Loss evaluation of HVAC and HVDC transmission solutions for large offshore wind farms

This paper presents a comparison of transmission losses for different technical transmission solutions for large offshore wind farms. Three technical solutions are analyzed, i.e. HVAC, HVDC Line Commutated Converter (LCC) and HVDC Voltage Source Converter (VSC). The losses for each technology are calculated for wind farms with different ratings and various distances to shore. In addition, solutions with combinations of two and the three different transmission technologies are analyzed and compared. Based on this comparison, further analysis regarding the economical feasibility can be performed in order to determine the most economic solutions for the transmission system of an offshore wind farm.     

输配一体化综合能源系统的运行多指标评估方法

为量化风电波动和设备随机故障等多重不确定因素对综合能源系统的影响,提出了一种输配一体化综合能源系统的运行多指标评估方法。在模型上,建立了含上层输网级能源网架和下层配网级能源枢纽的统一架构,精细刻画电/气/热等多种能源在发输配用全流程的耦合特性;在方法上,通过状态空间分割分别处理风电波动和设备故障场景,提出混合等分散蒙特卡洛抽样法改善评估收敛特性,并采用连续线性化方法求解最优多能流问题以平衡算法精度和速度,进一步提升评估效率;在指标上,面向低碳运行环境,建立计及运行经济性、系统可靠性、风电消纳性、能源环保性等在内的多指标评估框架,全面描述多重不确定因素对系统运行的影响。通过对包含17个能源枢纽的RTS79-40Node综合能源测试系统进行分析,验证了所提方法的有效性与合理性。     

Worldwide underground transmission cable practices

Underground transmission cables are a vital part of any power transmission system which means that the selection of a particular cable must be based upon many considerations ranging from the cost of losses to environmental concerns. The focus of this paper is on the design, selection and testing of power transmission cables within specific geographic regions. Design considerations on a regional basis includes temperature constraints, voltage and voltage stress limits, capacity and ampacity, backfill requirements, cooling and bonding. The material presented in this paper covers land based transmission cables only. Submarine cables, URD or UD cables are not included     

Series-impedance of underground transmission systems

A general solution for the magnetic field in the soil is developed that satisfies arbitrary boundary conditions on an underground cylindrical surface at a finite depth below an earth/air plane surface. A quasi-steady state hypothesis is assumed. The series impedance of an underground cable with a perfectly conducting sheath is evaluated taking into account skin effect in the soil. The numerical results are compared with F. Pollaczek's (1926) classical solution     

输变电设备的检修策略

针对当前检修定义混乱的情况,提出将检修过程分成检修策略层、检修安排层和检修具体实施层,检修策略主要是确定设备采取何种检修方式.论述三方面内容:一是明确检修策略与检修、检修方式和检修优化的关系;二是简要综述了检修策略的研究现状;最后提出了检修策略模型的建立过程.     

配电网网损分析与控制方法

针对中低压配电网的网损分析和运行优化,从理论线损计算方法、基于损耗最小化的运行优化措施和线损管理三方面对现有研究成果进行了综述和分析。因理论线损计算是配电网经济运行的基础,为此。重点综述了近几年理论线损计算方法所取得的最新研究进展,包括：针对传统线损算法的改进。改进前推回代法,最大网络流法的应用以及人工智能技术在中压配电网线损计算中的应用。同时从技术和管理两方面对线损控制措施进行了分析,指出了配电网经济运行和线损管理研究中有待解决的问题。     

Detection and location of dielectric fluid leaks on pipe-type cablesystems

The feasibility of using a hydrocarbon sensing wire to detect and accurately locate dielectric fluid leaks in power cables is shown. The construction of sensor cables developed for this purpose is described. The tests carried out on the cable are also described, and field trial results are reported. Because retrofitting old and operational feeders requires costly excavations, the system is suitable for installation on new feeders. However, use of boring techniques, which eliminate the disruption and expense of surface excavation by producing a small diameter tunnel beneath the surface, is an alternative option that is presently under investigation     

输配电价改革之探讨

依据汕头电网以及国内外的实际资料．论述了输配电价改革是解决当前电网企业融资能力差、电网建设滞后等问题,使企业走上良性发展的必然选择。从电网企业目前的资产状况、投融资方式、成本核算、税收政策、输配电划分界面等方面,较为全面地分析了当前输配电价改革面临的问题,并有针对性地提出了解决问题的建议。     

Magnetic field management techniques in transmission underground cables

Magnetic field management is concerned with the minimization of the effects of such fields on the public health, without sacrificing the effectiveness or reliability of the power system. The essential management techniques used for the underground transmission cables comprise geometry manipulation phase placement, and source shielding. In this paper, the simulation results of the standard recommended stack, triangular and flat configurations are presented. The simulations have been carried out for single and three phase cables. The resulting fields for different depths have been evaluated and compared. The results led to the conclusion that judicious placement of phases is a very powerful management technique to reduce the magnetic field as cost has not been changed. The appropriate phase placements corresponding to minimal field values are obtained.     

