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针对高压、超高压直流塑料电缆中存在的空间电荷效应,大多数直流电力电缆常采用改性方法提高其介电性能,如空间电荷特性、体积电阻率和击穿强度等。常用的改性方法主要有添加剂、共混、接枝和二元共聚4种。共混技术较广泛用以改性聚乙烯电缆,提高其介电性能。因此用电声脉冲法(PEA)测量了MPE与LDPE共混试样中的空间电荷分布;用高阻计测量了共混物的体积电阻率,用阶梯电压测量了共混物的交流击穿场强。试验结果表明,1%MPE与LDPE共混能有效降低空间电荷效应,提高交流击穿场强7.9%,略降低体积电阻率。最后讨论了共混物的物质结构、电荷陷阱及介电性能间的关系。 相似文献
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茂金属聚乙烯改性低密度聚乙烯中空间电荷的机理研究 总被引:10,自引:3,他引:10
针对高压,超高压直流塑料电缆中存在的空间电荷效应,文中选用与普通低密度聚乙烯(LDPE)化学结构相似的茂金属聚乙烯(MPE)作为成核剂与LDPE共混,用电声脉冲法(PEA)测量了共混物的空间电荷特性,以差示扫描量热法(DSC)研究了共混物的非等温结晶行为,用高阻计测量了共混物的体积电阻率的变化,结合聚合物的结晶和导电理论,讨论了共混物中空间电荷的形成和抑制机理。测试结果表明:1%的MPE与LDPE共混,能有效降低LDPE中空间电荷效应,提高结晶温度,降低体积电阻率。 相似文献
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Yamamoto Y. Ikeda M. Tanaka Y. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2004,11(5):881-890
In this paper electrical properties of a novel linear low-density polyethylene synthesized with a catalyst, developed by our unique technique, were measured. It was found that this polyethylene had a higher volume resistivity, a higher breakdown strength and less spacer charge accumulation than conventional high-pressure low-density polyethylene and linear low-density polyethylene. We also measured electrical properties of blends of the new polyethylene and the conventional low-density polyethylene and found that the blends which contained up to 90 wt% of the low-density polyethylene had nearly the same value as the new polyethylene. The morphologies of the polyethylene were observed by using transmission electron microscope (TEM) and found that the blends kept the characteristics shown in the new polyethylene up to 90 wt% of the low-density polyethylene content. The relationship between morphology and electrical properties is discussed and comparison is made between the new polyethylene with those of the conventional low-density polyethylenes. 相似文献
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Experiments were conducted to determine structural changes (degree of crystallinity) of PE (polyethylene), the development of treeing (velocity, shape), and changes of tan δ and breakdown strength as a result of thermal aging. The results show that thermal aging causes increased separation of spherulites. Overheating leads to the appearance of amorphous regions with dimensions exceeding the diameter of the neighboring spherulites. It is shown that the treeing channels develop faster in amorphous thermoplastic PE insulation than in a partially crystalline one and that tan δ increases, but the breakdown decreases with the time of thermal aging 相似文献
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氯化聚乙烯共混对聚乙烯的空间电荷效应的影响 总被引:2,自引:0,他引:2
在直流电场作用下 ,用电声脉冲法测量了低密度聚乙烯 (LDPE)中空间电荷的分布 ,计算结果表明 ,异极性空间电荷严重畸变试样中的电场的分布。以少量氯化聚乙烯 (CPE)混入低密度聚乙烯中 ,大大降低了试样中的空间电荷 ,电场分布趋向均匀。在正负极性直流预压短路树枝试验中 ,分别提高试样短路树枝起始电压 2 6 8%和 36 3%。通过直流预压和电晕电荷注入后 ,短路过程中空间电荷分布的测量 ,提出氯化聚乙烯的作用机理在于降低了聚乙烯中陷阱的深度和密度。 相似文献
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Fan Z.H. Yoshimura N. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1996,3(6):849-858
A small amount of phenolphthalein, acting as a nucleating agent, was added to low density polyethylene (LDPE) to modify the size and number of spherulites. The crystalline morphology was observed and analyzed with the aid of a chemical etching method. It was found that the growth of water trees is faster in LDPE samples in which spherulites are larger and the number of the spherulites is lower. In contrast, water trees grow more slowly in other LDPE samples in which spherulites are smaller in size and greater in number. On the other hand, three different kinds of additives, weak electrolyte and hydrophilic or hydrophobic substances, were added to the LDPE materials to investigate the influence of typical spherulite boundary regions on the growth of water trees. It was verified experimentally that during the process of crystallization, these three different additives are rejected and finally settled near the spherulite boundaries. Therefore, three kinds of boundary regions with different characteristics are formed. It has been concluded that hydrophillic boundary regions can strongly inhibit the growth of water trees, while the other two boundary regions (weak electrolyte, hydrophobic) have little influence on the water tree growth 相似文献
