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The aim of this thesis is to project an operation of bridge connection in distribution network in Čebín’s nodal area. The main task is to check a fulfilment of voltage tolerance in distribution substations 110 kV, load transformer control (400/110 kV, 110/VN kV), distribution power line 110 kV control and short - circuit conditions control. Relevant calculations are performed by dispatching control system, which works with the actual parameters of all distribution network‘s 110 kV facilities. The theoretical part of this thesis is devoted to the way of the calculation of stabilized operation and the short-circuit conditions. In practical part, first we perform an analyse of stabilized operation and the short-circuit conditions of distribution network 110 kV in actual operation. Next step deals with bridge connection design and analysing its operation. The operation of bridge connection is verificated even in specific conditions (disturbance state, increased load). The next section evaluates the results of the calculations. First we deal with actual operations evaluation and proposed the bridge connection. In the next section we evaluate the operation of the bridge connection in the specific operating conditions. Finally, we evaluate the losses in the distribution network 110 kV. If the calculations of the stabilized operation or the short-circuit conditions of distribution network discovers that some of its elements are overloaded, we propose changes to ensure safe and reliable operation of the distribution network.

Orientador: Carlos Roberto Minussi / Resumo: Esta pesquisa apresenta o desenvolvimento de uma ferramenta para a detecção e classificação de curtos-circuitos em sistemas de distribuição de energia elétrica, a qual é baseada no uso combinado da análise multirresolução e rede neural ARTMAP-fuzzy. A análise multirresolução permite a identificação de singularidades nas oscilografias e a rede da família ART garante ao sistema classificador a capacidade de aprendizado contínuo de novos padrões sem perder o conhecimento previamente adquirido. Todo o processo de diagnóstico é realizado em uma única etapa, reduzindo o custo computacional da metodologia. A eficiência do sistema é verificada por uma análise direta, na qual se contabiliza a quantidade total de acertos, e por uma avaliação comparativa, a qual envolve a substituição da rede ARTMAP-fuzzy pela rede ARTMAP-Euclideana. Resultados mostram que o sistema é eficiente, sendo capaz de detectar e classificar 100% das falhas elétricas. / Abstract: This research presents the development of a tool for the detection and classification of short circuits in electric power distribution systems, which is based on the combined use of multi-resolution analysis and fuzzy ARTMAP neural network. The multiresolution analysis allows the identification of singularities in the oscillographs and the ART family network guarantees to the classifier the ability to continuously learn new patterns without losing the previously acquired knowledge. The entire diagnostic process is performed in a single step, reducing the computational effort. The efficiency of the system is verified by a direct analysis, in which the total number of hits is counted, and by a comparative evaluation, which involves the replacement of the fuzzy ARTMAP network by the Euclidean ARTMAP network. Results show that the system is efficient, being able to detect and classify 100% of the electrical faults. / Mestre

