回路间距对电力电缆短路电动力的影响分析

为有效降低短路电动力对电缆和金具的损害，科学合理地确定电缆的回路间距，本文采用电磁耦合有限元法对高压大截面电缆短路电动力进行了数值计算和分析。建立了单、双回路下水平敷设和品型敷设的电缆三相短路电磁耦合有限元模型，计算并分析了短路电动力在时间和空间上的变化；分析得到了双回路水平和品型敷设下三相短路电动力最大值随回路间距变化的方程。结果表明，双回路短路电动力与回路间距满足特定函数关系，且存在一个电动力变化斜率的拐点，可根据该拐点确定回路间距。本文研究可为电缆短路电动力理论研究和工程设计施工提供理论和技术支撑。     

高压大截面电缆和金具短路电动力的电磁——结构耦合有限元分析

高压大截面电缆运行电流大,发生短路故障时产生的短路电动力大大高于普通电缆,更容易造成缆体和固定金具的损伤,威胁输配电安全。为了分析高压大截面电缆短路电动力对缆体和金具的影响,文中建立了330 kV高压大截面品型垂直蛇形敷设电缆的电磁—结构耦合有限元模型,使用Maxwell瞬态电磁场分析法计算出电缆的短路电动力体密度分布;采用顺序耦合法将电动力体密度耦合至结构场计算出电缆金具的应力分布;对缆体磁场分布、受力时变特性及金具的应力分布进行了分析。结果表明,缆体短路电动力的幅值随时间周期性衰减,夹具上表面和螺栓处、电缆支架远端和螺孔等部位在短路电动力下应力最大,具有最大受损风险。     

基于ANSYS的高压大截面电缆金具短路电动力和机械应力分析

采用暂态短路电流计算方法和有限元法,分析了高压大截面电缆短路电动力的计算过程,推导出高压大截面电缆金具短路电动力的计算公式,同时考虑电缆蛇形敷设因素、导体外层介质缓冲作用及电缆位移偏转量,引入短路电动力工频分量(50 Hz)修正系数K1和两倍工频分量(100 Hz)修正系数K2对作用在电缆金具上的短路电动力进行修正。基于ANSYS建立电缆金具系统三维有限元计算模型,分别研究电缆敷设跨距和相间距对金具应力场的影响,并对双桥子-桃乡220 k V电缆段进行计算。由计算结果可知,在螺杆中点处产生的应力最大,即该位置最易变形或拉裂,对于220 k V电缆工程中"一"字形排列形式,电缆敷设跨距和相间距分别应满足l≤2.7 m,0.28 m≤a≤0.30 m。     

考虑空气流场影响的电缆散热研究及其影响因素与经济性分析

根据传热学理论建立了考虑流场影响的电缆温度场计算模型,给定了电缆沟敷设电缆的温度场边界条件,并以电缆沟敷设6回路电缆为例验证了模型的正确性,该模型也可用于通风电缆沟(隧道)敷设电缆的温度场计算。研究了沟深和电缆层间距对电缆允许载流量的影响规律,并结合土建成本对电缆沟敷设方案进行了经济性分析。计算结果表明,在通过改善电缆散热效果来提高电缆载流量方面,电缆层间距优化比电缆沟深度优化能获得更佳效果;适当的电缆沟深度优化具有土建投资成本回收时间短的优点;实际电缆沟敷设方案选取时,应先考虑电缆层间距优化,再考虑电缆层间距和电缆沟深度的综合优化。     

电缆沟敷设方式下电缆温度场计算模型

针对电缆沟敷设方式下电力电缆的广泛应用以及传统方法载流量计算参数较难确定的不足,根据传热学的基本原理,利用有限单元自动划分法,建立了一种基于有限元法的电缆载流量计算模型,能够按照实际敷设情况的变化对模型参数进行修改。根据电缆的结构参数和周围敷设区域的物性参数分析了电缆沟中电缆区域温度场分布情况,并提出了一种基于二分法来计算电缆载流量的方法。可为优化电缆敷设方案提供理论依据。     

城市轨道交通高架区间牵引供电系统环网电缆新型敷设方案的应用

针对城市轨道交通高架区间牵引供电系统环网电缆的敷设,以广州地铁14号线一期供电系统工程采用的复合支架+电缆槽盖的新型敷设方案为例,通过总结工程应用经验,与传统的混凝土槽、电缆钢支架敷设方案进行对比,新型敷设方案克服了传统方案在以往工程应用中的主要缺点,为轨道交通高架区间电缆敷设提供了一个更优的应用方案选择.     

