0.1Hz下电缆介损测量技术的进展

运行实践表明,直流耐压试验对交联电缆不但是无效的,而且是有害的,必须寻找新的方法来代替它,目前比较成熟的方法是在0．1Hz下测量电缆的介质损,介绍了这种办法的最新进展。     

Preventive maintenance testing of shielded power cable systems

Power cable systems can play a critical role with respect to the reliability of industrial plants. This paper reports on a preventive maintenance tool for shielded power cable systems based on the location of partial discharges. It describes the principles of the technology and provides data covering tests conducted on over 6000 km of medium-voltage cables serving both electric utilities and industrial customers. It discusses the technical and economic advantages, as well as some of the limitations of the diagnostic test method     

GPS卫星测量系统在信息化供电公司中的应用

介绍了GPS测量系统的定位原理、相对坐标系建立、对不同坐标系地形图进行转换和在信息化供电公司中的3种应用方式.在信息化供电公司建设中推荐使用DGPS卫星测量方式.     

Condition assessment of cable insulation systems in operatingnuclear power plants

Four crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR) insulated cables were subjected to accelerated thermal, radiation, and sequential radiation and thermal exposure to simulate 20, 30, and 40 yr in-service environments in Ontario Hydro Nuclear Plants. Two sets of samples were evaluated. The first set contained 15 cm cable specimens in tubular form with the conductors removed, while the second set was made up of 4.3 m cable samples wound on mandrels. The cable samples were sequentially irradiated and thermally aged and subjected to an additional accident radiation exposure followed by a simulated loss of coolant accident (LOCA)/main steam line break (MSLB) steam test. During the steam test, samples were energized and their electrical characteristics continuously monitored. The material performance of the insulation was assessed using the 15 cm specimens during the various stages of aging exposure by conventional elongation measurement and by the use of micro-specimens with differential scanning calorimeter (DSC), oxidation induction time (OIT) and infrared carbonyl absorption techniques. The results from these samples were compared with the electrical performance of the cable samples wound on mandrels that had been subjected to the LOCA/MSLB steam test. The test results indicate that with the use of micro-specimens meaningful changes were obtained until the elongation values of the samples were reduced to 50% absolute. Electrical test data obtained for XLPE and EPR during the steam tests indicate that 50% absolute elongation values provide sufficient margin to withstand additional accident radiation, and to function electrically during design basis events     

城区电力电缆接头故障在线监测系统

现有的电力电缆接头温度在线监测系统大多由于现场监测装置供电困难、数据传输距离受限、需要进行大量的现场施工等原因,仅适合于发电厂、变电站内的使用。针对城区电力电缆接头点多量大、分布范围广等特点,研制了一套新的监测系统;监测系统现场装置以C8051F020单片机和Wavecom Q2406A模块为核心,对电缆接头温度数据采集和监测,利用全球移动通信系统(GSM)短消息服务来实现数据传输,完成远方监测与管理。经过实际运行检验,系统运行稳定可靠,收到了良好的效果。     

城区电力电缆接头故障在线监测系统

现有的电力电缆接头温度在线监测系统大多由于现场监测装置供电困难、数据传输距离受限、需要进行大量的现场施工等原因,仅适合于发电厂、变电站内的使用.针对城区电力电缆接头点多量大、分布范围广等特点,研制了一套新的监测系统;监测系统现场装置以C8051F020单片机和Wavecom Q2406A模块为核心,对电缆接头温度数据采集和监测,利用全球移动通信系统(GSM)短消息服务来实现数据传输,完成远方监测与管理.经过实际运行检验,系统运行稳定可靠,收到了良好的效果.     

