Parameters affecting economic selection of cable sizes

The evaluation of power cable costs considers the present worth of funds required for a new cable installation. Two components make up this cost, first the initial investment cost, and second, the cost of losses ever the life of the cable. Generally, for a given voltage class, the capital investment component increases as the conductor size increases. Conversely the losses decrease as conductor size increases. Selection of cable size is currently based on ampacity considerations; that is, a cable with a minimum acceptable cross-sectional area is usually selected without consideration of the cost of the losses that will occur during the life of the cable. Since the cost of losses over the lifetime of the cable may require substantial selection of a larger conductor size than required, ampacity consideration will often result in smaller value of losses and, hence, may lead to a lower overall cost. A number of examples which demonstrate sensitivity of the conductor cross-section and overall cost to variations in key parameters of the model are presented in the paper     

基于相位定位装置的中压电缆终端头运行电压定位方法研究

为了在线获取中压电缆的运行电压相位,为局部放电检测提供相位信息,提供了一种定位中压电缆运行电压相位的装置和方法。利用自制的金属贴片传感器在电缆终端头处耦合电压,通过分压原理在示波器得到金属贴片传感器上的电压相位,再通过对获取电压相位信息的反推得到电缆运行电压相位。该相位定位装置主要由金属贴片传感器、示波器以及同轴电缆构成。首先通过对相位定位装置进行电路模型等效和理论推导,计算出相位定位装置测得的电压相位与实际运行电压相位之间的相角差。最后在10 kV电缆终端头上进行实测,论证该理论分析的正确性和该方法的可靠性。在实验过程中还探索了在中压三相电缆终端不同位置进行测试对电压相位偏移角的影响,找到了测试的最优位置。     

Technical trends in medium voltage URD cable specifications

It has been more than thirty years since high molecular weight polyethylene (HMWPE) was first introduced as a commercial insulating material for medium voltage (15-35 kV) underground residential distribution (URD) cables. That began a dramatic expansion of utility electrical service that has led to the installation of several million miles of URD cables by over 3,000 utility companies across America. When early cables began failing prematurely, the industry was challenged to diagnose the causes and find corrective solutions that would give utilities the confidence to continue their commitment to underground cable. The past 25 years have been a story of constant technical improvements, increasingly tighter industry specifications and positive advancements in URD cable life performance. This paper discusses the significant technical changes that have taken place during this period and their impact on cable performance. The results of a 1983-1993 ten-year study of the major technical specification changes of the 25 largest Investor-Owned Electric Utility Companies (IOUs) is also presented. The data illustrate how quickly new cable technology is specified by these leading utilities and provide a clear picture of the key technical trends occurring throughout the utility industry during the 1990s     

磁悬浮交通用特种中压电缆的结构

上海磁悬浮已于2004年1月以430km／h的速度正式运行,一条30公里长的双轨线路连接着上海浦东国际机场和市区的地铁龙阳路车站,这是高速磁悬浮技术的首次商业应用。上海磁悬浮成功的商业运行有助于推动世界各地的磁悬浮项目,这些项目迄今为止一直处于试验阶段。     

老化中压电缆复合界面的放电特性研究

针对中压电缆热缩型中间接头界面受潮老化的放电特性做了相关研究,分别在不同的湿度环境下做了两类中间接头样本。通过对干燥电缆接头和受潮电缆接头界面间的放电特性做了对比,将整个放电过程分成了三个阶段,分别对比这三个阶段的不同放电特征。对击穿后的样本进行了解剖,观测到受潮界面和干燥界面绝缘失效后的电痕有差异。分析了造成放电特性和电痕差异的主要原因。得出了由于界面间水的作用,使得界面空腔被填满的同时降低了绝缘强度,虽然消弱了初始阶段的局部放电,但增加了后期的击穿概率。而造成不同的电痕特征的主要原因在于干燥界面间的放电对绝缘的劣化具有累积效应,所以放电主要集中在一条通道上。而潮湿界面在水的作用下,界面击穿发生在不同的位置,碳化痕迹分布较广。     

中压电缆终端高频电热老化试验装置的研制及分析

中压电缆终端被广泛应用于柔性交流输电和作为逆变器和电机的连接中,这些电缆终端可能会遭受到高频谐波电压的冲击,从而导致其绝缘迅速失效.本文研制了模拟电网高频谐波电压和工频大电流的电热老化试验装置.首先,通过信号发生器和功率放大器产生低压大电流信号,再通过高频变压器升压获得高频高压;同时通过工频试验变压器产生工频高压,将工...     

