Reconfiguration is needed to meet the fight-through and survivability requirements of a shipboard power system. Reconfiguration involves the re-arrangement of power system topology through the opening and switching of breakers, and adjusting of total generators and load values. When the power system is reconfigured, the protection system needs to be attuned to the new power system state. This thesis focuses on developing an adaptive protection scheme for shipboard power systems that will automatically update relay settings after changes in power system topology and operational state. The developed adaptive protection scheme employs four main algorithms to achieve its goal. A topology-recognition algorithm uses the statuses (open/close) of breakers to determine the topological-configuration of the system. A powerlow and a fault-analysis algorithm are used to determine the system?s normal and fault currents, respectively. A protection-setting algorithm is used to determine and set the operating parameters of all the relays in the system. The scheme was implemented in MATLAB miles and tested on various configurations of a notional shipboard power system. The tests results were verified in CAPE.

Microgrids form small-scale power grids with distributed energy resources such as wind generators, photovoltaic panels, fuel cells, energy storage systems, and controllable loads. The characteristics of a microgrid include bi-directional power flows, flexible modes of operation, as well as variable short circuit currents. Due to the weak injection of fault current and short period nature, the connection of microgrids to the distribution systems or sub-transmission systems creates serious challenges to existing over-current based protection systems. The protection of microgrids is gaining substantial attentions in recent years because of large-scale deployment of microgrids and its impacts to existing electricity infrastructures. New protection methodologies and solutions applicable for microgrids are studied and presented in this dissertation. To effectively protect the microgrids, three areas of study are conducted based on the latest technologies in the protection systems, computing platforms, and communication networks. Firstly, the Point of Interconnection protection using distance protection with residual voltage compensation method for an ungrounded microgrid network is presented. This study resolves the challenging issues of detecting single-phase-to-ground fault at the interconnection line of microgrid. It can correctly identify the fault, properly measure the fault location, and timely isolate the fault without jeopardizing the stability of downstream microgrid system and/or causing dangerous overvoltage and arcing conditions. Secondly, the distribution substation busbar protection using the synchrophasor data is studied to realize fast and reliable bus differential protection. Comparing with other busbar protection schemes, this method has the advantages of low cost, easy configuration, fast expansion, and no circuit limitation. Lastly, an adaptive protection solution for distribution feeders with microgrids is developed and tested using RTDS. This study focuses on providing a framework for microgrid over-current coordination to improve the reliability and dependability of the protected network. Overall, the research studies presented in this dissertation will provide the power industries with new insights and methodologies on microgrid protection. Together with other protection functions, the proposed methods can provide effective microgrid protection against dangerous faults, reduce arcing condition, increase the possibility of seamless islanding, and consequently improve the reliability and resilience of microgrids.

