Thesis (Ph. D.)--University of Hong Kong, 2004. / Also available in print.

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 169-180). Also available via World Wide Web.

No description available.

Dissertation submitted in compliance with the requirements for Master's Degree in Technology: Electrical Engineering (Light Current), Durban Institute of Technology, 2002. / Modern society as a whole seems destined to have an ever-increasing demand for power for both industrial and domestic use, as continued population growth means that cities, suburbs and industrial areas become larger and denser. At the same time the trend toward increased productivity in all segments of industry is influencing the development and techniques employed at locating faults in power cables and networks to ensure only limited downtime and reduced direct and indirect costs associated with the location of faults / M

Fault location for series compensated lines cannot be addressed sufficiently by conventional solutions developed for traditional uncompensated lines. Line-parameters vary with loading and weather conditions, and therefore settings used for fault location are often erroneous. Line-parameter free solutions for fault location are therefore more reliable and accurate than conventional solutions that require such settings. Hence, line-parameter free fault location algorithms for single-circuit and double-circuit series compensated transmission lines were developed during the research project. Single-circuit lines and double-circuit lines both present unique challenges for fault location. They also vary in the number of available measurements that can be used to arrive at a solution for distance to fault. A third algorithm is presented that allows the extension of existing short line algorithms to the case of long lines. This is done by providing a method for incorporating the line shunt admittance into these existing algorithms. The aforementioned three bodies of research work, form the focus of this thesis. The algorithms are derived using two-terminal synchronised current and voltage sampled measurements. Of these, the algorithms for series compensated lines are also derived for asynchronous measurements. Phasors are obtained by carrying out a Fast Fourier Transform, and then appropriate calculations are performed for distance to fault. The thesis covers the mathematical derivations of the algorithms, involving the algebraic reduction of non-linear equations in numerous variables into a single expression for distance to fault. The results for a variety of simulation tests are shown subsequently and discussed. Various fault resistances, fault types, degrees of series compensation, line lengths, fault levels are considered in the tests carried out. The algorithms are largely found to be highly accurate under these various conditions, and where the algorithms perform to a lesser degree of accuracy are highlighted and discussed. Lastly, a detailed chapter discussing future work is also included in the thesis.

Power quality related problems cause large financial losses in the order of billions worldwide. The evaluation process aimed at determining effective remedial actions starts with the correct identification and characterization of power quality disturbances. Measurements performed in the electrical power network and the corresponding collection and process of data are the primary method of characterization of the phenomena. The ideal deployment of monitoring devices would entail a monitor installed at each node of the network so that the power quality throughout the system could be directly assessed. In reality, however, technical and mostly economical constraints limit the number of monitors a network operator can install in the system. Power quality at non-monitored sites, therefore, has to be estimated by extrapolating the data from monitored sites. Consequently, it is crucial to identify the sites that provide the most accurate picture of the system’s overall power quality. Unfortunately, no recommended practices or guidelines for determining the minimum number and the best locations for optimal power quality monitoring have been prescribed in standards or reports. This thesis investigates voltage sag monitoring as part of a larger power quality monitoring scheme. The aim is to develop a methodology for optimal monitor placement for fault location and sag estimation. The thesis, divided in four main parts, focuses on network sag performance estimation and optimal monitor placement for fault localization and sag estimation. The introductory part of the thesis gives an overview of power quality surveys conducted around the world in recent years with special emphasis on the monitor placement criteria used. It also summarizes the main methods for network sag performance estimation proposed to date. The main part of the thesis firstly reviews the most referred optimal monitor placement method for sag estimation proposed in academia, highlighting its limitations. Then a robust fault location algorithm is proposed to enhance this method and overcome the identified limitations. The enhanced method is thereafter used as the basis for the generalization of one of the leading methods for optimal monitor placement for fault location in the second part of the thesis. The formulation of its optimization problem is extended for application in large power networks by adapting the modeling approach for the sag monitor placement problem. To reduce the high computational and memory burden associated with finding the optimal fault location monitor program, the thesis introduces a less memory intensive heuristic search algorithm in the third part of the thesis. A series of custom objective functions are proposed to be used with this algorithm to find optimal fault location and sag monitoring programs aimed at estimating the most critical events for customers. In the final part of the thesis, the main concepts and techniques introduced in the first three sections are combined to develop a synergistic approach to optimal monitor placement for sag characterization based on fault location. The suitability of the new method for techno-economic assessment of voltage sags using strategically or conventionally deployed monitors is established.

No description available.

The fault location and reconfigurable designs of Ripple Carry (RC) adders and Carry Save (CS) multipliers are studied in this thesis. The proposed designs can locate a faulty cell and reconfigure the faulty array to tolerate the faulty cell. Laser programming technique is used for fault location and reconfiguration. The key idea employed in the proposed methods is to perform diagnosis and reconfiguration at the same time. Appropriate fuses are programmed to locate a faulty cell, and the programmed fuses are also used for reconfiguration. This leads to small area overhead, and hence, substantial improvement in yield. Experimental results show that the yield enhancement of reconfigurable RC adders and CS multipliers is substantial compared with that of original RC adders and CS multipliers, respectively. / Master of Science

Power outages usually lead to customer complaints and revenue losses. Consequently, fast and accurate fault location on electric lines is needed so that repair work can be carried out as fast as possible. Chapter 2 describes novel fault location algorithms for radial and non-radial ungrounded power distribution systems. For both types of systems, fault location approaches using line to neutral or line to line measurements are presented. It’s assumed that network structure and parameters are known, so that during-fault bus impedance matrix of the system can be derived. Functions of bus impedance matrix and available measurements at substation are formulated, from which the unknown fault location can be estimated. Evaluation studies on fault location accuracy and robustness of fault location methods to load variations and measurement errors has been performed. Most existing fault location methods rely on measurements obtained from meters installed in power systems. To get the most from a limited number of meters available, optimal meter placement methods are needed. Chapter 3 presents a novel optimal meter placement algorithm to keep the system observable in terms of fault location determination. The observability of a fault location in power systems is defined first. Then, fault location observability analysis of the whole system is performed to determine the least number of meters needed and their best locations to achieve fault location observability. Case studies on fault location observability with limited meters are presented. Optimal meter deployment results based on the studied system with equal and varying monitoring cost for meters are displayed. To enhance fault location accuracy, an optimal fault location estimator for power distribution systems with distributed generation (DG) is described in Chapter 4. Voltages and currents at locations with power generation are adopted to give the best estimation of variables including measurements, fault location and fault resistances. Chi-square test is employed to detect and identify bad measurement. Evaluation studies are carried out to validate the effectiveness of optimal fault location estimator. A set of measurements with one bad measurement is utilized to test if a bad data can be identified successfully by the presented method.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 82-83). Also available via the Internet.