Thermal analysis of power cable systems in a trench inmulti-layered soil

A system of three underground cables in a trench is modelled using the finite difference method. The model accommodates most of the geometrical parameters and the working conditions. The heat dissipation from each individual cable is calculated for various parameters including the cables' diameters, the trench width and the spacing between cables. Some of the geometrical dimensions have great influence on improving the total ampacity of the system     

Failure analysis of composite dielectric of power capacitors indistribution systems

This paper describes the study of the reliability of capacitor units installed and operated in a distribution system during the period 1980 through 1990. Failures of capacitor units in distribution substations can be very costly to the supply of reliable power to consumers. To enhance utility reliability, failure analysis and rates, failure origin and physical damage causes were performed for these capacitor units. Two approaches, statistical and physical, were utilized in this study. In the statistical area, failure modes, reliability levels and failure causes are analyzed. The physical study mainly deals with the mechanism of deterioration of the composite dielectric, The results of the study on 2912 capacitor banks including 8736 capacitors installed at 153 distribution substations showed that the failure mode of capacitor units may be represented by a Weibull distribution and each capacitor manufactures has different failure rate. Analysis showed that partial discharge properties are a critical indicator for capacitor failure. Useful conclusions are presented both for power system operators and manufacturers. The methodology used in this study also applies to other equipment in the distribution system such as oil switches, transformers and insulators     

硅橡胶冷缩式电力电缆附件的应用

由于硅橡胶具有良好的电气和物理性能,硅橡胶冷缩式电缆附件的应用前景广阔.介绍硅橡胶和冷缩式电缆附件的性能特点以及应用中应注意的问题.     

预制分支电缆在供配电系统中应用的讨论

本文介绍了预制分支电缆的优越性,但与封闭式母线槽相比,还存在着不少的局限性与不足,因此目前尚无法完全取代母线槽在供配电系统中的重要位置,需对预制分支电缆的产品结构不断改进,进一步降低产品成本,增加推广力度。     

FTLD线形测温电缆在电厂电缆沟火灾报警系统中的应用

针对大坝发电有限责任公司#1～#4机组电缆沟火灾报警系统存在的问题,通过对当前各种以测温电缆与感温电缆为主要检测元件的火灾报警系统工作原理及性能进行分析比较,提出以美国进口的线形温度探测器--FTLD测温电缆作为系统主要检测元件组成的火灾预警系统,可连续实时监测电缆沟内各区域的最高温度,克服传统的"点式"温度传感器只能探测"某点"温度以及感温电缆只能输出开关量信号,在火灾已发生,达到定温点后才能发出报警信号的不足。使用该系统对大坝#1～#4机组电缆沟火灾报警系统及防火门自动关闭系统进行完善后,系统维护量大大减少,可靠性大大提高。     

Effects of voltage impulses on extruded dielectric cable life

Laboratory tests were performed to investigate the effects of lightning and thumping impulses on the performance of various 15 kV cable designs. The cable designs were aged in the laboratory using an accelerated water treeing test. Some samples were subjected to lightning impulses, some were subjected to thumping impulses, and some were aged without impulses applied. The impulse effects were evaluated using time to failure data, AC breakdown data, and impulse breakdown data. The results show that lightning or thumping impulses do not affect cable AC or impulse breakdown strength. There is also no visual difference between wafers taken from impulsed and control samples. However, there is a strong indication that lightning impulses can reduce cable life. Almost all the aging failures occurred while the cables were warm. No failures occurred during the impulse application. It is also shown that increased cable wall thickness extends cable life for the tree-resistant high-molecular-weight insulation material tested, but not for the crosslinked polyethylene insulation material tested     

光缆监测系统在电力通信网中的应用

文章针对目前电力系统光缆的维护现状及存在的弊端,提出光缆监测系统在电力通信网中应用的必要性,并着重从基本原理、系统构成以及功能体系3个方面对光缆监测系统进行了阐述。最后,介绍了光缆监测系统在蚌埠电力公司通信网中的应用。     

浅谈光缆在线监测系统在供电企业的应用

随着光纤通信网络的不断发展,光缆的维护和管理工作也日益上升为一个重要的问题。介绍贵阳供电局光纤通信网的现状,提出了光缆在线监测系统在电力企业应用的必要性。介绍了光缆在线监测系统工作流程、系统各部分的实现方法、以及贵阳供电局此次选择的监测方案,并阐述了系统应用后取的收效。     

