Um sistema elétrico de potência agrega toda a estrutura pela qual a energia elétrica percorre, desde a sua geração até o seu consumo final. Nas últimas décadas observou-se um significativo aumento da demanda e, consequentemente, um aumento das interligações entre sistemas, tornando assim a operação e o controle destes extremamente complexos. Com o fim de obter a desejada operação destes sistemas, inúmeros estudos na área de Proteção de Sistemas Elétricos são realizados, pois é sabido que a interrupção desses serviços causam transtornos que podem assumir proporções desastrosas. Em sistemas elétricos malhados, nos quais as correntes de curto-circuito podem ser bidirecionais e podem ter intensidades diferentes devido a alterações topológicas nos mesmos, coordenar relés de sobrecorrente pode ser uma tarefa muito trabalhosa caso não haja nenhuma ferramenta de apoio. Neste contexto, este trabalho visa o desenvolvimento de uma metodologia eficiente que determine os ajustes otimizados dos relés de sobrecorrente direcionais instalados em sistemas elétricos malhados de forma a garantir a rapidez na eliminação da falta, bem como a coordenação e seletividade, considerando as várias intensidades das correntes de curto-circuito. Seguindo essa linha de raciocínio, observou-se que o uso de técnicas metaheurísticas para lidar com o problema da coordenação de relés é capaz de alcançar resultados significativos. No presente projeto, dentre os algoritmos inteligentes estudados, optou-se por pesquisar a aplicação do Algoritmo Enxame de Partículas Evolutivo (Evolutionary Particle Swarm Optimization) por este apresentar como características as vantagens tanto do Algoritmo Enxame de Partículas (Particle Swarm Optimization) quanto as dos Algoritmos Genéticos, possuindo assim grande potencial para solução destes tipos de problemas. / An electric power system aggregates all the structure in which the electric energy travels, from its generation to the final user. In the last decades it has been observed a significative increase of the demand and, consequently, an increment of the number of interconnections between systems, making the operation and control of them extremely complex. Aiming to obtain a good operation of this kind of systems, a lot of effort in the research area of power system protection has been spent, because it is known that the interruption of this service causes disorders that may assume disastrous proportions. In meshed power systems, in which the shortcircuit currents might be bidirectional and might have different magnitudes due to topological changes on them, to coordinate overcurrent relays may be a really hard task if you do not have a support tool. Look in this context, this work aims the development of and efficient methodology thats determine the optimal parameters of the directional overcurrent relays in a meshed electric power system ensuring the quickness in the fault elimination, as well as the coordination and selectivity of the protection system, considering the various intensities of the short-circuit currents. Maintaining this line, it has been noticed that the use of metaheuristics to deal with the problem of relay coordination is capable of achieving promissory results. In the present research, among the studied intelligent algorithms, it was chosen to use in it the Evolutionary Particle Swarm Optimization, due to its features thats is the advantages of the Particle Swarm Optimization as well as the Genetic Algorithms ones, hence it has great potential do solve theses kind of problems.

