【作者】 刘斌；

【导师】 廖瑞金；

【作者基本信息】 重庆大学 ， 电气工程， 2012， 硕士

【摘要】 聚乙烯材料因为其优良的电气和机械性能被广泛地运用作各种电力电缆的绝缘材料。长期运行中的树枝化老化问题严重地影响了聚乙烯材料的使用寿命，是引起电缆绝缘损伤并导致故障的主要原因之一。为此，文中提出了添加蒙脱土的方法来提高聚乙烯材料的性能，同时利用外加交流电场对制备的聚乙烯材料进行了处理，在此基础上对材料的基本性能进行了测试与分析，并侧重研究改性后聚乙烯材料的介电性能和空间电荷特性。本文的主要研究成果如下：①采用熔融共混法将蒙脱土添加到低密度聚乙烯材料中，并对其进行外加交流电场处理。微观结构表征的结果表明：蒙脱土与低密度聚乙烯材料实现了插层复合，且蒙脱土在低密度聚乙烯中的分散较为均匀。基本性能测试的结果表明：添加蒙脱土以后，材料的热稳定性和击穿场强得到了提高；外加交流电场处理对了材料的热稳定性和击穿场强影响不大。②对添加蒙脱土的低密度聚乙烯材料的介电性能研究表明：添加蒙脱土以后，聚乙烯材料的相对介电常数大幅减小，但随着材料中蒙脱土含量的增加，相对介电常数增大；添加蒙脱土以后，材料的介损因数小幅升高，且介损因数随着蒙脱土含量的增加而增大。这说明：添加蒙脱土可以达到降低材料相对介电常数的效果，但必须选取合适的蒙脱土添加量；同时应该注意到蒙脱土的引入，会提高材料的介损因数。③经外加交流电场处理以后，添加蒙脱土的低密度聚乙烯材料的相对介电常数有小幅升高，且材料的相对介电常数随着外加交流电场强度的提高而增大；经外加交流电场处理以后，材料的介损因数频谱整体朝高频方向移动，具体表现为中频段材料的介损因数升高，而在低频段和高频段材料的介损因数降低。④对添加蒙脱土的低密度聚乙烯材料的空间电荷特性研究表明：添加蒙脱土有利于抑制聚乙烯材料内部的空间电荷积聚，但是随着蒙脱土含量的增加，抑制效果递减；添加蒙脱土以后，在去压时材料内部的残余空间电荷量减少，而且材料中蒙脱土含量越小，去压后材料内部残科的空间电荷量越小。⑤外加交流电场处理对添加有蒙脱土的低密度聚乙烯材料的空间电荷积聚也有抑制作用，但抑制的效果随材料中蒙脱土含量的增加而递减；同时，经过外加交流电场处理以后，去压时材料内部的空间电荷密度变小，但材料内部的空间电荷消散速度有所减慢。更多还原

【Abstract】 Polyethylene (PE) is widely used in various power cables as insulation materialbecause of its excellent electrical and mechanical properties. For long-term operation,insulation aging caused by electric tree has a great impact on lifetime of polyethylene,which is also major caurse for insulation damage and equipment failure. In order to finda solution to overcome this drawback, this paper puts forward a compounding methodto improve properties of PE materials by adding montmorillonite (MMT) into the lowdensity polyethylene (LDPE) matrix. In order to explore the possible way of furtherlyimproving PE materials’ properties, a pre-treatment of applying AC electric field wasperformed. Several measurements were carried out to evaluate basic properties of thematerial, especially, dielectric performance and space charge characteristics of themodified LDPE materials. The main research results are listed as follows:①By using melting blending method, organically modified MMT was addedinto LDPE to prepare MLDPE sample, and AC electric field was applied to MLDPE toprepare EMLDPE sample with a self-devised model. Results of relevant measurementsreveal that: the enlarged interlayer distance of MMT suggestes a successful intercalationcompounding of LDPE and MMT; the dispersion of MMT in LDPE is considerablelyeven and uniformed; with the additive of MMT, the material has a better thermalstability and higher breakdown strength; the AC electric field pretreatment has a slightimpact on thermal stability and breakdown strength of the materials.②After adding MMT into LDPE matrix: for MLDPE materials with1%of MMT,the relative permittivity greatly reduced compared with unmodified LDPE, but withincreased content of MMT in MLDPE, the relative permittivity increases; with theapplication of MMT, dielectric loss factor of the material increases slightly, and itincreases with higher content of MMT in MLDPE;③After AC electric field pre-treatment, EMLDPE material gains a small increasein relative permittivity, and the higher the applied electric field intensity is,the biggervalue of material’ relative permittivity is; the dielectric loss spectrum of the materialswitched towards high frequency direction after AC electric field pre-treatment, morespcsifically, the dielectric loss of EMLDPE material decreases in low and highfrequence region and increases in middium frenquence region.④The results of space charge measurement of the material show that: The application of MMT in LDPE helps restrain the accumulation of space charge inside thematerial, but its restraining effect declines with insceased content of MMT in LDPE;⑤The results of space charge measurement of the material show that: The ACelectric field pretreatment also helps restrain the accumulation of space charge insidethe material, and its restraining effect also declines with insceased content of MMT inLDPE; at the same time, after AC electric fields pre-treatment, the decay rate of spacecharge inside the material decreases.更多还原