绝缘试样的漏电痕迹劣化与环境因素的影响

目前尚无非常规环境下评估绝缘材料漏电痕迹劣化的国际标准,故按IEC60112和IEC60587国际标准论述了不同种类绝缘试样在紫外线照射、低气压、γ射线辐射、酸雨及高温环境下的漏电痕迹劣化特征,即紫外线照 射可改变环氧树脂的绝缘破坏时间;在低气压环境下聚碳酸酯的CTI值增大,聚对苯二甲酸乙二醇酯的CTI值减小;随着γ射线照射量的增加聚萘二酸丁醇酯的CTI值增大,聚对苯二甲酸丁二醇酯的CTI值减小;聚碳酸酯随着温度的升高CTI值增大;聚苯乙烯在酸雨环境下绝缘强度无明显变化。在非常规环境下,如果用CTI值变小的绝缘材料将导致电器设备绝缘过早击穿而引起电气事故。     

方波脉冲电压下温度对聚酰亚胺薄膜电气绝缘特性的影响

为了研究温度尤其是高温对变频牵引电机绕组匝间绝缘材料电气绝缘特性的影响,以聚酰亚胺纳米复合薄膜为研究对象,测试了薄膜的介电温度谱,研究了方波脉冲电压下温度θ对薄膜局部放电起始放电电压(partial discharge inception voltage,PDIV)、击穿电压Ub及老化寿命的影响,分析了薄膜在老化期间的空间电荷分布特性。研究结果表明:θ升高,薄膜高分子链热运动加剧,阻碍了分子链极性端基及侧链的取向极化作用,使薄膜的介电常数ε减小;同时,薄膜的介质损耗tanδ也因极化作用的减弱而减小,但因弛豫现象使介质损耗温度谱在110℃处出现1个峰值;θ升高,被陷阱捕获的电子更容易受激发而脱陷,易满足局部放电对初始电子的要求,使PDIV降低;载流子平均自由程增大,载流子能量增强,对薄膜高分子链的破坏作用加剧,导致Ub降低。空间电荷分布特性研究表明:θ升高,载流子能量增大,加速了薄膜高分子链降解并生成小分子及自由基,增大了薄膜的陷阱密度,载流子频繁地入陷与脱陷,进一步加剧了高分子的降解,使薄膜老化寿命明显缩短。研究为优化变频牵引电机绝缘系统的设计奠定了基础。     

重复脉冲电压下温度对变频电机绝缘局部放电统计特性影响研究

为研究温度对变频电机绝缘局部放电统计特性的影响规律,在不同温度条件下采用上升时间为25 ns的双极性对称重复脉冲电压对变频电机漆包绝缘进行测试,分析温度对局部放电起始电压、局部放电谱图、放电相位、放电幅值及放电次数等特征参量的影响规律。结果表明:在漆包线耐热等级155℃内,局部放电对称出现在重复脉冲电压的上升沿和下降沿,局部放电起始电压随温度升高而下降,放电相位随温度升高而减小,放电幅值随温度升高而增大,半周期内的放电次数随温度升高而减少。温度会影响绝缘材料的相对介电常数、表面电导率及用于激发电子崩初始电子的产生概率,并改变表面电场和空间电荷积累效应,最终导致局部放电起始电压和局部放电特性发生改变。     

橡胶材料与交联聚乙烯绝缘界面的电气特性

为了解电缆附件和绝缘所用橡胶绝缘材料、交联聚乙烯形成的绝缘界面电气性能与橡胶材料厚度、过盈量配合等几何尺寸变化间的关系试验研究了两平行环形电极在绝缘界面上形成一小间隙绝缘界面的击穿强度。试验结果表明:界面电气强度随着两者过盈量的增加有遂渐增大趋势,但随过盈量继续增大则呈饱和现象;当过盈量较小时,随着材料厚度增加,界面电气性能呈线性增长趋势(试验范围内);而过盈量增大后,随着厚度的增加,界面电气性能也出现增长饱和现象。     

