低压电缆截面和熔断器继电保护的配合关系

一般电缆截面是按:1.持续允许电流;2.短路时的热稳定性;3.电压损失△∪不超过5%;4.经济电流密度等四个条件来选择的。对于低压电路,一般按条件1选择电缆,并按条件3校验电缆的截面就可以了。一、低压厂变定时过流保护与电动机电缆熔断器的配合问题目前低压厂变都采用反时限继电保护了。但过去设计安装的低压厂变,是采用的速动和定时过流保护。在进行由速动和定时过流保护的整定计算时,对按上述条件1选择,并满足条件3要求的低压电动机电缆,当其电缆长度超过某一长度时,必需校验熔断器的熔断时间     

关于分布负荷低压电缆截面计算方法的探讨

在煤矿井下采煤工作面,有不少低压分布负荷,如运输机等。这些负荷功率大、距离远,故电缆截面计算时,常按电压损失预选,再按其它条件进行校验。过去这类分布负荷按电压损失计算所求得的截面为等截面,即各线段电缆截面均相同。这种计算方法存在有以下两个问题:第一是有色金属消耗量大,特别在计算截面与标准截面数据相差较大时,更加突出(如计算截面为53mm~2,选70mm~2的电     

电力工程蓄电池回路电缆截面选择

如蓄电池回路电缆截面选择过大会造成施工困难。结合蓄电池回路电缆截面选择的一般要求,对蓄电池的回路电流选择、允许电压降、电缆截面选择进行分析,结合工程实例计算并讨论了按允许电压降和温升两种方案的蓄电池回路电缆截面选择结果,论证减小蓄电池回路电缆截面的可能性。     

计算机在导线选择计算中的应用

本文介绍的计算机选取导线截面程序,在多分支供电线路导线截面选取及线路电压损失校验工作中尤为适用。计算机在执行该程序时,首先按允许电流选取导线截面,再进行电压损失校验;最后对导线截面最优处理,从中选出能使线路有色金属消耗量最少的各段导线截面。程序中还应用了数据文件检索系统,代替了人工查表法。     

电力电缆经济选型

电力电缆选择是电气设计的主要内容之一，传统的方法：首先根据敷设条件确定电缆的型号，然后根据负载电流选择电缆截面，最后校验其电压损失和热稳定性要求。这种方法只能谋求最小的初始投资，而无法顾及长期运行的经济性。     

单位长度等电压损失法的BASIC程序

单位长度等电压损失法是开式电网按电压损失选择导线截面的新方法,特别适用于煤矿井下无分支分布负荷低压电缆截面的选择计算(参见电工技术杂志1985年11期P.24)。该法比同一截面法可节省30%左右的有色金属,根据这一方法编制的BASIC程序,将大大减少煤矿井下供电设计的计     

拉格朗日乘数法在辐射式网络导线截面选择中的应用

当网络接有多个变电所,即构成幅射式网络,严格说,是不能通过负荷矩来校验导线截面的。图1为某110千伏输电系统,近年来由于负荷增加较快,变电所Ⅰ至变电所Ⅳ全线导线截面原设计均太小,必须换大。若用经济电流密度选好各段导线截面,并通过有关设计手册,用电压损失校验时,均能满足各段电压损失小于10％的要求。但从变电所Ⅰ到变电所Ⅳ电压损失是否仍小于10％,却心中无数(指查手册而言)。当电压损失超过10％时,将会给用户带来严重后果。为此,在辐射式网络导线截面选择中,可采用拉格朗日乘数法来计算。     

F—C回路电缆过负荷分析及对策

作者在本刊１９９６年第９期发表了“厂用电缆线电缆截面选择的建议”该文建议厂用电缆线采用Ｆ－Ｃ回路时,可不按短路热稳定条件而按额定电流选择电缆截面,本文进一步对该回路的我荷工况进行分析,认为该回路按额定电流选择电截截面,在１．４Ｉ和１．６Ｉ过负荷工况下,在允许的过负荷时间内,对保证电缆安全是无问题的,作者还对厂用电设计的技术规定,规程的修订提出一些建议。     

合闸电缆选择的商榷

合闸网路中电缆的截面一般按合闸时所允许的电压降条件进行选择。“交流高压断路器的操作机构技术标准JB-519-64规定”当合闸线圈温度不超过 80℃、加于合闸线圈端子上的电压在80—110％的额定范围内时,操作机构均应保证断路器可靠合闸(包括关合最大电流)。合闸电缆的截面由下式决定     