电力电缆讲座：第五讲 电览线路的运行管理

1　运行管理的基本任务电缆线路的运行管理工作是多方面的 ,其最基本的任务就是要确保电缆线路安全供电和减少事故发生。基本任务可以归纳为以下两方面。1 .1　使电缆适应电网和用户供电的需求电缆运行管理部门必须严密监视电缆设备的运行状态 ,使电缆线路始终适应电网和用户供电的需求 ,运行管理人员要使管辖范围的电缆线路处于受控状态。电缆的绝缘、导体和护层这三大组成部分 ,必须符合运行要求。( 1 )绝缘一定要合格。电缆及其附件的绝缘 ,必须与电网的绝缘水平相匹配 ,它的 U0 /U要与系统的中性点接地方式相一致。而且 ,绝缘要有一定…     

架空和电缆混合馈线的线损估算

提出了架空和电缆混合馈线的线损估算方法。在分析架空线和电缆线功率损耗的基础上,先构造混合馈线线损估算的非线性回归模型。模型以混合馈线所含架空线长度、电缆线长度、馈线首端的有功和无功功率为独立变量,通过高阶多项式反映混合馈线的损耗随独立变量变化的复杂关系。针对非线性线损估算模型中的待求回归系数,基于Gauss-Raphson法推导了迭代求解公式;设计了相应的计算程序,并采用实测数据对所提模型和算法进行了仿真计算和分析,得到的检验回归模型合理性指标表明,给出的线损估算模型有效、可行,为架空和电缆混合馈线的线损估算可提供高效率的途径。     

一种高精度的电力系统相量测量方法

在传统的离散傅里叶算法的基础上提出了一种新的相量测量算法,首先,对纯基波信号,该算法利用2个数据窗的DFT变换数据推导出了一个关于频率偏移的方程,解此方程后可以求出基波信号的频率、幅值及相位的精确解,在推导过程中无任何近似误差,有效减小计算量的同时提高了测量的精确性.接着,为了提高谐波情况下测量的精度,利用迭代法对原采样序列进行修正,然后在最终的修正序列上用前面的算法进行相量测量.最后,分别对存在谐波和噪声的情况进行了仿真,结果表明,该算法在各种情况下具有测量精度高的优点.     

Effects of voltage surges on extruded dielectric cable life projectupdate

Electric utility engineers have commented that extruded distribution cables frequently fail during or shortly after a thunder storm. These engineers also comment that failures often reoccur on cable circuits where previous failures were located with a thumper. Linemen at Georgia Power often make similar comments. To investigate this observation, crosslinked (XLPE) and tree retardant crosslinked (TRXLPE) power cable designs were subjected to accelerated water treeing tests. Samples were subjected to simulated lightning surges or simulated thumping surges. Crosslinked cables removed after 15 years of service operation were also subjected to these surges. The results show that, in some cases, lightning surges do reduce extruded distribution cable life. Also, high level thumping surges appear to reduce cable life once cables are well aged     

Telephone cable: overview and dielectric challenges

An overview of the common types of telephone wire and cable used in the United States and of related industry specifications is provided. Common insulating materials and selected electrical and physical parameters are discussed, along with several dielectric-related problems facing the industry. One is to reduce the migration of oil from cable filling gels into the insulation, where it adversely affects the electrical and physical properties. A second problem is how to reduce the overall fire hazard contributed by wire and cable installed in a building. A third problem is to develop twisted-pair copper cables that can handle increasingly higher data rates     

Frequency relaying based on instantaneous frequency measurement[power systems]

A frequency relay capable of under/over frequency and rate of change of frequency measurements has been implemented on a digital signal processor using an instantaneous frequency measuring algorithm. Careful attention to the filtering aspects of the relay is needed under dynamic conditions due to frequency modulation of the input signal. An algorithm for avoiding unwanted relay operation due to impulsive changes in the input signal is presented. Results are shown for simulated tests using computer-based relay testing equipment, and for overloads on a micromachine power system simulator