不同温度下含金属微粒的流动液体绝缘介质放电形成过程与机理分析

液体电介质的绝缘性能与其温度紧密相关,为了探究含金属微粒流动变压器油的放电特性,采用有限元法对不同油温下流动油中金属微粒的运动轨迹,以及金属微粒位置变化对电场的畸变程度进行了仿真,阐释了局部放电(PD)和击穿放电的过程及机理。同时,通过模拟实验,得到了不同油温下PD幅值、放电次数和相位的放电图谱、击穿电压以及放电后油色谱数据。结果表明:温度70℃时,随温度升高,PD逐渐减弱,油中气体含量呈减小趋势,击穿电压逐渐增大;当温度从70℃升高至80℃时,PD开始增强,油中气体含量开始增加,击穿电压开始减小;PD的相位主要集中在90°和270°附近,无明显的极性效应。     

不同温度下环氧玻纤布基板体积电阻率测试与内带电效应研究

温度是影响卫星绝缘材料绝缘性能及内带电效应充电状态的重要因素。本文采用三电极法测试了不同温度下星载电路板基板材料的体积电阻率变化规律，并在此基础上利用DICTAT程序仿真分析了温度对绝缘材料表面充电电位和内部最大电场的影响。结果表明：在-50～60℃下，基板材料的体积电阻率随温度的升高而减小，其变化幅值超过两个数量级；同时基板材料的表面充电电位幅值和内部电场强度均随温度的降低而上升，在温度低于0℃时存在较大的静电放电风险。     

水性环氧树脂对聚合物水泥混凝土材料电气性能的影响

以硫铝酸盐水泥(S)为基料,通过掺杂水性环氧树脂(E),采用浇注成型方式制备了SE系列新型聚合物水泥混凝土输电管道用绝缘材料。通过对该材料进行局部放电、扫描电子显微镜、电导率及热学性能测试,研究了微观形貌和电气性能的关联性,并计算了试样的电导活化能。结果表明:掺杂水性环氧树脂对聚合物混凝土材料的电气性能具有显著影响,局部放电起始电压随掺杂含量的增加先增大后减小,其中SE-7.5(水性环氧树脂的含量为0.075%)试样的局部放电起始电压最大。分析SEM的结果发现,SE-7.5试样的表面更为致密,孔隙率低,使得放电通道难以形成,导致其具有较大的局部放电起始电压。随着掺杂含量的增加,试样的电导率减小,电导活化能先增加后减小,SE-7.5试样的电导活化能最大,且具有更稳定的热性能。这是因为具有强粘接性的水性环氧树脂能够使水泥化合物粘接更紧密,适量的掺杂可以减小材料的孔隙率,改善材料的界面特性。当水性环氧树脂的掺杂含量为0.075%时,聚合物混凝土试样具有最佳的综合电气性能。     

电缆绝缘老化的判断

问 怎样判断电缆绝缘老化？答 绝缘材料性能随着时间发生不可逆下降的现象叫做绝缘老化。绝缘老化的表现形式有：击穿强度降低、介质损耗角正切增加、局部放电量增大、机械强度和其他性能降低等。     

SF6断路器喷口用复合PTFE电气性能的研究

高压SF6断路器喷口用聚四氟乙烯(PTFE)的粒径、填料的种类、粒径和添加量,对复合PTFE介电性能和耐电弧烧蚀性能都有着明显影响。应用正交设计软件设计了多种因素、每种因素不同水平组合的试验方案,研究了添加Al2O3, BN,MoS2的复合PTFE的电气性能受多种因素影响的变化规律。结果表明,添加无机填料能有效提高喷口材料耐电弧烧蚀性能,当填料种类不同时,复合FTFE的电弧烧蚀量依次为:复合MoS2的PTFE烧蚀量>复合Al2O,的PTFE烧蚀量> 复合BN的PTFE烧蚀量:复合PTFE相对介电常数随填料添加量的增加而增大,随温度的升高而减小;介质损耗角正切随填料的增加及温度的升高而增大。应用正交设计软件的分析功能,对电弧烧蚀试验结果进行了分析,得出填料添加量对烧蚀量的影响最为显著,其次为填料粒径,再次为填料粒径和PTFE粒径的交互作用。     

