used to study the permanent changes are Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and surface roughness measurement. The authors highlight the fact that there are permanent changes occurring in the material that lead to progressive degradation in the long run, even though there can be a complete recovery of surface hydrophobicity in a short time     

Failures in outdoor insulation caused by bird excrement

The bird excrement, combined with humidity, causes line outages in transmission lines. In order to standardize the criteria to solve the problem, a research project was developed in México. The solutions found in worldwide review can be classified into four groups: elimination of birds, devices of dissuasion, physical barriers, and covering devices. The first group includes all bird elimination techniques. These alternatives are forbidden in México, and in most of the countries. The second group has shown to be effective at the beginning of its application; however once the birds are habituated to the device, it loses its effectiveness. The efficiency of the third group, the use of physical barriers, is high, as demonstrated by more than a few review reports informing drastic reductions of flashovers on the transmission lines where they have been installed. The fourth group is conformed by components whose function is to protect or to cover the insulation. According to the experience in Mexico, covering devices have shown to be very effective. The contamination by bird excrement has not a unique solution. The most viable solution is a combination of alternatives. Even though, a solution adopted for a region may not be suitable for another region. Therefore, each case should be approached according to the particular conditions of the region.     

Surface recovery of silicone rubber used for HV outdoor insulation

Results of a study performed to obtain a better understanding of the material characteristics responsible for hydrophobicity recovery leading to a high wet surface resistance in silicone rubbers used for outdoor HV insulation, are reported. The samples were obtained from new and artificially aged HV insulators using HTV silicone rubbers (3 different formulations) as weathershed and RTV silicone rubbers (2 different formulations) as a protective coating. The main experimental facilities employed consist of a salt fog chamber for artificially aging the insulators, and a scanning electron microscope (SEM) for material studies. New results of practical significance that have emerged from this study are: (1) hydrophobicity recovery, predominantly due to diffusion of low molecular weight (LMW) silicone polymer chains, occurs with only a fraction (<20%) of the total LMW polymer content initially available in an unaged material surface, (2) LMW chain regeneration and hence surface hydrophobicity recovery occurs even after the initial supply of LMW polymer is depleted, and (3) hydrophobicity recovery is significantly affected by ambient temperature. The results show the same pattern for different formulations of HTV and RTV rubber materials studied. The X-ray Mapping feature in the SEM provides a visual indication of the diffusion process which is a noteworthy contribution     

城市室外照明常厍节能方法

目前节能减排已经成为考核地方政府领导班子政绩和中央负责人业绩的重点内容;实行节能减排问责制。城市照明的节能越来越引起管理部门的重视,本文针对城市室外照明工程中目前常用的几种节能方法,结合实便做以归纳概括,介绍了各自的优缺点和推荐使用场所。     

Silicone rubber dielectrics modified by inorganic fillers for outdoor high voltage insulation applications

The paper discusses the mechanisms by which inorganic fillers in silicone rubber dielectrics enhance the properties of thermal conductivity, relative permittivity, and electrical conductivity making them useful in outdoor high voltage insulation applications. The addition of alumina trihydrate or silica fillers to silicone elastomers, forming binary composites with enhanced thermal conductivity, is discussed in relation to filler type, particle size, shape, and concentration, and its use as a housing material for non-ceramic insulators to minimize material erosion at dry band arcing sites by lowering hot spot temperature. Also discussed is the enhanced relative permittivity of silicone dielectrics that is obtained through the addition of barium titanate powder which can be further increased with the addition of aluminium powder forming a tertiary composite, resulting in a significant grading of the surface electric field when applied as a housing material to high voltage bushings. Controlled electrical conductivity of silicone dielectrics is discussed through the use of antimony-doped tin oxide filler binary composites and when applied as a housing material to outdoor bushings, the pollution performance is greatly enhanced.     

