Before putting new power distribution installation into operation and before the connection to grid is needed to validate connectivity of the installation. Purpose of verification is to check compliance with the technical conditions of relevant regulations. Ones of the most important conditions include compliance with the prescribed connection voltage tolerance at the connecting device – and even in the worst-case – and provide necessary short-circuit capability of the other devices in a connected grid. Main task of my master’s thesis is just checking that the voltage tolerance and the control of short-circuit resistance. The calculations were performed by using the dispatching control system that works with the current parameters of the distribution system equipment 110 kV. Theoretical part of thesis describes two main points of the method of calculating the network operation and the method of calculating short-circuit conditions. Based on these theoretical processes are relevant input data processed and evaluated in the dispatching control system. The calculation and evaluate results are presented in the final part of the master’s work.

This thesis deals with steady running and short-circuit conditions in the 110 kV network, E. ON, fed from 110 kV Otrokovice. Substation Otrokovice ensures system transformation from 400 kV to 110 kV system through three transformers. In order to increase reliability of power supply and improved economy is considered to bridge the transition from the operation of two transformers in bridge operations of the three transformers. However, this brings with it significant worsening of short-circuit conditions in the 110 kV network. The task of this work is to evaluate and compare the two variants of operation in terms of steady running and short-circuit conditions in the network at 110 kV and then implement operational and technical measures. The introduction describes the electricity system and its parts. The theoretical part of the paper discusses ways of dealing with steady running and short circuit conditions of long lines. Practical part will deal with applications of knowledge on the network. The conclusion summarizes the most relevant information and the results assessed both variants.

This master thesis is focused on the synchronous generator mathematical model analysis. Based on the analysis are compiled mathematical models of main generator and exciter cooperating in brushless synchronous generator excitation system. Mathematical models of both machines are based on system of differential equations and their validity is verified in Matlab-Simulink. The master thesis is devided into three main parts. First part is focused on the derivation of differential equations to describe the behavior of electrical quantities of machines. In the second part are compiled and simulated mathematical models of both synchronous machines in Matlab-Simulink. The correctness of models are verified by approximate analytical calculations of selected steady and dynamic states. The last part is focused on design and simulation of concept for main generator rapid field winding deexcitation in brushless synchronous genereator excitation system.

This thesis deals with the steady operation and short-circuit conditions in the 110 kV network E.ON in a separate and parallel operation of nodal areas of Otrokovice substation and Sokolnice substation. The theoretical part is devoted to the calculation of steady state high-voltage systems using Newton's iterative method, transient phenomena that may occur in the power system short-circuit calculations and theories. The practical part deals with the actual calculations of steady state and short-circuit conditions in a separate and parallel operation of nodal areas Sokolnice-Otrokovice, which were calculated using the dispatching program. These calculations are then evaluated for possible use of involvement in actual operation. At the end there are suggestions on operational measures in the network 110 kV.

This thesis deals with load flow calculation of electrical network 110 kV before and after the connection to the 70MW gas supply and the 58MW steam and gas supply. This grid can be powered from two 400/110kV substations, namely Sokolnice and Otrokovice. The load flow calculation is realized for the power supply either from Otrokovice or Sokolnice. Furthermore, the calculation of the uni-phase and three phase short circuits in the substations of 110kV network is realized in this thesis. The result of the thesis is the assessment of the voltage ratio in the network, current load of the power line and short circuit resistance of the substations.

The thesis deals with the analysis of the grid node operation after the connection the nuclear unit. The aim of the master´s thesis is to describe the influence of network´s faults to a nuclear unit. Thesis is dealing with three fundamental problems. An influence of short circuits and power imbalance on the synchronous generator of nuclear power plant and its operation of the island network. The thesis is focused especially on the nuclear unit. However, in the case of any failure in the network, it´s necessary to check other units and their protections in the test system because unit failure could cause the disintegration of the power network. For the purposes of the simulation a test system of the power network has been developed. The test system was optimized in the LUG software, which is used to calculate the power network. Transient simulations are performed in the MODES software. Single faults are configured with scenarios. Results are generated into output files. Analysis of influence network´s faults on the synchronous generator of nuclear power plants. The ability of the synchronous generator to restore the primary steady state or hold the new steady state during changes in operating parameters of the network is one of the important parts of the safe and reliable operation of the power network. During the short circuit the damped transient actions occur. With the extension of the short circuit duration, the amplitude of the transient action increases. The risk of the stability loss of a synchronous generator increases. Therefore, the critical clearing time of a short circuit is being defined, which is the time when there is not any loss of stability. Critical clearing time of research generator is sufficient to turn off the short circuit with the help of its protection (the worst case is 0,8 s). For example, by comparison with the hydroelectric power plant, the critical clearing time is much longer. Models of other power plants have been designed with high reliability so in the case of these faults, it doesn’t cause the disintegration of the power network. Creation of island grid is characterized by strong current surges. Units must be resistant to these surges. In the island grid fast changes of the electrical parameters often occurs. Therefore, units must respond to these changes as quickly as possible and in the broadest limits. For this purpose an island operation regulator is being used. In the case of surplus island grid in steam power plants a dump condenser can be used. This is an important ability of steam power plants because the units are able to react quickly to changes of electrical parameters in island grid. The main result of this thesis is the behavior of the nuclear power plant during various faults in the power network. Researched generator of the nuclear power plant is highly stable against faults in the power network based on the findings. The results allow to continue in this topic with real network and real unit of nuclear power plant.