无机纳米掺杂XLPE电缆绝缘的力学性能与电气强度研究

通过自制掺杂纳米Si O_2和纳米炭黑的XLPE绝缘材料,研究了两种无机纳米颗粒对XLPE力学性能与电气强度的影响,测量了试样的拉伸率、断裂伸长率以及热老化前后的击穿电压和耐压时间。结果表明:添加纳米炭黑的XLPE试样具有最好的交联程度,材料韧性增加,而添加纳米Si O_2的XLPE试样的交联程度相对于纯XLPE试样变化不大,韧性减小,刚性增大;两种纳米颗粒的添加均使得XLPE电缆绝缘试样的击穿电压升高,同时耐压时间增加;热老化会降低XLPE绝缘材料的电气强度。     

Discharge energy and dc tracking resistance of organic insulatingmaterials

As an evaluation test method for surface insulation degradation of organic insulating materials, the tracking test method is described in IEC Publ.112 as a safe and reliable evaluation. This publication has now been applied to the material selection. Due to the fact that the experimental values of the comparative tracking index (CTI), have wide variations, problems in reliability testing are abundant. In this paper, the correlation is investigated between discharge energy and tracking resistance of organic insulating materials. The test method resembles the IEC Publ.112 method, but with the application of dc voltages. The number of drops to tracking failure was measured with samples of paper based phenolic laminate, polybutylene terephthalate and epoxy resin. Discharge currents were detected when discharge occurred on the sample surface. A Gaussian wavelet analysis was applied to show energy levels of discharge currents. It was found that the tendency of discharge energy on organic insulating materials corresponded to the CTI of dc tracking resistance, and the results were an improvement on the IEC Publ.112 method for grading materials. The tracking resistance of organic insulating materials could be deduced from the discharge energy     

Effects of atmospheric pressure on DC resistance to tracking of polymer insulating materials

Polymer insulating materials are required for use in high altitude regions. For the use of polymer insulating materials in such regions, it must be confirmed whether the resistance to tracking at high altitudes is different from that at altitudes near the sea level. In this paper, an artificial atmospheric chamber was set up to investigate the resistance to tracking on a polymer insulating surface at DC voltage application under a reduced pressure. The tests were carried out in accordance with IEC 60112. The test results showed that the dependences of the resistance to tracking for polymer insulating materials upon the decrease in ambient pressure could be classified into three types. One type is for paper-based phenolic laminate and polycarbonate, where the resistance increases with the decreasing ambient pressure; the second is for polybutylene terephthalate where the resistance decreases with the decreasing ambient pressure; the last type is for epoxy resin where the resistance is almost independent of the decrease in the pressure. A Gaussian wavelet analysis was applied to discharge currents to discuss correlations among the resistance to tracking, the discharge energy level and the ambient pressure. It was found that the data of resistance to tracking with some of the materials obtained at altitudes near sea level are inadequate for use in a high-altitude environment. Problems may occur with respect to the safety and reliability of polymer insulating materials when the DC resistance to tracking decreases under low-pressure conditions.     

阻燃隔热涂层在锂离子动力电池PACK中的应用

轻量化是电动汽车的发展趋势,电动汽车蓄电池PACK壳体往轻质金属和高分子复合材料方向发展,但这些材料无法通过外部火烧的实验规定,安全性能无法得到保证,本文采用了高效阻燃隔热涂层,使电动汽车蓄电池包系统具备了短时间内抵抗外部火焰的能力,给车上人员以救险或者逃生时间,具有重要的现实意义和广泛的应用前景。     

