Challenge of mixed insulating liquids for use in high-voltagetransformers.1. Investigation of mixed liquids

The aim of this work is to present results of investigations into mixtures of two insulating liquids, recently proposed as alternatives to mineral oil. The mixtures are a combination of the widely available mineral oil and a specific amount of ester liquid, which has similar electrical properties combined with fewer environmental risks but high hygroscopicity. The water saturation limit of esters is more than 40 times larger than that of mineral oils. Esters absorb water vapor from the air in larger quantities than mineral oil, and this hygroscopicity reduces the moisture content in solid insulation due to diffusion from the solid into the liquid, while the dielectric properties of ester liquids are only slightly changed . Although the life of an oil in service depends primarily on its initial quality, service conditions need to be considered also. The investigations have therefore been carried out on unaged mixed liquids as well as on specimens under severe ageing conditions. Pure liquids have also been investigated to provide baseline data for comparison purposes. The first part of the investigation compares the properties of the mixed liquids with those of pure liquids. The second part of the investigation, will evaluate the compatibility of the mixed liquids with insulating papers used in high-voltage transformers     

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     

从工程电介质进展看前沿课题

叙述工程电介质领域内近几年来取得的进展,重点介绍工程电介质理论的数学基础、固体聚合物绝缘的电击穿理论、纳米电介质、局部放电测量、空间电荷、电缆绕组电力设备、绝缘油、交联聚乙烯电力电缆、超导绝缘、有机电光器件、环境友好绝缘材料、塑料绝缘回收、变频电机绝缘、新材料、陶瓷介质和合成绝缘子方面的研究成果.     

防霉、防青苔型防污闪涂料原理和可能的应用

分析了温湿环境中电力系统现存的问题,认为绝缘设备表面滋长的青苔、霉菌等是影响此环境中电力设备安全稳定运行的重要原因,而在电力设备表面喷涂防霉防青苔型绝缘防污闪涂料是解决此问题的关键。同时分析了霉菌、青苔的生长机理以及防霉、防青苔涂料的原理,并综述了现阶段常用的防霉、防青苔的方法以及防霉、防青苔绝缘材料的研究现状以及在现场的施工工艺。最后展望了防霉、防青苔型防污闪涂料在电力系统的应用前景。     

Dielectric and thermoanalytical behavior and spectroscopic and kinetic evaluation of water in heat-resistant electrical insulating films

Nowadays, along with requirements for developing heat-resistant electrical insulating materials, various kinds of high polymers with polar structures are used, which are characterized by high heat-stability, good electrical properties, hydrophilic nature, etc. While their heat-stability is beneficial to their uses, their hydrophilic nature is sometimes detrimental, since the existence of water in electrical insulation is apt to deteriorate their electrical properties and dimensional stability. How water interacts with the polymer molecules in electrical insulating materials is an important issue to be solved; how inadequately the water can be classified into its free and bound forms in the materials has always been an interesting question. Heat resistant electrical insulating materials to be studied were selected and specimens conditioned by exposing them to moisture or immersing in water. The materials chosen were the following high polymeric films: Aramid, polyamide, biaxially oriented polyethylene terephthalate (PET), and biaxially-oriented polyethylene naphthalate (PEN); and an aromatic polyamide (Aramid) paper.     

500kV变压器段间雷电冲击试验模型的实现与电场的数值分析

应用二维四节点有限元电场数值分析的方法，通过对500kV电力变压器段间绝缘雷电冲击试验模型的关心区域内的电场与电场分布的比较，提出一种500kV变压器段间绝缘雷电冲击试验模型的简化方案，经对绝缘试验模型的电场数值分析，得出由段间固体绝缘材料与变压器油形成的油楔中会出现段间最大电场强度的结论。     

The effects of cellulose insulation quality on electrical intrinsicstrength

Cellulose serves as raw material for various electrical insulating materials, for instance, insulation paper and electrical pressboard. The practical application of these insulating materials involves situations where a reduction in strength may occur due to impurities, structurally inhomogeneous features, and ageing of the cellulose, or by boundary layer phenomena. The insulating capacity is restricted by such effects. In addition to knowing the factors that cause a reduction in strength, it is also important to know the intrinsic strength of pure cellulose insulation. Knowledge of dielectric imperfections is necessary in order to take advantage of the higher intrinsic dielectric strength and thus to achieve an optimal application of the insulating material. Based on the cellulose structure, material and structural influences and their relation to dielectric properties are investigated, and suggestions are given for better implementation of electrical intrinsic strength of cellulose insulation     