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Chao Zhang Mori T. Mizutani T. Ishioka M. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2003,10(3):435-443
Extruded films prepared from blends of low-density polyethylene (LDPE) and random copolymer of ethylene and propylene (EP) with the T-die method were studied with respect to electrical properties and morphology. Comparisons with data on blown films are made. These blends are of interest as improved LDPE for making XLPE for insulated power cable. In the high temperature region (90/spl deg/C), a specimen with a slightly higher EP content had higher impulse breakdown strength than that with a lower EP content, but no improvement of DC breakdown strength by blending could be found. The improvement of impulse breakdown strength (90/spl deg/C) is explained in terms of morphological changes by blending such as the orientation of chains in a film and the size of spherulites on the assumption of the thermal breakdown. In comparison, a T-die film had higher impulse breakdown strength than that of a blown film for the same composition. The impulse breakdown strength also increased with the use of the higher density LDPE. In the current versus electric field characteristics at 30/spl deg/C, the blend polymer with EP content of 5-10% showed a transition from LDPE behavior at low field region to EP behavior at high field region. However, no appreciable difference in current behavior among the specimens was observed at 90/spl deg/C, which suggests an incompatibility between the two materials that exists at 30/spl deg/C but not at 90/spl deg/C. 相似文献
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Extinction of spherulites and improvement of polyethylene properties by the use of lithium carbonate
Shigeru Yamamoto Chikataka Kawakami Yasuo Mizuyori 《Electrical Engineering in Japan》2004,148(2):22-38
Polyethylene (PE) consists of nonpolar molecular chains having simple structural units. Physically, this polymer is so stable and flexible that it is widely used for insulation of electric wires and power cables, as well as for fabrication of various molded products. The crystalline texture and the presence of spherulites are major factors determining the mechanical and electrical properties of polyethylene. For the purpose of improving these properties of PE, the spherulites are eliminated completely by heat mixing of PE with Li2CO3. PE processed in this manner is free of spherulites, has a uniform structure and excellent electrical, mechanical, and thermal properties, such as short treeing length, high dielectric breakdown strength, and high tearing impact strength. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 22–38, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10296 相似文献
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空间电荷相关研究是直流电介质材料特性研究的重要领域,聚乙烯则是主要的内绝缘材料之一。为了对高压直流条件下聚乙烯中的空间电荷现象进行深入研究,应用电声脉冲法空间电荷测量系统对高场强下低密度聚乙烯中的空间电荷现象进行测量,观察到了空间电荷包现象。研究结合不同热处理方法得到了不同微观形态的聚乙烯试品,并在不同场强下结合微观形态的变化对低密度聚乙烯的空间电荷包运动速率进行了分析。结果表明,聚乙烯的微观形态对空间电荷包特性有显著的影响,也对空间电荷包运动速率有明显的影响,结晶度越高,空间电荷包运动速率越小。 相似文献
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选择三种受阻酚类抗氧剂1010、1076、1035,分别考察其含量对过氧化物交联低密度聚乙烯(LDPE)热老化前后力学性能的影响,测试不同交联体系的凝胶含量。研究表明,三种受阻酚类抗氧剂均对LDPE的力学性能产生一定的影响,与没有添加抗氧剂的交联聚乙烯相比,其断裂伸长率均降低;添加1076的体系抗拉强度有所提高,而添加1010和1035的体系抗拉强度较小提高;当抗氧剂含量〈0.7%时,其对交联聚乙烯的凝胶含量影响不大。老化试验结果表明,抗氧剂含量较低(〈0.2%)时,交联聚乙烯耐热老化性能恶化,试样严重变形;当抗氧剂舍量较高时,热老化性能有所提高。 相似文献
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纳米ZnO/低密度聚乙烯复合材料的介电特性 总被引:3,自引:0,他引:3
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。 相似文献