牵引变电站供电线路进线档频繁电烧伤分析

从分析多个电铁牵引站供电线路进线档出现架空地线连接金具电腐蚀入手,着重分析了铁路负荷回流在牵引站地网及其进线各接地点处的分布;通过多次现场实测,并对等效回路模型及其各处电流分布的分析,得出了电铁牵引站供电线路进线档地线上存在较大电流的结论。讨论了牵引站供电线路进线档电烧伤事故频繁发生给电网安全运行带来的影响,并对现有技术条件和运行维护制度提出了相应的改进措施和建议。     

昌赣高铁某牵引站的计量错误接线分析及处理

高铁在我国已经较为普及,而高铁牵引站的供电方式相对特殊,其计量接线错误分析对比三相负荷平衡系统有明显差异.为掌握其差异性,针对高铁牵引站其中一相作为公共相运行及输电线路换相的特点,对昌赣高铁某牵引站实际案例中的计量回路错误接线进行相量图分析,后排查出Ub、Uc.反接造成供、受两侧计量电量相差巨大.经纠正后,共追补错误接...     

500 kV超高压输电线路金具挂环断裂原因及预防措施

针对5起500kV输电线路金具挂环断裂案例,总结故障原因,提出针对性预防措施,最后设计了应用物联网智能感知系统的金具挂环在线监测方法,以期减少金具挂环的故障率,进一步提高供电可靠性。     

南广铁路郁南牵引站220kV供电线路继电保护配置分析

通过对南广铁路郁南牵引站接入系统一次接线方案进行分析,比较单相接线和V/X接线对电气化铁路牵引负荷的影响,提出牵引站220 kV供电线路的继电保护配置原则,认为全线速动保护宜采用工频量差动保护来实现线路主保护.在对RCS-904微机距离保护与RCS-931微机光纤电流差动保护进行分析的基础上,阐述了南广铁路郁南牵引站供...     

一种电铁供电线路继电保护配置方案

针对电铁牵引站供电线路保护配置,结合电气化铁路负荷特性、牵引站一次主接线的情况,分析了配置距离保护的缺陷,提出了一种采用纯电流保护的改进配置方案,并对该方案下的整定原则进行了分析探讨。     

110 kV线路连接金具断裂原因分析及防范措施

对一起110 kV输电线路U形挂环断裂引起掉串的情况进行了介绍,从宏观分析、渗透检测、金相检测等方面着手对挂环断裂原因进行分析,最终找到断裂原因,并提出了金具在制造工艺控制和出厂质量检验、组装检查等防范措施,对今后预防金具断裂有一定借鉴作用.     

某线路球头挂板断裂失效分析

电力线路金具断裂失效直接影响电网正常、安全运行,给电力客户可靠供电和电网设备健康状态都带来一定影响,文章分析了一起球头挂板断裂失效原因和暴露出问题,依据分析结果提出了具体防范措施。     

基于牵引供电线路保护死区问题的探讨和实践

牵引供电线路与电力系统输电线路不同,前者使用的是交流两相,而变电站输出设备均为三相.由于保护配置及CT安装位置的原因,非供电相在变电站出线端可能存在保护死区,当发生非供电相单相接地故障时,母线差动保护及线路保护均不能快速动作切除故障.以一起牵引供电线路非供电相接地故障为例,分析牵引供电线路保护死区问题,并结合一、二次设备的配置,提出改进措施.     

某线路U型球头连接金具可靠性分析

对某线路U型球头挂环的材质和断裂原因进行分析,该球头挂环在线路运行时发生疲劳断裂,存在两种疲劳失效形式。结果发现该球头挂环材料性能不符合65Mn钢标准要求,金具设计未考虑金具疲劳性能,应从材料疲劳性能进行连接金具设计。     

220kV两相式电铁牵引站供电线路的短路故障计算及其保护整定原则分析

分析了单相牵引变压器短路阻抗的特点,并根据系统等值模型,对两相式电铁牵引站供电线路的短路故障计算进行了分析。结果表明,与一般三相电网相比,短路故障分析中单相牵引变压器的短路阻抗应乘以0.5的折算系数;两相式供电线路的负荷阻抗应乘以0.866的折算系数。结合实际工程中两相式电铁牵引站供电线路的保护配置和电网稳定性要求等情况对保护主要整定原则进行了深入分析,提出了差异化的距离保护、零序(和流)、保护TV断线过流保护整定原则。分析了各种重合闸方式的利弊,给出了推荐的重合闸方式整定原则。     

On a wing and a prayer

The article talks about recent Defense Research Projects Agency (DARPA) presolicitation notice in the area of hybrid insect micro-electromechanical systems (MEMs). DARPA's goal is to fund promising interdisciplinary research that will permit the creation of "insect-cyborgs"     