Time evolution of current through insulating paper under DC voltage stress

The use of paper in electrical insulation, especially in power transformers, remains a topical subject. The interest for the insulating paper, despite the emergence of many synthetic materials is ascribed to its low cost price and its ability to an oil impregnation. However its strong hydrophilic character remains the main difficulty for its implementation in electrical insulation. This affinity to water absorption and/or adsorption shows that a good understanding of the moisture effect becomes imperative. Several studies were carried out on the subject but a systematic study of the moisture effect on overall behavior of paper has not been achieved. This work is meant to be a contribution for this systematic investigation. The first step of this study, which is the object of the present article, concerns an examination of time variation of the electrical currents, under DC stress, for different moisture levels. A particular attention is given to the polarization and depolarization currents. These currents are examined during alternate charges and discharges sequences. An increase of the current, during the application of continuous voltage was noticed. This unexpected phenomenon would be related to an electro-dissociation and/or polarization processes.     

非线性有限元法在出线装置复合绝缘结构电场计算中的应用

极性反转是换流变压器出线结构复合绝缘的一种特殊工作状态,极性反转时由于空间电荷作用可导致绝缘介质内部及界面处电场畸变。另一方面,绝缘介质电性能参数是温度的函数,因此温度梯度导致的电性能参数改变同样会影响绝缘结构在极性反转过程中的瞬态电场分布。基于此,为了较准确地模拟复合绝缘结构在考虑温度分布条件下的极性反转瞬态电场,提出应用非线性有限元法对以上2种瞬态电场影响因素进行耦合分析。首先研究了油浸纸复合绝缘体系电性能参数与温度的关系;然后详细介绍了基于非线性有限元法的瞬态电场计算流程,并通过双层同轴复合绝缘结构模型验证了其有效性;最后对实际换流变压器出线装置的油纸-环氧浸渍典型复合绝缘结构建立了二维轴对称仿真计算模型,在考虑材料非线性的条件下对其极性反转瞬态电场变化过程进行了仿真分析。计算结果表明传统模拟方法与考虑材料非线性时的结果存在较大差异,且极性反转过程中复合绝缘结构易出现畸变严重的局部高场强区。     

描述高压直流电缆绝缘材料电导率的公式比较

以高压直流交联聚乙烯(cross-linked polymeric,XLPE)电缆为研究对象,研究讨论了现阶段描述直流电压下绝缘材料电导率公式对XLPE材料的适用情况。首先基于两种不同电导率公式推导了稳态下高压直流电缆中电场反转的临界温差、绝缘层温度分布、电场、电导率和距离电缆中心的乘积以及绝缘层电场分布,并通过比较有限元仿真结果和公式计算结果证明了所推公式的可靠性。然后通过对不同电导率公式计算值的比较,以及不同公式在相同条件下引起的绝缘材料热电特性,证明了公式互换的可能性。     

耐电晕耐电痕化绝缘材料研究进展

先进电工绝缘材料对电力装备的发展具有基础性、支撑性、先导性的作用,它决定着电力装备制造业的技术水平。耐电晕耐电痕化绝缘材料的发展对保障电力设备持久安全运行具有重要意义。从基础研究、应用研究以及产业现状等方面对耐电晕耐电痕化绝缘材料发展动态进行综述,对耐电晕耐电痕化绝缘材料发展趋势和未来研究方向进行了展望,对我国耐电晕耐电痕化绝缘材料的发展战略提出了建议。     

The effect of voltage distortion on ageing acceleration ofinsulation systems under partial discharge activity

This paper focuses on the features of harmonic distortion which may affect significantly the reliability of typical ac-power network equipment, such as low-voltage self-healing capacitors used for reactive power and harmonic compensation. Moreover, the effect of high-frequency pulse-like voltage generated by Adjustable Speed Drives (ASD) on electrical machine insulation is also investigated, resorting to life tests carried out on different insulating materials of the standard and “corona resistant” type, at electrical field levels able to incept partial discharges (PD)     

有机绝缘材料电晕老化测试系统的研制

为了对国内研究有机绝缘材料的耐电晕老化问题提供一个标准的试验平台,进而有助于相关试验方法等标准的制定,参照美国ASTMD2275-01固体电绝缘材料表面对电晕的耐压性标准试验方法中的试验装置,自行研制了一套先进的有机绝缘材料电晕老化测试系统。该系统包括电晕发生装置、测量装置、保护系统、环境控制及监测装置等,能在不同的试验条件下同时对多组试样进行电晕老化试验,并以LabView为软件平台实现对电流、电压、累积电荷量的实时采集计算和存储。利用该系统对高温硫化(HTV)硅橡胶进行初步电晕老化试验的结果表明,该系统能够按照设定的试验条件可靠稳定运行。     

