共查询到16条相似文献,搜索用时 194 毫秒
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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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由于高压直流塑料电缆运行中温度梯度效应会引起场强畸变,选用一种特殊的纳米粒子作为填料,通过熔融共混制备出不同填料质量分数(1%,3%,5%)的低密度聚乙烯(LDPE)纳米复合材料。通过扫描电镜(SEM)观察,证明纳米粒子在聚乙烯中分散均匀。利用电声脉冲(PEA)法研究了温度梯度场下LDPE纳米复合材料中的空间电荷及场强畸变特性;并测量了不同温度下的体积电阻率和直流击穿特性。结果表明,该种纳米粒子的添加能有效改善温度梯度场下聚乙烯绝缘中电荷积聚和场强的畸变现象,并提高聚乙烯的直流击穿强度。同时发现,该聚乙烯纳米复合材料体积电阻率随着温度升高呈现先升后降趋势。 相似文献
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论文研究了聚乙烯及聚乙烯——丙烯共聚物的共混物的冲击电压击穿强度和高次结构 ,发现通过共混可以改善高温下的冲击电压击穿强度 ,分析了样品的高次结构 ,发现共混可以减小聚乙烯的球晶尺寸 ,并提高样品沿拉伸方向的取向度。高次结构的这一变化被认为是导致冲击电压击穿强度改善的原因。 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
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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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Wang X. He H.Q. Tu D.M. Lei C. Du Q.G. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2008,15(2):319-326
Dielectric properties of low-density polyethylene (LDPE) blended with metallocene catalyzed polyethylene (MPE) to 1, 3, 5 wt% of the latter are reported. It was found that the 1 wt% MPE blend had the lowest volume resistivity, the highest direct current (DC) breakdown strength and the least accumulated space charge. The crystalline morphology of the blends was studied through differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and small-angle light scattering (SALS) measurements. It was found that blending increased the percentage crystallinity, decreased the spherulite size and caused the formation of imperfect spherulites, i.e. spherulites containing defects and impurities in their crystalline phases, and thus fewer impurities and defects on their boundaries. The improvement in dielectric properties of the blends, especially the 1 wt% MPE blend, is attributed to the increase in crystallinity and the formation of imperfect spherulites. 相似文献
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Murakami Y. Nemoto M. Okuzumi S. Masuda S. Nagao M. Hozumi N. Sekiguchi Y. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2008,15(1):33-39
To understand basic electric properties of nano-sized magnesium oxide (MgO) / low-density polyethylene (LDPE) nanocomposite under DC voltage application, the volume resistivity, the space charge distribution and the breakdown strength were investigated. By the addition of nano-sized MgO filler, both the DC breakdown strength and the volume resistivity of LDPE increased. At the average DC electric field of about 85 kV/mm and more, a positive packet space charge was observed in LDPE without MgO nano-filler, whereas a little homogeneous space charge was observed in MgO/LDPE nanocomposite material at the front of electrode. From these results, it is confirmed that the addition of MgO nano-filler leads to the improvement of DC electrical insulating properties of LDPE. 相似文献
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空间电荷对低密度聚乙烯电气击穿特性的影响 总被引:5,自引:3,他引:2
为解决聚乙烯用作电线电缆绝缘材料时所受空间电荷问题的困扰,采用在低密度聚乙烯(low density po-lyethylene,LDPE)试品上施加直流预电压使其中积聚一定量的空间电荷,然后测量试品击穿强度的方法,研究了空间电荷对LDPE击穿特性的影响。结果表明,与未经过预电压处理的LDPE的击穿强度相比,在经过较低场强(50 kV/mm)预电压处理后,预电压与击穿电压极性相同时击穿强度提高了约9%,极性相异时击穿强度降低约14%;而经过较高场强(150 kV/mm)预电压处理后,预电压时LDPE中出现空间电荷包现象,预电压后同极性击穿强度提高约19%,而异极性击穿强度反而上升约16%。分析认为空间电荷包在LDPE中的运动导致了部分空间电荷的中和,使得空间电荷积聚量减少,同时LDPE中可能的缺陷得到了一定程度的老炼而使介质得到了均匀化,从而使LDPE的击穿强度得到了提高。 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