数字通信电缆屏蔽技术的应用及其原理

随着数字通信网络不断地向多功能、大容量、高频率和高速率发展,对数字通信电缆抗电磁干扰的屏蔽性能提出了更高的要求。论述了数字通信电缆屏蔽原理,提出了几种屏蔽电缆选择和应用的前提条件;介绍了各种屏蔽技术和结构;对屏蔽电缆的接地系统也作了详细介绍,以便使通信电缆更好地应用于通信网络。     

P型环网结构的配电线载波组网方式研究

近年来,利用电力电缆屏蔽层载波通信传输配电自动化数据,是最经济、便捷和有效的一种可靠通信方式。城市小区普遍采用P型环网结构供电,采用电力电缆高频网桥耦合技术实现利用P型环网结构的电缆屏蔽层载波组网通信,是一种新的尝试,文章根据应用实例,通过现场测试多级分段电力电缆的屏蔽层信道的传输特性,分析载波组网通信效果,结果显示,利用多级分段电力电缆的屏蔽层载波通信传输配电自动化数据是可靠的。     

10 kV混合配电线路载波信道特性测试与分析

配电线载波通信以其安装简便、投资小、运行免费等优点,逐步成为城市配电自动化通信的重要通信方式.近年来,10 kV配电线屏蔽层载波通信一直是研究的热点.然而受制于城市10 kV配电线路改造的进度,配电线路出现大量屏蔽层不完整、地埋电缆与架空线路相结合的混合线路.此类线路是否可以实现载波通信,也成为配电自动化通信建设的研究重点.文章选择2条典型的10 kV混合配电线路,对其电缆阻抗、噪声、传输衰耗特性进行测试与分析.测试结果表明,采用卡接式电感耦合方式的混合配电线路可以作为载波通信的媒介,为城市配电自动化通信建设提供有效的解决方案.     

Implementation of shielding principles for magnetic field management of power cables

Adverse health effects due to magnetic fields is a matter of great concern and has been widely debated in recent years. Managing these fields is a challenge to researchers. One of the important sources of magnetic fields is power cables. Different management techniques have been studied. In this paper, passive shielding schemes are implemented to manage the magnetic fields of power cables. The various shielding schemes can be separated into two broad categories: shielding subject and shielding source. Both schemes are implemented in this paper. Passive shielding schemes are found to be the most powerful technique as the reductions obtained are sometimes as high as 97–98%. This scheme is a costly one, should be used only in assigned locations, and as such, there has to be a trade-off between the cost and the level for reduction desired and the health desired and the health hazards.     

VHDL语言设计数字电路

在许多家电和工业的控制电路中,为了提高电路的稳定性或控制精度,已经把模拟信号转化为数字信号进行处理,所以数字电路在实际生活当中占很重要的位置,本文详细介绍了如何用VHDL语言开发数字电路,大大的简化了对工控电路的设计并且减低了成本。     

地下通信电缆外套金属管道与附近铺设屏蔽线屏蔽效果的比较

提出了一种同时考虑感性耦合和阻性耦合时的地下导体电磁屏蔽的计算模型,利用该模型进行了地下金属管道对其内通信电缆和屏蔽线对其附近通信电缆的电磁屏蔽计算。计算结果表明,不仅从感性耦合的屏蔽效果考虑,则金属管道和屏蔽线对地下通信电缆屏蔽保护效果基本相同;从阻性耦合影响和对防雷影响的屏蔽效果考虑,则套装金属管道的效果要优于敷设屏蔽线。     

蓝牙技术及其应用展望

为实现数字设备间的无线快速通信，蓝牙技术是近年新生的技术，蓝牙协议体系由硬件模块，软件模块和高端应用层构成。它采用跳频技术，以及链路层的认证，加密，密钥管理功能和高层协议栈的PIN码等安全机制，与其它无线通信技术相比，蓝牙技术以其价廉，可移动性，开放性和安全，保密性而具有广泛的应用前景。     

通信电缆的抗干扰技术

分析了通信电缆电磁干扰信号的耦合方式、耦合途径。根据通信电缆的特性,研究了通信电缆的抗干扰措施。主要通过对通信电缆进行电磁屏蔽、接地、滤波等技术来减小外界对电缆的电磁干扰。同时也对高压输电线产生的电磁干扰影响作了探讨。     

中压环网结构的电缆屏蔽层传输特性的测试与分析

利用电力电缆屏蔽层进行载波信号传输,已成为国内外相关机构的研究热点。文章介绍了一个典型的由8段电力电缆通过线路开关连接成的环网结构,并对其供电电缆屏蔽层信道的传输特性(阻抗、噪声、传输特性)进行了全面的测试。测试结果和试验统计数据显示,采用高频桥接的多级电缆屏蔽层信道的传输特性基本满足载波组网通信可靠性要求,可以作为载波通信的信道,为城市小区配电自动化系统的通信系统提供了一种廉价且方便的解决方案。     

The Development and Commercialization of Ignition Suppressant, Moisture Barrier Instrument, Control and Power Cables

Plastic coated metal shielding tapes are becoming more and more prevalent in the wire and cable industry. When these tapes are bonded to a chlorinated polyethylene jacket, a moisture/chemical barrier sheath is created that can be utilized in cables for above, ground applications such as in cable trays, in conduit or for aerial use on messengers. These designs can also be used for direct burial and inside buildings. The physical properties of the shielding tapes, combined properties of the tape and jacket, and the properties of various cable designs are all discussed. Additionally, case histories are reviewed which describe the use of these cables in various industrial environments. Specifically, the development of such coated tapes and chlorinated polyethylene jackets provides wire and cable users with additional sheath designs which can be used to reduce expensive maintenance and extend cable service life.     

