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The potential impact of neurocompatible implantable devices to assist millions who suffer from brain and spinal cord injury or limb loss is tremendous, both in restoring patient health, as well as quality of life. Until now, no known reliable solution to this challenge has been found, with most of the current technology relying on nonneurocompatible materials such as silicon, tungsten, or platinum, and polymer insulators. Silicon carbide (SiC) and, in particular cubic-silicon carbide (3C–SiC), appears to be an ideal material to meet this challenging application: the evidence of bio- and hemocompatibility is increasing; it is a semiconductor that allows for tailored doping profiles and the seamless integration of electronics with the implants; it is highly durable, even within harsh, corrosive environments; and SiC is also an excellent thermal conductor. For the first time, a comprehensive analysis of 3C–SiC for neural device applications has been performed and is reported here. Starting with in vitro data from chapter: Cytotoxicity of 3C–SiC Investigated Through Strict Adherence to ISO 10993 and hemocompatibility data from chapter: Study of the Hemocompatibility of 3C–SiC and a -SiC Films Using ISO 10993-4, we add compelling in vivo biocompatibility data from two animal models to complete the 3C–SiC biological profile. We end by demonstrating advanced probe designs combining 3C–SiC neural probes with fully wireless-capable, application-specific neural recording chips. This chapter encompasses all of the required technology necessary to bring this material system to clinical trial. Additionally, we show that 3C–SiC is compatible within 2T field magnetic resonance imaging (MRI), which, if true for higher field MRI scanners, could revolutionize the way patients can receive diagnosis for advanced neurological disorders.

Целью данной дипломной работы являлось создание приложения на основе модели стержневого изолятора в среде мультифизического моделирования ComsolMultiphysics 5.0, в котором показаны основные параметры для проектирования, а также результаты расчета., The purpose of this thesis was to create a model-based insulators in application with modeling of ComsolMultiphysics 5.0, which shows the basic parameters for the design and calculation of results.

This paper reviews and discusses the rated strength of insulators as defined in ANSI, CSA, and IEC product standards. The definition of rated strength, which for a particular insulator, requires reference to the tests and acceptance requirements given in the appropriate standard for that insulator is discussed. An insulator may not exhibit noticeable changes at loads sufficient for the initiation of irreversible damage, referred to as its damage limit. The significance of this is discussed in the paper as insulator application loads which must be below the damage limit of the insulator and be made in accordance with the relevant standard, including consideration of the allowable variation in strength implied by strict conformance to the standard. Damage limits for ceramic and composite insulators based on the minimum allowable strength according to the current standards are given.

Hydrophobicity is a prominent characteristic of silicone rubber for polymer insulators. However, due to the environmental influence, the decrease even the loss of hydrophobicity will take place, which causes the essential concern on the electrical accidents induced by the ageing of polymer insulators. The accurate evaluation on the insulator hydrophobicity is increasingly required for the long-term performance of outdoor insulators in service. In this paper, based on dynamic dropping test (DDT), pattern characteristic of surface discharges generated by the dynamic behavior of water droplet was investigated to evaluate the hydrophobic properties of silicone rubber insulator at different ageing levels. The specimens were prepared by using the method of corona degradation and determined by HC levels from HC1 to HC6. Both the dynamic behavior of water droplet and the induced discharge phenomena were captured by using a high-speed camera fixed vertically to the sample surface. In order to quantify the surface discharges, methods of image processing and fractal dimension were employed to establish the relationship between the pattern characteristic of discharge light and the HC levels. The morphology of discharge region and the distribution of luminous brightness in relationship with the lapse time can provide an optical evaluation method for the insulator hydrophobicity. It is found that the number and duration of discharge light increase with the increase of HC level. The increasing tendency in brightness intensity and fractal dimension of discharge pattern can reveal the decrease of hydrophobicity. Therefore, the results obtained indicate that the pattern characteristic of discharge light in DDT method is sensitive to the hydrophobic properties, which can be applied as a non-contact method for hydrophobicity evaluation of polymer insulators.

The electric explosion of a conductor being part of an electric cable is studied. It is ascertained that the electric properties of a polymeric dielectric depend nonlinearly on the maintenance of the ultradisperse metal filler. In the course of the numerous heating-cooling processes of an insulator, a streamlining of the structure of a polymeric composite occurs.

