配电电缆及导线截面选择的经济技术分析

<正> 配电电缆(或导线)选择通常是根据敷设条件确定电缆型号,而后根据常用图、表选出适合其载流量要求并满足电压损失及热稳定要求的电缆截面。用这种方法选出的截面,技术上是可靠的,工程初投资也最低。但是这种选择结果是否最合理呢?我们知道,配电线路存在着电阻,它们所消耗浪费的电能是不能忽视     

埋管敷设方式下多回路电缆截面优化方案

目前,对多回路电缆常将所有回路的载流量需求均依据N-1选取,导致电缆截面选择裕度过大,且对同等电流不同截面的电缆而言,截面越小,损耗越大,故电缆经济性必需综合考虑电缆损耗。以某110 kV电缆送电工程为例,建立了多回路电缆热场分析模型,分析了不同故障情况,得到了各回路电缆载流量需求,同时结合不同敷设断面、敷设环境影响,并进行了综合经济性比选。结果表明：该模型优化了工程电缆截面,为多回路电缆工程的电缆截面优化提供了参考和依据。     

常用低压电缆截面选择时的经济性分析

本文通过对低压电缆在按载流量选择时一次投资及运行损耗费用与在其截面加大一级时的一次投资及运行损耗费用计算对比分析,提出了应适当按照经济截面来选择低压电缆的观点。     

220kV 2500mm~2电力电缆施工技术研究

2 500mm~2是目前上海地区220kV电力电缆所使用的最大截面规格,电缆线芯粗、绝缘厚,敷设难度极大。同时,在有电站中进行大截面电缆敷设,安全风险高。全线采用垂直蛇形敷设方法。施工时,根据现场实际地形、环境策划电缆盘就位方案,计算电缆敷设时受力分析,保证工程的顺利竣工。     

220kV枢纽站不同电压等级多回路大截面

对北京地区220kV枢纽站不同电压等级多回路、大截面电缆出线优化布置进行了介绍,阐述了大截面电缆出线优化布置原则,解决了多回路电缆纵横交叉跨越、布置混乱、不利于施工及运行维护问题,并结合实例工程对大截面电缆出线优化布置举例说明。     

消息报道

西安电炉研究所与无锡钢铁厂协作试制的电弧炉用大截面水冷电缆,已于八六年十二月底制出样品(见图)。其中截面4000mm~2的水冷电缆将用在无锡钢铁厂新建的30t电弧炉上。这种多股导线与接头一次冷压连接的大截面水冷电缆,以前都是从国外引进。据悉在87年下半年我国自行设计制造的大截面水冷电缆将接受用户订货。     

工业与民用建筑电气设计节能办法

论述了工业与民用建筑电气设计中合理地进行用电负荷计算、变压器的经济运行方式、合理设置计量装置、合理选择电线,电缆截面以及照明节能方法。     

电气设备导线截面选择的节能经济性分析

电气设备导线截面选择的节能经济性分析湖北制药厂范念琨１前言一般电气设备的导线截面选择应满足允许温升、电压损失、机械强度等要求。一些电气设计手册就是依据上述的三个要求制定了电气设备导线选择的专用表。例如，电动机的导线选择就可以根据其型号、功率，从各种电...     

火电厂中压电缆热稳定最小截面的一种估算方法

在火电厂6～10 kV厂用电系统中,电缆热稳定截面需要依据GB 50217—2018《电力工程电缆设计标准》中规定的方法进行反复验算后确定.当系统中回路较多时,计算量较大.给出了一种电缆热稳定截面的简化方法.通过对短路热稳定条件下电缆导体所允许最小截面的表达式进行变换,并对该表达式进行简化拟合,在系统电源供给短路电流的...     

中压交、直流配网供电能力比较

在原有中压交流配网电缆线路保持继续使用的前提下,对中压交、直流配网的供电能力进行了比较。考虑电缆线路绝缘要求,对直流配网运行电压的选择进行了讨论。在电缆线路的导线截面、电流密度与绝缘水平相当的前提下,从线路损耗、沿线电压损失和最大供电容量等方面对交、直流配电方式进行了理论推导和分析比较,并结合实际电缆参数对10kV电压等级的交流配网与±7.5kV电压等级的直流配网进行了计算比较,得出了在电缆线路绝缘水平相同的情况下中压直流配网在线路损耗、供电半径、最大供电容量等方面优于中压交流配网的结论。     

测量导体截面积的方法比较

导体的截面积一般为标称截面积,是确定导体特定尺寸的数值.导体的截面积是电线电缆的一个重要性能指标,在实际工作中,确定导体的截面积尤为重要,对比了几种测量导体截面的几种方法,对测试数据的准确性加以比较.     

Effects of the cross‐sectional area ratios and contact resistance on the performance of a cascaded thermoelectric generator

Thermoelectric generator offers many advantages such as high durability, environmental protection, and high reliability. Since the geometric optimization of a thermoelectric generator is a proper way to improve the performance, this study considers the multiparameter optimization of thermoelectric generators to investigate the effect of cross‐sectional area ratios and contact resistance on the performance of thermoelectric generator. Here, a ∏ ‐type cascaded thermoelectric system with two stages including two p‐legs and two n‐legs is examined numerically by ANSYS Workbench. The effectiveness and efficiency are obtained for different electric contact resistances. The results show that with a decreasing of the electric contact resistance, the efficiency and effectiveness are increased. Also, higher output power and efficiency of the TEG device are observed with a suitable ratio of cross‐sectional area.     