A expansão de geração distribuída nos sistemas de distribuição e de subtransmissão de energia elétrica em todo o mundo tem sua origem na reestruturação do setor elétrico, na necessidade de aproveitamento de diferentes fontes primárias de energia, nos avanços tecnológicos, nos incentivos governamentais e na maior conscientização sobre conservação ambiental. Com tal expansão, surge a necessidade de avaliar os impactos dessa forma de geração na operação das redes elétricas, principalmente das redes de distribuição, as quais foram inicialmente projetadas para operar considerando apenas a subestação de distribuição como fonte de energia. Entre esses impactos, um importante item a co0nsiderar é a detecção de ilhamento. Tal ocorrência é altamente indesejada pelas concessionárias distribuidoras de energia elétrica as quais estabelecem que os proprietários de geradores distribuídos devem instalar um sistema de proteção capaz de detectar ilhamentos. Dentre os métodos empregados para detecção de ilhamento os mais comuns para este propósito são os relés baseados em medidas de freqüência (relé de sub/sobrefreqüência, relé de taxa de variação de freqüência). Tais dispositivos são fortemente dependentes do desbalanço de potência ativa na rede ilhada e podem falhar caso esses desbalanços sejam pequenos. Ressalta-se que o comportamento variável da carga em sistemas de distribuição e a possibilidade de formação de diversas ilhas podem originar diferentes níveis de desbalanço de potência ativa e reativa. Conseqüentemente, pode haver vários cenários de operação em que os relés previamente citados falharão em detectar ilhamento. Neste contexto, esta dissertação de Mestrado propõe metodologias de proteção adaptativa anti-ilhamento aplicadas a relés baseados em medidas de freqüência, que visem a proteção do sistema elétrico e do gerador distribuído na maioria das condições de desbalanço de potência ativa e reativa que possam ocorrer na rede elétrica. Os geradores distribuídos a serem analisados são do tipo síncrono devido a sua grande utilização em pequenas centrais hidroelétricas e térmicas. São propostas duas metodologias: uma baseada em simulações dinâmicas e outra baseada em fórmulas analíticas. Os resultados obtidos foram satisfatórios para vários cenários de operação de um gerador distribuído conectado em uma rede de distribuição. Além disso, as vantagens e limitações de cada método são apresentadas e discutidas. / Distributed generation expansion worldwide has been caused by the de-regulamentation of the electricity sector, by the necessity to explore different energy resources, by technological advances, by government incentives and by environmental concerns associated with energy production. Such expansion brings the necessity to assess he impacts caused by distributed generators on the distribution systems, which were designed to operate considering the utility substation as the only power source. Among these impacts, on that deserves major attention is islanding detection. Utilities recommend that distributed generators\' owners provide efficient anti-islanding protection installed at the point of common coupling between the generator and the grid. Common anti-islanding protection schemes are composed by frequency-based relays (standard frequency relay and/or rate of change of frequency relay). These devices are strongly dependent on the active power imbalance in the islanded system and they can fail to detect an islanding condition if such power imbalance is small. Therefore, it is worth pointing that the variable power consumption of the distribution system\'s loads and the possibility of creating several energized islands can originate different power imbalance levels. Consequently, there may be various operating scenarios in which the frequency-based relays will fail to detect islanding. In this context, this work proposes adaptive methods to adjust frequency-based relays in order to provide effective anti-islanding protection considering different power imbalance levels. Synchronous generators are studied, since their wide application in distributed generation plants, such as small hydro and thermal power plants. Two methods are proposed: one is a simulation-based method and the other is based on analytical formulas. Both methods presented good results considering all the operating scenarios tested with a distributed generator connected to a distribution system. Furthermore, their advantages and limitations are presented and discussed.

A expansão de geração distribuída nos sistemas de distribuição e de subtransmissão de energia elétrica em todo o mundo tem sua origem na reestruturação do setor elétrico, na necessidade de aproveitamento de diferentes fontes primárias de energia, nos avanços tecnológicos, nos incentivos governamentais e na maior conscientização sobre conservação ambiental. Com tal expansão, surge a necessidade de avaliar os impactos dessa forma de geração na operação das redes elétricas, principalmente das redes de distribuição, as quais foram inicialmente projetadas para operar considerando apenas a subestação de distribuição como fonte de energia. Entre esses impactos, um importante item a co0nsiderar é a detecção de ilhamento. Tal ocorrência é altamente indesejada pelas concessionárias distribuidoras de energia elétrica as quais estabelecem que os proprietários de geradores distribuídos devem instalar um sistema de proteção capaz de detectar ilhamentos. Dentre os métodos empregados para detecção de ilhamento os mais comuns para este propósito são os relés baseados em medidas de freqüência (relé de sub/sobrefreqüência, relé de taxa de variação de freqüência). Tais dispositivos são fortemente dependentes do desbalanço de potência ativa na rede ilhada e podem falhar caso esses desbalanços sejam pequenos. Ressalta-se que o comportamento variável da carga em sistemas de distribuição e a possibilidade de formação de diversas ilhas podem originar diferentes níveis de desbalanço de potência ativa e reativa. Conseqüentemente, pode haver vários cenários de operação em que os relés previamente citados falharão em detectar ilhamento. Neste contexto, esta dissertação de Mestrado propõe metodologias de proteção adaptativa anti-ilhamento aplicadas a relés baseados em medidas de freqüência, que visem a proteção do sistema elétrico e do gerador distribuído na maioria das condições de desbalanço de potência ativa e reativa que possam ocorrer na rede elétrica. Os geradores distribuídos a serem analisados são do tipo síncrono devido a sua grande utilização em pequenas centrais hidroelétricas e térmicas. São propostas duas metodologias: uma baseada em simulações dinâmicas e outra baseada em fórmulas analíticas. Os resultados obtidos foram satisfatórios para vários cenários de operação de um gerador distribuído conectado em uma rede de distribuição. Além disso, as vantagens e limitações de cada método são apresentadas e discutidas. / Distributed generation expansion worldwide has been caused by the de-regulamentation of the electricity sector, by the necessity to explore different energy resources, by technological advances, by government incentives and by environmental concerns associated with energy production. Such expansion brings the necessity to assess he impacts caused by distributed generators on the distribution systems, which were designed to operate considering the utility substation as the only power source. Among these impacts, on that deserves major attention is islanding detection. Utilities recommend that distributed generators\' owners provide efficient anti-islanding protection installed at the point of common coupling between the generator and the grid. Common anti-islanding protection schemes are composed by frequency-based relays (standard frequency relay and/or rate of change of frequency relay). These devices are strongly dependent on the active power imbalance in the islanded system and they can fail to detect an islanding condition if such power imbalance is small. Therefore, it is worth pointing that the variable power consumption of the distribution system\'s loads and the possibility of creating several energized islands can originate different power imbalance levels. Consequently, there may be various operating scenarios in which the frequency-based relays will fail to detect islanding. In this context, this work proposes adaptive methods to adjust frequency-based relays in order to provide effective anti-islanding protection considering different power imbalance levels. Synchronous generators are studied, since their wide application in distributed generation plants, such as small hydro and thermal power plants. Two methods are proposed: one is a simulation-based method and the other is based on analytical formulas. Both methods presented good results considering all the operating scenarios tested with a distributed generator connected to a distribution system. Furthermore, their advantages and limitations are presented and discussed.

