XLPE电缆绝缘老化与剩余寿命评估的试验方法

电缆投入运行后.绝缘会受到电、热、机械、水分等因素的作用而发生老化,影响电缆的运行可靠性和使用寿命.XLPE电缆的绝缘状态与剩余寿命的评估是目前的热点问题,相对于定性的分析,对电缆剩余寿命的定量评估更有实际价值.文章总结了XLPE电缆绝缘老化机理并调研了几种定量分析电缆剩余寿命的方法:击穿电压对比法,介质损耗因素法和直流泄漏电流法.可为从事电缆运行情况和寿命研究的技术人员提供参考.     

交流电场下XLPE绝缘空间电荷研究综述

XLPE电缆目前广泛地应用于电力系统中,如何评估和预测现场运行电缆的老化及早期劣化的程度,是电缆绝缘状态评估的重要内容,然而这项研究在国内仍是空白。XLPE电缆的制造工艺过程、运行中的过电压和温升以及耐压试验过程都可能造成XLPE电缆绝缘特性的改变,导致绝缘性能下降,形成陷阱,特别是空间电荷的形成,畸变原有电场分布,直接影响XLPE电缆的绝缘特性。大量研究表明,在直流电场下空间电荷危害XLPE电缆绝缘,关于交流电压下空间电荷对XLPE电缆绝缘影响的探索较少。综述了交流电场下空间电荷效应对XLPE电缆绝缘影响的相关研究成果,并介绍了测量固体介质空间电荷分布的电声脉冲法,为从空间电荷测量角度研究XLPE电缆绝缘老化程度和状态评估提供了参考。     

直流交联聚乙烯电缆绝缘状态检测方法研究

随着新能源发电并网的发展,直流交联聚乙烯(XLPE)电缆的应用越来越广泛,但如何有效检测运行中直流电缆的运行状态以及对其状态的评价等仍是难题。通过搭建直流XLPE电缆局部放电和泄漏电流检测试验平台,在XLPE电缆半导电层残留缺陷模型基础上,研究了不同电压幅值与电压极性下局部放电和泄漏电流的特征。试验结果表明:局部放电和泄漏电流均可检测到电缆缺陷,其中局部放电在负极性电压作用下并且电压较高时更容易检测到电缆缺陷,泄漏电流在正极性电压作用下的特征变化明显,当外施电压低于额定电压时也可测得明显的变化量,有利于运行电缆的状态检测与评估。最后提出了运行条件下直流电缆状态利用泄漏电流进行带电检测的可行性,对提升直流XLPE电缆状态检测能力具有重要价值。     

直流交联聚乙烯电缆绝缘状态检测方法研究

随着新能源发电并网的发展,直流交联聚乙烯(XLPE)电缆的应用越来越广泛,但如何有效检测运行中直流电缆的运行状态以及对其状态的评价等仍是难题。通过搭建直流XLPE电缆局部放电和泄漏电流检测试验平台,在XLPE电缆半导电层残留缺陷模型基础上,研究了不同电压幅值与电压极性下局部放电和泄漏电流的特征。试验结果表明:局部放电和泄漏电流均可检测到电缆缺陷,其中局部放电在负极性电压作用下并且电压较高时更容易检测到电缆缺陷,泄漏电流在正极性电压作用下的特征变化明显,当外施电压低于额定电压时也可测得明显的变化量,有利于运行电缆的状态检测与评估。最后提出了运行条件下直流电缆状态利用泄漏电流进行带电检测的可行性,对提升直流XLPE电缆状态检测能力具有重要价值。     

交流电压下基于空间电荷效应的XLPE电缆绝缘老化研究现状

交联聚乙烯(XLPE)电缆以其优良的机械和电气性能广泛应用于现代电力系统。研究表明,在直流电压作用下绝缘中容易形成空间电荷,导致电场畸变,加速绝缘老化。国内外很少关于交流电压下空间电荷对XLPE电缆绝缘影响的研究。本文综述了交流电压下空间电荷对XLPE电缆绝缘老化的影响及其作用机理,并介绍了交流电压下测量空间电荷分布的改进的电声脉冲法。结果表明,交流电压下,空间电荷分布特性影响XLPE电缆绝缘老化。     