Com o objetivo de orientar e agilizar a busca do local de curto circuitos em redes primárias aéreas de distribuição de energia, esta pesquisa propõe uma metodologia para localização de áreas com maior probabilidade de ser sede do defeito, utilizando variáveis Heurísticas. A metodologia Heurística se aplica em problemas que envolvem variáveis com incertezas, que podem ser avaliadas por meio de recursos empíricos e na experiência de especialistas. Dentre as variáveis influentes no cálculo de curto circuito, foram consideradas como mais relevantes: a resistência de defeito, a tensão pré falta, a impedância do sistema equivalente a montante da subestação e a impedância da rede. A metodologia proposta se fundamenta no conhecimento das correntes e tensões oscilografadas no barramento da subestação por ocasião da ocorrência de um curto circuito e, por outro lado no pré-calculo de correntes de curto circuito heurísticas ao longo da rede. No âmbito da pesquisa foram realizados testes de campo para levantamento da variável heurística resistência de defeito, resumidos neste texto e documentados no CD - ROM em anexo. Foi desenvolvido um software que permitiu a efetiva aplicação da proposta desta pesquisa em vários alimentadores de uma Distribuidora, cujos resultados comprovaram a eficiência da metodologia. / With the aim of guiding and speeding up the search of a short circuits place in primary networks of energy distribution this research proposes a methodology for locating higher probability areas of fault, making use of Heuristic variables. The Heuristic methodology is applied in problems that involve variables with uncertainties, which can be evaluated with empirical tools and specialists experience. Among the influential variables in the short circuit calculation, as most relevant were considered: the faults resistance, the pre fault tension, the equivalent system impedance upstream of the substation and the electrical grid impedance. The proposed methodology relies on the knowledge of currents and tensions oscillografed in the substation bus in consequence of a short circuit and, in another way on the pre calculation of heuristic short circuit currents along the grid. In the research scope field tests were performed with the aim of collecting the fault resistance heuristic variable, resumed in this text and documented on the CD-ROM attached. A software that allowed the actual implementation of this researchs purpose in various feeders of a distributor has been developed, with results that confirmed the efficiency of this methodology.

Electrical contacts provide a well-proven solution to switching various loads in a wide variety of applications, such as power distribution, control applications, automotive and telecommunications. However, electrical contacts are known for limited reliability due to degradation effects upon the switching contacts due to arcing and fretting. Essentially, the life of the device may be determined by the limited life of the contacts. Failure to trip, spurious tripping and contact welding can, in critical applications such as control systems for avionics and nuclear power application, cause significant costs due to downtime, as well as safety implications. Prognostics provides a way to assess the remaining useful life (RUL) of a component based on its current state of health and its anticipated future usage and operating conditions. In this thesis, the effects of contact wear on a set of electromagnetic relays used in an avionic power controller is examined, and how contact resistance combined with a prognostic approach, can be used to ascertain the RUL of the device. Two methodologies are presented, firstly a Physics based Model (PbM) of the degradation using the predicted material loss due to arc damage. Secondly a computationally efficient technique using posterior degradation data to form a state space model in real time via a Sliding Window Recursive Least Squares (SWRLS) algorithm. Health monitoring using the presented techniques can provide knowledge of impending failure in high reliability applications where the risks associated with loss-of-functionality are too high to endure. The future states of the systems has been estimated based on a Particle and Kalman-filter projection of the models via a Bayesian framework. Performance of the prognostication health management algorithm during the contacts life has been quantified using performance evaluation metrics. Model predictions have been correlated with experimental data. Prognostic metrics including Prognostic Horizon (PH), alpha-Lamda (α-λ), and Relative Accuracy have been used to assess the performance of the damage proxies and a comparison of the two models made.

Um relé de distância utilizado na proteção de Linhas de Transmissão é usualmente projetado para atuar sob condições fixas de operação. Portanto, o desempenho destes relés é afetado pela mudança no ponto de operação do sistema. Grandes avanços, relativos à proteção, podem ser alcançados com a implementação de reconhecimento de padrões para o diagnóstico de faltas em sistemas elétricos de potência. Este trabalho demonstra a utilização de Redes Neurais Artificiais operando como um classificador de padrões para a operação de um relé de distância. O projeto utiliza a magnitude dos fasores das três fases de corrente e tensão, de um dos barramentos da Linha de Transmissão, como dados de entrada. O uso de Redes Neurais Artificiais resulta em um melhor desempenho do relé, mantendo seu alcance mesmo diante de diferentes condições de falta ou mudanças no ponto de operação do sistema. / A distance relay for the protection of transmission lines is usually designed on the basis of fixed settings. The performance of such relays is therefore affected by the changing network parameters. The implementation of a pattern recognizer for power system diagnosis can provide great advances in the protection field. This work demonstrates the use of an Artificial Neural Network as a pattern classifier for a distance relay operation. The scheme utilizes the magnitudes of three phase voltage and current phasors, from one busbar of the transmission line, as inputs. An improved performance with the use of an Artificial Neural Networks approach is experienced once the relay can operate correctly, keeping the reach when faced with different fault conditions as well as network parameters change.

