High frequency transients and electromagnetic interference within 69 kV substations

This paper presents an analysis of the experimental measurements of fast transients and their electromagnetic interference on the protection system in air isolated distribution substations. Transients were recorded in the relay inputs of potential and current transformers due to switching operations in a 69 kV bus bar. A peak overvoltage of up to 6.5 kV and frequencies of around 1 MHz and above, were recorded in secondary circuits that are rated 115 V. The current presented fast transients with relatively small amplitudes and lower frequencies than the recorded voltages. The transients caused relay failures leading to the unnecessary disconnection of the substation. Transients are supposed to be related to radiated and conducted interferences caused by the electric arc during switching operations. Transient voltage and currents are analyzed, and the results are compared with others from the literature. Some solutions are presented to mitigate the failures of the protection relays.     

关于500kV变电站工频电磁场强度的研究

根据500 kV变电站工频电磁场强度现场测试情况,对500 kV变电站工作场所和设备的工频电场和磁场强度进行研究,得出电场和磁场强度的分布规律及特点。从保障作业人员和公众健康、促进企业安全经济运行的角度,提出电磁场防护的措施及管理办法。     

Reduction of the edge steepness of electromagnetic surges in gas-insulated substations

Contents In this paper a methodology for reducing the edge steepness of electromagnetic surges in gas-insulated substations is presented. The damping of the waves results from the utilization of the skin effect by means of a semiconducting coating of the substation's inner conductor. An analytical calculation of the attenuation factor shows the behaviour of a surge's different frequency portions. FDTD-simulations confirm the flattening of the wave fronts by the damping layer. Finally, a comparison with an uncoated structure shows the advantages of the coating.

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Verminderung der Flankensteilheit elektromagnetischer Sprungwellen in gasisolierten Schaltanlagen

Übersicht Es wird eine Möglichkeit zur Verminderung der Flankensteilheit von elektromagnetischen Wellen in gasisolierten Schaltanlagen vorgestellt. Die Dämpfung der Wellen erfolgt unter Ausnutzen des Skineffekts durch eine halbleitende Beschichtung des Innenleiters der Schaltanlage. Anhand einer analytischen Berechnung des Dämpfungskoeffizienten wird das Verhalten der unterschiedlichen Frequenzanteile der Sprungwellen aufgezeigt. FDTD-Simulationen bestätigen die Abflachung der Wellenstirn durch die Dämpfungsschicht. Abschließend zeigt ein Vergleich mit einer unbeschichteten Anordnung die Vorteile der Beschichtung auf.

     

Reduction of low voltage power cables electromagnetic field emission in MV/LV substations

In this paper a solution to reduce magnetic field emission levels generated by MV/LV substation power cables is proposed. The reduction is obtained by the arrangement of the phases in a proper way and by shielding the cables with magnetic or conductive materials. The effects introduced by these two options have been analyzed by means of simulations, using finite elements method calculation software, and by experimental measurements. The introduced results allow selecting an optimal arrangement and the best screening material in order to reduce the magnetic fields in those directions required to protect.     

瞬态电磁场辐射敏感度测试系统

随着科学技术的发展,各种电子设备大量使用,电磁干扰成为关注的焦点,要进行电磁干扰实验首先必须建立模拟电磁场.本文介绍了可以模拟核电磁脉冲的瞬态电磁场辐射敏感度测试系统,论述了该测试系统建立的必要性、功能、系统组成及使用方法.     

继电保护装置的电磁干扰实例分析

随着微机型继电保护的广泛应用,继电保护装置和二次回路的电磁干扰问题越来越引起电力工程界的重视.该文分析了电力系统中常见的电磁干扰,讨论了继电保护的常见干扰源、耦合途径和抑制手段,对实际工程中发生的两起继电保护电磁干扰问题进行了深入的研究,分析了干扰产生的原因,提出了相应的现场处理意见,具有一定的理论意义和工程实用价值.     

Transient electromagnetic plane wave reflection from a dielectricslab

Reflection of a transient plane wave normally incident upon a lossless dielectric slab is analyzed via the Fourier transform. The exact expression for the time-harmonic field is used in the inverse Fourier transform to obtain the transient response to a class of exponential exciting functions. Cauchy's integral theorem and the Poisson sum formula yield closed-form expressions for the unit step and impulse response functions     

航空单相交流电源电磁干扰分析和抑制

本文以飞机的单相交流电源为例,分析航空单相交流电源的工作环境,找出导致交流电源产生电磁干扰的原因,给出抑制交流电源电磁干扰的原理和方法.在不改动总体设计的基础上,针对实际情况提出屏蔽、搭接和滤波等电磁干扰抑制措施,并重点对滤波技术进行了讨论.     

