硅烷交联聚乙烯电缆绝缘料

简述了电线电缆用硅烷交联聚乙烯绝缘料的交联原理、分类、配方、工艺、设备,并介绍了硅烷自然交联聚乙烯绝缘料在应用和使用过程中的一些特征以及影响该材料交联状况的因素。     

一步法硅烷交联电缆交联度的影响因素分析

本文通过工艺实验研究,分析了一步法硅烷交联电缆绝缘的交联度的影响因素,包括挤出温度、交联温度和时间,以及材料选择等,从而为最佳交联工艺提供了科学的根据。     

不同交联方式对交联聚乙烯电缆结晶形态影响的研究

利用差视扫描量热分析方法研究了聚乙烯的过氧化物交联、硅烷交联、辐照交联方法对交联聚乙烯电缆绝缘的结晶形态的影响,发现聚乙烯交联的方法不一样,材料所经历的热历史差异很大,从而交联后聚乙烯的结晶形态差异也很大。交联聚乙烯的结晶过程和交联过程存在互相作用．因此在利用交联方法改性提高聚乙烯性能的同时,还要尽可能控制热过程,使材料聚集态结构处于合理的状态,才能使交联聚乙烯绝缘具有更优异的性能．     

交联聚乙烯绝缘电缆内的水树枝

阐述了水/电加速树枝试验和线路运行电缆发生故障后,在交联聚乙烯绝缘内存在的水树枝现象。通过显微观察,揭示和比较了交联聚乙烯电缆内水树枝对其寿命的影响。     

交联聚乙烯电缆中的水树

水树对交联聚乙烯电缆运行寿命有害。本文通过在交联聚乙烯绝缘料试片和原尺寸交联聚乙烯电缆上进行的加速水树引发试验,观察研究水树枝的生长特性,比较二种不同交联方法对水树生长的影响。最后探讨了形成水树的可能机理。     

交联聚乙烯电缆绝缘交联度径向非均匀性探讨

在交联聚乙烯电缆交联度测试中,热延伸法测量表明,高压交联电缆绝缘内层的延伸率大于外层,说明绝缘内层的交联度小于外层,但凝胶含量试验方法的测试结果却与热延伸试验的结果完全相反,通过分析认为是内、外层绝缘结晶形态和结晶度的不同导致了凝胶含量试验法测试交联度的不准确性;此外,通过物理机械性能试验,发现绝缘内层的抗拉强度和伸长率小于外层,这些结果说明电缆绝缘交联度存在径向的非均匀性。     

应用红外光谱仪测量交联度

应用红外光谱仪测量交联度主题词：交联聚乙烯绝缘，交联度，光谱分析，测量本文介绍了用美国Ｗｉｌｋｓ公司的Ｍｉｒａｎ１Ａ型红外光谱仪快速测定交联度的方法。原理交联聚乙烯绝缘电缆的交联度，可通过聚合物中残余的未反应的过氧化物的红外吸收来确定。通过比较ＤＯＰ...     

交联电缆绝缘厚度的合理控制

基于GB/T 12706—2008取消了对3.6/6~26/35 kV交联电缆绝缘平均厚度的要求,从影响绝缘厚度控制因素的分析着手,阐述了从设备及操作上采取控制偏心度等措施后调整绝缘厚度的可行性。     

硅烷自然交联聚乙烯绝缘料的性能分析

分析了硅烷自然交联聚乙烯绝缘料的交联时间和环境温度、环境湿度、绝缘厚度的关系;同时,也分析了材料的老化性能和热收缩性能与交联性能的关系,对用户的使用有指导意义。     

引进开发硅油交联生产工艺的探讨

用硅油交联工艺生产的交联聚乙烯绝缘电缆,绝缘中的微孔数量少、尺寸小,尤其适于高压、超高压交联电缆的生产,我国电缆厂家应突破传统观念的束缚,不要一味地在立塔高度上争高低,而忽略了交联工艺的创新和独具特色。     