Les travaux de la thèse se focalisent sur la protection des réseaux de distribution HTA en présence des générateurs distribués (éoliennes, fermes solaires,...). Dans un premier temps, un état de l’art a été réalisé sur les comportements des générateurs en creux de tension, leurs impacts sur le système de protection et les pistes de solution proposées pour y remédier. L’étape suivante est la mise au point d’algorithmes directionnels de détection de défauts, sans mesure de tension. Ces algorithmes s’appuient sur la décomposition en composantes symétriques des courants mesurés. Ces relais doivent empêcher le déclenchement intempestif de protections de surintensité dû au courant de défaut provenant des générateurs distribués. Ils sont moins coûteux par rapport à ceux traditionnels car les capteurs de tension, qui sont indispensables pour ces derniers, peuvent être enlevés. Après détection d’un défaut sur critère de seuil simple (max de I ou max de I résiduel), la direction est évaluée à l’aide d’un algorithme en delta basé sur les rapports courants inverse-homopolaire ou inverse-direct, selon le type de défaut (monophasé ou biphasé). En se basant sur ces rapports, un classifieur SVM (Support Vector Machines), entrainé préalablement à partir des simulations, donne ensuite l’estimation de la direction du défaut (amont ou aval par rapport au relais). La bonne performance de ces algorithmes a été montrée dans la thèse pour différents paramètres du réseau et en présence de différents types de générateurs. Le développement de tels algorithmes favorise la mise en œuvre des protections en réseau, qui pourraient être installées dans les futurs Smart Grids. / This research focuses on the protection of MV distribution networks with Distributed Generators (DGs), such as wind farms or photovoltaic farms, etc. First, the state of art is carried out on fault behaviour of DGs, their impacts on protection system and the mitigation solutions. Next, algorithms are developed for directional relays without voltage sensors. Based on the symmetrical component method, these algorithms help the overcurrent protections to avoid the false tripping issue due to fault contribution of DGs. With the suppression of voltage sensors, such directional relays become cheaper in comparison with the traditional ones. Following the fault detection (the phase or residual current reaches the pick-up value) and depending on fault type (line-to-ground or line-to-line fault), the ratios between the variation (before and during fault) of negative-zero sequence or negative-positive sequence currents are calculated. From these ratios, a SVM (Support Vector Machines) classifier estimates the fault direction (upstream or downstream the detector). The classifier is trained beforehand from transient simulations. This survey shows good performances of the directional algorithms with different network parameters and different kinds of DGs. Such algorithms could be implemented in protections along the feeders in the future smart grids.

Com o objetivo de orientar e agilizar a busca do local de curto circuitos em redes primárias aéreas de distribuição de energia, esta pesquisa propõe uma metodologia para localização de áreas com maior probabilidade de ser sede do defeito, utilizando variáveis Heurísticas. A metodologia Heurística se aplica em problemas que envolvem variáveis com incertezas, que podem ser avaliadas por meio de recursos empíricos e na experiência de especialistas. Dentre as variáveis influentes no cálculo de curto circuito, foram consideradas como mais relevantes: a resistência de defeito, a tensão pré falta, a impedância do sistema equivalente a montante da subestação e a impedância da rede. A metodologia proposta se fundamenta no conhecimento das correntes e tensões oscilografadas no barramento da subestação por ocasião da ocorrência de um curto circuito e, por outro lado no pré-calculo de correntes de curto circuito heurísticas ao longo da rede. No âmbito da pesquisa foram realizados testes de campo para levantamento da variável heurística resistência de defeito, resumidos neste texto e documentados no CD - ROM em anexo. Foi desenvolvido um software que permitiu a efetiva aplicação da proposta desta pesquisa em vários alimentadores de uma Distribuidora, cujos resultados comprovaram a eficiência da metodologia. / With the aim of guiding and speeding up the search of a short circuits place in primary networks of energy distribution this research proposes a methodology for locating higher probability areas of fault, making use of Heuristic variables. The Heuristic methodology is applied in problems that involve variables with uncertainties, which can be evaluated with empirical tools and specialists experience. Among the influential variables in the short circuit calculation, as most relevant were considered: the faults resistance, the pre fault tension, the equivalent system impedance upstream of the substation and the electrical grid impedance. The proposed methodology relies on the knowledge of currents and tensions oscillografed in the substation bus in consequence of a short circuit and, in another way on the pre calculation of heuristic short circuit currents along the grid. In the research scope field tests were performed with the aim of collecting the fault resistance heuristic variable, resumed in this text and documented on the CD-ROM attached. A software that allowed the actual implementation of this researchs purpose in various feeders of a distributor has been developed, with results that confirmed the efficiency of this methodology.