Optimization of cooling effects with fins of variable cross-sections

ABSTRACT

Vertical fins radially mounted on heated circular horizontal plates are capable of enhancing free-convection cooling effects. Here we have numerically and experimentally shown that fins whose cross sectional shape is trapezoidal can provide greater cooling effects than their rectangular counterparts. Simulations and experiments are based on the Galerkin finite element method and TES1310 type-K thermocouple measurements. Three mechanisms responsible for cooling effect improvements are identified: (1) dominance of cooling strength near the rims of circular plates; (2) vertical surface area increase due to trapezoidal geometries; and (3) entrained-flow retardation due to pseudo-stagnation pressures. Our work can help guide heat transfer communities to design fins of varying cross sectional area.     

变压器冷却油道中异型三通阻力特性研究

对大型变压器冷却油道中具有典型意义的狭缝状异型三通的流动阻力特性进行了实验研究,分析了在分流与合流的四种模态下,流动阻力系数与流量比及通道截面比间关系,所得出结果可用于分析计算变压器冷却油道。     

某水电站复杂非杆系结构程序化配筋设计

针对复杂非杆系结构配筋设计难度较大的问题,以某混凝土拱坝孔口为例,运用ABAQUS软件分析了最不利工况条件下的孔口应力。依据拉应力图形法原理,采用C#程序语言编制了配筋程序,实现了截面的剖切、应力的平面投影、拉应力面积的计算以及配筋截面面积计算等功能。研究结果可为非杆系结构工程配筋设计与施工提供参考。     

Performance and optimization analysis of SRC profile fins subject to simultaneous heat and mass transfer

Fin material near the tip of a uniform cross sectional (UC) fin does not participate actively in transferring heat. This effect may seem to have progressed much with the increase in fin length. A uniform cross sectional fin with a step reduction in local cross section (SRC) not only increases the effective utilization of fin material near the tip but also it promotes the ease of fabrication. In this study, an effort has been devoted to determine analytically the overall fin performance of both longitudinal and pin fins of SRC profile under fully dry, partially wet and fully wet conditions. The effect of various design and psychometric parameters on the fin performance of SRC fins has been investigated and compared it is with the corresponding UC fin. A scheme for optimizing SRC fins has also been demonstrated in the present work. From the result, it can be highlighted that the optimum values of Biot number and aspect ratio of SRC fins increase with the increase in relative humidity for the same fin volume. In comparison with the UC fin for the identical fin volume, the SRC fin transfers more rate of heat and consequently, this difference in heat transfer rate increases slowly with the relative humidity.     

不同压水室的圆盘泵非定常特性及内部流动机理研究

针对圆盘泵的非连续叶片特殊叶轮结构,压水室的匹配设计对其整体水力特性提升具有重要意义。基于现场试验和CFX仿真分析结果,验证了湍流模型非定常仿真的可靠性。依据压水室结构参数理论分析结果,选取6种不同过流断面面积的压水室进行数值模拟和多维度内部流场分析,结果表明:随着过流断面面积的增加,6种不同压水室方案的叶轮中心呈现低压区,压力沿径向先增加后减小最后趋于相对稳定;高压区呈中心对称分布,主要位于叶轮和压水室交界并靠近叶轮出口一侧处,最大压力区域出现在压水室出口的近端位置;压水室过流面积越小,叶轮出口处漩涡越为明显,漩涡沿圆周扩散严重,随着压水室过流面积的增加,漩涡明显减弱,过流面积过大,漩涡明显加强。     

低压聚乙烯电缆紫外交联热流场研究

紫外光交联辐照箱中,高压紫外汞灯作为辐射源,产生的辐射能使反射罩、灯管及聚乙烯电缆表面的温度升高,若温度过高会使电缆绝缘层表面发生热氧化,甚至导致表面焦糊,严重使反射罩等受热部件产生热变形.为了改善汞灯与电缆表面的过热问题,本文基于计算传热学和计算流体动力学（CFD）原理,首先对低压电缆紫外交联箱内部进行三维湍流流场建模,研究交联过程中电缆表面速度场,然后以电缆二维截面为研究对象,对电缆截面温度场进行数值模拟.结果表明,在低压电缆内,绝缘与导体之间的热传导对绝缘层内的温度分布起了主要作用,装置内绝缘层表面的对流换热直接影响电缆温度.     

从阻抗试验值推求气垫调压室稳定断面

通过对气垫调压室底部阻抗模型试验成果的分析研究,采用试验结果与理论计算相结合的方法,得出了能够较真实地反映调压室底部阻抗等因素对气垫调压室波动稳定断面影响的截面积计算公工,算例表明,在合理教育调压室底部阻抗等因素原情况下,气垫调压室的稳定断面可予以减小。     

Effective parameters on second law analysis for semicircular ducts in laminar flow and constant wall heat flux

Entropy generation for semi-cylindrical ducts is obtained analytically for laminar flow and subjected to constant wall heat flux boundary conditions. Affecting parameters such as heat flux rate, Reynolds number and cross sectional are studied for entropy generation. It is concluded that cross-sectional area and wall heat flux have considerable effect on entropy generation. For the increasing value of these parameters, both entropy generation and pumping power ratio are increased at fixed Reynolds number.