The water tree resistance of chemically crosslinked polyethylene and of low density polyethylene were compared in order to elucidate whether the crosslinking itself influences or not the water tree characteristics of polymeric cable insulation materials. For this purpose, water trees were grown in compression moulded disks, obtained from pellets of either thermoplastic or chemically crosslinked polyethylene. Three types of crosslinked polyethylene were evaluated: one containing only peroxide (XLA) and two others having, besides peroxide, a tree retarding additive system (XLB and XLC), and the results were compared with those obtained on their thermoplastic correspondents (A, B and C). Results were determined for both Water Tree Propagation and Water Tree Initiation. The results obtained for Water Tree Propagation indicate that there is generally a large difference between the types (A, B & C) yet only small difference between thermoplastic and crosslinked samples. However for two cases (A & B) these small differences between crosslinking are statistically significant. The complementary Water Tree Initiation results show both large and significant differences between material types and the crosslinking.

This paper presents a review discussing methods of determination the resistance to corona discharges and ozone of polymeric materials for applications in outdoor insulation. It also describes a part of international activities within CIGRE WG D1.01 aiming to develop suitable methodology for the testing, which includes designing the necessary test arrangement, defining test conditions and finally exemplifying results of the treatment by monitoring changes of electrical, mechanical and structural properties of some materials.

Aging, under contaminated conditions, manifests itself by tracking and/or erosion of polymer materials and insulators and usually leads to failure of insulators. Aging is still one of the main causes of the registered failures of polymer insulators in the field. Consequently, to improve both materials and insulator designs, it is important to understand the mechanisms of aging, as well as the factors surrounding aging, and the best way to do this is through actual field experience. However, the problem with field experience is that it often requires a very long time before any noticeable changes become evident. For this reason, several laboratory accelerated tests have been developed to evaluate aging of polymer materials and insulators.

Lightning overvoltages were causing problems on overhead lines well before Tesla and Edison argued over the merits of ac and dc. Many of the overvoltage protection methods for distribution lines follow the same philosophy as that used for telegraph and telephone lines. Modern guides for improving distribution-line lightning performance, such as IEEE 1410, still distinguish between unpreventable outages caused by direct flashes to phase conductors and preventable faults that are caused by flashes to objects or the ground near the line.

Silicone rubber for polymer insulator has an excellent hydrophobicity with recovery properties, resulting in higher pollution performance. However it is inevitable that even silicone rubber polymer insulators start generating corona discharge with time under humid and polluted conditions. And such a corona discharge causes rubber damage because of acid generation. Since it is assumed that the corona discharge characteristics depend on humidity and polluted conditions, corona discharge tests were conducted on silicone rubber polymer insulators by changing humidity and polluted conditions. As a result, it was verified that the corona discharge phenomena were affected by humidity and pollution even on silicone rubber polymer insulators, and that contribution of corona rings to suppressing the discharge was not large.

This paper describes the breakdown poperties of porcelain and polymer insulators using the UV camera. The experiment was carried out using condition of voltage at the KS C IEC 60060-1(2006). As these results, corona discharge in porcelain insulator was generated the weakness point of insulator union. And the corona discharge of polymer insulator happened in union of power source. Also, we could confirm easily weakness part of these insulators by ultraviolet image through the corona discharge. Besides, in the comparison with the exciting technique of ultrasonic detection, it confirmed that deterioration steps are corrected. These steps are possible to judge the deterioration of power facilities through reliable date. Hereafter, this study as the diagnostic technology suitable for the sites is used.

The purpose of this study is an investigation upstream of polymer insulator ageing and rupture. We studied the electrical and physicochemical properties of a low-density polyethylene (LDPE) used in high-power insulated cables. Space charge measurements using pulsed electroacoustic method and thermally stimulated depolarization current (TSDC) were carried out on LDPE samples, with and without antioxidant, at different temperatures. TSDC peaks were observed only in the presence of an antioxidant. Furthermore, a TSDC anomalous peak was revealed for the sample containing an antioxidant and polarized at 50°C. All the TSDC peaks are interpreted as trapped charges and can be explained by measuring the space charge distribution within the sample bulk. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Composite insulators are considered mature products and a broad range of insulator types is nowadays available, including line insulators, hollow-core insulators and apparatus insulators, for applications ranging from distribution voltages to the highest transmission voltages. This development has created a need to elaborate diagnostic methods and tools for determining the quality of composite insulators. A review on recognized insulator faults and methods for their detection is provided.