Smart radial distribution grids will include advanced metering infrastructure (AMI) and significant distributed generators (DGs) connected close to loads. DGs in these radial distribution systems (RDS) introduce bidirectional power flows (BPFs) and contribute to fault current. These BPFs may cause unwanted tripping of existing overcurrent (OC) protection devices and result in permanent outages for a large number of customers. This thesis presents a protection approach that modified an existing overcurrent protection scheme to reduce the number of customers affected by faults in RDS with DGs. Further, a technique is presented that utilizes customers loading information from smart meters in AMI to improve the sensitivity of substation OC relays by adaptively changing the pickup settings. The modified protection approach involves predefining zones in RDS with DGs and installing directional OC relays and circuit breakers at the zonal boundaries. Zonal boundary relays determine faulted zones by sharing information on the direction of detected faults current using binary state signals over a communication medium. The technique to adapt the substation relay pickup settings uses the demand measurements from smart meters for two 12-hour intervals from the previous day to determine the maximum diversified demand at the relay?s location. The pickup settings of the substation relay for the two 12-hour intervals during the following day for the zone supplied by the substation are adaptively set based on the current that corresponds to the maximum diversified demand from the previous day. The techniques were validated through simulations in EMTP/PSCAD using an expanded IEEE 34 node radial test feeder that included DGs and a secondary distribution level. By decentralizing the control of the zonal boundary breakers, the single point of failure was eliminated in the modified protection approach. The cases studied showed that the modified protection approach allows for selective identification and isolation of the faulted zones. Also, the sensitivity of the substation OC relay was improved by at least 24% by using the pickup settings for the two 12-hour intervals from the smart meter demand measurements compared to the pickup settings computed using the conventional methodology based on the maximum loading of the zone.

