绝缘封装用环氧树脂固化物的湿热老化特性

环氧树脂容易受到湿热环境的侵蚀而发生绝缘性能劣化,进而直接影响电力系统运行的安全性与稳定性.为明确环氧树脂材料在湿热环境下的介电性能变化趋势,该研究对环氧树脂固化试样进行湿热老化实验,探究老化温度对其介电性能的影响规律,并对湿热老化机理进行分析.实验结果表明:环氧树脂试样在湿热老化后因吸湿出现质量增加,水分子对环氧树脂基体的塑化作用使其玻璃化转变温度降低.湿热老化后环氧树脂的体积电阻率下降,而相对介电常数和介质损耗因数增大,低频区尤为明显.用瓦格纳热击穿理论解释了环氧树脂试样击穿现象,相对介电常数和介质损耗因数增大都会导致环氧树脂的工频交流击穿强度下降.湿热老化温度升高加速了环氧树脂的吸湿进程,使其平衡状态的吸湿量增大,造成介电性能进一步下降.     

纳米ZnO/低密度聚乙烯复合材料的介电特性

聚合物纳米复合材料因其优良的介电、机械等性能在电介质领域得到广泛的应用。纳米粒子改性聚乙烯基绝缘材料具有很好的研究价值及工程意义。该文主要研究了表面经分散剂处理的纳米ZnO粒子添加剂与低密度聚乙烯(LDPE)共混物的介电特性。结果表明5%含量的纳米ZnO添加剂能有效提高聚乙烯基复合材料的体积电阻率和交流击穿强度。同时纳米添加剂虽增加了体内的残余电荷,但能有效抑制电极同极性电荷的注入。另外由于聚合物纳米复合材料的界面特异性,使得介电常数随着纳米ZnO含量的增加呈先减小后增大趋势,而损耗值却线性增加。纳米ZnO/聚乙烯复合材料介电性能提高归因于纳米粒子与聚乙烯分子间类同于深陷阱的界面效应。     

空气中不同温度下环氧树脂绝缘子表面电荷消散过程的实验研究

表面电荷的消散与绝缘材料的表面电阻率和体积电阻率有关,而温度的变化会影响绝缘材料的表面电阻率和体积电阻率。为了研究环氧树脂绝缘子在不同温度下的表面电荷消散规律,建立了一套测量系统,采用有源静电探头法,对空气中在针板电极下的环氧树脂圆板绝缘子施加直流电压后进行了表面电位的测量。研究结果表明:各种配方的环氧树脂圆板绝缘子在不同温度下的消散过程都近似呈指数衰减规律;环氧树脂圆板绝缘子的表面电荷消散主要通过沿表面消散的方式进行;表面电阻率越高,表面电荷消散速率就越小;套管在实际运行过程中温度会高于常温,在选用环氧树脂材料时,应考虑其在工作温度范围内的电阻率变化,在保证绝缘强度的同时,尽量选择表面电阻率小的环氧树脂材料,以减少绝缘子表面电荷积聚。该研究结果对超大型直流穿墙套管中的环氧树脂绝缘支撑件的工程设计有借鉴意义。     

大型水轮发电机绝缘参数对定子线棒端部电场和电位分布的影响

应用COMSOL软件建立了定子线棒端部的有限元仿真模型,分析了绝缘材料电性能参数对线棒端部表面电场及电位分布的影响。结果表明：随着主绝缘相对介电常数的增大,线棒端部表面最大电场增大,主绝缘材料的相对介电常数选择偏小为佳;主绝缘材料电阻率对线棒端部表面最大电场的影响不显著。各级防晕层的相对介电常数对线棒表面最大电场变化影...     

高压直流电缆聚乙烯绝缘材料研究现状

聚乙烯类材料因其优异的介电性能被广泛应用于高压直流电缆绝缘。直流电缆运行过程中,绝缘材料电导率随温度梯度变化和直流电场下空间电荷的积聚而变化,导致绝缘材料内部电场畸变,是目前高压直流聚乙烯电缆绝缘发展面临的严峻问题。该文通过综合国内外研究,论述了高压直流电缆聚乙烯绝缘材料的研究进展,分析了改性聚乙烯绝缘材料的介电性能和作用机理,最后展望了高压直流聚乙烯绝缘材料的发展趋势。研究结果表明,纳米掺杂改性能够有效抑制聚乙烯绝缘材料内部空间电荷的积累,改善聚乙烯绝缘材料直流电导率的温度特性;共混改性生产免交联的聚乙烯绝缘材料能够提高其介电性能;电压稳定剂能提高聚乙烯绝缘材料的耐电树枝性能,具有良好的发展前景;超纯净聚乙烯绝缘材料是高压直流聚乙烯电缆绝缘材料研发的基础和重点。这些研究成果的总结可为未来高压直流电缆聚乙烯绝缘材料的研究和发展提供参考。     