电力自动化远动通道监测系统的研究与实现

文章针对电力自动化远动通道监测的实际要求，提出了模拟远动电路及“四遥”数字远动通道监测方案和系统综合设计，实现了远程集中监测。通过对系统的实际开发、应用过程及其技术功能解析，体会到电力通信网监测系统在满足了对直流电源系统、机房动力环境等远程监测的基本需求后，开发和实现对远动模拟电路、“四遥”数字通道监测，将是建设电力通信综合监测系统的重要内容和发展方向。希望能为未来电力通信综合监测系统的发展起到一定的启示作用。     

PLC在卷取电机供电系统中的应用

可编程控制器已成为一种重要的、应用场合广泛的工业控制器,它是一种数字运算操作的电子控制设备,可以通过数字式或模式输入输出控制各种类型的机械或生产过程,介绍了应用在宝钢冷轧厂张力卷以机供电回路中的ＰＬＣ控制系统,阐述了其控制要求、系统配置、硬件电路和软件。运行结果表明ＰＬＣ系统提高了运行的可靠性与灵活性,增强了抗干扰能力。     

基于DeviceNet的伺服系统集成控制

基于CAN总线技术和CIP协议的DeviceNet现场总线,用于将现场工业设备、可编程控制器和工控机连接到网络,从而免去了昂贵复杂的硬接线,具有开放、低成本、高效率、高可靠等特点.作为工厂自动化(FA)不可缺少的部分,伺服系统正朝着小型化、网络化的方向迅速发展.Ultra 3000系列产品功能强大,能提供强大的网络通信功能和可选的SERCOS和DeviceNet网络接口.本文提出了一种基于DeviceNet的SLC Ultra 3000伺服控制系统,介绍了Ultra 3000驱动器的DeviceNet接口,并给出了典型应用实例的硬件配置和软件方案.     

一种基于数字控制的功率因数校正（PFC）电路系统的研究

由于模拟控制电路不易更改,模拟控制的PFC电路很难在宽输入电压范围内工作在理想状态。本文研究了一种基于数字控制的PFC电路,提出一种具有输入电压前馈的数字平均电流控制策略。该策略通过加入输入电压检测环节来校正控制参数,从而使PFC电路在宽输入电压范围内保持了良好的校正效果。实验结果表明该控制策略达到了预期效果,证明了理论分析的正确性。     

EMP作用下的电缆耦合及屏蔽效能试验分析

介绍了三同轴法、线注入法、功率吸收钳法、混波室法等电缆屏蔽效能测试方法.进行了电磁脉冲作用下的同轴电缆和裸线耦合试验,探讨了该环境下同轴电缆屏蔽效能的测试方法.试验分析表明,电缆耦合后的波形为衰减振荡波,振荡周期正比于电缆的电长度,频谱与照射场的频谱不一致,裸线的耦合输出衰减较快.根据试验数据,采用峰值场强法计算的电缆屏蔽效能与峰值电压法的结果吻合,所以可采用峰值场强法对电缆进行电磁脉冲的屏蔽效能测试.电磁脉冲作用下的同轴电缆屏蔽效能较相当频段连续波作用下的略低.     

现场总线控制技术在电厂中的应用研究

分析了现场总线控制系统的结构和技术特点。与现行的DCS相比,FCS最显著的特征 是开放性、分散性和数字通信,可节省硬件数量与投资、节省控制电缆和安装维护费用。给 用户高度的系统集成主动权,并提高系统的精度和可靠性。     

电磁兼容性设计在通信设备结构设计中的应用

电磁兼容性设计是通信设备结构设计中的重要环节。本文介绍了在通信设备的结构设计中进行EMC设计时的相关理论和设计策略。依据EMC的基本原理,综合考虑了屏蔽材料、屏蔽方式、缝隙和孔的处理等诸多因素,并在对孔处理中提出了运用回归拟合的经验公式进行设计的方法,大大减小了设计误差。     

Compact disc players in the laboratory: experiments in opticalstorage, error correction, and optical fiber communication

The compact disc player is a synergy of optics, communication theory, digital signal processing, and control engineering. This familiar consumer product may be employed as a cost-effective laboratory instrument to teach the fundamentals of optical storage, error detection and correction, and optical communication. The compact disc audio system, from analog input, through optical storage and distribution, to audio reproduction, provides an excellent model of a complete real-world optical transmission and storage system. A series of experiments, which illustrate some of the more significant operational principles of the compact disc player, are presented in this contribution. Optical read-out and the physics of information density are explored through a set of experiments in optical storage. Error detection and correction are studied experimentally by evaluating the performance of the compact disc player's error control system. The design of an optical fiber communication system is studied by extracting the channel bit stream from a compact disc player, transmitting it over an optical fiber link, and then reinserting it back into the compact disc player for audio reproduction     

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.     

对称数字通信电缆结构回波损耗影响因素分析

结构回波损耗是评价数字通信用对称通信电缆传输性能的重要指标之一,本文从理论上分析了几种对称数字通信电缆结构参数不均匀性对电缆结构回波损耗的影响。