Η έννοια της ψηφιακής αναμετάδοσης έχει μελετηθεί σαν ένα ϑεωρητικό πρόβλημα από την πλευρά της ϑεωρίας της πληροφορίας στις δεκαετίες του ’70 και ’80 όπου υπολογίστηκε η χωρητικότητα συστημάτων με ένα αναμεταδότη. Το σενάριο στο οποίο η επικοινωνία δύο τερματικών σταθμών πραγματοποείται με τη ϐοήθεια ενός τρίτου το οποίο αναλαμβάνει να αναμεταδόσει την πληροφορία, υλοποιήθηκε αρχικά στους δορυφόρους με ανακλαστική επανεκπομπή. Ενδιαφέρον, σύμφωνα με όσα γνωρίζουμε, προκαλεί το γεγονός ότι δεν υπήρχε έως πολύ πρόσφατα καμία εργασία σχετική με την ϑεωρία της αναμετάδοσης - πιο πιθανή αιτία η μη ύπαρξη σχετικών εφαρμογών. Με την ωριμότητα των ψηφιακών ασύρματων επικοινωνιών και λόγω των ϱαγδαία αυξανόμενων αναγκών για επικοινωνίες υψηλής απόδοσης, ϕαίνεται ότι έφτασε η ώρα για την ανάπτυξη ‘‘έξυπνης’’ αναμετάδοσης στο άμεσο μέλλον. Η παρούσα διδακτορική διατριβή (DD) έρχεται να συμβάλλει προς την κατεύθυνση αυ- τή και να δώσει στους μελετητές των ψηφιακών επικοινωνιών νέες τεχνικές και εργαλεία αναλύοντας και μελετώντας στο ϕυσικό επίπεδο τα ασύρματα τηλεπικοινωνιακά συστήματα (ή δίκτυα) πολλαπλών αλμάτων με μη-αναγεννητικούς αναμεταδότες δηλ. συστήματα στα οποία το σήμα εκπέμπεται από τον πηγαίο κόμβο και ϕθάνει στον κόμβο προορισμού διαμέσου ενός ή περισσοτέρων αναμεταδοτών. Με την τεχνική αυτή καταπολεμούμε τους δύο ϐασικούς παράγοντες υποβάθμισης του εκπεμπόμενου σήματος που είναι η μειωμένη μέση ισχύς λήψης λόγω απόστασης ή/και εμποδίων, και οι διακυμάνσεις του σήματος στη λήψη του, εξαιτίας του ϕαινομένου των διαλείψεων. Βασικός σκοπός της DD είναι η αξιολόγηση των επιδόσεων των συστημάτων πολλαπλών αλμάτων, που λειτουργούν σε περιβάλλον διαλείψεων Rayleigh ή Nakagami-m, με δείκτες επιδόσεων όπως ο μέσος λό- γος σήματος προς ϑόρυβο (ΛΣΘ), η πιθανότητα διακοπής της επικοινωνίας (ΠDΕ) και η μέση πιθανότητα σφάλματος bit (ΜΠΣΒ). Για να επιτευχθούν τα παραπάνω στα πολυαλ- ματικά συστήματα, απαιτείται η στατιστική μελέτη του απ’ άκρο-σε-άκρο ΛΣΘ στην έξο- δο του κόμβου προορισμού για την εξαγωγή σημαντικών στατιστικών συναρτήσεων όπως της συνάρτησης πυκνότητας πιθανότητας (ΣΠΠ), της συνάρτησης αθροιστικής πιθανότητας (ΣΑΠ), της ϱοπο-γεννήτριας συνάρτησης (ΡΓΣ) και των ϱοπών. Οι δείκτες επίδοσης παρουσιάζονται είτε σε κλειστές μαθηματικές μορφές οι οποίες εξάγουν άμεσα αποτελέ- σματα, είτε σε αναλυτικές μορφές για τις οποίες η χρήση της αριθμητικής ολοκλήρωσης είναι απαραίτητη μέσω γνωστών μαθηματικών λογισμικών όπως MATHEMATICA ή MAPLE. Παράλληλα, όπου απαιτείται, παρουσιάζονται αποτελέσματα προσομοίωσης Monte Carlo για την επαλήθευση των αριθμητικών αποτελεσμάτων. Λαμβάνοντας υπόψην όλα τα παραπάνω, ερευνάται ένα σύστημα N αλμάτων σε περι- ϐάλλον διαλείψεων Nakagami-m και παράγονται τόσο σημαντικά αποτελέσματα για την επίδοσή τους όσο και ένα καινοτόμο στατιστικό ϑεώρημα για τη ΡΓΣ τυχαίων μεταβλητών Γάμμα. Η επίδοση των συστημάτων αυτών αξιολογείται για μη-αναγεννητικούς αναμε- ταδότες και συγκεκριμένα, τόσο για αναμεταδότες μεταβλητού κέρδους (ΑΜΚ) δηλ. το κέρδος τους εξαρτάται από την εκτίμηση της κατάστασης του καναλιού (ή κέρδος κανα- λιού) στην είσοδό τους, όσο και για αναμεταδότες σταθερού κέρδους (ΑΣΚ). Επίσης στη DD προτείνεται ένα νέος τύπου μη-αναγεννητικού αναμεταδότη, ο αναμεταδότης συνδυα- σμένου κέρδους (ΑΣυΚ), του οποίου η επίδοση εξετάζεται σε ένα σύστημα διπλού άλματος (δηλ. σ’ ένα σύστημα με έναν αναμεταδότη). Η επίδοσή του συγκρίνεται με αυτή του ΑΜΚ. Η επίδοση του ΑΣυΚ εμφανίζεται να είναι καλύτερη σε κάποιες περιπτώσεις απ’ αυτήν του ΑΜΚ. Ιδιαίτερη ϐαρύτητα δίνεται τέλος και στη μελέτη πολυαλματικών συστημάτων επικοινω- νίας με διαφορική συνεργασία χρηστών. Τα συστήματα αυτά διαφέρουν από τα συμβατικά πολυαλματικά διότι εκμεταλλεύονται τα πλεονεκτήματα της ‘‘εικονικής’’ διαφορικής εκ- πομπής στον πηγαίο κόμβο και τη διαφορική λήψη στον