温度对聚乙烯水树枝老化特性的影响

为研究温度对PE水树枝老化特性的影响,选用低密度聚乙烯(LDPE)、过氧化物(DCP)交联聚乙烯(XLPE)作为试验材料。在室温(20°C)、40°C、60°C、80°C 4个温度下,采用水针电极法培养水树枝,用金相显微镜观测水树枝形态,并统计水树枝尺寸和引发率。研究发现,在60°C以上,温度对PE水树枝老化特性影响显著;水树枝的引发率随温度的升高先减小后增大;水树枝的尺寸随温度的升高总体呈现增大的趋势;LDPE和XLPE的试验得到类似的结果,但XLPE的抗水树枝老化性能优于LDPE。同时研究发现,随温度的升高,材料的力学性能大幅下降。经分析认为,交联限制大晶块的形成,使材料的力学性能增强,是XLPE抗水树枝化性能优于LDPE的两个主要原因;高温下两种材料力学性能下降、微孔膨胀、水分和盐离子的加速扩散是高温下水树枝劣化加速的主要原因。     

110 kV交联电缆绝缘层热分析研究

通过差示扫描量热法热分析技术,研究了110kV交联聚乙烯绝缘电缆绝缘层的聚集态结构。发现电缆工艺中的热过程和热历史会造成超高压交联电缆绝缘层各部分结晶形态分布的不同,中层聚集态结构均匀性较好,内层、外层结晶程度低于中层;材料的熔融热焓ΔHm能敏感地反映其结晶形态差异。用热处理前后ΔHm的变化量来判断内应力消除效果应比用测定常规物理机械性能变化量更合理。     

超临界锅炉冷态启动汽水分离器温度场和应力场的数值分析

以600 MW超临界锅炉汽水分离器为研究对象,采用三维有限元方法,对冷态启动过程中汽水分离器的温度场、应力场进行了分析,得到了冷态启动过程中汽水分离器的温度分布,以此为基础计算了热应力、机械应力以及两者耦合的总应力的变化规律。结果表明,在汽水分离器汽水引入管区域存在较大的应力集中,最危险部位位于筒体内壁靠近汽水引入管的椭圆孔长轴处。     

下游坝面浅槽式压力管道施工仿真研究

本文以三峡水电站下游坝面浅槽式钢衬钢筋混凝土压力管道为研究对象，通过混凝土施工仿真计算的方法，重点研究了管道与坝体的相互作用。管道施工期温度场与应力场、管道在充水受荷前的初始温度与应力状态以及管道施工方案的优化等四个问题。结果表明，后浇筑管道与大坝接缝面会出现较大的拉应力，同时会使大坝迎水面竖向压力不断减小；管道在施工期将出现环向及轴向拉应力，尤以斜直段表现最为明显；管道在充水受荷前存在不可忽视的初始状态，不同部位的初始温度与应力状态不同，在设计时应分别参考使用，根据温度场与应力场的计算结果，提出了一种较优的施工计划，以使管道在施工期以及受荷前处于较佳的初始状态。     

低放热、低粘度、高韧性环氧树脂室温固化剂的性能研究

改性胺类环氧树脂固化剂是干式变压器与互感器等电气设备理想的封装材料。通过对自制改性胺类环氧树脂固化剂的固化特性及物理机械性能进行了实验研究,结果表明,该固化剂具有低放热、低粘度、高韧性和室温固化的特点,可用作建筑结构胶与裂缝灌注胶的专用固化剂,适合于复合材料湿法成型及户外施工。     

银盘水电站基础约束区混凝土高温浇筑温控措施与效果

大体积混凝土高温浇筑温控防裂是现代大体积混凝土结构设计、施工中十分重要的研究课题，对于保证大体积混凝土施工质量、加快施工进度等具有关键性作用。银盘水电站受截流时间推后及左岸边坡地质等因素制约，整个二期工程基础约束区混凝土全在高温季节施工。通过采取事前专题研究及技术咨询，过程采取原材料的优选、调整配合比、严格控制混凝土出机口温度和浇筑温度、个性化初期冷却通水等综合控制措施，成功攻克高温季节基础约束区混凝土浇筑的难关，取得了良好的效果，为高温季节水电站基础约束区大体积混凝土浇筑积累了宝贵经验。     

