Electrical insulating impregnating epoxy-izocyanate compound

The technological and operational properties of epoxy-izocyanate compound are described in this article. It is shown that the technological properties of this compound, such as viscosity and time of gelation, can vary largely. A hardened compound has very high operational characteristics of up to 220–240°C. The variability of the application of epoxy-izocyanate compound for creating high-heat-resistant systems of electric insulation is shown.     

Modern electrical insulating impregnating compounds

A comparative analysis and trends in the development of electrical insulating impregnating compounds manufactured in Russia and abroad are given. A tendency toward increasing the output of more heat-resistant compounds is revealed.     

Degradation of insulating materials under electrical stress

An avalanche of physical and physicochemical phenomena, often self-sustained, leads to the end of life of an insulating material. The collapse of the insulating role of a material is mostly due to the electrical field stress. The path leading from the catastrophic situation, the breakdown, back to its origin is followed in the present paper. A defect, pre-existing or created by the in-service stresses, gives rise to an ionization process in a volume bounded by insulating walls. With time the process does not remain identical due to both changes in the material and gas evolution, which makes it difficult to interpret the detected electrical signal. The end of life will occur through microcracks in which new discharges are initiated, activating the propagation of these structural failures. This change of structure of the insulating material when due to the existence of water molecules will lead to the same kind of final degradation. The polymeric insulating materials could contain additives but they lead only to a partial healing. From polymers of low complexity such as the PE used in cables, assuming that there is no pre-existing defect, one endeavors to understand how a microstructure reacts with a local field or accumulated charges. The present paper summarizes the thoughts of the author pertaining to the problems of aging and dielectric breakdown in organic insulating materials, processes often given a concrete form through experiments.     

Life tests of electric insulating epoxyisocyanate impregnating compound

Electric insulating epoxyisocyanate impregnating compound (EPIC) is tested with respect to its electrical (specific spatial electrical resistance, tangent of dielectric losses, and electrical strength), mechanical (cementing ability) and chemical (mass losses) properties. It is shown that an epoxyisocyanate impregnating compound is a heat resistant compound of C-class and it can operate for a long time under 200°C and for a short time under 260°C.     

Simulation of electrical tree growth in solid insulating materials

Contents In this paper the electrical tree growth in solid insulating materials is modeled using von Neumann's Cellular Automata (CA). The model is based upon the assumption that the electric stress at the end of a conducting tip quite often approaches the dielectric strength of the material and that progressive breakdown can occur by electrical tree formation. Because of tree advancement, the potential distribution into the insulating material changes with time and is calculated at each time step. An algorithm for the simulation of electrical tree growth in solid dielectrics based on this model has been developed. The algorithm is also used to simulate breakdown in solid dielectrics containing square or spherical voids.

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Simulation des Wachstums elektrischer Bäume in Festisolierstoffen

Übersicht In diesem Artikel wird das Wachstum der elektrischen Bäume in Festisolierstoffen mittels von Neumannscher zellularer Automaten modelliert. Dieses Modell geht davon aus, daß das elektrische Feld an der Spitze der Elektrode oft in der Nähe der dielektrischen Festigkeit vom Material liegt und das ein fortschreitender Durch-schlag durch elektrische Bäume möglich ist. Durch das Wachsen der elektrischen Bäume ändert sich die Spannungsverteilung innerhalb des Festisolierstoffes mit der Zeit und wird in jedem Zeitschritt berechnet. Ein Algorithmus für die Simulation des Wachstums eines elektrischen Baums in Festisolierstoffen ist entwickelt worden. Der Algorithmus kann auch den Durchschlag in Festisolierstoffen mit zylindrischen oder kugelförmigen Hohlräumen simulieren.

     

变压器绝缘电阻试验中容易忽视的几个问题

介绍了绝缘电阻受温度及外界电磁场干扰等因素的影响 ,提出了解决办法 ,避免一些错误判断给生产运行带来影响     

Some peculiarities of measuring arc resistance of insulating enamels

The influence of the method of measurement, type of substrate, and some other factors on the results of determining the arc resistance of insulating enamels is considered. Recommendations on conducting testing are made.     

Properties of electrical insulating materials at cryogenictemperatures: A literature review

Many insulating materials and systems for superconducting electrical equipment have been developed in response to the severe demands of safe usage, such as in cryogenic temperature, high mechanical stresses, high radiation, etc. They have been designed to fulfill very extreme service conditions, either at liquid helium or liquid nitrogen temperatures. Whatever the future industrial development, there is already abundant knowledge about insulating materials at cryogenic temperatures, and the feasibility has been proven. Many laboratories in the world continue research to increase this knowledge and to fill in the remaining gaps     

Analysis of surface conditions of electrical insulating structures under influence of precipitation

The method of estimating the humidity insulator’s surface under the influence of rain is considered. A way of increasing the water-repellent properties (water repellency) of a surface is proposed. Tests are conducted and positive results are obtained.     

