【摘要】 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。更多还原

【Abstract】 Space charge effect is undesirable for HV and EHV plastic power cable.Up to now,the insulating materials of most DC power cables are traditional modified polyethylene(PE) in order to have superior dielectric properties such as space charge accumulation,volume resistivity,breakdown strength and so on.The common modification can be achieved by various methods such as the uses of additives,blending,grafting and copolymerization.In general,blending is a widely used technique to improve dielectric properties of PE.Based on blending technique,metallocene catalyzed polyethylene(MPE) is blended into low-density polyethylene(LDPE) in this paper.Then the space charge profile in the blends is measured by pulsed electro-acoustic(PEA) method.And at the same time,the volume resistivity of blends is measured by micro-current detector.In addition,the AC breakdown strength of blends is measured by step voltage.It is shown by test results that LDPE blending with 1% of MPE could effectively decrease the space charge effect,increase the AC breakdown strength by 7.9% and slightly reduce the volume resisitivity.The test results of the resistivity are consistent with that of space charges.It is validated that the blending by proper amount of MPE could decrease the deep traps,increase the shallow traps and the charge mobility in LDPE.Polyethylene is a typical semicrystalline including crystal phase and amorphous phase.The electrical breakdown path advances along the boundaries of spherulites,or trans-crystal,or lamella of LDPE,which means that electrical breakdown path go through amorphous area in polymers.So the increase of AC breakdown strength may be related with the micro-structure and crystalline morphology of LDPE,such as the increase of crystal phase and the decrease of amorphous,or the increase of crystallinity can improve the breakdown strength.At the end of this paper,the relation among material structure,charge trap and dielectric properties in the blends is analyzed and discussed.更多还原