The thesis reports the results of comprehensive studies carried out to explore the impact of midpoint FACTS Controllers (STATCOM and SVC) on the generator distance phase backup protection in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. In addition, practical, feasible and simple solutions to mitigate the adverse impact of midpoint FACTS Controllers on the generator distance phase backup protection are explored. The results of these studies show that midpoint FACTS Controllers have an adverse effect on the generator distance phase backup protection. This adverse effect, which can be in the form of underreach, overreach or a time delay, varies according to the fault type, fault location and generator loading. Moreover, it has been found that the adverse effect of the midpoint FACTS Controllers extends to affect the coordination between the generator distance phase backup protection and the generator steady-state overexcited capability limit. The Support Vector Machines classification technique is proposed as a replacement for the existing generator distance phase backup protection relay in order to alleviate potential problems. It has been demonstrated that this technique is a very promising solution, as it is fast, reliable and has a high performance efficiency. This will result in enhancing the coordination between the generator phase backup protection and the generator steady-state overexcited capability limit in the presence of midpoint FACTS Controllers. The thesis also presents the results of investigations carried out to explore the impact of the generator distance phase backup protection relay on the generator overexcitation thermal capability. The results of these investigations reveal that with the relay settings according to the current standards, the generator is over-protected and the generator distance phase backup protection relay restricts the generator overexcitation thermal capability during system disturbances. This restriction does not allow the supply of the maximum reactive power of the generating unit during such events. The restriction on the generator overexcitation thermal capability caused by the generator distance phase backup protection relay highlights the necessity to revise the relay settings. The proposed solution in this thesis is to reduce the generator distance phase backup protection relay reach in order to provide secure performance during system disturbances.

The thesis reports the results of comprehensive studies carried out to explore the impact of midpoint FACTS Controllers (STATCOM and SVC) on the generator distance phase backup protection in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. In addition, practical, feasible and simple solutions to mitigate the adverse impact of midpoint FACTS Controllers on the generator distance phase backup protection are explored. The results of these studies show that midpoint FACTS Controllers have an adverse effect on the generator distance phase backup protection. This adverse effect, which can be in the form of underreach, overreach or a time delay, varies according to the fault type, fault location and generator loading. Moreover, it has been found that the adverse effect of the midpoint FACTS Controllers extends to affect the coordination between the generator distance phase backup protection and the generator steady-state overexcited capability limit. The Support Vector Machines classification technique is proposed as a replacement for the existing generator distance phase backup protection relay in order to alleviate potential problems. It has been demonstrated that this technique is a very promising solution, as it is fast, reliable and has a high performance efficiency. This will result in enhancing the coordination between the generator phase backup protection and the generator steady-state overexcited capability limit in the presence of midpoint FACTS Controllers. The thesis also presents the results of investigations carried out to explore the impact of the generator distance phase backup protection relay on the generator overexcitation thermal capability. The results of these investigations reveal that with the relay settings according to the current standards, the generator is over-protected and the generator distance phase backup protection relay restricts the generator overexcitation thermal capability during system disturbances. This restriction does not allow the supply of the maximum reactive power of the generating unit during such events. The restriction on the generator overexcitation thermal capability caused by the generator distance phase backup protection relay highlights the necessity to revise the relay settings. The proposed solution in this thesis is to reduce the generator distance phase backup protection relay reach in order to provide secure performance during system disturbances.

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Ziel der Arbeit war es, eine Client-Server-basierte Loesung zu entwickeln, welche eine Backupfunktionalitaet in einer heterogenen Workstationumgebung mit dezentralen Filesystemen bereitstellt. Das System sollte mit Hilfe einer Scriptsprache implemetiert werden, um die Systemunabhaengigkeit der Komponenten zu gewaehrleisten. Zu diesem Zwecke wurde als Grundlage das ¨Remote Scripting Environment¨, welches Gegenstand der Diplomarbeit von Andre Glaesz am Lehrstuhl Betriebssysteme war, gewaehlt.

Fuel cell technology has undergone significant development in the past 15 years, spurred in part by its unique energy conversion characteristics; directly converting chemical energy to electrical energy. As fuel cell technology has past through the prototype/pre-commercialisation development, there is increasing interest in manufacturing and application issues. Of the six different fuel cell types pursued commercially, the Proton Exchange Membrane (PEM) fuel cell has received the greatest amount of research and development investment due to its suitability in a variety of applications. A particular application, to which state-of-the art PEMFC technology is suited, is backup/uninterruptible power supply (UPS) systems, or stand-by power systems. The most important feature of any backup/UPS system is reliability. Traditional backup power systems, such as those utilising valve regulated lead acid (VRLA) batteries, employ remote testing protocols that acquire battery state-of-health and state-of-charge information. This information plays a critical role in system management and reliability assurance. A similar testing protocol developed for a PEM fuel cell would be a valuable contribution to the commercialization of these systems for backup/UPS applications. This thesis presents a novel testing and analysis procedure, specifically designed for a PEM fuel cell in a backup power application. The test procedure electronically probes the fuel cell in the absence of hydrogen. Thus, the fuel cell is in an inactive, or passive, state throughout the testing process. The procedure is referred to as the passive state dynamic behaviour (PSDB) test. Analysis and interpretation of the passive test results is achieved by determining the circuit parameter values of an equivalent circuit model (ECM). A novel ECM of a fuel cell in a passive state is proposed, in which physical properties of the fuel cell are attributed to the circuit model components. Therefore, insight into the physical state of the fuel cell is achieved by determining the values of the circuit model parameters. A method for determining the circuit parameter values of many series connected cells (a stack) using the results from a single stack test is also presented. The PSDB test enables each cell in a fuel cell stack to be tested and analysed using a simple procedure that can be incorporated into a fuel cell system designed for backup power applications. An experimental system for implementing the PSDB test and evaluating the active performance of three different PEM fuel cells was developed. Each fuel cell exhibited the same characteristic voltage transient when subjected to the PSDB test. The proposed ECM was shown to accurately model the observed transient voltage behaviour of a single cell and many series connected cells. An example of how the PSDB test can provide information on the active functionality of a fuel cell is developed. This method consists of establishing baseline performance of the fuel cell in an active state, in conjunction with a PSDB test and identification of model parameter values. A subsequent PSDB test is used to detect changes in the state of the fuel cell that correspond to performance changes when the stack is active. An explicit example is provided, where certain cells in a stack were purposefully humidified. The change in state of the cells was identified by the PSDB test, and the performance change of the effected cells was successfully predicted. The experimental test results verify the theory presented in relation to the PSDB test and equivalent circuit model.