κόμβο προορισμού. Οι δείκτες επίδοσης εξετάζονται είτε για συστήματα διαφορικής συνεργασίας ενός χρήστη, είτε για πολλούς χρήστες με διαφορικό δέκτη συνδυασμού επιλογής ή μεγίστου λόγου στον κόμβο προορισμού, αντίστοιχα. / The concept of digital relaying has been studied as a theoretical problem from a network information theory perspective in 70’s and 80’s, and capacity regions of simple relaying channels have been evaluated. The scenario where the communication between two terminal is achieved with the help of a third terminal, was firstly implemented in bentpipe satellites. To the best of our knowledge, there has been no other analytical study on this concept until very recently due to the fact that there were no foreseeable applications at that time. With the maturity of digital wireless technologies and with the overwhelming demand for high data rate coverage, it seems that time has finally arrived for the implementation of intelligent relaying. The present PhD thesis contributes in that direction and gives to researchers of digital communications new techniques and smart tools by analyzing and studying multihop wireless communications systems in physical layer. In multihop systems, the source terminal transmits a signal which arrives to the destination terminal via a number of relays. By applying relayed transmission we mitigate two main reasons that causes Quality of Service degradation of the received signal, which are the low average receive power, induced by the presence of obstacles or by long distance, or due to the fluctuations in the received signal induced by fading effects. The main subject of this PhD is the evaluation of the performance metrics of multihop wireless communications systems, operating over Rayleigh or Nakagamim fading channels such as average signaltonoise ratio (SNR), outage probability and average biterror rate. To achieve this, the statistics of the equivalent endtoend SNR at the output of the destination terminal is required and specifically the probability density function, the cumulative distribution function, the moments and moment generating function (MGF). The performance metrics are presented either in closed forms giving direct results or in analytical ones where the results are extracted via numerical integration with the use of standard mathematical software packages such as MATHEMATICA or MAPLE. Additionally, Monte Carlo simulation results are also presented for the verification of the numerical results. Considering all the above, a multihop system with Nhops over Nakagamim environment is studied, and important performance results are derived. Also, a novel statistical result regarding the MGF of the product of rational powers of Gamma random variables is presented for the first time in the technical literature. The performance metrics of the multihop system are evaluated for nonregenerative relays and specifically, for both channel state information (CSI)based and fixed gain relays. Moreover, in this PhD thesis a new type of relay is presented, the combined gain relay (CGR), and its performance is studied in dualhop systems. The performance of the CGRs is compared to CSIbased ones whose amplification gain depends on the channel state at their input. It is interesting that CGR performs better in some situations than CSI ones. Finally, we concentrate on multihop wireless communications systems with cooperative diversity. Cooperative diversity systems differ from conventional multihop ones since exploits the benefits of virtual transmit diversity in the source terminal and diversity reception in the destination terminal. Performance analysis is conducted for cooperative diversity systems with one or more users (relays) and selection combiner or maximal ratio combiner at the destination terminal, correspondingly.