Polymer insulators made of silicone rubber (SIRs) can suffer from algal fouling in tropical and even temperate regions. The purpose of the present study was to understand the hydrophobic behavior and leakage current characteristics of algal- fouled SIR materials when exposed to wet and contaminated conditions. Salt-fog tests were conducted on SIR samples colonized with the treatable alga Chlorella vulgaris. SIR samples covered with non-soluble kaolin powder at a deposition density comparable to that for the alga-treated SIRs were also evaluated. Results show that algal fouling considerably reduced the SIR hydrophobicity compared to the kaolin powder, which resulted in the development of a large leakage current. A major component of the leakage current produced on algal-fouled SIR is dry-band discharge, which leads to material degradation involving tracking and erosion.

Artificial pollution tests have been carried out to study AC flashover performances of various types of porcelain, glass, and polymeric insulators in this paper. The experimental results show that the polluted flashover voltage Uf is affected by equivalent salt deposit density rhoESDD and nonsoluble deposit density rhoNSDD, the influences of which are independent of each other. Based on the analyses of the flashover voltages, the correction formulas of the flashover voltages Uf of various insulators at various rhoESDD and rhoNSDD levels are pointed out. The experimental results also show that there is a distinct difference among the flashover voltages of various types of polluted insulators. At the same pollution degree, the antipollution performance of the fog-type glass insulator is better than those of the outer-rib porcelain insulators. In terms of the effectiveness of creepage distance of insulators, the antipollution performance of polymeric insulators is superior to those of porcelain and glass insulators.

The testing of modern polymer insulators designed for transmission facilities for light stability under the action of solar radiation is considered. The technique of accelerated testing including irradiation of the samples with ultraviolet radiation using a large solar furnace has been proposed.

To understand the effects of forest fires on polymer insulators for transmission lines, the forest fire simulation tests were performed with polymer and porcelain insulators at Gochang testing center. These tests consisted of energizing 90 kV at line-to-ground voltage of 154 kV lines and open flame rising up to as being measured at insulator surface. Mechanical and electrical characteristics such as specific mechanical load, leakage current, low frequency dry flashover voltage and impulse flashover voltage were analyzed for the polymer insulators before, during and after simulation tests compared with porcelain insulators. At the end of fire simulation tests, there was no detrimental deterioration of any insulators. All insulators passed the criteria of KEPCO specification. This study showed that forest fire simulation had no impact on polymer insulators.

This article presents a comprehensive bibliographic survey pertaining to multistress and field aging of polymeric insulators.

This paper describes concentrated discharges on polluted insulators in the laboratory and in the field. The authors have observed the concentrated discharges at the high-voltage laboratories in Stuttgart, Zittau, and Mannheim, Germany, and Wroclaw, Poland. The concentrated discharges were also documented under natural conditions. These discharges are very dangerous especially for high-voltage apparatus, bushings, and polymer insulators. It has been shown that due to uneven voltage distribution at very low surface conductivity, the concentrated discharges can ignite even under uniformly polluted and uniformly wetted insulators

Effect of humidity on flashover voltage of four kinds of porcelain and one polymer insulators was studied experimentally for several years under natural humidity condition in Japan. It was found that the existing IEC humidity correction seems to be proper for most insulators regardless of the kind of applied voltage but that change may be necessary for pin type insulator under positive lightning impulse voltage application and for unit suspension disk and station post insulators under AC voltage application. Key-Words: Insulators, Flashover voltage, Absolute humidity, Humidity correction

This paper considers the effects of a cross-arm on a contaminated polymer insulator at different angles (90°, 60° and 45°) with negative and positive impulses. An experiment was conducted using a 10 kV polymer insulator that was contaminated with 4 % salt (a mixture of distilled water and sodium chloride). From the experiment, the behaviour of the voltage breakdown and leakage current of the contaminated insulator positioned at different angles from the cross-arm was evaluated under different impulse polarities. The results show that the values of the breakdown voltage and leakage current decrease with angle when using the 90° angle as a reference. The reason for this study into the effects of the cross-arm on a contaminated polymer insulator is because in the real case, when the insulators are installed on an angle tower, the forces or tensions due to the weather conditions (especially under strong winds) and from the distribution lines themselves will force the installed insulators to be tilted from its original 90° angle position.