Made available in DSpace on 2014-06-12T15:56:49Z (GMT). No. of bitstreams: 2 arquivo2997_1.pdf: 2902249 bytes, checksum: 0400469daafc0cecd48c85c7dffb770d (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / O atual modelo de negócios de uma empresa moderna está cada vez mais dependente das tecnologias e dos sistemas de informação. Com isso, é necessário que se mantenha os dados protegidos através de uma cópia segurança, conhecida como backup, que garantirá a restauração e migração dos dados quando necessário. Além disso, é comum uma empresa adotar mais de um Sistema de Gerenciamento de Banco de Dados (SGBD) para armazenamento dos dados, gerando ambientes heterogêneos e dificultando a interoperabilidade entre os sistemas quando necessário. Isso porque os SGBD existentes realizam backup, restauração e migração dos dados sob tecnologias específicas e limitadas como (Oracle, Sqlserver, Mysql), não permitindo a restauração dos dados em outros SGBD, somente no seu ambiente de origem. Nesse contexto, este trabalho propõe o desenvolvimento de uma estrutura padrão para os arquivos de backup, utilizando a linguagem de marcação eXtensible Markup Language (XML), denominada como Backup Markup Language (BKPML). A BKPML tem por objetivo desvincular a dependência dos arquivos de backup de sua fonte de origem, possibilitando manter a interoperabilidade necessária entre SGBD heterogêneos através dos arquivos de backup, e a transformação dos dados para arquivos secundários, como TEXTO, EXCEL, JavaScript Object Notation (JSON), YAML Ain t Markup Language (YAML), Comma-Separated Values (CSV) e XML. Para isso, foi necessário o desenvolvimento de uma ferramenta responsável por administrar os arquivos BKPML gerados. Como proposta de armazenamento seguro, além do armazenamento local, este trabalho utiliza Cloud Computing como alternativa para armazenamento dos arquivos BKPML

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Multi-radio multi-channel wireless mesh networks (WMNs) have been the focus of numerous research efforts during the past few years. These efforts aimed at extending the utilization of technologies based on the IEEE 802.11 standard in large-scale communities and even for city wide networking. However, mesh nodes in these networks are typically limited in their resources (e.g., bandwidth, power and radio interfaces). Such a limitation has led to an unsatisfactory network performance as well as users dissatisfaction. This dissertation addresses three important performance issues related to WMNs, namely, network performance enhancement, network survivability and green communications. To address the first issue, a novel quality of service (QoS) aware joint channel assignment (CA) and routing algorithm is developed. The proposed algorithm employs both dynamic and static CA techniques and corresponding link schedules that maximize the network throughput and minimize the delay and packet loss ratio. Next, the thesis addresses the problem of network survivability and theoretically analyzes the effects of node failure probabilities on the ability of the remaining network nodes to maintain their connectivity. A tight upper bound on the node failure probabilities needed to maintain full network connectivity on the one hand is first developed. On the other hand, a lower bound, at which the system loses connectivity, is also derived. We show that these bounds are dependent only on the nodes' geometric distribution and density. Based on the premise that failure of nodes in a small area may lead to failure of dependent nodes in other areas due to the quick divergence of traffic in these areas, an efficient node failure backup scheme is presented. The scheme relies on the capacity of the surviving network components in order to find new paths that do not overload the neighbours of the failed node which reduces the probability of generating congestion. Finally, the thesis addresses the problem of realizing energy-efficient WMNs that can operate using renewable energy sources. In these systems, batteries are often used to store and regulate the use of the supplied green energy to transmit the received data at each network router in order to overcome the problem of supply fluctuating of various energy sources. To realize these networks, the behaviour of the residual energy of the battery at a heavily loaded green wireless mesh node with a general traffic arrival and energy charging functions is first analyzed. Based on obtained theoretical results, both an online and an offline QoS aware packet scheduling schemes are proposed to minimize the probability of depleting the battery. Each of the aforementioned contributions is supported with various experimental evaluations to demonstrate the achieved performance enhancements.

This diploma thesis focuses on ways of backing up data and their practical use in a specific proposal for Transroute Group s.r.o.. In the introduction part the theoretical knowledge on this issue is presented. Next part of the thesis deals with the analysis of the current state of backup in the company. This section is followed by a chapter where several solutions are presented each with their financial evaluation. The ending part is composed of the choice of a specific solution and a time estimate for its implementation.