More electric aircraft is an electrification scheme of aircraft system with high technical feasibility and good economy. It can reduce the weight of aircraft structure, improve maintenance efficiency and reduce fire hazards. However, the electrification of aircraft system will drastically increase the proportion of electrical equipment, the total power demand and the difficulty of fault diagnosis. This paper uses the energy management method to take up the challenge, with focus on fault diagnosis of permanent-magnet synchronous machines (PMSMs), adaptive load shedding and energy efficient aircraft design. A literature review of the concept evolution from all/more-electric aircraft to energy-optimized aircraft is presented. The main issues of the aircraft electrification process are summarized, and followed by an introduction to the current research and methods. The model of the aircraft electrical system is qualitatively and mathematically recalled, including the generator, the battery, the DC motor, the AC motor, and the electric power converter. The accuracy and computation cost of the aircraft model depends on the complexity of the subsystem models that are involved. Therefore, the level of detail that is necessary for a good precision-versus-simulation-time ratio is discussed by taking the electric system of an industrial level hybrid energy quadcoptor UAV as an example. The analysis shows that the bi-directional instruments, i.e. the electric machine, should be modeled in details while other components can be simplified. PMSMs are a group of on-board electric machines with promising future prospects because of high power density and stability. The model of PMSMs is further developed in this work, especially in the inter-turn and phase-to-phase short-circuit conditions. In case of inter-turn short-circuit fault, a winding-function-based and a fault-current-based model are separately developed. The accuracy of both models are verified and compared through experimental results. The fault-current-based modeling method is applied to the phase-to-phase short-circuit fault and experimentally examined and discussed. General condition monitoring methods require the use of a large number of sensors. A fault detection and isolation method that can have low requirement of sensor is recalled and inherited. The description of the fault phase identification index using this method is relatively imprecise, which is not applicable to the inter-turn short-circuit fault. In this work, the analytical expression of the faulty phase identification index is derived based on the fault models. A method to isolate inter-turn and phase-to-phase short-circuit faults is proposed by a combination of the current- and the voltage-signature residuals. This development expands the application scope of the original fault detection and isolation tool and improves its accuracy. The validity of this fault diagnosis method has been verified by experimental results.Load management is developed to guarantee the normal operation of critical loads by shedding some other loads in case of emergency. Generally, binary decisions are made: either something has gone wrong or everything is fine. However, different types of fault influence the working performance of the load and the entire network in different ways. There are multiple states between totally wrong and pure fine, and the load management decision should be adaptive to each state. In this work, fuzzy logic method is used to degrade the load priority according to the instantaneous working state. Combining it with the fault detection and isolation process, a fault-tolerant adaptive load management is achieved. Finally, this work discusses the aircraft design from the energy management point of view, which consists of the energy efficiency analysis and the multidisciplinary energy efficient design of the integrated aircraft system. The first thermodynamic efficiency has been widely used as a common parameter for depicting the energy utilization, i.e. the ratio of output to input power of the system. However, it ignores the irreversible increase of the entropy and cannot reveal the upper limit of the available work of the system.Based on the second thermodynamic law, this work uses the exergy parameters to analyze the energy utilization of a MEA design scheme. Based on the exergy analysis, an energy-efficient aircraft design method is proposed by optimizing the exergy lost of the whole design. The method could provide a global optimization reference for the integrated aircraft design of a MEA. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Currently, the nodal areas of Neznášov substation and Krasíkov substation, which belong to ČEZd distribution network 110 kV – East, are operand as separate units. In the defined setting, each nodal area comprises of two 400/110 kV transformers. In the case of failure of the transformer T401 or T402, the criterion N-1 for twenty percent of the rated output is not met. Such problem can be solved by parallel operation of nodal areas of Neznášov substation and Krasíkov substation. The principal as well as practical aim of this thesis is to interconnect the bridge operated connection in separated areas into parallel/loop operation of nodal areas (supplied by 400/110 kV transformers). Computing software is used to calculate the steady state and short-circuit conditions in the distribution network 110 kV for separate and parallel operation of mentioned nodal areas. Power flow analysis is aimed at assessment and evaluation of voltage conditions, transformers loading (400/110 kV and 110/vn) as well as 110 kV lines loading. Obtained short-circuit indices is used to examine short-circuit, withstand capability of the 110 kV substation. Finally, benefits as well as drawbacks of the separate and parallel operation are compared and evaluated. If necessary, the technical arrangements are proposed/designed in order to allow parallel operation of nodal areas Neznášov substation and Krasíkov substation.

This master's thesis consists of three parts. The theoretical part deals with short-circuit conditions in the electricity supply system and with the method of their calculation. The practical part includes the programming process of a programme; description of programme properties and functionality. The third part contains the verification of an accurate programme calculation of the examples.

While changing the connection of the power transformators we have to find out if the powered distribution network can accept this change and if it will fulfil the set conditions. Important is to keep the range of permitted voltage on separate distribution points of this network and to find out proportions on separate circuits. This is connected with a circuit load which cannot exceed its limit (transmission capacity). The network is checked against outages of separate circuits (N-1) and we try to find out if other circuits are not overloaded during the transmission of the outaged circuit’s power. We can also suggest various other possible outages. It is also important to find out whether separate distribution points agree with their short-circuit capabilities. Overall we investigate advantages of this circuit. The theoretical part describes the means of calculation of the network functioning and short-circuit conditions. All the calculated results (dispatcher control system Sinaut Spectrum) for the given circuits of power transformators are processed and evaluated in the practical part of the thesis.