一种XLPE电缆料中杂质颗粒高分辨力测量的方法

通过分析透镜的成像规律,提出了一种利用光学系统的小孔对光的衍射作用,使像函数的特定部分进行了展宽,在不损失测量速度的情况下进一步提高交联聚乙烯(XLPE)电缆绝缘中杂质颗粒测量分辨力的新方法.在尺寸测量解算中利用三次样条函数对CCD像元输出进行插值,计算出阈值对应的位置,再由测量阈值计算出该值对应的像元位置.基于该原理工作的测量系统可获得分辨力为20 μm,准确度为±5μm的实际测量结果,并且测量速度约每小时1kg.该方法能够实现对高压交联聚乙烯(XLPE)电缆绝缘料和电缆超净生产中的杂质颗粒高速、高分辨力自动检测.     

Analysis of electrical activity associated with inclined-planetracking and erosion of insulating materials

Surface electrical activity and physical changes were measured and compared for several types of outdoor insulation materials, using a standard test method. The leakage current activities during the inclined-plane test (ASTM D2303) were measured by using four representative materials: a silicone with high (>70% by weight) loading of alumina trihydrate (ATH), a silicone with no ATH, a poly ethylene vinyl acetate (EVA), and a glazed porcelain. Quantitatively, the severity of the inclined-plane test was defined by detailed leakage current measurements. Qualitatively, it is observed that the test was severe enough to damage the glaze on porcelain. The study enabled us to compare polymers with porcelain, silicones containing no ATH vs. high loading of ATH, and silicones with EVA. The analysis showed that electrical activity, particularly the average leakage current and the distribution of peak current, depended on the surface wettability of the materials by the contaminant solution. The compound formulation is more important than the generic polymer types. It was demonstrated that silicone with no ATH, and EVA with only a medium level of ATH, exhibited excellent tracking and erosion resistance, comparable to the silicone highly filled with ATH. The presence of ATH is not absolutely necessary to achieve the superior tracking and erosion resistance of a silicone elastomer     

New electric insulating materials for the insulation systems of rotating electrical machines

A wide range of nomenclature and properties for new materials for the insulation of high voltage electrical machines and traction motors of F and H insulation classes developed at Elinar Holding Company are presented in the report.     

High voltage insulating structures for accelerators: simulation oftransient electrical stresses

Calculations have been made to increase the HV performance of some components and to explain electrical failures of electrostatic accelerators. These involve simulations of static stresses and transient overvoltages, especially on insulating boards and electrodes occurring before or during breakdown. Changes made in the structure of the machines over the last years and new ideas to improve the static and dynamic behaviour are presented. The application of this study and HV tests recently led to a nominal potential near 20 MV without sparking     

基于CCD的XLPE电缆料杂质颗粒测量系统的研制

应用电子耦合摄像器件（CCD）一维扫描和试样的行进构成对试样的二维扫描检测方法,研制经XLPE电缆料杂质颗粒测量系统,论文分析了透镜,CCD器件对分辨率的影响,在选定扫描视场下优化了分辨率;测量系统分辨率在20mm视场下达到35um,模板实验测中率为100％,测量每公斤料的颗粒误判率为零,用于110kV交联电缆绝缘料测量,最小颗粒为120um时,测量速度可达2．6kg/h。     

Application of the Kalman filter for electrical endurancecharacterization of insulating materials and systems

The Kalman filter algorithm is applied to the results of accelerated life tests performed on insulating materials and systems carried out for electrical endurance characterization purposes. It consists of a recursive procedure that applies to the failure-time percentiles obtained from life tests, on the basis of the inverse power or the exponential models, and provides estimates of the endurance indices which give particular weight to the results of the life tests performed at the lowest test stresses. This allows more meaningful endurance characterization and accurate life prediction. This paper provides the algorithms for Kalman filter applications, giving emphasis to error estimation, as well as the method for calculation of confidence limits of life-line parameters and predicted failure times. The proposed Kalman filter procedure is applied to the experimental results of accelerated life tests relevant to different insulating materials and systems     

Discussion on application of the Weibull distribution to electrical breakdown of insulating materials

The Weibull distribution is commonly used for statistical processing of breakdown data of electrical insulation. The statistical theory of breakdown that has been proposed since the 1970s has introduced a two-variables Weibull distribution in order to take into account both the stress applied and the failure times. In this paper this distribution is thoroughly discussed and then rejected. Indeed, the random variable is only one; the other is an independent variable that becomes random only through the first, with the same shape parameter. The case of breakdown after electrical or multiple-stress aging (electric strength test on aged specimens) is also examined and the probability distribution function is written even in the general case, where the probability is a function of several variables. Only one of the latter, i.e. the electric strength ES, is the random variable while the others, such as the applied stresses and the time at which the ES measurement is performed, are independent     

电缆绝缘电阻在线测量的研究

介绍了一种新的电缆绝缘电阻的测量方法──电压、电流两次测量法,并用微机进行信号处理,它主要用于绝缘电阻的在线测量。     

绝缘材料、电工合金行业标准制修订进程

随着我国标准化工作的进一步拓深．标准化工作呈现出以下特征．一是标准化工作从传统的工农业产品向高新技术、信息技术、环境保护和管理、产品安全和卫生、服务等领域不断扩展。二是国家标准体系基本建立,截止到2005年底已颁布了国家标准21000多项（不含工程建设标准）．行业标准58489多项,地方标准7000多项．企业标准60多万项．基本形成了以国家标准为龙头．行业标准、地方标准和企业标准相互协调配套覆盖国民经济各个领域的标准体系。