谐振接地系统单相接地故障仿真分析

针对谐振接地系统发生单相接地故障时因故障线路电流很小且方向不确定而导致选线难度大的问题,从理论上分析了谐振接地系统发生单相接地故障时的零序电压、零序电流变化规律;在Matlab软件中建立了小电流接地系统仿真模型,并分别对中性点不接地系统、全补偿谐振接地系统、过补偿谐振接地系统、欠补偿谐振接地系统进行了仿真分析,仿真结果与理论分析结果一致,进而得出结论:发生单相接地故障时,中性点不接地系统可选用基于幅值和方向等稳态分量的选线方法,谐振接地系统不可选用该种选线方法,但两种系统可选用同一种基于暂态分量的选线方法。     

小电流接地系统选线注入信号的频率分析

注入信号法是广泛应用于小电流接地系统单相接地故障的选线方法,实际应用中由于接地故障电阻大,容易发生选线失败的现象。文章通过分析注入信号法的基本原理及注入信号的流通路径,借助Matlab仿真,研究了注入信号频率对选线效果的影响,得出了降低注入信号的频率可以减小非故障线路对信号电流的分流作用、提高注入法的适用范围和选线准确率的结论。     

煤矿谐振接地故障模糊综合选线方法

针对谐振接地系统中依据稳态分量的故障选线方法失效的问题,从暂态分量角度甄选了零序能量法、小波变换法和增强小波包法进行分析。引入模糊综合选线方法对3种方法进行集成,并运用层次分析法确定3种方法的权重。仿真分析结果表明,零序能量法和增强小波包法的可靠性较好,而小波变换法出现了误判,可靠性较差;模糊综合选线方法没有受到其他错误信号的干扰,给出了正确结论,具有较强的可靠性。     

基于局部全局一致性学习算法的故障选线方法

针对现有故障选线方法用于中性点经消弧线圈接地系统或相电压过零点附近发生故障时选线不准确的问题,提出一种基于局部全局一致性学习算法的小电流选线方法,即首先对线路接地故障原始信号进行傅里叶变换,然后将各故障信号的特征量输入局部全局一致性学习算法,通过标签循环传递判断故障特征信号,从而选出故障线路。通过Matlab仿真模型与实验室测试平台对该方法进行了研究,结果表明该方法具有较高的选线可靠性与准确性。     

基于能量与相关性的谐振接地系统选线新方法

针对谐振接地系统单一选线方法易发生误判、易受训练样本影响等问题,提出基于能量与相关性的谐振接地系统选线新方法。首先计算线路各相电流突变量和每条线路的综合相关系数,然后用经验模态分解算法计算每条线路相电流突变量所对应的固有模态能量权重系数,取每条线路三相固有模态能量权重系数中的最大值作为本线路的综合能量系数值,最后通过二维判据求取特征距离。仿真结果表明,基于能量与相关性的谐振接地系统选线新方法实现了母线故障判别,且在一定程度上提高了判据裕度,适用范围更广。     

基于小波暂态能量的自适应故障选线新方法

针对当前小电流接地系统在相电压过零时发生故障选线准确率不高的问题,分析了小电流接地系统发生单相接地故障后零序电流的频率特征。提出了一种基于小波暂态能量的故障初始角自适应故障选线新方法,该方法利用快速傅里叶变换获取电压相位估算故障初始角,并根据能量最大值原理进行故障选线。通过理论分析,数字仿真实验,证明了所提出的方法基本不受过渡电阻、故障初始角、电弧故障和故障距离的影响,能够准确快速地选出故障线路。     

Prony算法在电网接地故障分析中的计算机应用

小电流接地系统中单相接地故障的暂态信号往往作为故障选线的重要依据。本文对Prony算法的原理和计算机实现进行了分析,并通过仿真示例说明了Prony算法能够有效辨识接地故障信号的幅值和相位信息,进而实现为小电流接地系统接地故障选线提供重要参考。     

基于ARM小波复合判据的小电流接地系统故障选线的研究与设计

针对小电流接地系统单相接地故障选线准确度低的难题,分析故障时电压、电流的信号特征,提出采用复合判据的故障选线方案,从而提高故障选线的准确度.本文设计了一种基于ARM的嵌入式高速数据采集及复合判据选线算法的故障选线系统,该系统以LPC2138微处理器为核心,利用硬件同步与软件纠错相结合的方法实现电网故障模拟量信号的采集与处理;该系统可通过RS-422总线与主CPU通信完成数据的存储、传输与处理;也可通过本地人机交互接口对系统进行维护和升级.     