L’amélioration des systèmes de conversion d’énergie rend les dispositifs à base de SiC très attractifs pour leur efficacité, compacité et robustesse. Cependant, leur comportement en réponse à un défaut de court-circuit doit être soigneusement étudié pour assurer la fiabilité des systèmes. Ce travail de recherche porte sur les problèmes de robustesse et de fiabilité du MOSFET SiC sous contraintes de court-circuit. Cette étude repose sur des caractérisations électriques et microstructurales. La somme de toutes les caractérisations avant, pendant et après les tests de robustesse ainsi que l’analyse microstructurale permet de définir des hypothèses sur l’origine physique de la défaillance pour ce type de composants. De plus, la mesure de la capacité est introduite au cours des tests de vieillissement en tant qu’indicateur de santé et outil clé pour remonter à l’origine physique du défaut. / The improvement of power conversion systems makes SiC devices very attractive for efficiency, compacity and robustness. However, their behavior in response to short circuit mode must be carefulli studied to ensure the reliability of systems. This research work deals with the SiC MOSFET robustness and reliability issues under short-circuit constraints. It is based upon electrical and microstructural characterizations. The sum of all the characterizations before, during and after the robustness tests as well as microstructural analysis allow to define hypotheses regarding the physical origin of failure of such components. Also, caoacitance measurement is introduced during aging tests as a health indicator and a key tool to go back to the physical origin of the defect.

I denna rapport utfördes en selektivplan på uppdrag av Kraftkällan Konsult för ett elnätsbolag i södra Sverige. Det visades att elnätet hade selektiva problem i samtliga stationer mellan reläskydden. Problemen har uppstått då karakteristiken i elnätet ändrats i samband med ombyggnationer. För att lösa problemen simulerades en modell av elnätet i PowerTools för att ta reda på kortslutningsströmmarna och nya selektivkurvor ritades efter dessa. Rekommendationer för högspänningssäkringar i nätstationer har också gjorts baserat på de nya kortslutningsströmmarna.

Les Systèmes Agroalimentaires Localisés représentent des formes d'organisation de productionet de consommation particulières. Ils se différencient des systèmes agro-industriels dans larelation singulière qui unit les hommes, les produits et le territoire, dans la valorisation deressources spécifiques et dans des modalités de coordination géographiquement et socialementsituées. Un nombre croissant d'initiatives cherchent à les mettre en œuvre au travers descircuits courts, des circuits de proximité ou des projets alimentaires territoriaux.Nos travaux proposent d'éclairer d'un regard sociologique les mécanismes de construction deces systèmes alimentaires à partir de l'étude fine d'expériences pionnières. Nous mobilisons lescadres d'analyse déployés par la sociologie de l'innovation et de l'acteur-réseau d'une part, etpar la sociologie des réseaux d'autre part. L'expérience de la coopérative agricole Fermes deFigeac témoigne des processus d'activation du lien entre l'agriculture, l'alimentation et leterritoire, et de valorisation des ressources spécifiques. Ils se matérialisent dans les réseauxsociotechniques qui portent les circuits alimentaires territorialisés. Inspirés du modèle de lacoopération agricole, les responsables de l'organisation soutiennent l'expérimentation d'unedémarche de gouvernance alimentaire afin de coordonner les stratégies individuelles dans desstratégies coopératives pour répondre aux enjeux collectifs de développement.Les analyses révèlent les processus de traduction, de transformation et de médiation quiinterviennent au sein des organisations et à leurs frontières. Ces opérations s'avèrentnécessaires aux constructions collectives et aux coordinations des acteurs (humains et objets,individus et collectifs). Nous montrons le rôle des positions intermédiaires dans l'articulationdes stratégies et les capacités d'adaptation et d'innovation. Nous rendons également compte dela diversité et la variabilité des formes relationnelles qui accompagnent ces dynamiques.Menés dans le cadre d'une recherche-action, nos travaux s'inscrivent dans la volonté de coproductionthéorique et empirique. D'un point de vue opérationnel, nous attirons l'attentionsur l'importance des médiations (animations, documents, échanges…) dans les processuscollectifs et coopératifs et de l'indétermination (imprévisibilité) des dynamiques de changement.Nous proposons de tenir compte des réseaux secondaires et d'identifier les acteursintermédiaires (au-delà des représentants formels) dans les analyses de gouvernance alimentaireterritoriale. / Local Agri-Food System (SYAL) represents a particular form of organization of production andconsumption. SYAL differs from agro-industrial system as it encompass the singular web ofrelationship which unit people, the qualification of products and territory through the valuationof specific resources and the types of coordination that are geographically and socially situated.An increasing number of initiatives try to implement them, through short food circuits,proximity supply chains or local food projects.Our work proposes an empirical journey and a sociological theorizing of the mechanismsthrough which a particular local agri-food system has been enhanced. We mobilize theframeworks of Actor-Network-Theory (ANT) on one hand and by the Social Network Analysis(SNA) on the other hand. We took the opportunity of an in depth study of an agriculturalcooperative named “Fermes of Figeac” to decipher processes of structuration of associationbetween farming practices, food provisioning, territorial human agency and valuation'sprocesses of the specific resources. Those associations are materialized in socio-technicalnetworks, which supported territorialized food supply chain. Inspired by the foundationalmodel of agricultural cooperation, the managerial core set of the organization has experimentedan approach of food provision governance in order to transform individual strategies in cooperativestrategies with the aim to answer sustainable challenge at the local level.Analyses based on ANT and SNA methodology assess translation's, transformation's andmediation's processes that intervene within organizations and on their borders. Going beyond afunctional analysis, we also analyze the collective construction and the coordination of humanagency and objects, at both individual and collective levels. We particularly shed light on therole of intermediation positions in strategic articulations and of the capacities of adaptation andinnovation. We also report the diversity and the variability of the relational forms that sustaindynamics of change.Released in an action-research approach, our work intends to articulate theoretical andempirical production. From an operational point of view, we draw attention to mediations(animations, documents, exchanges…) in the collective and co-operative processes and to theunpredictability of dynamics of change. This leads to take into account secondary networks andto identify intermediaries (beyond the formal core set of managers) in the analysis of territorialfood governance.