I detta examensarbete utreds möjligheten att med hjälp av nya smarta elmätare få en ökad inblick i elkvalitén i elnäten samt att ge nätägare möjligheten att automatiskt eller via fjärrsignal koppla bort solcellsanläggningar i de fall de orsakar dålig elkvalité. Motiveringen till studien har varit att en ökad utbyggnad av solcellsanläggningar med tilhörande växelriktare och en trolig framtida ökning av snabbladdare och andra olinjära laster i näten ökar utmaningen för elnätsföretag att klara gällande krav på elkvalité. Samtidigt har utvecklingen av elmätare gjort att de idag har många funktioner som elnätsföretag kan dra nytta av på sätt som tidigare inte varit möjligt. Studien inleddes med en litteratur-studie där information om vad elmätare idag är kapabla till togs fram. Ett praktiskt test genomfördes på en solcellsanläggning där en elmätare installerades och konfigurerades att koppla bort solcellerna vid över-spänning. Studien har visat att smarta elmätare bör kunna användas som ett långsammare, sekundärt skydd som kopplar bort solceller i de fall som växelriktarna brister i sina säkerhetsfunktioner. Elmätarna kommer också kunna ge nätägare en mängd intressant information om elkvalitén. / In this thesis the possibility for smart meters to give utility companies an increased knowledge about the power quality in the grid has been investigated. During the investigation the possibility to use smart meters to automatically or by remote control disconnect solar power units in case of poor power quality caused by the production units has also been researched. The motivation to perform the study was that a future increase in distributed generation, rapid chargers for electric vehicles and other non-linear loads will make it harder for utility companies to meet the demands concerning power quality. At the same time electricity meters has developed over time and are today capable of providing grid operators with functions that has not been possible in the past. The first part of the study focused on obtaining information about what smart meters are capable of today through a literary study. A practical test was conducted on a solar power unit where a smart meter was installed and configured to automatically disconnect the solar power unit in case of over voltage. The study has shown that smart meters could be used as a slower, secondary protection that disconnects the solar power units in cases where the solar inverters safety functions fails. The smart meters will also be able to give grid operators a large amount of information about the power quality in the grid.

Doctor of Philosophy / Electrical and Computer Engineering / Anil Pahwa / Noel N. Schulz / Microgrids with distributed generators have changed how protection and control systems are designed. Protection systems in conventional U.S. distribution systems are radial with the assumption that current flows always from the utility source to the end user. However, in a microgrid with distributed generators, currents along power lines do not always flow in one direction. Therefore, protection systems must be adapted to different circuit paths depending on distributed generator sites in the microgrid and maximum fuse ampere ratings on busses. Adaptive overcurrent protection focuses on objectives and constraints based on operation, maximum load demand, equipment, and utility service limitations. Adaptive overcurrent protection was designed to protect the power lines and bus feeders of the microgrid with distributed generators by coordinating fuses and relays in the microgrid. Adaptive overcurrent protection was based on the relay setting group and protection logic methods. Non-real-time simulator (NRTS) and real-time simulator (RTS) experiments were performed with computer-based simulators. Tests with two relays in the loop proved that primary relays tripped faster than backup relays for selectivity coordination in the adaptive overcurrent protection system. Relay test results from tripping and non-tripping tests showed that adaptive inverse time overcurrent protection achieved selectivity, speed, and reliability. The RTS and NRTS with two relays in the loop techniques were described and compared in this work. The author was the first graduate student to implement real-time simulation with two relays in the loop at the Burns & McDonnell - K-State Smart Grid Laboratory. The RTS experimental circuit and project are detailed in this work so other graduate students can apply this technique with relays in the loop in smart grid research areas such as phasor measurement units, adaptive protection, communication, and cyber security applications.