降损技术措施在配电网运行和改造中的应用

结合珠海电力局配电网运行和城网改造的情况,提出了合理调整配电网的运行电压,更换原有导线为大截面导线,深入负荷中心供电,降低配电变压器的三相色荷不平衡度,开展配电变压器的经济运行和加强无功功率管理,提高配网功率因素这6种降低配电网损耗的技术措施。     

Loss distribution analysis and accurate calculation method for bulk-power MMC

Accurate evaluation of power losses in a modular multilevel converter (MMC) is very important for circuit component selection, cooling system design, and reliability analysis of power transmission systems. However, the existing converter valve loss calculation methods using the nearest level modulation (NLM) method and the traditional sortingbased capacitor voltage balancing strategy are inaccurate since the submodule (SM) switching logics in the MMC arms are uncertain. To solve this problem, the switching principle of the SMs in the sorting-based voltage balancing strategy is analyzed. An accurate MMC power loss calculation method based on the analysis of loss distribution of various SM topologies, including half-bridge submodule (HBSM), full-bridge submodule (FBSM) and clamp double submodule (CDSM), is proposed in this paper. The method can accurately calculate the losses caused by the extra switching actions during the capacitor voltage balancing process, thus greatly increasing the calculation accuracy of switching losses compared with existing methods. Simulation results based on a practical±350 kV/1000 MW MMC-HVDC system with variety of MMC topologies with diferent voltage balancing strategies demonstrate the efectiveness of the proposed method.     

Traveling wave fault locator for mixed,overhead, and underground teed transmission feeders

Society is increasingly concerned about the environmental impact of energy systems, and prefers to locate power lines underground. This is especially true in regions of outstanding natural beauty or if they affect environmental/political/planning constrained areas. However, the use of underground sections within a predominantly overhead feeder introduces significant problems for the auto‐reclosure of circuit breakers. Auto‐reclosure is important on an overhead feeder, since most faults are transient and, once the feeder has been de‐energized, the insulation strength of the air at the fault recovers and the line can be restored to service. Faults on an underground cable are different because, once the insulation is damaged, the fault is normally permanent. In addition, if the breaker is allowed to reclose onto a cable fault, the area of damage increases and health and safety concerns exist for humans in the vicinity of the faulted cable section. The main purpose of the traveling‐wave‐based measurement scheme described in this paper is to locate a fault on a teed transmission feeder with mixed overhead and underground sections. Simulation results demonstrate that the fault locator can accurately locate all realistic faults, including ones that are high resistance or occur at nonideal points on wave. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

考虑输电网与柔性互联配电网交互影响的可靠性评估方法

对输电网与柔性互联配电网组成的输配电网络整体采用故障枚举法进行可靠性评估时,除去分析输电网与配电网内部故障对各自供电可靠性的影响之外,还需考虑故障场景下输电网与配电网间的交互影响。本文在现有输电网与配电网各自独立的可靠性评估算法基础上,针对输配电网络组成的整体研究其可靠性评估方法。本文方法可计及故障条件下输电网与配电网运行状态间的相互关联,将输电网故障后的节点负荷减载细化为配电网优化后的负荷切除方案,提升输电网可靠性评估结果精度的同时,将应对输电网故障导致的配电网负荷损失纳入配电网可靠性评估。此外,在输电网可靠性评估中计及了配电网内部故障导致的输电网节点供电负荷损失及其对输电网运行可靠性造成的影响。针对输配电网络整体,基于故障枚举采用解析法计算得到输配电网络可靠性指标,算例分析结果验证了所建立可靠性评估模型的有效性。     

输变电设备在线监测装置的试验体系和项目

为了检验输变电设备在线监测系统的功能和可靠性,需要进行一系列试验.在总结在线监测系统的应用经验和参考相关标准的基础上,首次全面提出了试验体系包括型式试验、出厂试验、交接试验、特殊试验和抽样试验,以及包括准确度试验、模拟试验、绝缘试验、环境试验、电磁兼容试验、机械性能试验、连续通电试验和可靠性试验等试验项目的具体内容和指标要求.     

高压直流输电系统安全性评价专家系统

借鉴利用现有网络技术,设计了基于知识库的高压直流输电系统安全性评价专家系统,可对各种安全性评价数据和资料实行高效管理,实现数据的有效存储、交换和查询。介绍了系统安全性评价的业务流程以及体系结构,对专家系统知识库的构建进行了阐述:系统知识库由规则库和事实库构成,表示方法采用产生式规则表示法,并描述了其数据结构。实践证明基于知识库的安全性评价系统能够有效提高安全评价的效率,提高可用性和准确性。     

高温超导交流输电电缆导体层电流分布研究

本文通过对高温超导输电电缆导体各层电磁平衡方程组的建立,结合高温超导材料的电磁特性,提出影响导体各层电流均匀分布的相关结构参数关系表达式。通过对这些结构参数组合的调整,提出了使导体各层电流均匀的原则和方法。拟合及有详试验表明,本文的研究原则和方法是可行的。     

35kV及以下输配电线路重要跨越改造

针对35 kV及以下线路重要跨越改造的特点,对采用搭设跨越架、专业跨越架工具、编织防护网等3种典型方式进行线路跨越改造工作进行阐述。并举例说明10 kV及以下线路重要跨越改造的典型措施。     

500 kV浏河-徐行输变电工程系统调试

500kV浏河-徐行输变电工程是上海电网由外部受电的第3条通道,对增加上海电网区外受电能力、满足地区用电增长有着重要的作用.为确保系统调试顺利进行,在设计、基建、调试、运行、调度等各个环节都加强管理,相关单位密切配合,落实了大量的组织和技术管理工作,并严格按照华东电网调试规范的要求,考核了各类新投运的500kV一、二次设备,为电网安全生产运行提供了重要技术依据.