长距离低压电力电缆截面积的选择与优化

对民用建筑领域低压电缆截面积的选择方法进行介绍。依据允许温升、经济电流、热稳定性、允许电压降、机械强度和接地故障保护灵敏度校验,确定低压电缆截面积。结合实际工程项目,对长距离低压配电电缆的截面积进行选择,利用改变电缆的敷设方式,减少电缆的截面积,并通过校验电压降,验证减小电缆截面积的可行性。通过优化敷设路径,缩短电缆长度,减少有色金属的使用,达到降低建设成本的目的。     

XLPE高压电缆短路故障电流在线监测装置设计

通过分析XLPE高压电缆线路短路故障电流回路的特点,设计了XLPE高压电缆短路故障电流在线监测装置.当线路发生短路故障时,短路故障电流在线监测装置实时采集故障电流的大小与方向信息,并根据监测数据分析故障电流回路特性,对于电缆-架空线混合线路,判断故障发生在电缆侧还是架空线侧;对于金属护套交叉互联的长电缆线路,判断故障发生在哪个交叉互联区间.该装置大大缩短了电缆线路发生短路故障后的抢修时间,提高了供电可靠性.     

Accelerated cable life testing of EPR-insulated medium voltagedistribution cables

This paper presents results aimed at developing a reliable accelerated aging tank test for EPR-insulated cables. Aging was performed at 2 to 4 times rated voltage on load cycling to temperatures of 45°C, 60°C, 75°C, and 90°C at the conductor with water in the conductor strands and outside the cable. Results show that cable failure is more rapid at the highest electrical stress and lowest conductor load cycle temperature. Cables aged at higher temperatures and various levels of electrical stress rarely failed and retained in excess of 40% of their original breakdown strength after 1500+ days of aging. Aging performed at 90°C load cycle temperature and 4 times rated voltage with air on the outside and water at the conductor of the cable showed more rapid loss of life than with water outside. Results indicate the optimum aging conditions for EPR-insulated cables in the accelerated cable life test (ACLT) differ significantly from those previously observed for XLPE-insulated cables, and that the appropriate test methodology for EPR-insulated cables requires additional study     

高温超导电缆在城市地下输电系统应用的可行性研究

大城市有可能最先采用商业化运行高温超导电缆 ,用于城市地下交流输电系统。其主要应用目标是用于地下电缆工程改造 ,利用现有排管以高温超导电缆取代现有的常导电缆 ,增加地下电缆传输容量以及采用高温超导电缆将巨大电能 (1GVA以上 )输入到城市负荷中心。采用常导电力电缆传输 1GVA以上的电能进入中心城区 ,输电电压一般要求为 5 0 0 k V。在城市中心区不可能建设 5 0 0 k V变电站。 5 0 0 k V电缆线路所需的 5 0 0 k V大长度电缆和相应附件 ,目前尚未研制开发。采用高温超导电缆将有可能降低输电电压等级 ,可以采用 2 2 0 k V高温超导电缆将 1GVA以上的电能输入到城市负荷中心 ,满足特大型城市负荷中心供电需求。采用 110 k V高温超导电缆 ,亦有可能传输 1GVA左右电能。本文通过对交流高温超导电缆系列设计计算对额定电压 35 k V、110 k V、2 2 0 k V的高温超导电缆 ,按不同传输电流 (或传输容量 ) ,以高温超导电缆的传输效率 (损耗与传输容量比 )、高温超导电缆外径限值和超导导体绕制结构限制条件 ,确定高温超导电缆适用性界定条件 ,提出城市地下输电、配电系统用高温超导电缆可行方案。     

High-voltage testing of medium-voltage shielded power cables

Medium-voltage power cables rated 2001-35000 V are tested using both 60 Hz AC voltage and DC voltage before leaving the cable manufacturing plant. Shielded medium-voltage cables are also required to meet the corona extinction level voltage established. These shielded cables are to be free of partial discharge at voltages well above operating voltages. In addition to these factory tests, the user normally requires a DC high-potential test after installation and sometimes a test is required when the cable is still on the reel. These various tests are also discussed     

