基于广域测量系统的潮流转移识别方法

电力系统中的潮流转移会引起线路事故过负荷及其距离Ⅲ段保护误动作,这是导致连锁跳闸,最终发生大停电事故的重要因素之一。为此,利用广域测量系统(wide area measurement system,WAMS)的优势,提出一种潮流转移识别方案。根据三相电流增量及零序电流的大小来区分线路过负荷和不对称短路故障,根据电压幅值的大小来区分线路过负荷和对称短路故障,并提出了相应的识别判据。考虑到系统振荡对判据判断的影响和故障切除后过负荷发生的情况,提出了具体的潮流转移识别策略,并给出了实现流程,该策略可有效防止距离Ⅲ段元件在事故过负荷时误动,并能保证在故障时可靠开放距离Ⅲ段保护。通过对新英格兰10机39节点系统进行仿真,验证了该方法的有效性。     

Dual-setting directional over-current relays: An optimal coordination in multiple source meshed distribution networks

To guarantee a safe operating scheme against the probable faults, an accurate and fast relaying scheme is of high priority. This challenge seems to be more sophisticated in multiple source meshed distribution networks hosting distributed generations (DGs). In this case, the current experiences bidirectional flows. More recently, dual-setting over-current relays are evolved as competent countermeasures for such cases. In this way, establishing an optimal coordination strategy is recognized as the first prerequisite in assuring a safe protection scheme. To this end, the present study aims at minimizing the overall operating time of primary and backup relays. Typically, the coordination problem is carried out by adjusting two parameters namely, pick up current (Ip) and time dial setting (TDS). In contradiction, the proposed approach follows a user-defined settings supported by some operating rules. Thus, besides the aforementioned settings, the coefficients of the inverse-time characteristics are also optimized. In other words, more flexibility is attained in adjusting relay’s characteristic in regard of the network’s loading and topological changes. Furthermore, inclusion of operating rules in main objectives, not only reduces the sum of operating time of all relays, but also increases the efficiency of backup relays regarding the break points in meshed networks. In other words, the covering zone by each backup relay is increased. The proposed approach demonstrates a non-linear programming fashion which is tackled based on genetic algorithm (GA). Several numerical studies are carried out to interrogate the validity of the proposed approach encountering different fault scenarios. The obtained results are encouraging.     

双中继协作通信的功率分配改进方案

为克服信息处于深度衰落情况下单中继协作困难,减少多中继协作目的端信号处理的复杂度,给出了双中继节点参与协作通信的功率分配方案。两个中继节点分别采用放大转发(AF)、译码转发(DF)以及混合译码放大转发(HDAF)3种协作方式进行通信。在满足一定的中断概率和节点功率限制情况下,利用MATLAB软件中的Fmincon优化函数,得到了各节点的最小发射功率。数值分析表明,在相同条件下,两个中继节点采用HDAF协作方式比采用AF协作方式、DF协作方式消耗的系统总功率分别少4~9 dBm、0.5~1 dBm,最大限度地节约了系统功率的消耗。     

ND++ – an extended IPv6 Neighbor Discovery protocol for enhanced stateless address autoconfiguration in MANETs

Recent trends in information and communications technologies are oriented toward the design of the Future Internet and the Internet of Things. While IPv6‐based mobile ad hoc networks (MANETs) are emerging as an important building block of these new technologies, it is necessary to come up with adequate self‐configuration capabilities allowing for seamless and automated configuration of addresses in mobile environment. The mechanisms of stateless address autoconfiguration proposed for IPv6 networks are supposed to automate some configuration steps; however, they would need to be aligned with the requirements imposed by MANET networks. Therefore, in this article, we present Neighbor Discovery ++ – an extended IPv6 Neighbor Discovery protocol for enhanced duplicate address detection in MANETs, which provides increased coverage of network nodes, while minimizing protocol overhead. It exploits efficient flooding mechanism on the basis of the multipoint relay concept, which makes it an interesting approach also for large‐scale networks. Trials performed on the designated real‐world testbed platform indicate that ND++ is a promising solution to support efficient address autoconfiguration in MANETs. Copyright © 2012 John Wiley & Sons, Ltd.     

