CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Com o aumento na demanda de energia elÃtrica e a exigÃncia de maior confiabilidade, seguranÃa e eficiÃncia na operaÃÃo de sistemas elÃtricos de potÃncia por parte dos ÃrgÃos reguladores, aumentou a necessidade por profissionais cada vez mais qualificados em planejamento e operaÃÃo dos sistemas de potÃncia. No entanto, com a necessidade de atualizaÃÃo tÃcnica continuada e em decorrÃncia da polÃtica de racionalizaÃÃo de custos e de disponibilizaÃÃo de pessoal, as tÃcnicas de ensino a distÃncia tÃm evoluÃdo e alcanÃado abrangÃncia nas mais diferentes Ãreas do conhecimento. Este trabalho apresenta um Simulador para Treinamento Presencial e a DistÃncia em OperaÃÃo e ProteÃÃo de Sistemas ElÃtricos (STOP). O simulador STOP à desenvolvido em Java, podendo ser utilizado em ambientes: Unix, Linux, Windows, MacOS. O STOP pode ser aplicado em treinamento presencial e a distÃncia e està voltado à capacitaÃÃo de estudantes de engenharia, tÃcnicos e profissionais da Ãrea de sistemas elÃtricos de potÃncia. O STOP està integrado a um Ambiente Virtual de Aprendizagem (AVA), o Moodle. A integraÃÃo enriquece o ensino-aprendizado tornando-o mais efetivo com o uso de uma ferramenta capaz de simular situaÃÃes reais. Os simuladores em ambientes virtuais sÃo alternativas para a reduÃÃo de custos em empresas e instituiÃÃes de ensino. O simulador STOP à um software composto de diagramas unifilares, com a representaÃÃo dos principais componentes do sistema de proteÃÃo, tornando possÃvel ao usuÃrio simular faltas e reconfigurar o sistema elÃtrico, por meio de ajustes de relÃs para coordenaÃÃo da proteÃÃo e redefiniÃÃo de parÃmetros. / As the demand for electrical energy increases and requirements from regulatory agencies for improved reliability, security and efficiency on the operation of electric power systems, the need for professionals ever more qualified on planning and operation power systems also increases. However, with the need for continued technical update and as a result of rationalization policies of costs and provision of personnel for training, the distance learning techniques have evolved and reached different areas of knowledge. This work presents a Simulator for Presence and Distance Learning about Operation and Protection of Electric Systems (STOP). The STOP Simulator is developed in Java, which enables it to be used in the following systems: Unix, Linux, Windows, MacOS. The STOP can be applied in class as well as distance training and is directed to the training of engineering students, technicians and professionals specialized on electric power systems. The STOP is integrated to a Learning Virtual Environment (AVA), the Moodle. The integration enhances the teaching-learning process making it more effective by using a tool able to simulate real life situations. Simulators in virtual environments are an alternative to reducing costs in companies and educational institutions. The STOP is a software tool featuring one-line diagrams with the main components of the protection system, short-circuits simulation and reconfiguration of the system by setting relays for coordination of the system protection and redefinition of parameters.

A synchro-generator and a unijunction transistor oscillator in conjunction with a silicon-controlled rectifier form a detection and relay circuit for voltages appearing across the field of a three-phase alternator generated by negative-phase-sequence currents due to unbalanced conditions. Readings were taken of the times required for operation of the relay for various conditions of unbalance. Statistical studies were made to enable time predictions to be offered. It was concluded that the scheme offers the possibility of faster operation, and hence better protection and system stability, than is possible with existing types. In addition, the scheme will result in no loss of dependability over existing types, and the relay portion offers outstanding ruggedness and sensitivity. / M.S.

Thesis (M.Eng.)--Memorial University of Newfoundland, 1999. / Bibliography: leaves 140-143.

