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[已经解决 ] 1.5PAPER INSULATED CABLES

P:2016-11-09 15:39:21

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已经翻译过的资料,不小心误删,在此补上

1.5PAPER INSULATED CABLES

The firstimportant line insulated with paper was installed by Sebastian de Ferrantiin 1890 between Deptford (on the south side of the River Thames) andthe City of London, for single-phase operation at 10,000 volts [3]. Some ofthese mains were still in use at the original voltage after more than 50 years.The cables consisted of two concentric copper conductors insulated with widestrips of paper applied helically around the conductor and saturated with arosin-based oil. The insulated conductors were forced into an iron pipe filledwith bitumen and installed in 20-foot lengths inside train tunnels under theriver. This system operated successfully for 43 years and may be the source ofthe “40 year life” of power cables [4].

In theperiod between 1885 and 1887, cables insulated with helically applied nar-rowpaper strips saturated with paraffin and later in a rosin compound and cov-eredwith a lead sheath (very similar in design to those used at the present time)were manufactured in the United States by the Norwich Wire Company. Thesewere the first flexible paper-insulated cables, and all subsequent progress hasbeen made through improvements in the general design.

Paper-insulatedcables were improved through the following years by:

  1. Theintroduction of the shielded design of multiple conductor cables by MartinHochstadter in 1914. This cable is still known as Type H.

  2. LuigiEmanueli’sdemonstration in 1920 that voids due to expansion and contraction could becontrolled by the use of a thin oil impregnating fluid and reservoirs. Thispermitted the voltages to be raised to 69 kV and higher.

  3. The1927 patent by H. W. Fisher and R. W. Atkinson revealed that the dielectricstrength of impregnated paper-insulated cable could be greatly increased bymaintaining the insulating system under pressure. This system was not usedcommercially until the 1932 installation of a 200 psi pressur-ized cable inLondon.

Impregnatedpaper became the most common form of insulation for cables used for bulktransmission and distribution of electrical power, particularly for operatingvoltages of 12.5 kV and above, where low dielectric loss,low dissipation factor, and high ionization level are important factors indetermining the cable life.

Impregnatedpaper insulation consists of multiple layers of paper tapes, each tape from 2.5to 7.5 mils in thickness, wrapped helically around the conductor to beinsulated. The entire wall of paper tapes is then heated, vacuum dried, andimpregnated with an insulat-ing fluid. The quality of the impregnated paperinsulation depends not only on the proper-ties and characteristics of the paperand impregnating fluid, but also on the mechanical application of the papertapes over the conductor, the thoroughness of the vacuum drying, and thecontrol of the saturating and cooling cycles during the manufacturing.

Originally,most of the paper used was made from Manila-rope fiber. This was erratic in itsphysical properties and not always susceptible to adequate oil penetra-tion.Increased knowledge of the chemical treatment of the wood (in order to obtainpure cellulose by the adjustment of the fiber content and removal oflignin), the con-trol of tear resistance, and the availability of long fiberstock resulted in the almost universal use of wood pulp paper in cables after1900.

Theimpregnating compound was changed from a rosin-based compound to a pure mineraloilcirca 1925, or oil blended to obtain higher viscosity, untilpolybutene replaced oil circa 1983.

Paper-insulated,lead-covered cables were the predominant power cables of all the large,metropolitan transmission and distribution systems in the United States, andthe rest of the world, throughout the twentieth century. Their reliability wasexcellent. It was, however, necessary to have a high degree of skill for propersplic-ing and terminating. A shift toward extruded dielectric cables beganabout 1975 in those metropolitan areas, but the majority of the distributioncables of the large cities remained paper-insulated, lead-covered cables as thecentury ended.

Considerableresearch has been carried out by the utilities, technical organizations, andmanufacturers of cables to obtain improved paper and laminatedpolypropylene-paper-polypropylene (PPP, now used in transmission cables) tapesand insulating fluids that are able to withstand high, continuous operatingtemperatures.