This paper reviews a study of the inclination angle of an insulator due to mechanical forces imposed by overhead conductors. The angle theoretically shortens the effective leakage path and flashover distance of the insulator, thus change the electrical performance of the insulator. To take it into consideration, this study had focused on experimental works to investigate effect of insulator inclination to the breakdown voltage and leakage current. Regards to the important of wetness to improve surface conductivity of insulator surface, authors have considered to conduct the test in wet conditions. In addition, standard lightning voltage was applied according to IEC 60060 in both positive and negative impulses. Based on the test, the performance of an insulator under positive and negative impulses was compared accordingly. A significant reduction of breakdown voltage was recorded when the angle decreased. The reduction was recorded as high as 17 %. Meanwhile, the breakdown voltage was much higher under negative impulses compared to positive impulses which showed a difference of 12 % to 14 % and the leakage current increased by 17 % due to the inclination angle. The calculation of U50 with consideration of the reduction factor was suggested and briefly discussed.

In practice insulators are exposed to various weather conditions throughout the year and they influence surface of the polymeric insulators. This paper deals with study on the leakage current of polluted polymeric insulators. It is well known that polymeric insulators are having very good hydrophobicity. Researchers are presently working on the recovery of hydrophobicity and also on hydrophobicity of polluted polymeric insulators. In this regard, it is to be understood that whether hydrophobicity still persists for medium and heavily polluted polymeric insulators. ie, whether hydrophobicity transfer occurs on a polluted polymer insulators. This experimental investigation is being carried out in order to understand whether hydrophobicity persists for thin, medium and thickly coated polymeric insulators. The paper gives the results of the experiments. It can be observed from the results that thin coating on polymer insulators results in lower current and the thickly coated polymer insulators draws higher currents and the current drawn by the medium coated insulator falls in between.

With the development of EHV and UHV transmission technology, more and more transmission lines are built across high altitude regions in China. The pollution flashover performances in high altitude regions are affected not only by the pollutants but also by the atmospheric parameters. To study the performance of insulators at high altitudes, six commonly used porcelain, glass and polymer insulators were tested in three high altitude sites with altitudes of 2820, 3575 and 4484m. In this paper, the AC pollution flashover performance of these insulators were modeled and computed at high altitudes, taking into account of the ESDD, NSDD, the pressure and temperature. Further, the respective influences of ESDD, NSDD, air pressure and ambient temperature on flashover voltage gradient were analyzed. The results indicate that polymer insulators have 48.72% higher flashover voltage gradient than porcelain and 72.35% higher than glass insulators at 59kPa (corresponding to 4484m). These results will help to select the type and number of insulators in the high altitude regions.

Evaluating the electrical tracking and erosion resistance of polymeric housing materials is an essential task performed in the development of outdoor insulators. Tracking refers to the formation of a carbonaceous path on the surface of the insulation housing; whereas, erosion indicates weight loss of the housing material. An absolute realization of the electrical tracking and erosion resistance is not possible and therefore relative ranking of materials is the outcome that can be obtained in the standard electrical tracking and erosion tests. With the early utilization of organic insulating materials, failure due to tracking was a major concern, and therefore standard screening methods were proposed to mainly evaluate the tracking rather than the erosion resistance. Erosion is more important since the application of tracking-resistant composites compounded with high levels of inorganic fillers or possessing inorganic backbones such as silicones.

Tracking and erosion is an important constraint for the long term evaluation of polymeric insulators used in high voltage transmission. In the present work, experiments are conducted on different polymer insulator samples; to evaluate these insulating samples a Recurrence plot (RP) analysis is adopted. The results of the recurrence plot analysis of discharge current sequence confirms that a discharge process is prolonged if the number of droplets containing contaminants is increased. Also the quantitative indicators: recurrence rate (RR) and Determinism (DET) are used to evaluate the performance of various polymeric insulating materials.

Comprehensive standard tests were conducted on 33 kV line-post porcelain insulators in order to improve their performance in harsh environment in comparison to the newly introduced polymeric ones. These tests are the lightning impulse withstand and flashover tests, and the AC artificial pollution tests. The latter were conducted in a salt-fog chamber. Silicone rubber insulators showed superior performance than adding heat-shrinkable and wraparound creepage extenders to the existing line-post porcelain insulators or using new polymeric insulators.