基于小波包分解和残差网络的故障选线方法

分布式电源与电缆在配电网中大量应用和配电网繁重的检修任务，都对有源谐振接地系统的故障选线带来新的挑战，于是提出一种基于小波包分解和残差网络的故障选线方法。从理论上分析不同故障情况下零序电流的频谱特征，运用小波包分解突出过渡电阻、故障距离和故障初始相角对零序电流的影响。通过残差神经网络模拟出不同故障情况与各馈线运行状态之间的映射关系。上述方法同样适应于有馈线检修停运时导致拓扑结构变化的运行情况，也可运用在出现双重故障的配电网中。通过仿真验证，所提方法在各种故障情况下选线依然准确、可靠且适应性强。     

基于PSO-SVM的小电流接地故障选线方法

针对小电流接地系统,现有故障选线方法的精度不高,为此提出基于粒子群优化向量机（PSO‐SVM ）的选线方案。在搭建小电流接地系统仿真模型的基础上,采用M atlab进行PSO优化算法仿真实验,根据不同的接地情况获得故障时各线路零序电流,利用小波包变换（WPT ）与傅里叶变换（FFT ）从零序电流中提取暂态分量、谐波分量、五次谐波分量作为PSO‐SVM输入特征进行训练,用训练好的SVM 对测试样本行检测,得到选线结果。仿真结果表明,该方法使学习训练速度加快、自适应能力增强、选线精度提高进,且其不受接地电阻、故障距离等因素影响。     

Putting the ‘theory’ back into grounded theory: guidelines for grounded theory studies in information systems

Over the past decade, there has been increasing interest in the use of grounded theory in information systems research. Grounded theory is a qualitative research method that seeks to develop theory that is grounded in data systematically gathered and analysed. The purpose of this paper is to suggest guidelines for grounded theory studies in information systems. Our guidelines are based on a framework for theorizing in grounded theory studies that focuses on conceptualization and theory scope. Our hope is that the guidelines will help to raise the quality and aspirations of grounded theory studies in information systems.     

接地电阻自动监测系统的设计与实现

摘要：接地电阻可靠接地对电力系统的安全具有重要意义，目前接地电阻的测量主要靠人工手动测量，进行一次测量需要花费大量的时间和资金。针对这种现状，本文基于自动测试理论，网络通信和嵌入式技术设计出一套接地电阻自动监测系统。系统的测试终端能够自动测量接地电阻，多个终端的测量结果通过网络自动上传，监测人员只需操作软件即可完成测量过程。本系统的设计和实现提高了接地电阻的自动测量技术水平，系统已在铁路系统的电力部门投入运行。     

MCS－8098测控系统信号处理电路的设计

以８０９８单片机测控系统为例，就传感器输出信号的接地、放大以及电平转换等问题进行了讲座，并给出了相应的实用电路。     

露天矿高压接地保护开关柜

GJBD-6-1型露天矿高压电网单相接地保护多路供电移动开关柜,综合应用了电力、电子和无线电技术。在技术上有突出的实质性特点和显著的进步。采用本开关柜可缩小矿山停电范围,减少停电时间,提高设备作业率。本文介绍该开关柜的工作原理、技术性能、在现场进行工业试验及生产考核结果。     

Are We There Yet? A Technique to Determine Theoretical Saturation

Although the concept of theoretical saturation (ThS) was first introduced by Glaser and Strauss's grounded theory methodology, it is now more widely used as a fundamental concept in interview-based qualitative research. Despite its widespread use, the concept is nebulous and lacks systematization. An extensive literature review in 2007, and again in 2013, shows that this inexactitude characterizes most claims for using ThS. Yet qualitative methodologists seem strangely reluctant to accept criticism or possible improvement. By assuming ThS to be an analogue of the principle of diminishing returns, we propose a quantitative technique for determining ThS using lognormal distribution principles. Applying the technique to three large data sets provided strong evidence that the method is efficacious. Usefully, this study also shows both that the technique is not affected by the order of interviews and that corpus size is not necessarily a true indication of theoretical saturation.     