The role of inorganic fillers in silicone rubber for outdoor insulation alumina tri-hydrate or silica

A systematic study to understand how alumina tri-hydrate (ATH) and silica fillers improve the erosion resistance of silicone rubber during dry band arcing showed that the thermal conductivity of the resulting composite material is the main criterion governing material erosion. The thermal conductivity of the composite material is dependent on the thermal conductivity, concentration, particle size, and bonding of the filler particles to the silicone matrix. In this context, either filler can be shown to perform better than the other, depending on the formulation, in the ASTM inclined plane tracking and erosion test. Therefore, the industry perception that ATH filler imports better erosion resistance than silica in silicone rubber can be misleading. The release of water of hydration from ATH appears to have a secondary effect that may be more relevant in silicone compositions having a low concentration of a filler.     

The evolution of electrical insulation technology in Japan

Today Japan has a leading position in insulation technology worldwide. The international community may be interested in learning how Japan attained this position. The history of this accomplishment will give invaluable suggestions to engineers and managers both in industrialized countries and in developing countries. It is the duty of Japanese engineers, in turn, to provide the historical information in a language understood by the Western community. This paper gives some insights into the history of Japanese insulation technology     

A recent development in the electrical insulation systems ofgenerators and transformers

Mica/epoxy and oil/cellulose have dominated insulation systems of rotating machines and power transformers for over 100 years. In recent years, however, XLPE cables have been introduced to generators and transformers as HV windings. This has resulted in a new type of generator (Powerformer^TM), a new type of wind-power system (Windformer^TM) and a new type of transformer (Dryformer^TM). The new types of HV generator and transformer offer high efficiency, long life and low environmental impact and give new possibilities for the design of HV apparatus. The products developed represent new demonstrated possibilities in HV electromagnetism utilizing the potential in Maxwell's equations     

Progress in Japan in electrical insulation at high temperatures

It is expected that the use of electrical equipment at high temperatures will increase in the future, and the demand for heat-resistant insulation that can be used at temperatures above 300°C will increase. In addition, this high temperature electrical equipment will need to be higher in voltage and have a larger capacity. Accordingly, research and development will be needed to study the high temperature behavior of insulating materials, the insulation manufacturing process, and functional evaluation methods of insulation systems. Progress in Japan in R&D of insulation systems at higher temperatures is discussed     

Diagnostic methods for GIS-insulated switchgear insulation using external antenna

A partial discharge detection system was developed using an external antenna that can be easily installed on the outside of the GIS. The antenna is fitted closely to the outer circumference of the insulation spacer, and it can detect electromagnetic radiation of the partial discharge with high sensitivity. To have high sensitivity even in noisy condition, three kinds of methods that can eliminate external noise effectively were verified. In addition, the locating method of defect based on distance attenuation was confirmed. Actually, the insulation monitoring system which employs the antenna is used in a substation that had already been installed. At present, it is operating satisfactorily.     

Evaluation methods on polymer materials for surface of outdoor insulators

Performance of nonceramic insulators is strongly related to hydrophobicity of the surface. Therefore, it is useful to evaluate the characteristics of the surface of organic insulating materials. To characterize the methods for the evaluation, some measurements were conducted on silicon rubber (SR), EPDM, PMMA and polyethylene (PE). The influence of irradiation with a mercury lamp was detected through measurements of contact angle, formation time of water film, and mass analysis of released gases under irradiation of electron beam. Measurement of the contact angle by using polar and nonpolar liquids revealed that silicon rubber (SR) was the most resistant against UV radiation. SR also showed recovery of hydrophobicity after UV irradiation. Measurement of the current flowing across the surface of materials exposed to artificial fog showed good agreement to the measurement of contact angle. Infrared absorption spectroscopic analysis enabled the intensity of oxidation of highly UV-deteriorated organic insulating materials to be detected. Radicals on the surface of specimens were specified from the result of mass analysis of released gases. From these results, the nature of deterioration of organic insulating materials irradiated by UV is discussed.     