66kV交流交联聚乙烯电缆线路改为直流运行的直流载流量

将交流电缆线路改为直流运行是提高电缆线路输送功率的有效途径之一,确定交流电缆的直流载流量对电缆的交流改直流运行意义重大。为此,采用解析法和数值法分析了空气中敷设66 kV电压等级交流交联聚乙烯(XLPE)电缆的直流载流量,开展了直流载流试验;同时采用数值法计算了直埋敷设2根平行排列交流电缆的直流载流量,并计算了电缆改为直流运行后的输送功率。计算结果表明:对于空气中敷设的交流电缆,采用解析法和数值法得到的直流载流量与试验测试结果基本一致(780 A);直埋敷设交流电缆的直流载流量约为710 A;当交流电缆改为直流运行的工作电压取57 kV时,其输送功率和原交流系统相等。上述结果验证了解析法在计算高压(66 kV)电缆直流载流量时的适用性,同时为后续66 kV交流电缆线路改为直流运行奠定了基础。     

电缆不同敷设方式下温度场与载流量的仿真计算

电缆广泛应用于现代城市配电网中,其运行可靠性与电缆的载流量与温升关系密切,精确计算电缆的载流量和温度场分布对于电网的可靠、经济运行具有重要意义。文章结合电缆的损耗对电缆沟的生热、散热过程进行了分析。采用COMSOL有限元多物理场分析软件,运用有限元分析方法模拟了8.7/15 k V YJV 1析软件,的XLPE三回路电力电缆沟正常敷设与不规则敷设情况下的载流量与温度场分布。数据证明,电缆敷设的位置与密集程度影响着电缆的载流量,密集程度越高,载流量越低。因此,按照规程要求分层敷设电缆束才能降低电缆的工作温度及延长寿命,电缆集群不宜集中敷设于底部。     

高压直流海缆选型及防护

以实际海缆工程设计为例,首先,通过对直流电缆绝缘材料分析以及电缆载流量的计算,确定高压直流海缆的型号;其次,通过对直流海缆与通信电缆临近情况分析,计算得出直流海缆与通信电缆并行敷设时安全距离以及交叉时直流海缆与通信电缆交叉角度控制;最后,详细给出了海缆与管线交越及不良地质处敷设保护性措施的两种方案,综合其优缺点,采用了保护套管保护的方案。     

关于高压电力电缆在桥梁上敷设的方案设计要点

由于广州市地理位置位于珠三角的珠江入海口,电力电缆也因此成为市区内跨越江河湖海等水道的一种常用的输电方式。对于在桥梁上敷设电缆,需要同时考虑桥梁与电缆的结构特性以及各自运行的安全,因此对电缆线路的敷设形式有着特殊的要求。对110 kV以上电压等级电力电缆在道路桥梁上的敷设方案进行讨论,提出主要设计要点以及敷设参数计算方法,可为将来的工程提供参考。     

Interference of nonlinear ferromagnetic pipeline on magnetic fieldproduced by power lines

The investigation of the magnetic field produced by power lines has drawn a lot of attention from researchers. Since sharing space by buried power lines and pipelines has become commonplace, it is of interest to investigate the influence of the pipeline. In this paper, we study the change of the magnetic field produced by buried cables, due to an additional steel pipe nearby. A Fourier series technique is used to calculate the magnetic field. An iterative procedure is employed to handle the nonlinear characteristics of the steel pipe and to determine the varying permeability in it. The calculated results of the magnetic field are compared with those produced by buried cables without the additional pipe. The comparison shows that the steel pipe close to buried cables may significantly alter the magnetic field     

一种电磁超声检测用脉冲激励电源的研制

针对电磁超声检测中换能器能量转化效率低、缺陷检测灵敏度不高等问题,研制出一种新型参数可调的脉冲激励电源。本文主要介绍该激励电源的控制、驱动、功率放大及反馈等电路单元的具体实现方案。实验结果和实际应用表明,该激励电源具有多种参数可调、输出功率大、工作安全稳定等特点,适用于钢板和钢管裂纹缺陷的电磁超声检测。     

Evaluation of the Shielding Properties of Cable Trays for Use in an Industrial Environment

The proper shielding of control cables in an industrial control system is an important part of the system's design. With the advent of direct digital and analog process control in large industrial facilities such as steel mills and power plants, the minimumization of interference induced in the communication link between the in-plant transducers and analog or digital controller becomes an important problem. The communication link may be very short, or run for several miles, depending upon the installation. In most cases, this link is a pair of electrical conductors. It is often necessary to shield these control and instrumentation cables. This paper describes a series of tests that were developed to determine the shielding efficiency of cable trays made of various types of material. Tests are described for both electromagnetic and electrostatic fields. As in most engineering decisions, the final choice of material must be the result of a compromise.     