深圳变电站第三台联络变压器进线方案分析

本文针对深圳变电站超规模扩建第三台联络变压器的500 k V进线方案,分别采用交联聚乙烯(XLPE)电缆和气体绝缘管道母线(GIB)进行技术经济比较。GIB较XLPE电缆具有工艺成熟、性能优越、安全可靠的技术优势,同时在全寿命周期来看经济可行。深圳站第三台联络变压器进线最终采用750单相米的500 k VGIB架空敷设,敷设路径包括屋面、围墙、道路以及狭窄区域。通过技术参数、方案设计、地基处理三方面总结工程经验,为GIB在空间紧张、布置困难的变电工程中应用提供参考。     

基于热重和拉伸实验的XLPE电缆绝缘热老化状态分析及机理研究

工况下交联聚乙烯电缆绝缘材料的老化会导致其较预期相对较早达到寿命终点,威胁输电系统的可靠运行。采用热老化来模拟工况环境下电缆的老化过程,选取100 ℃、120 ℃和140 ℃和160 ℃ 4个不同的老化温度,在每个温度点选取6个老化阶段,研究不同老化温度和老化时间对XLPE电缆绝缘试样性能的影响。通过热重和拉伸测试研究电缆的热性能、机械性能及其结构随老化程度的变化,得到电缆绝缘试样的热老化活化能、起始分解温度、最快分解温度、终止分解温度、断裂伸长率和拉伸强度等参数。研究结果表明：活化能、起始分解温度、最快分解温度和断裂伸长率对电缆老化状态较为敏感;随着老化温度从100 ℃增加到160 ℃,这些参数均呈现先略微增大后迅速减小的趋势,说明XLPE电缆绝缘材料热老化在低温范围以结晶作用为主,而在高温范围以热裂解为主。     

XLPE表面缺陷对电场及击穿电压的影响

电缆中间接头施工过程中易造成XLPE表面划伤、附着污染颗粒和表面受潮三种缺陷,为评估缺陷对接头运行性能的影响,建立了电缆中间接头XLPE绝缘片状模型,分析了不同缺陷下电场的变化,探究了不同缺陷对电场及击穿电压的影响程度。结果表明,XLPE在划伤时划痕处的电场产生严重畸变,为非划痕处的1.6倍;受潮时XLPE表面附着污染水中导电杂质越多,污染水的电导率越高,从而使其导电性能增强,电场强度变大,是同界面处非受潮部分的1.22~1.40倍;XLPE表面附着污染颗粒时,颗粒与其交界面处电场发生较严重畸变,是同界面无缺陷时的1.50倍左右,划痕对XLPE绝缘的电场影响最严重。通过试验结果显示正常无缺陷时的击穿电压为129.6kV,划伤缺陷的击穿电压为59.1kV,受潮缺陷的击穿电压为69.7kV,杂质缺陷的击穿电压为59.2kV,划痕对XLPE绝缘的击穿电压影响最严重。研究成果为探究不同缺陷对电缆中间接头XLPE绝缘性能的影响提供了重要依据。     

基于集对分析动态加权法的XLPE绝缘老化状态评估

针对现有XLPE电缆绝缘老化状态评估方法缺乏综合性评估和可靠性差的问题,通过综合试验数据分析,提出一种基于集对分析动态加权法的电缆绝缘老化状态评估方法。首先为统一计算评估体系中各指标参量的相对观测值,提出了"等价失效值"的概念,然后利用集对分析法求解各参量与状态等级之间的联系度,最后引入动态加权函数求解各性能指标与状态等级的总体联系度以获取评估结果。实例分析表明,所提方法在电缆绝缘老化状态评估上综合性强、可靠性高且简洁有效;所构造的绝缘老化规律曲线能够较好地反映该区域电缆绝缘老化情况,可为该区域现役电缆运维及电网改造提供指导。     

中压交联电缆的交流试验方法分析

针对中压交联电缆交流耐压在上海电网实施中存在的问题,研究了中压交联电缆的交流试验方法,提出了现场试验标准,并提升了试验参数;研发了车载试验设备,提高了试验能力和可操作性,为上海以及其他地区开展电缆交流耐压工作提供了依据。     

中低压直流配电系统关键技术

中低压直流配电系统的发展对区域性电能传输,提高新能源的普及率,提高交直流互联电网的运行安全性具有重要意义.本文首先总结了许多国家提出的中低压直流配电系统方案和计划,然后详细阐述了中国在建的中低压直流配电系统项目案例的现状. 基于这些工程案例,本文分析了中低压直流配电系统的拓扑结构,设备,运行控制技术和直流故障保护等关键...     