欧洲新开发的地下、中压架空的电力电缆

1.低压电缆整个欧洲有一种倾向,那就是不使用EPDM绝缘和PVC护套,而使用经过硅烷交联的TPE-O族塑性体,不过要以得到足够的柔软性为条件。在材料从XLPE向热塑聚合物过渡的过程中,应考虑到成本、再利用以及其他因素。因为需要连续的硫化线,其固化更昂贵。还有一个因素是挤出速度慢     

"Applied" science [ICEA medium voltage power cable specifications]

The Insulated Cable Engineers Association (ICEA) has issued new standards, published by the National Electric Manufacturing Association (NEMA) for solid-dielectric insulated power cables. These new standards are: ICEA S-95-658-1999/NEMA WC70, Standard for Nonshielded Power Cables Rated 2000 Volts or Less for the Distribution of Electrical Energy; ICEA S-96-659-1999/NEMA WC 71, Nonshielded Power Cables Rated 2001-5000 Volts for the Distribution of Electrical Energy; and ICEA S-93-639-2000/NEMA WC 74, 5-46 kV Shielded Power Cable for Use in the Transmission and Distribution of Electric Energy. These standards are written as "application standards" rather than the "insulation material-based standards" of the past and have been updated to reflect the latest conductor constructions, insulations, and jacket materials used to manufacture wires and cables. The advantage of this approach is that all insulations suitable for use on a specific product can be contained in a single document. This article provides information on the existing NEMA/ICEA and ANSI/ICEA standards, the changes to these standards, and information on the new standards.     

中压配电网电压调节技术比较分析及其方案选择

比较分析几种中压配电网电压调节技术,证明有源主配网多级电压协调控制的电压调节技术具有调节范围全局性、信息集成度高、电压调节控制效果好等优点,是今后调压技术的发展方向。分析结果表明,中压配电网电压调节技术方案的选择应结合配电网实际情况,因地制宜,兼顾经济投资,科学分析,合理选择。     

载波信号在中压地埋电缆中的耦合原理及信道模型

载波信号在中压地埋电缆中的耦合特性及信道模型是分析其传输特性的基础。在电磁感应原理基础上,结合卡接式电感耦合器耦合方式及中压地埋电缆的结构形式,推导卡接式电感耦合器的耦合模型。然后依据实际中压配网拓扑结构及电缆接地方式,利用多导体传输线理论及支路追加法搭建载波信号在中压地埋电缆中的信道模型。最后在信道模型基础上,分析载波信号在中压地埋电缆各导电层中的传输特性及不同位置的总传输特性,并对其进行了仿真及实验室测试。结果显示:载波信号在三相缆芯中传输特性完全一致;载波信号强度在铠装层最大,屏蔽层次之,三相缆芯最小;每流经一次环网柜,载波信号强度均会出现-15 dB左右的衰减。     

New developments in medium and high voltage cable with laminatesheaths as moisture barriers

The development of medium- and high-voltage cables with moisture barriers as a countermeasure to water treeing is reviewed. The moisture barrie can take traditional forms, including extruded or welded metallic tubes. The latest moisture-barrier cable designs use laminate sheaths. The traditional design approaches and the evolution of the laminate sheath are discussed. The various designs, under-jacket with foil or sheet, or on-core, are described. Design considerations are also discussed. Information on deployment in the field and standardization activities is also included     

中压环网结构的电缆屏蔽层传输特性的测试与分析

利用电力电缆屏蔽层进行载波信号传输,已成为国内外相关机构的研究热点。文章介绍了一个典型的由8段电力电缆通过线路开关连接成的环网结构,并对其供电电缆屏蔽层信道的传输特性(阻抗、噪声、传输特性)进行了全面的测试。测试结果和试验统计数据显示,采用高频桥接的多级电缆屏蔽层信道的传输特性基本满足载波组网通信可靠性要求,可以作为载波通信的信道,为城市小区配电自动化系统的通信系统提供了一种廉价且方便的解决方案。     

中低压铜芯电缆经济电流密度的更新与分析

在过去几年中,铜价上升的幅度很大,导致铜芯电缆成本成倍增长,经济截面有减小的趋势,因此以前确定的经济截面是否仍满足载流量要求有待验证.对中低压铜芯电缆的材料费等原始数据进行了系统的收集和整理,据此更新了经济电流密度数据,并通过引入电缆类型系数,使得经济电流密度数据得以更加简洁,进而方便查阅.再者,结合实例分析了更新后的经济电流密度的稳定性,考察了更新前后经济电流密度的变化情况,验证了更新后的经济选型数据的经济性和准确性.     