The thesis deals with the problematics of short-circuit current of synchronous machine. The first section focuses on the theoretical process of short-circuit current of synchronous machine and describes how this transient process changes throughout it's duration and with what reactances and time constants it is defined. Subsequently, this section deals with the methodics of tests of the snychronous machine,which may be used to set it's reactances. The second part of the work focuses on measurement of the short-circuit current in a specific synchronous machine. Further, there are measurements of processes of the short-circuit in time and their analysis. The last section of the thesis deals with the simulation of short-circuit current process. The simulation is ran by the Matlab/Simulink software. Simulated processes of short-circuit are then compared with the results of measurements from the previous section of the thesis.

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Les travaux de cette thèse ont été menés dans le cadre d’une collaboration entre les laboratoires SATIE et LTN IFSTTAR. Ils portent principalement, sur l’étude de la robustesse des composants JFET SiC de puissance pour des applications de découpage à haute fréquence, forte puissance surfacique et à haute température lorsqu’ils sont soumis à des régimes extrêmes de fonctionnement. Les travaux présentés traitent également de façon plus générale l’étude de la durée de vie de packaging dédiés à ce type de composants et adaptés à la haute température pour des applications aéronautiques. La robustesse de différents lots des VJFETs SiC d’un fabricant particulier (SemiSouth) a été étudiée en régimes d’avalanche et de court circuit afin de déterminer les énergies que peuvent supporter ces composants dans ces modes de fonctionnement particuliers en cherchant notamment à quantifier la température du cristal et à mettre en évidence les mécanismes physiques à l’origine des défaillances. Nous avons ainsi également développé un modèle éléments finis thermique afin d’estimer la température de jonction du JFET SiC lors des régimes extrêmes pour chercher à relier l’apparition de la défaillance à la température. Finalement, nous décrivons des mécanismes physiques à l’origine des dégradations lors de la répétition de tels régimes extrêmes de fonctionnement expliquant à terme la destruction par vieillissement des transistors. Un substrat céramique à base de Si3N4 a été le support des études menées dans le cadre de cette thèse sur le packaging. Nous avons caractérisé les dégradations de ces substrats par des analyses acoustiques après vieillissement par cyclage thermique de forte amplitude. Un modèle thermomécanique a été développé afin d’estimer les contraintes mécaniques dans l’assemblage et valider les résultats expérimentaux obtenus. Enfin, nous avons également initiés des travaux de diagnostic thermique sur des puces JFET SiC, par des mesures d’impédance thermique pouvant être utilisées pour la détection de défauts de délaminage dans un assemblage de puissance. / The work presented in this thesis was conducted between SATIE and LTN IFSTTAR laboratories. It focuses on the study of the robustness of SiC power components subjected to hard working conditions for high switching frequency, high power density and high temperature applications. The work also presents a study on the robustness of a dedicated package adapted to high temperature applications. The robustness of several SiC VJFETs from a particular manufacturer (SemiSouth) was studied in avalanche and short circuit modes in order to estimate the energies that can withstand these components in these operating modes. The experimental protocol also includes thermal models to quantify the crystal temperature and to highlight the ageing physical mechanisms causing failure. Therefore, we had developed a finite element model to estimate the thermal junction temperature of the SiC JFET in extreme working conditions to try to relate the failure to the maximum temperature reached after each cycle. Finally, we described the physical mechanisms behind the degradations that explain ultimately the destruction of ageing transistors under repetitive avalanche mode. A ceramic substrate made of Si3N4 has been the support of studies conducted in this thesis on the packaging reliability. We characterized the degradation of these substrates by acoustic analysis after ageing by thermal cycling of high amplitude. A thermo-mechanical model was developed to estimate the mechanical stresses in the assembly and validate the experimental results. Finally, we have initiated thermal diagnostic studies on SiC JFET chips. We have shown that thermal impedance measurements can be used for the detection of delamination defects in a power assembly.