Life cycle cost assessment of wind power–hydrogen coupled integrated energy system

Aiming at the economic evaluation of wind power-hydrogen coupled integrated energy system (WPHCIES), a life-cycle economic assessment method of integrated energy system is proposed. Firstly, the integrated scheme and operation mode of integrated energy system are given. Secondly, with the net profit of the integrated energy system in the whole life cycle as objectives and the energy flow and stable operation of the system as constraints, a mathematical model for the economic evaluation of the given integrated energy system in the whole life cycle is constructed, and the payback period and net profit of life cycle of the given system can be reckoned by the model. Finally, taking a wind farm in South China as background, the life cycle economic evaluation model of the proposed system is simulated and calculated, and the effects of both the ratio of hydrogen production from wind power and the ratio of hydrogen to fuel cell on the net profit of wind power-hydrogen coupled integrated energy system during the payback period and the whole life cycle are further analyzed. In addition, the comparison demonstrated that the capital return period of the wind farm can be reduced from 11 years to 8.13 years, and the cumulative net income can be increased from 0.67 billion yuan to 0.93 billion yuan by reasonably choosing the power ratio of hydrogen production from wind power.     

Committee Report-recommended Practice on Specific Aspects of Cable Installation in Power-Generating Stations

In the late 1940's high voltage pipe-type feeders were first installed in the United States. Since that time, over 2360 circuit miles of underground high voltage pipe-type cables have been installed throughout the country. Con Edison has approximately 652 circuit miles of high pressure pipe-type cable on its system, operating at 69, 138 or 345 kV. The typical pipe-type cable system is comprised of a steel pipe, containing 3 cables, with splices located at intervals of approximately 2000 feet. The pipe is filled with dielectric fluid which is maintained at a nominal operating pressure of 200 psig. Pressurization on the feeder is maintained automatically by pumping plants. For the 345 kV system, these plants sometimes include cooling capability. As the pipe type cable system grows older, leaks of dielectric fluid develop. The major causes of leaks are corrosion, contractor damages, effects of stray currents and localized pipe wear due to vibration. Quick detection and location of dielectric fluid leaks, particularly without the need to deenergize the feeder, is of prime importance to the utility industry. Raychem Corporation has been involved with the development of sensor cables for the detection and location of fluid leaks such as water and gasoline. This technology has been enhanced to address the problem of pipe type cable dielectric fluid leaks and a new system has been developed. The new system uses a sensor cable which is buried in the trench with the pipe type cable.     

西北750 kV示范工程输电线路OPGW光缆防振特性的研究

介绍了光纤复合架空地线(OPGW)光缆在国内第一个超高压西北750 kV官亭-兰州东输电线路的应用。结合西北750 kV输电线路的特点和对OPGW的要求,描述了750 kV输电线路OPGW光缆的结构设计的特点,同时通过750 kV官亭-兰州东输电线路大档距OPGW光缆防振特性的研究,为西北750 kV输电线路1 235m大档距OPGW光缆推荐了满足技术条件的直线档防振方案,并提供了测试结果及分析意见,对探索和积累750 kV超高压等级上OPGW光缆的设计和运行经验具有现实意义。     

Electrical collector system options for large offshore wind farms

The work presented is part of the EC FP6 DOWNVIND project activities, which focus on the requirements and implications of very large offshore wind farms. A comparative analysis of various design options for the electrical collector system of large offshore wind farms is presented, and the advantages and disadvantages in terms of their steady-state performance and economics are discussed. The case under consideration is that of a proposed 1-GW wind farm located off the northeast coast of Scotland. The impact on power losses and voltage level changes on the collector system busbars are investigated under various operating conditions. Contingency conditions of losing one of the cables to the hub end are also explored for collector system designs with redundant cables. Finally, the authors introduce an alternative design, based on conceptual ringed arrangements, and its advantages are illustrated and discussed     