The power industry is currently in the process of re-inventing itself. The unbundling of the traditional monopolistic structure that gave birth to a deregulated electricity market, the mass tendency towards a greener use of energy, the new emphasis on distributed generation and alternative renewable resources, and new emerging technologies have revolutionized the century old industry. Recent blackouts offer testimonies of the crucial role played by protection relays in a reliable power system. It is argued that embracing the paradigm shift of adaptive protection is a fundamental step towards a reliable power grid. The adaptive philosophy of protection systems acknowledges that relays may change their characteristics in order to tailor their operation to prevailing system conditions. The purpose of this dissertation is to present methodology to implement a security/dependability adaptive protection scheme. It is argued that the likelihood of hidden failures and potential cascading events can be significantly reduced by adjusting the security/dependability balance of protection systems to better suit prevailing system conditions. The proposed methodology is based on Wide Area Measurements (WAMs) obtained with the aid of Phasor Measurement Units (PMUs). A Data Mining algorithm known as Decision Trees is used to classify the power system state and to predict the optimal security/dependability bias of a critical protection scheme. / Ph. D.

As the world moves further into the 21st century, the electricity demand worldwide continues to rapidly grow. The power systems that supply this growing demand continue to be pushed closer to their limits. When those limits are exceeded, system blackouts occur that have massive societal and economical impact. Power system protection relays make up a piece of these limits and can be important factors in preventing or causing a system blackout. The purpose of this thesis is to present a working implementation of an adaptive protection scheme known as the adaptive voting scheme, used to alter the security/dependability balance of protection schemes. It is argued that as power system conditions change, the ability of protection relays to adjust the security/dependability balance based on those conditions can allow relays to play a part in preventing power system catastrophes. It is shown that the adaptive voting scheme can be implemented on existing protection technology given Wide Area Measurements (WAMs) provided by Phasor Measurement Units (PMUs). The proposed implementation characteristics allow numerous existing protection practices to be used without changing the basic operation of the practices. / Master of Science

The electrical distribution system in the United States is considered one of the most complicated machines in existence. Electrical phenomena in such a complex system can inflict serious self-harm. This requires damage prevention from protection schemes. Until recently, there was a safe gap between capacity to deliver power and the demand. Therefore, these protection schemes focused on dependability allowing the disconnection of lines, transformers, or other devices with the purpose of isolating the faulted element. On some occasions, the disconnections made were not necessary. The other extreme of reliability calls for security. This aspect of reliability calls for the operation of the protective devices only for faults within the intended area of protection. There is a tradeoff here; where a dependable protection scheme will assuredly prevent damage, it is prone to unnecessary operation which can lead to cascading outages. Where a secure scheme will not operate unnecessarily, it is prone to pieces of the system becoming damaged when relays fail to operate properly. With microprocessor based relaying schemes, a hybrid reliability focus is attainable through adaptive relaying. Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system. These adjustments can help to avoid relay miss-operation. Adjustments could include, but are not limited to, the logging of data for post-mortem analysis, communication throughout the system, as well changing relay parameters. Several concepts will be discussed, one of which will be implemented to prove the value of the new tools available. / Master of Science