A functional auxiliary module for 1st-zone conventional distance relays of double-circuit lines to eliminate high fault resistance-introduced under-reach

This paper presents design steps of an auxiliary module intended to function in conjunction with under-operation 1st-zone conventional distance relays of double-circuit transmission lines. The proposed module pursues the objective of eliminating the underreach of associated ground elements, arising from single-line-to-ground faults of high resistance. It is founded on the online estimation of the fault distance during the faults, through the roots of a non-linear algebraic equation developed in the sequence networks. The equation is mathematically discussed and a fitting numerical algorithm efficiently finding its roots with no concern about the computation burden is chosen. In order to be applicable to the lines of any lengths, particularly long lines, the proposed module is developed through the distributed-parameter based model of double-circuit lines. In addition, it employs only the data acquired at the relaying location and is independent of the network configuration. Important considerations are made for the proposed module, making its function both dependable and secure. Simulation studies conducted in MATLAB and PSCAD/EMTDC examine the proposed module in a variety of influencing situations, and confirm that it accurately fulfills its intended objective within the time frame of the distance protection.     

电动机保护器发展综述

介绍了电动机保护器的发展历程、技术特点与发展方向,并着重阐述了电子式和智能型两种电动机保护器的主要特点。     

玻璃纤维制造中温度控制系统的三种方案

玻璃纤维广泛的应用在居民生活、工业和军事中,制造玻璃纤维需要将玻璃高温熔化,融化的温度需要控制在某一数值.文章主要介绍玻纤制造中温控系统的三种控制方案,针对每一种方案的原理和组成进行介绍,并分析各种方案的优缺点.     

电磁继电器接触失效机理判别方法

传统判断电磁继电器接触失效的方法是仅监测接触压降是否超限,因未合理利用运行过程中特性参数的变化信息,不足以判别接触失效机理。本文通过监测继电器多个特性参数多方面获取接触失效信息,考虑到参数变化的随机性和冗余性,提出基于主元分析(PCA)和距离判别分析的电磁继电器接触失效机理判别方法。该方法首先对试验样品进行可靠性寿命试验并在线记录整个过程多个特性参数的变化规律。采用主元法对多特性参数构成的高维空间进行降维处理,从中提取主要特征,并按实际失效机理不同进行分类。最后,以已有样品的试验数据为训练样本,采用距离判别分析方法对新样品失效机理进行判别。该方法既避免了单参数判别信息不足,又减小了多参数之间的相互干扰对判别过程的不利影响。     

密封式电磁继电器步进应力加速寿命试验的分析方法

根据步进应力加速寿命试验原理,提出了一种快速评价密封式电磁继电器贮存寿命的试验方法。在定数截尾场合下,建立寿命分布服从威布尔分布的继电器步进应力加速寿命试验模型,采用似然方法计算出继电器在正常应力水平下的寿命特征。结合部件寿命信息给出Newton—Raphson迭代公式的初始值确定方法,为预测继电器贮存寿命提供了依据。利用随机模拟方法举例,验证了所提理论的正确性和有效性。     

一种结合威望的D2D通信中继选择算法

为了使终端直通通信能够公平有效地选择中继节点,提出了一种基于威望的中继选择算法．利用威望从社会域的角度描述了设备作为中继的意愿和能力; 同时在物理域分析了设备之间在不同传输模式下的数据传输情况; 采用博弈论的方法在候选中继设备中选出适合的中继,避免了社会关系弱、剩余能量低的设备被选作中继．结果表明,与随机选择算法和最大吞吐量算法相比,该算法提高了系统的吞吐量、终端直通链路的覆盖率以及中继选择的合理性．