Experience with voltage control from large offshore windfarms: the Danish case

This paper gives an overview of the state of the art and lists future challenges to reactive power and voltage control in the Danish transmission system in relation to large offshore windfarms. Today, the reliable and stable operation of the Danish transmission system is based on the voltage and frequency control carried out at central, conventional power plants. Moreover, the control of some larger decentralized combined heat and power units is activated for voltage control and system balancing, which is specific for the Danish system. In the years to come, according to the government's goal of increasing the share of renewable energy sources in the Danish power system, the share of large offshore windfarms in the Danish power generation mix will increase greatly, replacing central power plants, including their control characteristics during periods of strong winds. Large offshore windfarms must therefore provide the transmission system with the necessary voltage and frequency control, e.g. ancillary services, and ensure secure operation of the power system through their contribution to system service. Danish experience, based on the operation of a system with two large offshore windfarms and several smaller ones, has shown that the efficient use of windfarms' reactive power and voltage control for the on‐land transmission system might be limited by several factors. Among such limiting factors are the reactive power and current capability limits of the electronic power converters and switchable capacitor banks of the offshore wind turbines, which are smaller than those of central power plants measured per unit of the active power rating. Combine this with the use of AC cables, tens of kilometres long, to connect the large offshore windfarms to the on‐land transmission system, the reactive power range available to the transmission system gets poor. The Transmission System Operator should already take such limiting factors and alternative solutions for efficient reactive power and voltage control, such as incorporation of a reactive power compensation unit at the on‐land point of connection or evaluation of a Voltage Sourced Converter‐High Voltage Direct Current instead of an AC connection, into consideration during the planning phase for a windfarm connection. Copyright © 2009 John Wiley & Sons, Ltd.     

Optimization of solar systems using artificial neural-networks and genetic algorithms

The objective of this work is to use artificial intelligence methods, like artificial neural-networks and genetic algorithms, to optimize a solar-energy system in order to maximize its economic benefits. The system is modeled using a TRNSYS computer program and the climatic conditions of Cyprus, included in a typical meteorological year (TMY) file. An artificial neural-network is trained using the results of a small number of TRNSYS simulations, to learn the correlation of collector area and storage-tank size on the auxiliary energy required by the system from which the life-cycle savings can be estimated. Subsequently, a genetic algorithm is employed to estimate the optimum size of these two parameters, for maximizing life-cycle savings: thus the design time is reduced substantially. As an example, the optimization of an industrial process heat-system employing flat-plate collectors is presented. The optimum solutions obtained from the present methodology give increased life-cycle savings of 4.9 and 3.1% when subsidized and non-subsidized fuel prices are used respectively, as compared to solutions obtained by the traditional trial-and-error method. The present method greatly reduces the time required by design engineers to find the optimum solution and in many cases reaches a solution that could not be easily obtained from simple modeling programs or by trial-and-error, which in most cases depends on the intuition of the engineer.     

Life-cycle energy of residential buildings in China

In the context of rapid urbanization and new construction in rural China, residential building energy consumption has the potential to increase with the expected increase in demand. A process-based hybrid life-cycle assessment model is used to quantify the life-cycle energy use for both urban and rural residential buildings in China and determine the energy use characteristics of each life cycle phase. An input–output model for the pre-use phases is based on 2007 Chinese economic benchmark data. A process-based life-cycle assessment model for estimating the operation and demolition phases uses historical energy-intensity data. Results show that operation energy in both urban and rural residential buildings is dominant and varies from 75% to 86% of life cycle energy respectively. Gaps in living standards as well as differences in building structure and materials result in a life-cycle energy intensity of urban residential buildings that is 20% higher than that of rural residential buildings. The life-cycle energy of urban residential buildings is most sensitive to the reduction of operational energy intensity excluding heating energy which depends on both the occupants' energy-saving behavior as well as the performance of the building itself.     

光伏系统中蓄电池充电过程的建模与仿真

蓄电池的充放电管理一直是其控制器的关键.为提高光伏系统中蓄电池的充电效率,延长蓄电池使用寿命,采用脉宽调制的三段式充电策略(快速充电、脉冲式恒压充电及浮充电),利用MATLAB/Simulink软件平台对整个系统进行建模并仿真,为光伏系统中蓄电池的充放电管理提供了参考与依据.仿真结果验证了系统仿真模型的可用性和通用价值以及蓄电池控制策略的可行性和合理性,并表明在此蓄电池管理策略下可提高蓄电池充电效率,延长其使用寿命.