This article reviews the different components, conductors, semiconductive shields, insulation, sheaths, and jackets, that make up extruded, high-voltage cables. The different types of conductors are described as are the different insulation systems that are available for medium and HV cables. There is a comparison of the two main insulators used in extruded HV cables, EPR, and XLPE. Each material has some properties that are better than those of the other material.

Recent studies in the polymer and polymer-composite literature have focused on technology to facilitate self-healing of epoxy polymers that crack on aging, for which no outside intervention is necessary. The self-healing process is referred to as autonomic healing. The concept of self-healing is not new, but healing without the necessity of outside action to facilitate the process is novel. The state of the technology as of the time of this study is reviewed, and the suitability for utility applications is the focus of this paper.

The paper investigates the effects of specimen configuration on the deterioration of silicone rubber insulators in a salt fog ageing test. A cyclic salt fog ageing test was conducted on three types of high-temperature vulcanized silicone rubber (HTV SiR) specimens: two types of insulators having sheds, and plain rods without sheds. The test was based fundamentally on the CIGRE WG 15-04 specifications. After 50 test cycles, the three types of specimens showed different degrees of surface deterioration. Erosion on the straight shed insulator was more severe than that on the alternate shed insulator even though the two had the same leakage distance. No erosion was observed on the rod-type specimens, which had shorter leakage distances than the insulator-type specimens.

This study investigated variation leakage current maximum value and waveform considering applied voltage phase angel by simulating three environmental conditions, such as fog, salt fog, and kaolin contamination .As the result of applied voltage phase angel characteristics, leakage currents presented almost in phases in the early stage regardless of environmental conditions just after applying the voltage, and the phase of leakage currents certain phase lags for the discharge of the applied voltage when surface discharges occurred due to the continuous environmental contamination. In addition, the difference in phase significantly increased according to the intensity of discharges. The change in distortion rates according to the environmental contamination presented a nearly same level just after applying the voltage. The distortion rate of third harmonic for the fundamental wave presented by the order of fog>salt fog>kaolin when surface discharges occurred due to the applied voltage for certain continued periods. In the case of the fog and salt fog, the scale of spectrums decreased according to the increase in frequencies from the results of the analysis of high frequencies. In addition, the even number frequency presented a relatively large level compared to the odd number frequency under the kaolin contamination.

This paper presents the investigation results of the effect of the core diameter on the flashover voltage of cylindrical polymer insulators under contaminated and heavy fog conditions. The specimens had the same or very similar shed profiles but different core diameters. The results confirmed a large reduction in flashover voltage when the core diameter was increased from 26 mm for transmission line insulators to 73 mm for post insulators; however, change is not so significant from post insulators to bushing shells having larger core diameters. Higher flashover voltages of line insulators are attributable to the large difference in the leakage current density between the trunk and shed portions so that the wetting conditions are very different between these portions. This causes the applied voltage to the whole insulator to be divided and allotted to almost all the dried trunks, preventing the concentration of the applied voltage to only a few portions, resulting in higher flashover voltages. The quantitative assessment of contamination flashover voltage characteristics of hydrophobic polymer insulators presented in this paper will be helpful in the selection and design of polymer insulators for contamination areas. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This paper presented the simulation results on electric field performances of medium voltage polymer type insulator while its mechanical conditions were reviewed. The purpose of this study is to investigate the electric field behaviour of 33kV polymer type insulator under different weather conditions by mean humidity and pollution. In addition, outdoor service environments of the insulator were reviewed as they are realized to have worldwide issues on degradation of polymeric material. Using 2D simulation, the electric field was found higher nearer to the end fittings whereby increased up to 38.89% under humidity and pollution. Also, the electric field behaviour along the cross section of weathersheds increased up to 661.59% under humidity and 547.30% under pollution. Meanwhile the weak points along the insulator were identified according to the magnitude of electric field strength. This research also verified the sharp edges and the thickness of the material of insulator as one of the factors that affect electric field strength.

Corona has been identified as one of the major factor in degradation. Corona in practice occurs in two ways, one is due to improper hardware design, another one is due to the water droplet corona. The impact of the former one is more compared to later and has got larger attention in recent literature. In the present work the corona degradation studies are conducted on different types of polymeric insulator samples. A specially designed HV source along with the corona chamber is employed. A single needle electrode is used to generate the corona on the various polymeric samples used for the study. Simulation of the electric stress on the sample subjected to the AC corona, using charge simulation method (CSM) is attempted. Results of the experimental investigation obtained for various samples are analysed and presented.