母线槽截面的选择

针对国家标准未对母线槽的截面加以规定,分析了额定电流与截面的关系,介绍了最佳截面和经济电流,提出了根据母线槽制造厂提供的样本,其额定电流值相应的电流密度仅仅满足热稳试验,不是经济电流密度。实际运行结果表明,取母线槽额定电流值的1/2来选择母线槽截面积,可较接近最佳截面。     

高压长线路短路法融冰可行性探讨

高压长线路实现短路法融冰的关键是获得大容量的融冰电源。文章通过对几种典型线路融冰需要的电流、电压和容量进行计算,得出结论：长300 km、4′300mm2的500 kV线路融冰需要建设一个4 kA、50 kV规模的直流电源;若能建设一个融冰电源与静补无功补偿装置合一的HVDCice则更为理想;利用系统中300 MW或以下功率的发电机和变压器,对长度不超过200 km的220 kV及以下线路进行交流融冰在技术上也是可行的;移动式柴油发电机能满足输电线路大跨越和小截面短线融冰的要求。     

Mitigation of switching‐induced transient electromagnetic interference on control cable using Ni–Zn ferrite rings over cable sheath in gas‐insulated substations

The transient electromagnetic fields during switching operation in gas‐insulated substations (GISs) have rise times on the order of nanoseconds. These fields leak into the external environment through the discontinuities of gas‐insulated modules and affect the control cables and induce the transient voltage on cables, which results in malfunctioning of the equipment. The amplitudes of the electric and magnetic fields could be a few tens of kilovolts per meter and a few hundred amperes per meter according to layout of GIS, respectively. In this work, the induced voltage in the central conductor of a control cable and the induced current in its sheath, which is parallel to bus duct in a GIS with rated voltage of 230 kV, are calculated. Influence of the sheath material on the induced voltage and the type of its grounding on the induced current are analyzed. Furthermore, the impact of installing ferrite rings over the control cable sheath in mitigating the induced voltage and current is investigated. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

下穿铁路220 kV电缆爆炸原因分析

近年来,铁路运营里程不断创下新高,铁路线位选址与高压输电线路走廊的冲突无法避免。在某些特殊地形条件下,架空高压输电线路需改电缆下穿铁路。由于高压电缆结构复杂、敷设环境特殊,一旦在下穿铁路段发生爆炸将对周围设备及铁路运营安全造成严重威胁。针对某地220 kV电缆投切时发生爆炸这一情况,利用ATP⁃EMTP中的JMATI电缆模型建立了220 kV电缆投切过电压计算模型,结合故障录波图对实际合闸电压暂态过程进行了复现,考虑操作过电压的分散性,采用统计开关计算了电缆在该运行工况下可能出现的最高过电压倍数,结合计算结论对电缆爆炸原因进行了分析,认为造成电缆爆炸的原因应是电缆接头本身工艺或是安装问题,有必要对同种电缆接头质量进行进一步管控。采用的故障建模方法及校验过程也可为今后同类电缆故障的运行状态分析提供借鉴。     

Analysis of co‐axial transmission lines with arbitrary cross‐section

A numerical model for the determination of electromagnetic fields and characteristic impedance of co‐axial cables with arbitrary cross‐section is developed, based on dyadic Green's functions and the moment method. The advantages of the method are generality, simplicity and accuracy of its results. Besides this, the fields are represented as series over orthogonal functions, which can be useful in the solution of some problems, such as discontinuity between lines of different cross sections. A numerical application to cables of rectangular cross‐section shows the accuracy of the method. Copyright © 1999 John Wiley & Sons, Ltd.     

Accelerated aging of extruded dielectric power cables. II. Lifetesting of 15 kV XLPE-insulated cables

For pt.I see ibid., vol.7, no.2, p.596-602 (1992). Preliminary results are described in which 15 kV XLPE cables were subjected to accelerated aging tests under a variety of controlled voltage stress and thermal load cycle conditions, with loss of life being calculated for each set of conditions in terms of the geometric mean time to failure (GMTF). The relative influence of voltage stress and load cycle temperature are discussed. Accelerated aging results show a reduction in GMTF for 15 kV XLPE-insulated cables as the voltage stress or conductor load cycle temperature is increased in a controlled manner. The relative influence of voltage stress versus load cycle temperature can be compared. The GMTF increases more in going from 90°C to 60°C at constant applied voltage stress than in going from 4X to 2X rated voltage at constant load cycle temperature conditions