Today's electric power system is operated under increasingly stressed conditions. As electrical demand increases, the existing grid is operated closer to its stable operating limits while maintaining high reliability of electric power delivery to its customers. Protective schemes are designed to account for pressures towards unstable operation, but there is always a tradeoff between security and dependability of this protection. Adaptive relaying schemes that can change or modify their operation based on prevailing system conditions are an example of a protective scheme increasing reliability of the power system. The purpose of this thesis is to validate and analyze implementation of the Security-Dependability Adaptive Voting Scheme. It is demonstrated that this scheme can be implemented with a select few Phasor Measurement Units (PMUs) reporting positive sequence currents to a Phasor Data Concentrator (PDC). At the PDC, the state of the power system is defined as Stressed or Safe and a set of relays either vote or perform normal operation, respectively. The Adaptive Voting Scheme was implemented using two configurations: hardware- and software-based PDC solutions. Each was shown to be functional, effective, and practical for implementation. Practicality was based on the latency of Wide Area Measurement (WAM) devices and the added latency of relay voting operation during Stressed conditions. Phasor Measurement Units (PMUs), Phasor Data Concentrators (PDCs), and relay operation delays were quantified to determine the benefits and limitations of WAMS protection and implementation of the voting scheme. It is proposed that the delays injected into the existing protection schemes would have minimal effect on the voting scheme but must be accounted for when implementing power system controls due to the real-time requirements of the data. / Master of Science

The differences between shipboard and land based power systems are explored to support the main focus of this work. A model was developed for simulating hidden failures on shipboard integrated propulsion plants, IPP. The model was then used to evaluate the segregation of the IPP high voltage, HV, buses in a similar fashion as a shipboard firemain. The HV buses were segregated when loss of propulsion power would put the ship as risk. This new treatment reduces the region of vulnerability by providing a high impedance boundary that limits the effects of a hidden failure of a current magnitude or differential based protective element, without the installation of any additional hardware or software. It is shown that this protection could be further improved through the use of a simple adaptive protection scheme that disarms unneeded protective elements in certain configurations. / Master of Science

During the operation in a modern power distribution system, some abnormal events may happen, such as over-voltage, faults, under-frequency and overloading, and so on. These abnormal events may cause a power outage in a distribution system or damages on the equipment in a distribution system. Hence these abnormal events should be identified and isolated by protection systems as quickly as possible to make sure we can maintain a stable and reliable distribution system to supply adequate electric power to the largest number of consumers as we can. To sum up, we need stable and reliable protection systems to satisfy this requirement. Chapter 1 of the dissertation is a brief introduction to my research contents. Firstly, the background of a distribution system and the protection systems in a power system will be introduced in the first subchapter. Then there will be a review of existing methods of optimum coordination of overcurrent relays using different optimal techniques. The dissertation outline will be illustrated in the end. Chapter 2 of the dissertation describes a novel method of optimum online adaptive coordination of overcurrent relays using the genetic algorithm. In this chapter, the basic idea of the proposed methods will be explained in the first subchapter. It includes the genetic algorithm concepts and details about how it works as an optimal technique. Then three different types of simulation systems will be used in this part. The first one is a basic distribution system without distributed generations (DGs); the second one is similar to the first one but with load variations; the last simulation system is similar to the first one but with a distributed generation in it. Using three different simulation systems will demonstrate that the coordination of overcurrent relays is influenced by different operating conditions of the distribution system. In Chapter 3, a larger sized distribution system with more distributed generations and loads will be simulated and used for verifying the proposed method in a more realistic environment. In addition, the effects of fault location on the optimum coordination of overcurrent relays will be discussed here. In Chapter 4, the optimal differential evolution (DE) technique will be introduced. Because of the requirement of the online adaptive function, the optimal process needs to be accomplished as soon as possible. Through the comparison between genetic algorithm and differential evolution on the optimum coordination of overcurrent relays, we found that differential evolution is much faster than the genetic algorithm, especially when the size of the distribution system grows. Therefore, the differential evolution optimal technique is more suited than the genetic algorithm to realize online adaptive function. Chapter 5 presents the conclusion of the research work that has been done in this dissertation.