MOSFET‐C‐based grounded active inductors with electronically tunable properties

In this study, two new grounded metal oxide semiconductor field effect transistor (MOSFET)‐C active inductors (AIs) are proposed. The proposed AIs contain only eight MOS transistors and a single grounded capacitor that is attractive for integrated circuit fabrication. Inductance values of them can be electronically tuned by a single control voltage. They do not include any current sources. Therefore, the designs of the proposed AIs are simple and useful. They do not suffer from body effects. Hence, they can be designed with low power supply voltages. Simulation results by using the Cadence analog environment program with 180 nm Taiwan Semiconductor Manufacturing Company (TSMC) nm technology parameters are carried out to indicate the performance of them. Layouts of both proposed AIs occupy the same area of about 78 μm × 78 μm. Postlayout simulation results are given to confirm the validity of the theoretical analysis.     

Important characteristics of software development team members: an empirical investigation using Repertory Grid

An information system is typically developed by a team of information systems (IS) professionals. Research shows that teams staffed with the right people are more likely to be effective and efficient. There is a paucity of study that examines the important traits of IS professionals in team contexts. The objective of this research is to identify and understand the important characteristics of good team members in software development projects. We applied an established psychological technique (Repertory Grid) to guide our interviews with 21 experienced IS professionals, who have had extensive experience in software development teams. The comprehensive list of important characteristics was analysed qualitatively using open coding method of grounded theory. Fifty‐nine unique characteristics were identified and classified into eight categories. Among them, attitude/motivation, knowledge, interpersonal/communication skills, and working/cognitive ability were perceived by research participants to be the most important categories. Our study provides a context‐specific (i.e. software development team) evaluation of important characteristics of IS professionals. The results have significant implications for IS recruiting, IS training, IS staffing, and IS human resource management. Our study also supplements the research on management of IS development teams.     

Systems development approach: transcending methodology

Abstract.  This paper presents the findings of an empirical study investigating the nature of the process of information systems development. These findings are used to identify systems development approach, which extends understanding of the information systems development process beyond the levels of methodology and technical expertise. The term approach expresses the rich, varied, and complex ways in which professionals deal with development situations. The term transcends methodological components – which can be combined, tailored, or omitted altogether. Within approach, a framework for method choice, a key diagnostic scheme, and the use of a central repository reveal the significant background activity that goes into developing information systems. It is suggested that the information systems development process ultimately involves a professional using an approach to intervene in a problematic situation for developing the organization's information and, if needed, other systems. This understanding has implications for examining the field's ineffectiveness in relation to the approach adopted – rather than the methodology used.     

TOWARD A COMPUTATIONAL ANALYSIS OF PROBABILISTIC ARGUMENTATION FRAMEWORKS

In this article we analyze probabilistic argumentation frameworks (PAFs), defined as an extension of Dung abstract argumentation frameworks in which each argument n is asserted with a probability p_n. The debate around PAFs has so far centered on their theoretical definition and basic properties. This work contributes to their computational analysis by proposing a first recursive algorithm to compute the probability of acceptance of each argument under grounded and preferred semantics and by studying the behavior of PAFs with respect to reinstatement, cycles, and changes in argument structure. The computational tools proposed may provide strategic information for agents selecting the next step in an open argumentation process and they represent a contribution in the debate about gradualism in abstract argumentation.     

小电流接地系统单相接地选线装置设计与实现

针对小电流接地故障诊断难的问题,设计了一个基于零序电流、零序电压的实时检测系统,对供电系统进行检测并对故障线路进行选线。采用了多任务、可移植、可裁剪的嵌入式操作系统μC/OS-II。为防止中性点带补偿系统对于故障线路的过补偿影响,系统还加入了补偿零序导纳判据对这种接地情况下的故障进行检测。选线系统采用零序电压触发方式,既提高了实时性,也增大了选线的准确性。