集中监控中心站电磁干扰影响的分析与控制

分析了集中监控中心站在运行中存在的各种电磁干扰源 ,对这些干扰源对微机保护、微机监控及工作人员可能造成的危害 ,提出了消除这些危害的切实可行的措施。相应措施亦适应无人值班变电站。     

重频电磁脉冲对氢闸流管触发影响的研究

以氢闸流管栅极触发电路为研究对象,建立了共地耦合干扰模型,并进行了栅极共地耦合电磁干扰研究,实验在重复频率电磁脉冲(EMP)环境下进行。结果表明,重复频率电磁脉冲的传导干扰对氢闸流管的触发系统产生影响,其数量增多与间隔减小均使误触发的可能性增大。对比理论分析与实验结果,认为电磁脉冲的数量增多与间隔减小均可导致传导干扰增强从而使氢闸流管误触发趋势增大。     

开关电源的电磁干扰产生原因及抑制方法

由于开关电源本身的工作特性使得电磁干扰问题相当突出,其干扰信号经传导和辐射对电子设备、通信系统等产生电磁污染.从电磁干扰产生的机理人手,着重论述了开关电源中的整流电路电流断续、功率开天管的高速开关动作瞬间的电压、电流瞬间变化时产生电磁干扰的原因以及电磁干扰的危害,总结了不同场合下最大限度地抑制电磁干扰的方法和措施.提出了抑制电路设计参数的估算关系式,经仿真实验抑制电路对电磁干扰抑制效果明显.     

Smart industrial substations

The smart industrial substations enhances plant electrical personnel safety by physically removing the operator from the arc flash zone. The smart industrial substations shifts electrical technician functions from time-consuming tasks in front of substations equipments to time-saving tasks away from the substations. The smart industrial substation is a "best fit" integration of traditional and modern substation devices with local/remote human-machine interfaces (HMIs), pagers, and cell phones.     

矿用变频器辐射电磁干扰特性分析

为了研究矿用变频器运行状态下电磁辐射分布特性,基于以电压源型两电平变频器为核心的调速系统,在分析调速系统工作机理与干扰源的基础上,采用矩量法和天线理论相结合的方式,在电磁场仿真软件FEKO中搭建了变频器天线模型.通过模型仿真结果,分析了调速系统稳态下的干扰特性.研究结果表明:变频器外壳起到了很好的屏蔽作用,内部电磁干扰...     

一起由于电磁干扰造成断路器误合闸的事故分析

对一起由于测控装置同期开入回路受到电磁干扰后误动,造成主变压器中压侧断路器误合闸的严重事故进行了详细分析,并说明了电磁干扰使得光耦元件“瞬态饱和”的现象和原理,指出了测控装置设计不当的地方,并由制造厂家进行了改进。     

An oscilloscope method for eliminating the interference and disturbance voltages for the earthing measurements of large earthing systems in substations

This article describes an oscilloscope method for eliminating the interference and disturbance voltages for the earthing measurements of large, extended or interconnected earthing systems in substations where the impedance to earth is very low (|Z_E| < 0.3 Ω). The presented oscilloscope method is based on a heavy-current injected method at network frequency. Two ways of obtaining the final result from oscilloscope measurements are described and presented with practical examples. The accuracy of this method using an oscilloscope was confirmed by a comparison with results obtained using conventional methods for practical cases of touch-voltage measurements, i.e., the beat method and the polarity-reversal method. These comparative measurements were made in three substations. The article also describes the advantages of this method.     

GPS技术在变电站中的应用

介绍了全球定位系统（GPS）技术在变电站中的应用,详细地分析了对时编码格式、系统的组网方式以及现场测试技术等,并针对目前GPS对时系统存在的主要问题提出了相应的解决办法。     

Solutions to electromagnetic interference problems between cochlear implants and GSM phones.

For persons using cochlear implants, electromagnetic compatibility (EMC) problems may sometimes be an obstacle to using digital cellular telephones. This study aimed at exploring the benefit of three new assistive listening device prototypes that eliminate or diminish EMC problems. Ten experienced cochlear implant users listened in quiet to running speech samples and a sentence test on a landline phone, a digital cellular phone with and without three prototypes. The subjects' performance was assessed using a sentence test, a subjective visual analog scale, and by ranking the best and the poorest listening condition. Compared to the other test conditions, listening to a digital cellular phone alone revealed, on average, the poorest sentence recognition scores (29%) and the poorest results in four different subjective judgments (the amount of disturbances, the clarity of the message, the quality of the sound, overall judgment) with all three implant systems tested. The prototypes generally helped the implantees to recognize speech better on the cellular telephone (by 10-21 percent units, on average). Use of assistive listening devices and further development of EMC of both cochlear implant systems and digital cellular phones needs to take place to enable smooth use of digital cellular phones for all implantees.     

Condition assessment of contacts in gas-insulated substations

A new method for assessing the condition of electric contacts and joints inside gas-insulated substations (GISs) that overcomes the limitations of conventional diagnostic methods is proposed. The contact resistance in degraded or overstressed electrical contacts varies slightly when currents of different amplitudes are passed. The diagnostic method is based on detecting this nonlinear behavior. For testing of the contacts in large GIS, excitation currents up to several thousand amperes are required. By using a capacitor-based current supply, such currents can be achieved with a portable source. The testing can be carried out without dismantling the GIS. No earlier measurements or manufacturer specifications are required. In full-scale testing under realistic operating conditions on 145-420 kV GIS using prototype instrumentation a very good sensitivity for detecting contact degradation in an early stage was obtained.     

数字化变电站中采样值同步技术研究

认为采样值同步技术是实现数字化变电站过程总线通信的难点之一。阐述了基于外部源的硬接线同步和基于IEEE 1588的网络同步两种方案,指出方案实现的关键因素,从硬件设计、同步误差、冗余性和互操作性等方面对这两种方案进行了分析和比较。研究结果对数字化变电站中采样值同步设计具有参考意义。