低温环境下环氧树脂氧化铝复合材料的介电性能变化规律研究

为了研究极寒地区环氧树脂复合材料应用的可靠性,制备了微米Al_2O_3填料含量分别为0、20%、50%和75%的环氧树脂试样,采用恒温试验箱对试样进行低温冷冻处理,并测试了试样的介质损耗因数和介电常数,得到不同温度下、不同Al_2O_3含量环氧树脂材料的介电性能变化规律,分析了环氧树脂复合材料介电性能变化的原因。结果表明:随着微米Al_2O_3填料含量的增加,环氧树脂复合材料的介质损耗因数减小,相对介电常数增大;随着温度的降低,环氧树脂复合材料的介质损耗因数呈先增大后减小的趋势,相对介电常数呈减小趋势。     

交联聚乙烯热老化与绝缘性能的关联关系

为研究交联聚乙烯（cross-linked polyethylene,XLPE）绝缘材料的热分解活化能、电气特性和力学特性随热老化程度变化的规律,对交流电力电缆绝缘用XLPE材料在110 ℃下开展加速热老化实验。采用热失重（thermogravimtric analyzer, TGA）测试手段,对XLPE在20~600 ℃的热分解行为进行研究;采用交流击穿测试、宽频介电谱测试及体积电阻率测试,研究老化后XLPE试样的电气特性;采用拉伸实验测试,研究老化后XLPE试样的力学特性。结果表明：热老化使得XLPE的交联结构和结晶状态被破坏,XLPE活化能呈减小趋势。由于氧化反应快速进行,使得XLPE分子链发生断裂,交联结构变弱,导致XLPE绝缘材料严重劣化,其活化能、击穿强度、体积电阻率、弹性模量和断裂伸长率随老化时间增长呈下降趋势,而介电常数、介电损耗和电导率呈增加趋势。     

精炼菜籽绝缘油的介电性能

为了研究植物绝缘油在变压器等充油高压电气设备中的应用,分析了精炼处理后菜籽绝缘油的主要介电性能,并进行了试验研究和理论分析,采用介电谱测试仪测量了菜籽绝缘油试品的相对介电常数和介质损耗因数,分析了两性能参数随试验温度、频率变化的规律,并参照相关标准对菜籽绝缘油的体积电阻率进行了研究。同时,测试了#25矿物绝缘油相应的介电性能参数。通过比较分析两类绝缘油介电性能参数温度谱、频率谱的试验结果发现,相对于矿物绝缘油,植物绝缘油具有良好的介电性能。     

交联聚乙烯热老化与绝缘性能的关联关系

为研究交联聚乙烯（cross-linked polyethylene,XLPE）绝缘材料的热分解活化能、电气特性和力学特性随热老化程度变化的规律,对交流电力电缆绝缘用XLPE材料在110 ℃下开展加速热老化实验。采用热失重（thermogravimtric analyzer, TGA）测试手段,对XLPE在20~600 ℃的热分解行为进行研究;采用交流击穿测试、宽频介电谱测试及体积电阻率测试,研究老化后XLPE试样的电气特性;采用拉伸实验测试,研究老化后XLPE试样的力学特性。结果表明：热老化使得XLPE的交联结构和结晶状态被破坏,XLPE活化能呈减小趋势。由于氧化反应快速进行,使得XLPE分子链发生断裂,交联结构变弱,导致XLPE绝缘材料严重劣化,其活化能、击穿强度、体积电阻率、弹性模量和断裂伸长率随老化时间增长呈下降趋势,而介电常数、介电损耗和电导率呈增加趋势。     

220kV高压交流电缆用交联聚乙烯绝缘材料的性能研究

采用熔融共混法制备了220 kV高压交流电缆用交联聚乙烯绝缘材料预混料,采用后吸收法工艺制备交联聚乙烯绝缘材料.研究了国产高压交流绝缘材料与同电压等级进口材料在杂质含量、力学性能、体积电阻率、热老化性能、加工工艺性能等方面的差异,发现相关问题及差距,对国内高压电缆材料研发有一定参考意义.     