Because modern society is strongly dependent on a reliable power supply, there is an urgent need to develop more reliable high voltage insulators. While porcelain and glass have dominated insulator materials for a long period of time, there is renewed interest in polymeric and semiconducting glaze insulators. This paper provides a brief description of composite insulators, including a discussion of their benefits, aging of housing materials, and brittle fracture phenomenon. The paper also discusses the benefits of using insulators with semiconducting glaze surfaces, and identifies four broad issues that are being addressed by the present research on outdoor insulation.

In this work, an improved version of a brittle fracture model, based on the formation of nitric acid in service through corona discharges, ozone, and moisture, is presented and is used to explain several different modes of brittle fracture. Similar to Part I, we refer throughout this article to the insulators as nonceramic insulators (NCIs). To prevent brittle fracture in-service, its causes must be first established. To prevent brittle fracture in-service, its causes must be first established.

Despite the extensive investigations carried out on the pollution performance of outdoor insulators, the flashover characteristic and its interaction with insulator shape is still not very well understood. In this paper, we present findings of experiments which allow quantifying the effects of insulator geometry on the flashover voltage. Two main parameters were considered: the flashover current (maximum magnitude of leakage current just before flashover) and the flashover voltage. Known difficulties related to accurate measurement of these parameters which are due to parallel partial arcs on some insulators, have been quantified using control insulators and simple modelling approaches. Furthermore, the effect of insulator shape on arc length has been quantified using nonuniform pollution techniques.

Nonceramic insulators, also referred to as composite, polymer or polymeric insulators, are used in overhead transmission lines with line voltages in the range of 69 to 735 kV. Despite the many benefits that nonceramic insulators offer in comparison with their porcelain counterparts, they can fail mechanically in service by rod fracture. One of the mechanical failure modes of the insulators is a failure process called brittle fracture, which is caused by the stress corrosion cracking (SCC) of the GRP rods. The process is catastrophic and unpredictable, leading to the drop of energized transmission lines. The most important characteristics of the brittle fracture process, which can occasionally affect high voltage nonceramic transmission line insulators, leading to their catastrophic in-service failures, have been presented in this article. In addition, several experimental techniques were suggested for the simulation of brittle fracture under laboratory conditions. Only the most important aspects of brittle fracture process have been discussed here.

Salt fog ageing tests are widely conducted for evaluating anti-tracking/anti-erosion performance of housing materials for outdoor polymer insulators. A detailed test method, however, is not yet standardized and round robin tests have been conducted for standardization all over the world. Here we have investigated the effect of fog conditions on the deterioration of silicone rubber under two different salt fog conditions generated by an ultrasonic humidifier and an IEC nozzle. In spite of the same injection rate and the same salinity, comparable results from the viewpoints of leakage/discharge currents and the degree of surface deterioration could not be obtained between the two salt fog conditions generated by the ultrasonic humidifier and the IEC nozzle. Almost comparable test results, however, were obtained under the two salt fog conditions generated by the ultrasonic humidifier and the IEC nozzle after controlling the salt fog particle size distribution.

Existing brittle fracture models have been reviewed and their applicability to explain the in-service brittle fracture failure of composite (nonceramic) insulators is evaluated. It is shown that the only brittle fracture model that can explain all aspects of the brittle fracture process is a model based on the formation of nitric acid solutions in-service. The chemical cause of brittle fracture is identified in this work and recommendations are made on how to avoid brittle fracture in-service by proper selection of composite insulator rods resistant to brittle fracture. An attempt is made to clarify misconceptions that exist in the literature regarding the causes of brittle fracture and the most suitable prevention methods.

The chemical environment responsible for the brittle fracture failure of composite (non-ceramic) insulators is determined. Also previously reported observations by the authors are verified. Five non-ceramic composite suspension insulators and one composite guide were subjected to FTIR analysis. Out of the six field failed units, five insulators showed significant levels of nitrate on their brittle fracture surfaces with small traces of nitrate also found on the fracture surfaces of the composite guide. The results strongly indicate that the most probable cause of brittle fracture failure of composite RV insulators in-service is the formation of nitrate and thus nitric acid. This is consistent with the observations and conclusions previously reported by the authors.