Fluxes of electromagnetic field energy in HTSC transformers

The transfer of electric power in an HTSC electromagnetic system is considered using the Poynting vector. An analysis of the process of transfer of electromagnetic field energy in HTSC transformers with and without an iron core is given. It is shown that the power of an HTSC transformer increases when its magnetic core is made from amorphous electrical steel. Schemes of HTSC transformers with a localized magnetic field are given with cylindrical and disk symmetrical interleaved windings providing the cost-saving process of transfer of large electromagnetic energy at a high degree of its uniformity and improve the factor of nonuniformity of electromagnetic flux density.     

磁悬浮列车系统中的通信线力线路危险路遭受电影响的评估

本文提出一种通信线路遭受电力线路危险影响的评估方法。电力线路对通信线路的干扰 ,主要是由于电力线路电压和电流通过感性、容性和阻性耦合造成的。在平行长度较大时 ,带金属保护套的电力电缆对通信线路的干扰主要取决于感性耦合。本文建立了在最严重情况下电力线路对通信线路上产生的感应电压计算模型。上海磁悬浮列车示范运营线是世界上第一条投入商业运营的高速磁悬浮列车线 ,由于此系统中有数段 1 1 0kV电缆和通信线平行 ,通信线路上产生的原始感应电压大大地超过了我国相关国家标准的允许值。通过电力电缆金属保护层的三相交叉互联 ,并且在一大段电缆的两侧的金属保护层同相互联接地 ,大大地降低通信线路上产生的感应电压。该补偿方法有效地解决了上海磁悬浮列车系统中通信线路与电力线路的感性耦合问题。     

Transient characteristics of power cables: a new approach based on Poynting's theorem

Frequency-dependent transmission line parameters are analysed using Poynting's theorem. Using the general formulation of impedance and admittance matrices and solution for electromagnetic field vectors, wave propagation characteristics of the transmission line are obtained. The method is particularly useful for power cables, in which electromagnetic effects such as the proximity effect and electromagnetic shielding are strong. Calculations of underground eccentric cable characteristics illustrate the method. New formulae for inductances and conductor internal impedances are derived and new results for the propagation constant are given.     

Electromagnetic transport and confinement of liquid metals

Applications in which electromagnetic forces are used to stir, transport, dispense, and/or confine liquid metal are described. Applications include the electromagnetic trough, the electromagnetic mould, pedestal melting, thin strip casting, and levitation casting. Fundamentals relating to the production of electromagnetic forces are reviewed, a number of important applications are discussed, essential design limitations are identified, and the question of modeling for design purposes is considered. It is shown that with present technology, electromagnetic confinement methods cannot be expected to support ferrostatic heads in excess of 10-25 cm. This limit imposes a constraint on the development of new applications, such as the extension of the electromagnetic mold to steel casting and the use of electromagnetic confinement in the strip-casting process     

用于XLPE电力电缆局放检测的宽频带电磁耦合法的研究

对用于 XL PE电力电缆局部放电检测的宽频带电磁耦合法进行了研究 ,针对带铁氧体磁芯的罗哥夫斯基线圈型电流耦合器 ,讨论了几个主要参数对其传递函数的幅频特性的影响。模拟实验和电缆局放测量表明 ,应用此电流耦合器来检测 XL PE电缆的局放是可行的     

Iron Losses in Cable Supports and Members of Tunnels Adjacent to Large Power Transmission Cables

Iron losses in cable supports and members of tunnels in large power transmission were measured and analyzed by arranging cables in various configurations in tunnels of actual size and about 10 m long in order to study iron losses which come from cable supports and members of tunnels adjacent to large power transmission cables installed in tunnels. Cable supports used in the study were typically made of square hollow steel pipe and L-bar. A box culvert tunnel, a steel segment tunnel and a reinforced concrete segment tunnel, which are widely used as tunnels for large power transmission cables, were prepared for the measurement. Theoretical expressions for qualitatively evaluating iron losses in various cable supports and members of tunnels were derived, and their validity was confirmed by experiments.     

交联聚乙烯电缆局部放电在线监测系统研制

监测局部放电是评价电力电缆绝缘状况的重要手段,而目前国内对电力电缆局部放电进行测量所用的系统频率较低,为此文中研究了用宽频带电磁耦合法来检测交联聚乙烯(XLPE)电力电缆的局部放电.它由Rogowski线圈型电流传感器、放大器、滤波器和数字示波器组成,带宽为1 MHz～20 MHz,符合宽频带检测的要求.对不同模拟缺陷和电缆上人为缺陷的检测表明,该方法与IEC 60270的方法相比具有一定的灵敏度,可以有效检测到局部放电信号,并且可以很好地识别出不同典型缺陷的局部放电.