An indicator of a defect in a high-voltage insulating structure

To monitor the insulation of high-voltage equipment, different kinds of devices, including in situ ones, are used. This paper considers the possibility of using optical indicators—light emitters mounted on the insulation structure of high-voltage lines and substations—as such devices. The principle of operation of an optical indicator is as follows. The electric field distribution over an insulation structure changes with breakage of the integrity of its separate parts; when the potential difference at a damaged section decreases, the voltage at the undamaged part correspondingly increases. A faulty condition of the insulating structure can be determined using the light intensity of an indicator installed in the section of the insulating structure or pylon, since the luminance depends on the voltage drop across its terminals. Experiments showed that such insulation failure can visually be determined without using any additional devices, for example, during routine inspections. It is shown that it is possible to produce indicators that are easy to manufacture and do not require any additional maintenance.     

电压互感器的绝缘结构和老化因素及应对措施

介绍了按绝缘介质分类的干式、浇注式、油浸式和气体式4类电压互感器的结构及按电压等级、使用环境的不同所采取的不同方式的电压互感器的绝缘结构。由于电气设备的绝缘在长期运行过程中会发生一系列如固体介质软化或溶解等形态变化、低分子化合物和增塑剂的挥发等的物理变化,以及如氧化、电解、电离、生成新物质等的化学变化,即绝缘的老化,最终导致绝缘失效,电力设备不能继续运行,阐述了未来电压互感器的绝缘设计寿命将按用户预期使用的寿命来设计,通过在绝缘可靠性设计中引入应力一强度干涉理论,对电压互感器的绝缘寿命薄弱环节进行优化设计。     

Drying of transformer insulation using zeolite

Power and distribution transformers are some of the most important components in the power network. The presence of moisture in a transformer deteriorates the transformer insulation by decreasing both the electrical and mechanical strength of the solid insulation. It is of great importance to pay attention to the moisture content of composite insulation systems in order to maintain low dielectric loss, high dielectric breakdown strength and low rates of degradation of the insulating system in HV equipment. In this paper, an approach to the said problem is presented. With the application of a synthetic hygroscopic mineral (molecular sieve zeolites) - a revolutionary, environment friendly, multipurpose mineral - a continuous drying process of the transformer oil during operation without the need for service interruption is achieved. A study of the effects of zeolite on the electrical and dielectric behaviour of the insulating liquid of the transformer is included in this paper.     

Evaluation of electrical tests on transformer board

In electrical tests on insulating materials for transformers, general, in-model test arrangements varying the parameters of electrical properties are established. These values cannot be transferred to real transformer insulation without further consideration. However, from these individual test results with their differing statistical variations of parameters of electrical proportions, statements about the electrical strength of the insulation are drawn and evaluated     

基于SCADA/AM/FM/GIS的电气设备绝缘在线监测系统的设计

从配网中SCADA与AM／FM／GIS系统的集成入手，得出当前集成的SCADA／AM／FM／GIS在线系统只监控了电力系统没备的宏观运行特性，而未考虑电气没备的绝缘运行状态及故障诊断情况，具有一定的局限性 通过分析电气设备绝缘在线监测系统的原理，提出一种将SCADA／AM／FM／GIS与电气设备绝缘在线临测系统相结合的思想、依此思路集成的新系统，既能全面地反映电力系统及设备的运行状态，又能监测电气设备的在线绝缘状态，具有较好的经济、实用价值。通过实例分析得出基于SCADA／AM／FM／GIS的设备绝缘仵线监测系统的设计方法，经在实际中应用，具有很好的效果。     

500 kV主变系统检修中PRTV涂料应用效果探讨

处于潮湿及污染环境中的主变压器套管、输电线路绝缘子等电力设备常会发生污闪放电、泄漏量增大等现象,在检修中使用了PRTV绝缘涂料进行处理,讨论了其重要技术特性及注意事项,并通过相关电气试验方法对使用效果进行了验证.实践研究结果显示,在检修维护工作中合理使用PRTV绝缘涂料能够有效提升500 kV高压电气主设备的运行安全稳...