A description is given of some properties of the corona discharge when propagating over a cylindrical polytetrafluoroethylene insulator surface placed along the axis of a rod-plane electrode arrangement. A scanning electrostatic probe has been used to measure the density of charge deposited on the surface; it is shown that the total net deposited charge is small compared with the total charge injected into the gap. The velocity of propagation has been measured. Effects of preceding coronas on succeeding ones and the nature of deposited charge after breakdown are described. Discussion is given in terms of electron lifetimes and attachment and photoemission processes.

The applications of polymers and rubber materials to electrical power apparatus and cables are reviewed. Polymers and rubber materials have been widely used as insulation and structure materials because of their excellent electrical/mechanical properties and easy manufacturing. They have played an important role to the development of high-performance apparatus in this half century. OF (Oil-Filled) cables are replaced with cross-linked polyethylene cables except UHV (Ultra High Voltage) AC and DC cables. Polymer insulators become popular in the field of outdoor insulators. Polymeric materials are also very important in transformers, rotating machines, GIS (Gas Insulated Switchgear) and so on.On the other hand, polymers and rubber materials are rather weak at heat-resistance and ageing (degradation). Recent compact and high-performance power apparatus have strongly required the improved heat-resistance and long-term stability of polymers and rubber materials.

A composite micro-textured surface structure is proposed and demonstrated to enhance the surface flashover strength of polymer insulators used in vacuum. The structure is fabricated in two stages, with periodic triangular grooves of approximately 210 μm in width formed in the first stage and micro-holes of approximately 2 μm coated on the inner surface of grooves in the second. The aim is to exploit the synergistic effects between the grooves and micro-holes to suppress the secondary electron yield to obtain a better flashover performance. To acquire insulators with the composite micro-textured surface, the CO2 laser processing technique is applied to treat the surface of the PMMA insulators. The test results show that the flashover voltages of the insulators with the two-stage fabricated structure increase by 150% compared with the untreated samples in the best state. Compared with the traditional macro-groove structures on insulators, the proposed composite micro-textured insulators exhibit a better sur...

Organic field-effect transistors (OFETs) have received considerable attention across the world due to their potential applications in integrated circuits for large-area, flexible and low-cost electronics, and a series of breakthroughs in their research have been made in the past decade. Although numerous novel organic semiconductive materials with outstanding properties have been synthesized, the fabrication of OFETs and the investigation of amorphous polymer insulators (APIs) are attracting more and more research interest due to their significance in semiconductor growth, charge transport and device stability. In this review, an introduction to APIs and OFETs is given, and the following aspects are then successively discussed: commonly used APIs in OFETs, applications of API in high-performance OFETs, low-energy-consumption OFETs, functional OFETs, and self-healing OFETs. In the last section, a projection of some future trends for APIs in OFETs is presented.

Considering the performance of insulators versus lightning effects is an important issue for insulation coordination in distribution lines. In this paper, the performance of a polymer insulator (33 kV) versus lightning induced voltage under different weather conditions was considered in transient domain and the profile of the voltage and fields along the insulator were evaluated and the results discussed accordingly. The results showed that the lightning induced voltage can have a great effect on the profile of the voltage and the fields along an insulator and also the weather conditions can profoundly affect the protection level of an insulator. Therefore, in order to set an appropriate protection level on the distribution line, consideration of the behaviour of an insulator under different weather conditions based on local data can be helpful.

There are two types of the 765kV transmission line(hereinafter T/L), namely double and single circuit lines. But the single circuit line has no fungible line, so dead line work is very difficult. Moreover it's very hard to set a no-power day for maintenance of the line also. Due to such reasons the 765kV single circuit T/L will be maintained by live line work using bare-handing method and helicopter live working. But in case of the bare-hand method, it's difficult to approach conductors from tower posts because of the complicated tower structures with many step bolts and configuration. Especially tower arm length is very long. So in order to access to the live parts easily on the towers, this paper presents the stepping pendulum method by using two polymer insulator strings or two insulating supports. Moreover this paper proposes application propriety of the stepping pendulum method to long arms in UHV lines.

In this paper, the outdoor polymer insulator was studied and the related electrical and mechanical conditions were reviewed. Moreover, different outdoor insulators were technically compared together. Furthermore, voltage distribution along a real polymer 33kV insulator was studied and the results were discussed accordingly. On the other hand, the voltage and electric field profiles at longitudinal and cross sections under different voltage levels were considered and discussed.