Environmental factors affecting DC resistance to tracking of polyethylene

Resistance to tracking of insulating materials has been studied by many investigators using the test method of IEC Publication 112. This method has now been applied to materials selection. There is no internationally recommended method for determining DC resistance to tracking because the experimental values of the comparative tracking index (CTI) are obtained only under AC voltage. The environmental factors affecting DC resistance to tracking of organic insulating materials are still far from being well understood. This paper presents a study of the effects of gamma-ray irradiation, atmospheric pressure, and sample temperature on the DC resistance to tracking of polyethylene. Samples were irradiated in air up to 1 MGy with a dose rate of 10 kGy/h using a /sup 60/Co gamma source. The resistance to tracking on applying DC or AC voltage was examined. We found that the DC resistance to tracking is lower than the AC resistance. As the total radiation dose is increased, the DC and AC resistance to tracking both increase. The erosion depth, weight loss and contact angle affected by the radiation have been studied under combined environmental conditions. A nonlinear correlation was observed. As the total irradiation dose was increased, the DC resistance to tracking decreased with decreasing pressure from 100 kPa to 50 kPa. When the samples were above room temperature the DC resistance to tracking decreased.     

核电站电缆用耐辐照无卤低烟阻燃绝缘材料的研制

在合理选用基体材料、阻燃剂、活性剂、防老剂等配合材料的基础上,采用正交试验的方法研究了苯基硅橡胶和三元乙丙橡胶（PVMQ—EPDM）掺混比、氢氧化镁用量和白炭黑用量对材料力学性能、阻燃性能、电绝缘性能和耐辐照性能的影响规律,确定了耐辐照无卤阻燃苯基硅橡胶．三元乙丙橡胶共混绝缘材料的配方。该绝缘材料具有高阻燃性能、抗辐照性能,同时具有良好的机械性能,可适用于核电站电缆绝缘材料等要求耐辐照和无卤阻燃的场合。     

聚合物绝缘材料的漏电起痕性

叙述了聚合物绝缘材料漏电起痕的形成机理,聚合物绝缘材料的结构对漏电起痕的影响进行了分析,含有共轭双键．苯核,杂环的聚合物绝缘材料耐漏电起痕差。对国内常用聚合物绝缘材料耐漏电起痕性能作了评价,为了提高耐漏电起痕性,除了使用不含或少含共轭双键结构的聚合物外,可加入适量的氢氧化铝。     

线缆阻燃材料和阻燃技术的发展

随着经济建设速度的不断加快,阻燃线缆被广泛地应用于各种场合。线缆阻燃材料的合理选择是提高线缆安全性能和减少火灾隐患的关键。对线缆阻燃材料的阻燃方法、阻燃剂的种类和选用原则等进行了阐述,并针对不同的线缆基体聚合物提出了相应的阻燃剂体系。最后还介绍了线缆阻燃技术的发展趋势。     

有机绝缘耐电痕性的评定与发展

介绍了国内外有机绝缘电痕破坏现象的研究及IEC60112,IEC60587和ASTMD213262T国际标准试验法;分析和比较了各种试验法的电极配置、试验条件和适用范围等。鉴于各种标准试验法未明确规定非常规环境,指出在低气压、高温及放射线环境下有机绝缘耐电痕性的变化可能导致电气绝缘事故发生;综合论述了有机绝缘电痕破坏的发生机理及本研究领域的发展趋势。     

Classical Electrostatic Description of the Work Function and Ionization Energy of Insulators

A simple classical model utilizing image forces has been developed which shows that the energy required to extract an electron from an insulating particle depends inversely on: 1) the size of the particle, 2) the dielectric constant, and 3) the maximum natural excursion distance of the electron from the surface of the insulating particle. As anticipated, data confirm that the ionization energy of an insulating polymer molecule is inversely related to the number of monomer units in the polymer molecule. Considering the solid insulator as the limiting case of a macroscropic particle, the predicted work function of the solid is the minimum value of the steadily decreasing ionization energy with size. This is in agreement with the limited data which show that the work function of an insulating polymer is approximately 1/2 of the ionization energy of the monomer in the gas phase. The model also predicts that the work function decreases with increasing dielectric constant in agreement with some limited available data.