现行WGMOA试验方法存在问题及分析

现行无间隙金属氧化物避雷器(WGMOA)试验方法是从碳化硅避雷器(SiCA)试验方法移值过来的。但WGMOA的工作电阻片(MOR)与SiCA的工作电阻片在电网运行电压下参数的工况是完全不同的。对SiCA有效的试验方法并不一定对WGMOA有效。文章列举了三个“误把”作为实例 :(1)误把8/20μs冲击电流作为雷电流标准波形 ;(2)误把MOR加速老化试验当作MOR寿命试验 ;(3)误把SiCA动作负载当作WGMOA动作负载。文章提醒人们正确认识现行试验方法 ,排除误区 ,重视革新试验方法。     

Polymer outdoor insulating materials. Part I: Comparison ofporcelain and polymer electrical insulation

It is the objective of this series of articles, beginning in this issue, to review for users the benefits of polymer insulating materials. Material science, design, and processing conditions all influence performance and must be considered. Using silicone as an example, we will discuss performance considerations and present data on performance counter to common industry perceptions. The series goal is to acquaint the user with relevant topics so that more informed decisions can be made in the evaluation, selection, and use of outdoor polymer material insulation. In Part I, a comparison of porcelain and polymer properties is presented, including the relative advantages of each     

隔热与阻热技术在日本节能中的发展与应用

在节能减排的背景下,为降低热能损失,隔热与阻热技术的发展越发显现其重要性。分析日本近年来能耗现状与发展隔热阻热技术的必要性,从原理上对隔热阻热技术进行分析,重点介绍隔热与阻热技术在日本节能领域中的应用实例。实例证明,隔热与阻热技术可以很好地节约能源、降低能耗与二氧化碳的排放,值得推广应用。     

History of vacuum circuit breakers and recent developments in Japan

Vacuum circuit breakers (VCBs) have been developed and widely applied in Japan to meet the requirements of increasing energy consumption and also in national security of various areas. As a result, for example, a 168 kV two break porcelain type and a 100 kA one break VCB have already appeared in the Japanese market and they are currently being exported to world-wide markets. VCBs interrupt currents in vacuum, and this means they do not exhaust dissolved gases which are sometimes harmful to the human body or cause effects on the environment. Therefore, by its nature, the recycling of materials and safety to the human body have been realized, and also no global warming effects would be expected. Energy is extremely essential and important in human daily life, and many types of circuit breakers play important roles in electrical power transmission and distribution systems to maintain the systems reliability and safety by switching the systems under several conditions. Since vacuum circuit breakers possess a lot of advantages such as high current interrupting capabilities, small size, and low cost, they will be used much more in the future, and at this moment, we believe it is very worthy to discuss and consider thoroughly future trends of VCBs. In this paper, the results of the developments in Japan will be reviewed, the reflection of the results will be stated, and the subjects of engineering in the 21st century will be discussed. These will include recycling, safeguards to the human body and the fireless nature of VCBs; and it will be demonstrated that the developmental works of VCBs are being wonderfully explored in Japan now and in the future.     

Correlation of damage, dry band arcing energy, and temperature in inclined plane testing of silicone rubber for outdoor insulation

Silicone rubber samples, filled with 30% alumina trihydrate, subjected to the ASTM inclined plane test, show good correlation between the measured harmonic power components of dry band arcing and the surface temperature recorded with a thermovision camera. The simultaneous study of the low frequency fast Fourier transform and variations in temperature shows that when the temperature rises above 100/spl deg/C there is a well defined increase in the low frequency harmonic components of the measured power; however, this trend is not verified by the fundamental component. The eroded mass of the samples is measured independently by a laser approach and a model to rank the tested samples using the inclined plane test is developed. The model is validated by applying it to both the recorded harmonic power components and temperature, resulting in the correct ranking of damage on the samples tested in the inclined plane test.