温度对植物绝缘油纸介电响应特性的影响

本文分析了大豆油基植物绝缘油和棕榈油基植物绝缘油的相对介电常数、介质损耗因数、体积电阻率等参数,在不同温度下测试了两种植物油纸绝缘系统的频域介电谱。结果表明:两种不同油基的植物绝缘油相对介电常数不同;黏度低的植物绝缘油极化损耗更强;植物绝缘油的极性越强,体积电阻率越低,电导率越高;温度对植物油纸绝缘的频域介电谱曲线有较大的影响,温度升高使频域介电谱曲线向高频方向平移。     

微米氮化硼-纳米氧化铝复合环氧材料的导热与绝缘特性

环氧树脂(epoxy resin, EP)以其粘附力强、绝缘性能好等优点,在电气领域中得到广泛应用。但环氧树脂的低热导率限制其在器件中的使用,尤其在高频条件下。文中通过多巴胺改性微米氮化硼和纳米氧化铝,将制备的微纳米二元填料填充环氧树脂,研究环氧树脂复合材料的导热性能和电气绝缘性能。结果表明,质量分数22.5%BN和7.5%Al2O3环氧树脂复合材料的导热系数可以达到1.35 W/(m·K),相比于纯EP增加了812.5%,而介电损耗维持在较低水平。高频击穿实验结果展示出复合材料击穿时间明显提高,比纯环氧树脂提高了387%。该种方法制备所得的环氧树脂复合材料,具有热导率高、介电损耗低、高频击穿强度大等优点,为开发适用于高频电力电子器件的导热绝缘材料提供参考。     

High-field dielectric properties of polypropylene films in high-temperature region

Nonpolar polymers are used widely as electrical insulation materials, and their operating conditions sometimes become high-electric field and high temperature. Under these conditions, the conduction loss is assumed to affect the dielectric properties and to make the ac dissipation factor (tan δ) increase. Therefore the high-field dielectric properties of polymeric materials in the high-temperature region become very important. This paper describes the high-field dielectric properties of polypropylene films measured at 50 and 400 Hz above room temperature with the new electrodes developed by authors. At low temperature, the high-field tan δ is independent of the frequency of the applied field. However, at high-temperature, the high-field tan δ becomes almost inversely proportional to the frequency, namely, the conductivity is independent of the frequency. The theoretical analysis shows that the high-field dielectric loss is governed by two processes: one is the loss which appears only under ac field; and the other is conduction loss which appears also under dc field. The latter loss becomes prominent under high-electric field at high temperature.     

TLM simulation of microwave hybrid sintering of multiple samples in a multimode cavity

Microwave heating technology is a powerful mean to ensure successful sintering of ceramic materials. In sintering experiments, low loss insulators, conductors and high‐loss ceramics are microwaved so as to get optimal mechanical and structural properties. It is known that low‐loss ceramic materials such alumina and zirconia exhibit long waiting time before reaching a critical coupling temperature at which microwaves can be readily absorbed. On the other hand, some ceramics such as silicon carbid have a high loss factor and therefore can be used as a process stimulus for microwave sintering of microwave transparent ceramics. Furthermore, successful sintering experiments often require the use of carefully designed insulating structure in order to minimize thermal gradients caused by heat loss from surfaces. All these problems have led to the introduction of microwave hybrid heating (MHH) schemes using higher dielectric loss susceptors, insulation or coating. Since MHH depend mainly on human expertise, the optimization of sintering experiments will certainly benefit from numerical simulations. The transmission line matrix (TLM) is used to study two MHH schemes where both a susceptor and an insulating matrix were, respectively, used as process stimulus for microwave heating of multiple alumina samples within a three‐dimensional multimode cavity. The effects of such MHH schemes and target settings on electric field distribution and power absorption rates are reported in this paper. Copyright © 2003 John Wiley & Sons, Ltd.     

风力发电机绝缘系统耐盐雾性能研究

通过对风力发电机线圈进行绝缘电阻率、工频耐压、介质损耗等试验,研究了定子线圈在耐盐雾条件下的各项电性能.结果表明:随盐雾试验时间的增加,绝缘系统的电气性能降低.其原因是绝缘系统憎水性降低,绝缘层浸渍漆产生放电气隙,以及绝缘材料的劣化变质所致.     