Weld lines in power cable insulation

The quality of XLPE insulation of power cables has improved markedly in recent years, and insulation failures caused by contamination have diminished. As a result, focus has shifted on the effects of insulation morphology. There are concerns about the weld lines regarding the anisotropy and frozen-in mechanical stress. The weld line that is formed has different properties than the matrix and the region is considered to be a mechanically weak point. In a recent study, seams were observed in the XLPE insulation of power cable. Their type and intensity vary because of the melt temperature and homogeneity in the extrusion. The mass distribution also has a certain influence. Typically, the seams are quite harmless for the dielectric properties of the insulation. Occasionally, severe weld lines may be considered as possible weak regions in the insulation construction. By performing electrical needle tests on four cable samples, it was found that the weld line containing sector of the cable is measurably weaker than the insulation in general. The rotating mass distributor, or more specifically, the conical extrusion was able to modify, level out and reduce seam effect. While there is no guarantee that the extrusion will have high insulation quality, it is possible to reduce the seams. The traditional extrusion process, however, should be considered as a less robust solution than the rotating mass distributor with respect to the seams.     

Electrical treeing in mechanically prestressed insulation

For several years it has been apparent that the mechanical characteristics of insulating materials have a pronounced influence on their electrical breakdown by treeing. As a consequence of this discovery, it is possible to look again from a different perspective at the treeing behavior in materials containing fillers and barriers. The effect of temperature on treeing can be interpreted in terms of the effect of temperature on the various mechanical properties of the material, and of any particulate or solid barrier inclusions. The internal mechanical stresses produced in resin samples containing cast-in metallic electrodes can affect treeing behavior both positively and negatively, depending on whether this stress in the material is tensile or compressive. In the light of this experience it has been found possible to enhance the treeing resistance of electrical insulation by using these mechanical effects in the most advantageous way, viz. by mechanically prestressing the material by the inclusion of fibers in tension; a method which is akin to that employed in the prestressing of concrete     

流动温压成型时间和温度对粘结钕铁硼/铁氧体复合磁体性能的影响

采用快淬NdFeB磁粉和铁氧体磁粉复合,流动温压成型制备出各向同性粘结钕铁硼/铁氧体复合磁体,研究了流动温压工艺对磁体密度和磁性能的影响.结果表明,随着流动温压成型时间的延长和温度的增高,磁体剩磁Br、内禀矫顽力Hcj、最大磁能积(BH)max和密度增大,当达到一定值后开始减小.矫顽力温度系数β随成型时间的延长有下降的...     

Effects of frequency, temperature, compression, and air pressure onthe dielectric properties of a multilayer stack of dry kraft paper

Kraft paper is used extensively in the electricity supply industry for the insulation of HV apparatus, such as transformers, capacitors and cables. Because of the fibrous nature of the paper, many layers are stacked or rolled to obtain the required electric strength. The insulation is thus a combination of cellulose and an impregnating fluid, which may be a liquid, a gas or vacuum. The dielectric properties of such a system depend on the dryness, temperature, frequency and the degree of mechanical compression. Although the effects of moisture, temperature and frequency on the dielectric properties of kraft paper have been studied, very little work has been done on the effect of compressive stress, particularly long-term effects. Results are presented of measurements, in the frequency range 50 Hz to 20 kHz, of the effects of compressive stress and temperature on the real and imaginary parts of the complex relative permittivity of a multilayer stack of dry kraft paper under vacuum. The variations of the dc resistance with compressive stress and temperature also are reported. Results are given of the variation of the dielectric properties of a stack of paper following a step change in either the temperature or the air pressure. The long-term variations are attributed to the slow diffusion of ions through the stack, particularly those held at the interfaces between layers