<p>Recently, energy storage systems have become more focused towards sustainable energy sources like LIBs due to attractive attributes like high energy density and volumetric density which make them extremely competitive compared to other energy sources for many portable and non-portable applications (smartphones, eVTOLs, stationary storage systems, electric vehicle and so on). Longer cycling stability, capacitance retentive power, lower self-discharge rate and high voltage window are qualitative features in LIB. Even though LIBs are rechargeable energy storage systems, all cells decay and degrade over time causing capacity and power fade due to a number of factors such as manufacturing defects, usage outside the normal operating conditions, and other abuse conditions like overcharge, over-discharge and indentation. This work presents a systematic investigation of several off-nominal conditions which are typically observed in LIBs such as overcharge, over-discharge, nail indentation, periodic overcharge, and over-discharge in order to form a comparative analysis on the effect of each of these conditions on cycle life aging, morphological changes on the cell components and also to evaluate potential internal short circuit (ISC) mechanisms. The cell failure mechanism induced by each condition and its negative impact on the electrochemical performance has been rigorously analyzed in this work based on the proper protocols. The correlation of the galvanostatic performance with the morphological change of the individual electrodes was also scrutinized under SEM and EDS to demarcate the severity of the defect into Li-ion cells. The practical off-nominal condition analysis of LIB will pave the way for more reliable cell functioning and recommendations to be considered to effectively analyze these off-nominal conditions. The analysis was divided into two parts; 1) curve-based analysis which included capacity fade, internal resistance, Incremental & Differential capacity analysis and EIS analysis 2) disassembly-based analysis which consisted of post-mortem visual inspection, morphology-based analysis using electron microscopy and composition analysis. From the capacity fade and IR evolution study, it was observed that periodic off-nominal conditions exhibited the highest rate of capacity fade and the greatest increase in DC internal resistance consistently. The least rate of capacity loss was shown by overcharged and no defect cells and a similar trend for DCIR values as well indicating that there was a positive correlation between capacity fade and internal resistance evolution. From the EIS study a slightly different trend was observed with the overcharged cell exhibiting the highest ohmic resistance and the no defect cell XV </p> <p>the least indicating ORI as an aging mechanism in overcharged and periodic overcharge/over-discharged cells. Another interesting observation was that the highest change in change transfer resistance was shown by over-discharged cell followed by nail-indented and overcharged cells and the least for cells subjected to periodic off-nominal conditions. This was attributed to a large amount of delamination caused by particle cracking in no defect cells causing LAM in these cells, lithium plating in Overcharged, copper current collector dissolution in over-discharged cells which resulted in LLI as the primary aging mechanism in these cells. This was further confirmed by ICA-DVA curve analysis at various capacity fades, postmortem inspection and SEM-EDS analysis. The periodic overcharged cells underwent a combination of degradation mechanisms including LAM from delamination, LLI through lithium deposition on the separators and Contact loss due to electrolyte vaporization causing active material adhesion on the separator and vice versa. The last degradation mechanism exacerbated the rate of increase of internal resistance by blocking pathways for Li+ ion diffusion. To summarize, while no defect and nail-indented cells exhibited primarily one aging mechanism (ORI) other cells exhibited a combination of degradation modes and the decoupling of these modes became increasingly indistinguishable for the cells subjected to periodic off-nominal conditions. Interestingly, no manifestation of soft or hard Internal short circuits was observed in the tested cells. However, it should be noted that for the periodic overcharged cells which underwent excessive lithium plating on the separators and charring of electrodes, dendrite formation could potentially have caused ISC upon further cycling. This cements the fact that periodic off-nominal conditions exacerbate the possibility of sudden failures and accelerate degradation in Li-ion cells. </p>