Relays can be used in cellular systems to increase coverage as well as reduce the total power consumed by mobiles in a cell. This latter benefit is particularly useful for mobiles operating on a depleted battery. The relay can be a mobile, a car or any other device with the appropriate communication capabilities. In thesis we analyze the impact of using relays under different situations. We first consider the problem of reducing total power consumed in the system by employing relays intelligently. We find that in a simulated, fully random, mobile cellular network for CDMA (Code Division Multiple Access), significant energy savings are possible ranging from 1.76 dB to 8.45 dB. In addition to reducing power needs, relays can increase the coverage area of a cell by enabling mobiles located in dead spots to place relayed calls. We note that use of relays can increase the useful service area by about 10% with real life scenarios. We observe that in heavy building density areas there is more need of relays as compared to low building density areas. However, the chance of finding relays is greater in low building density areas. Indeed, having more available idle nodes helps in choosing relays, so we conclude that unlike present day implementations of cellular networks, the base station should admit more mobiles (beyond the capacity of the cell) even if they are not placing calls since they can be used as relays. One constraint of using relays is the potential to add interference in the same cell and in neighboring cells. This is particularly true if the relays are not under power control. Based on our analysis, we conclude that in interference limited systems like CDMA the relays have to be under power control otherwise we will reduce the total capacity by creating more dead spots. Thus, we believe that either the base station should be responsible to allocate relays or relays should be provided with enough intelligence to do power control of the downlink. Finally, we show how utility of data services can be increased by use of relays.

This research analyzes the linkage between power system disturbances and failures in relaying systems. The annual disturbance reports prepared by the North American Electric Reliability Council were examined. It has been found that relaying system failures plays very important role in power system cascading outages. The type of relaying system failures that are the most troublesome are the ones that have a potential to remain hidden until being exposed by some abnormal power system states to trigger relay misoperations. Each commonly used relaying scheme in transmission system is examined for any hidden failures that can lead to relay misoperations and multiple power system contingencies. Each hidden failure mode has a region, called region of vulnerability. Inside this region, some abnormal power system states can expose the hidden failure. The reach of the region depends largely on the settings of the relay in question. A method of computing the relative importance of each region of vulnerability, called vulnerability index, was proposed. The calculation of the index can be based on some measurements of power system performances. In this research, the stability measurements of the system following some contingencies that may occur in the region are chosen. With this approach, vulnerable relays can be identified. A preventive method was proposed so that the number of relay misoperations due to hidden failures and, ultimately, the number of power system disturbances can be reduced. / Ph. D.