Fundamental aspects of excitation and propagation of on-line partial discharge signals in three-phase medium voltage cable systems

On-line partial discharge (PD) detection of three-phase belted medium voltage cable connections results in a number of interpretation differences as compared to off-line measurements where only one phase is energized. The induced currents and charges in the phase conductors and earth screen upon a PD not only depend on the discharge site, but also become phase angle dependent. Furthermore, simulations show that the PD distribution itself varies with the amount of eccentricity of the rotating electric field and may differ from the off-line distributions obtained with a linear field. Finally, the PD propagation in a multi-conductor cable also alters the signals measured at the cable terminals. In this paper, induced charges and PD distributions are studied by means of computer simulation. The cable propagation characteristics are verified by measurements.     

中压配电电压和电压序列应用情况分析

经过长时间的电压等级提升、调整和简化,我国电网逐步形成了相对统一的电压序列,对促进我国电网建设和经济社会发展发挥了重要作用,但随着我国城乡经济和电网建设的持续快速发展,我国电网有必要进一步调整和简化电压序列.国家电网公司和南方电网公司先后开展了电压序列优化的综合研究和论证,主要涉及提高中压和简化电压序列2个方面.描述和分析了国内外电压等级、电压序列的发展和应用情况,归纳了发展规律和趋势;着重通过典型案例分析总结了提高中压配电电压的主要方式,可为我国各级电网公司开展电压序列优化工作提供参考.     

用交流电压进行高压XLPE绝缘电缆线路的现场试验

根据XLPE绝缘电缆用直流电压进行现场试验的经验,要求开发新的方法。现在有一种移动式调频串联揩振装置能够用交流电压进行试验,这意味着适用于塑料绝缘电缆敷设后的试验将有重大突破。配有经由户外户内开关设备而接至电缆线路的连接线,以满足不同用户的要求。     

高压电缆故障测寻及定位方法

介绍了高压电力电缆的故障类型、故障查找步骤以及国内外常用的故障检测方法。通过对高压电力电缆的故障部位、故障类型以及相对应的预定位方法以及对其精确定位的分析和探讨,较为全面地提出了一整套行之有效的电力电缆故障测试方法。     

用极低频以局放和损耗因数测量来鉴定中压电缆的新成果

引　言本文介绍采用一个 0 .1周正弦波极低频电源诊断系统进行现场试验的真实结果。这一采用新技术的新型诊断工具为地下电缆系统和电网的用户提供高效的测量步骤以判断老化特性、更换的需要程度以及更精确的投资规划预测。此外 ,远在击穿发生前这个方法提供了适时更换和对初期故障的预测。普遍使用这种诊断工具可以戏剧般地降低拥有者的投资 ,更换、维护和‘停电’的成本 ,同时可以得到较高的系统可靠性和配电的冗余度。以往 ,中压和高压电缆是用直流做试验的。它的好处是现场试验设备重量轻、便携带、使用方便和经济。在引入如聚乙烯、交…     

基于电-热场联合分析的EPR中压电缆终端异常热点仿真分析及优化

25 kV乙丙橡胶(EPR)中压电缆终端因其自身的结构特性,内部电-热场分布不均,局部易出现异常畸变热点问题,而在安装电缆终端时出现的划伤缺陷加大了问题的严重程度,加速缺陷周围绝缘材料的老化,大幅降低了绝缘性能。为解决该问题,提出了一种电导率与电场、温度相关的非线性应力管材料,采用COMSOL仿真方法对比研究了使用高介质材料与非线性材料制作应力管时电缆终端内部的电-热场分布。结果表明,经优化后电缆终端的电-热场分布畸变程度能得到有效缓解;对于存在划伤缺陷的情况,优化后的电缆终端的电-热场畸变程度低于其出现击穿现象的阈值,表明其能够在缺陷情况下相对安全运行。同时采用热成像仪现场测试电缆终端温度分布,结果验证了经优化后电缆终端表面异常发热情况的改善效果。     

中压配电网电力线载波通信系统自适应频点选择算法

在电力线载波通信中应用正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术需要进行频点的优选。在分析信道输入阻抗对电压传输特性影响的基础上,提出一种基于在线测量信道输入电抗的频点优选算法。首先在默认频点下完成通信节点的入网,然后通过在线监测信道输入电抗筛选出部分频点,在这些频点处测试上、下行信号强度,通过简单计算优选频点作为子载波通道。以保定市实际中压配网为例进行仿真验证。仿真结果表明所提算法在保证通信质量前提下,可以筛选掉大量不可用频点,提高了频点优化速度。