Impregnatedpaper insulation has excellent electrical properties, such as high dielectricstrength, low dissipation factor, and dielectric loss. Because of these prop-erties,the thickness of impregnated paper insulation was considerably less than forrubber or varnished cambric insulations for the same working voltages.Polyethylene and cross-linked polyethylene cables in the distribution classesare frequently made with the same wall thickness as today’s impregnated papercables.

1.5纸绝缘电缆

在1890年,纸绝缘电缆首次被用在英国的德弗德弗和伦敦之间,整个项目是由塞马斯蒂安.德.弗兰蒂推动。电缆为单相10000伏。一些电缆,在50年后,仍可运行在原工作电压下。电缆是由两根同轴的绝缘铜导体组成,绝缘是由宽纸带螺旋绕包而成,并浸渍松香基的油。绝缘导体被穿进铁管中,填充沥青。然后安装在河底的管道中,这些电缆每20英尺为一节。这个系统成功了运行了43年,这也可能是电力电缆“40年寿命”的由来

在1885和1887期间,美国诺威奇电缆公司用窄纸带浸渍石蜡做为绝缘,然后再浸渍松香,最后铅护套(这种设计已经非常近似现代电缆)。这是第一个纸绝缘柔性电缆。并且在后续的设计中,又有一系列的改进。

在接下来的几年里,纸绝缘电缆被持续改进着:

1.在1914年,马丁开发了多芯导体的电缆。这种电缆被命名为“H型”。

2.在1920年,路易吉证实,气隙的扩张和收缩可以通过轻质防腐油和储油装置来改善。这使电压可以升到69KV及以上。

3.在1927年,费希尔和艾特金森申请了一项提高纸绝缘电缆电压的专利。当给绝缘系统施加压力时,可以显著的提高绝缘介质强度。但这种系统在1932年才实现商业化。在伦敦安了一条工作在200psi的纸绝缘电力电缆。

浸渍纸绝缘成为了大规模电力传输及分配的最通用模式。尤其对于12.5kv及以上的电力系统。纸绝缘具有低介电损耗,低介质损耗角,高介电常数。这此特性对电缆的寿命都很有利。

浸渍纸绝缘是由多层纸带,螺旋绕包而成,每层纸带的厚度在2.5至7.5mils(译者注:1mil是千分之一英寸)之间。然后纸绝缘被整体加热,真空干燥,用绝缘液体浸渍。纸绝缘的品质不仅是由纸带和油的特性所决定的,同时也受纸带包覆情况,真空干燥程度,以及在加工过程中浸渍和冷却的情况影响。

起初,大部分的绝缘纸是由麻纤维制作的。这种绝缘纸的物理特性不稳定,而且不能充分胜任油的穿透。随着木制品加工技术的提升,抗张强度和长纤维含量都得到了有效控制。在1900年后,木浆绝缘纸,得到了广泛应用。

大约在1925年,浸渍油由松香基的混合物,发展成纯矿物油或都其混合物,以提高粘度。直到1983年,聚(异)丁烯才取代了矿物油。

在美国及世界各地,整个20世纪的大规模输配电系统,被纸绝缘和铅套电缆所垄断。但是,这种电缆对接头和端子的要求很高。大约1975年,挤出绝缘电缆开始在一些大城市应用用。但是,到20世纪结束时,大部分大城市的电力传输系统依然使用纸绝缘和铅护套电缆。

机构、研发组织和电缆厂,进行了大量的研究,来改善纸绝缘电缆。开发了层叠结构的PPP绝缘(聚丙烯-纸-聚丙烯,现在应用于变压器电缆)。同时也开发出了能够承受更高温度的绝缘油。

浸渍纸绝缘具有极其优秀的电性能,例如高介电强度,低介质损耗角正切值和低介电损耗。由于这些特殊,在相同电压下,浸渍纸绝缘比橡胶绝缘及浸渍麻布绝缘的厚度要薄。通常纸绝缘电缆的厚度和现在输配电领域聚乙烯及交联聚乙烯的绝缘厚度一样

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