Electric power systems are among the most complex man made systems on the world. Most of the time, they operate under quasi-steady state. With the ever increasing load demand and the advent of the deregulated power market recently, the power systems are pushed more often to operate close to their design limits and with more uncertainty of the system operating mode. With the increasing complexity and more interconnected systems, power systems are operating closer to their performance limits. As a result, maintaining system security and facilitating efficient system operation have been challenging tasks. Transmission systems are considered the most vital components in power systems connecting both generating/substation and consumer areas with several interconnected networks. In the past, they were owned by regulated, vertically integrated utility companies. They have been designed and operated so that conditions in close proximity to security boundaries are not frequently encountered. However, in the new open access environment, operating conditions tend to be much closer to security boundaries, as transmission use is increasing in sudden and unpredictable directions. Transmission unbundling, coupled with other regulatory requirements, has made new transmission facility construction more difficult. Unfortunately these transmission lines are frequently subjected to a wide variety of faults. Thus, providing proper protective functions for them is essential. Generally the protection of Extra High Voltage (EHV) and Ultra High Voltage (UHV) transmission lines are carried out by the use of distance relays in view of the fact that they provide fast fault clearance and system coordination. Transmission line relaying involves detection, classification and location of transmission line faults. Fast detections of faults enable quick isolation of the faulty line from service and hence, protecting it from the harmful effects of fault. Classification of faults means identification of the type of fault and faulted line section, and this information is required for finding the fault location and assessing the extent of repair work to be carried out. Accurate fault location is necessary for facilitating quick repair and restoration of the line, to improve the reliability and availability of the power supply. Generally, the protection system using conventional distance relaying algorithm involves three zones. The first zone (Z1) of the relay is set to detect faults on 80%90% of the protected line without any intentional time delay. The second zone (Z2) is set to protect the remainder of the line plus an adequate margin. Second zone relays are time delayed for 1530 cycles to coordinate with relays at remote bus. The settings of the third zone (Z3) ideally will cover the protected line, plus all of the longest line leaving the remote station. Z3 of a distance relay is used to provide the remote backup protection in case of the failure of the primary protection. Since Z3 covers an adjacent line, a large infeed (outfeed) from the remote terminal causes the relay to underreach (overreach). Thus, a very large load at the remote terminal may cause distance relays to mal-operate. Settings for conventional distance relays are selected to avoid overreach/underreach operation under the worst case scenarios. Studies of significant power system disturbances reported by North American Electric Reliability Council (NERC) indicate that protective relays are involved, one way or another, in 75% of the major disturbances and the most troublesome ones are backup protection relays. With their limited view of the interconnected network based on their locally measured inputs, conventional backup protection relays generally take actions to protect a localized region of the network without considering the impact on the whole network. Relay mal-operations or unintended operations due to overload, power swing, and relay hidden failure are the main factors contributing to the blackouts. Most of the problems are associated with relays tripping too many healthy lines. Since a relay makes the decision automatically to remove a component from the system according to its internal mechanism, the relay mal-operation or unintended operation can make an effective influence on the system stability. Approaches to reduce the relay misbehavior need to be identified. Real time monitoring tools to assess the relay misbehavior are needed, providing the system operator, the accurate information about unfolding events. Existing transmission line protection scheme still has drawbacks. Advanced fault analysis mechanism to enhance the system dependability and security simultaneously is desirable. Relay settings play a significant role in major blackouts. So correct settings should be calculated and coordinated by suitable studies. Attempts are to be made to employ highly accurate AI techniques in protective system implementation. The research work focussed on developing knowledge based intelligent tools for the improving the transmission system security. A process to obtain knowledgebase using SVMs for ready post-fault diagnosis purpose is developed. SVMs are used as Intelligent tool for identifying the faulted line that is emanating from a substation and finding the distance from the substation. The approach uses phasor values of the line voltages and currents after the fault has been detected. The approach is particularly important for post-fault diagnosis of any mal-operation of relays following a disturbance in the neighboring line connected to the same substation. This may help in improving the fault monitoring/diagnosis process and coordination of the protective relays, thus assuring secure operation of the power systems. The approach based on SVMs, exploits the first part of this goal. For comparison, a classifier and regression tools based on the RBFNNs was also investigated. The RBFNNs and SVM networks are introduced and considered as an appropriate tool for pattern recognition problems. Results on a practical 24Bus equivalent EHV transmission system of Indian Southern region and on IEEE39 bus New England system are presented to illustrate the proposed method. In a large connected power network, the number of generators are more in number and their set patterns number will be large. As the line flows are sensitive to generator set patterns, it is difficult to consider all the combinations of generators while simulating the training and testing patterns as input to SVMs. To simulate the training and testing patterns corresponding to possible changes in line flows to meet the load in the present deregulated environment, line flow sensitive generators set to be identified/merit-listed. In this regard, to identify the most sensitive generators for a particular line of interest, a method from the literature is adopted and developed a software program based on the graph theory concepts. Case studies on generator contributions towards loads and transmission lines are illustrated on an equivalent 33bus system, a part of Indian Northern grid with major part of Uttar Pradesh and also with an equivalent 246bus system of practical Indian Southern grid. A distance relay coordination approach is proposed using detailed simulation studies, taking into account various operating conditions and fault resistances. Support Vector Machines as a pattern classifier is used for obtaining distance relay coordination. The scheme uses the apparent impedance values observed during fault as inputs. SVMs are used to build the underlying concept between reach of different zones and the impedance trajectory during fault. An improved performance with the use of SVMs, keeping the reach when faced with different fault conditions as well as line flow changes are illustrated with an equivalent 246bus system of practical Indian Southern grid and also with an equivalent 265bus system of practical Indian Western grid. A strategy of Supportive System is described to aid the conventional protection philosophy in combating situations where protection systems are mal-operated and/or information is missing and provide selective and secure coordination. Highly accurate identification/discrimination of zones plays a key role in effective implementation of the region-wide supportive system. This typically requires a multiclass SVM classifier to effectively analyze/build the underlying concept between reach of different zones and the apparent impedance trajectory during fault. Different multiclass methods are compared for their performance with respect to accuracy, number of iterations, number of support vectors, training and testing time. The performance analysis of these methods is presented on three data sets belonging to the training and testing patterns of three supportive systems for a region, part of a network, which is an equivalent 265bus system of practical Indian Western grid.

This study concerns frequency relays and voltage relays applied to the protection of synchronous distributed generators operating in reactive power control mode without a frequency regulation function. The effect of active and reactive powers combination, load power factor, and reactive power imbalance are investigated for their implication for the anti-islanding setting of the frequency relay. Results reveal that the effect of these factors must be considered when setting the relay for islanding detection. For the voltage relay, results reveal that the effect of active and reactive powers combination, load power factor, and active power imbalance must be considered when setting the relay for islanding detection. The effect of multi-stage tripping on the frequency relay ability to detect island was also investigated. Results show that multistage tripping can improve the anti-islanding performance of the frequency relay. / Electrical Engineering / M. Tech. (Electrical Engineering)