利用光伏电池给蓄电池充电

磷酸锂铁（LiFePO4）电池对比钻基德Li离子/聚合物电池,具有安全性性高、浮充电压小、自放电率低、使用寿命长等一系列优点。本文所述LT36521C为可实现太阳能跟踪、单块式补偿蓄电池充电的集成电路。当LT3652由单块太阳能电池板供电时,其输入调节回路能确保在最大输出功率下工作,充分体现出这一新型太阳能充电器的优越特性。     

Making a Case for a New Connector

The emergence of quick lock connectors, particularly quick lock versions of the SMA and N connectors (QMA and QN, respectively), was an inevitable development in the RF connector industry and is of significant importance in that nearly 50% of all practical applications for RF connectors are currently supported by either SMA or N. Once QMA and QN can achieve similarity in cost and performance to the present SMA and N connectors, they will take the place of their predecessors in most applications, creating a huge new market. Our RF team has long been dedicated to research and development of these two connector types in the hopes of creating an optimal design. In this article, we will show some of the results of our research.     

Chaos in a series circuit with a nonlinear capacitor and a nonlinear inductor

This paper proposes a nonlinear circuit that generates chaotic oscillations. The proposed nonlinear circuit includes a nonlinear capacitor and a nonlinear inductor by using Generalized Impedance Converters. Both computational experiments and experiments on real circuits show that the region for chaotic oscillation is very wide, demonstrating that the proposed circuit is effective as a chaos generator. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 35–42, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10361     

Electric potential near a tip of a local discharge on a conductive film

To develop a propagation model of a local discharge on a wet polluted insulator, the authors have examined characteristics of the local discharge on an electrolytic solution simulating the wet polluted insulator surface. The local discharge was propagated on the solution under the impulse voltage. A shape of a contacting surface between the local discharge and the solution has been already obtained by the authors. By using the contacting surface, an electric potential near a tip of the local discharge on a conductive film of 1 mm in thickness was calculated. Furthermore, the potential was measured with a probe. The calculated values and the measured values of the electric potential agreed well regardless of the propagation length of the local discharge, the width of the conductive film, the resistivity of the conductive film, the peak value of the applied voltage and the applied voltage waveform.     

Power losses in a conducting ring enclosing a conductor with a transient current

Contents In the paper Joule power losses are calculated in a conducting ring enclosing a conductor with a transient current having an alternating component.—Theoretical calculation and numerical computation are worked out basing on a link Bubnov-Galerkin method in its numerical version using the finite elements for the conductor with the Time-Stepping algorithm for the time discretization.—On the basis of numerical computation, graphs of the relative power losses are plotted as a time function.

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Leistungsverluste in einem leitenden Ring, der einen Leiter mit einem instationären Strom umschließt

Übersicht In diesem Beitrag werden die Joulschen Leistungsverluste in einem leitenden Ring berechnet, der einen Leiter umschließt, in dem ein instationärer Strom mit Wechselanteil fließt. Die theoretischen Betrachtungen und numerischen Berechnungen hat man in Anlehnung an die Bubnov-Galerkin-Methode (in ihrer numerischen Variante, die von einen Leiter unter Verwendung der Methode der finiten Elemente realisiert wird) in Verbindung mit einem Schritt-Algorithmus mit der diskretisierten Zeit ausgeführt. Auf der Grundlage numerischer Berechnungen sind Diagramme für die relative Leistung in Abhängigkeit von der Zeit dargestellt.

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List of symbols Symbol Unit Physical parameter - B Wb/m² magnetic induction vector - H A/m magnetic field intensity vector - H, H A/m -component of the magnetic field vector - E V/m electrical field vector - E _r ,E _z V/m components of the electric field - f s^–1 frequency - I A current intensity (r.m.s. value) - L H inductance - P W power losses - P ₀ W power losses for d.c. - R resistance - t sec time - ^–1 m_–1 electric conductivity of the conductor - Hm^–1 magnetic permeability - _ijk m² finite element area - basis function - rad s^–1 pulsation - N _i ,N _j ,N _k function of finite element shape - 3.141593... - region - ² Laplace's operator - r, ,z cylindrical coordinates - ^h region approximating the region - ^e finite element region - M number of discretization points of the region - V number of finite elements - (N–1) number of steps - i, j, k indices of vertices of triangular finite element     

Development of a deceleration control system for a winding machine based on a microcontroller

The development of an automatic deceleration system for a winding machine in a siderurgy factory is presented in this paper. The proposed system controls the speed of a winding machine in order to obtain the optimum stop point in terms of security and fast production. The system is based on a microcontroller and an extremely simple hardware. The system has been tested for two years and results evince a very good mean time between failures.     

Simulation of a generator for a wind-power unit

Analysis of excitation systems of generators for wind-power units is carried out, a software package for generator simulation is presented, and the sequence of the generator design is presented.     

When a feature detector becomes a feature generator

The neural network approach is reviewed in the context of studies in the animal and human visual systems. An attempt is made to explain perception, memory, and learning as a feedback loop similar to the one used in the ALOPEX optimization concept. Applications in pattern recognition and image processing are discussed. Experiments using visual evoked potentials in humans are described.