Common insulating properties in insulating materials

Insulating materials exist in a variety of different forms, including gas, liquid, solid, and vacuum, and different forms of insulating materials have significantly different dielectric strengths and insulating properties. Power transmission/substation facilities for UHV AC and 500 kV DC power transmission and 500 kV underground power transmission facilities have been designed and constructed by taking advantage of the insulating properties of various insulating materials and structures so that they conform to the demanded insulation specifications. Conventionally, insulating material technology has been developed by making a close study of apparatuses and insulating materials individually. In this paper, as a new attempt, the insulating properties of various insulating materials/apparatuses are cross-sectionally compared and examined from an entirely new viewpoint through the assessment of commonalities and differences between them. A listing of lightning impulse and AC dielectric strength data is prepared and systematically positioned from the standpoint of material and structure, and compared and evaluated in a unified way from the viewpoint of typical indices of insulating properties including the "n" value of the V-t characteristic, Weibull parameters, and impulse ratio. Further, an insulation assessment of apparatuses is systematically made with consideration given to their sizes and structures as well as the insulating materials themselves. As a result, it was found, for example, that the design field strengths of power capacitors were high and those of generators were not, and there was a noticeable difference in design field strength between SF/sub 6/ gas insulated apparatuses and oil-immersed transformers. It is expected that the analysis conducted from an entirely new angle may provide a new approach to the development of apparatus insulation technology and to the rationalization of insulation design.     

Influence of water absorption on high‐frequency characteristics of insulation layers of printed circuit boards

The influence of water absorption on complex permittivities of various insulating materials used for printed circuit boards was investigated in the frequency range of K‐band (18–26 GHz). Experimental results revealed that the influence of water absorption on complex permittivity, the dielectric loss factor tanδ, in particular, was considerably high. For example, the dielectric loss of polyimide film at 85°C, 85% RH became 10 times larger than that at room temperature and humidity. Since the complex permittivities, however, retained the initial values when the specimens are dried, the water in the specimen should exist freely at the internal interfaces of the materials. The increase of permittivity directly affects the performance of printed circuit boards at high frequencies, so that it is important to clarify the influence of water on dielectric properties of insulations. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

变压器材料的温度特性对绕组频率响应的影响

研究冷轧硅钢片铁心磁性能和油纸绝缘介电性能对绕组频率响应的温度效应。推导稀疏线圈在有铁心和空心时的阻抗差异与铁心复磁导率,以及绝缘材料的阻抗与其复介电常数的频率依赖关系。在频率范围从1k Hz到1MHz对铁心复磁导率、油和纸绝缘复介电常数和模型变压器两种绕组的频率响应进行从110℃自然降温到30℃的试验研究。获得铁心复磁导率、油和纸绝缘材料复介电常数随温度变化的规律,探讨了纸占比对油纸复合绝缘介电特性的影响,讨论铁心和油纸绝缘单独作用时绕组频率响应特征的变化趋势。进而用变压器这2种材料温度特性结合绕组等效电路解释了模型变压器层式绕组和饼式绕组的频率响应随温度变化的特征,认为绕组等效(合成)电感与等效电容的乘积变化最终决定了(反)谐振频率移动方向。为了正确地解释变压器绕组频率响应,应密切关注绕组变形试验时的温度。     

A new polyimide film for VLSI and its electrical characterization

Multilevel structures consisting of alternating metal and dielectric layers are necessary to achieve interconnection in high density or VLSI (very large scale integration) circuits using either MOS or bipolar technology. Polyimide is one of the excellent high temperature heat-resistant polymers in organic materials and has good planarization capability and electrical insulating properties. In this work, following the synthesis of DAPDS (4,4'-bis (3-aminophenoxy)diphenyl sulfone), by nucleophilic aromatic substitution of 4,4'-dichlorodiphenyl sulfone with m-aminophenol, DAPDS/pyromellitic dianhydride based soluble and processable fully imidized polyimide was synthesized successfully by using solution imidization technique. Using this specific polyimide, a metal-polyimide-silicon MIS (metal polyimide silicon) structure was manufactured. Electrical properties of the MIS capacitance have been examined. The planarizing and patterning characteristics and electrical characteristics such as current vs. voltage, breakdown field strength, permittivity and capacitance vs. voltage for quasi-static and high frequency measurements are discussed. The results are compared with conventional dielectric films used in integrated circuit fabrication