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Calculation of short circuit currents in electtrical network
Reiter, Martin ; Vaculík, Petr (referee) ; Toman, Petr (advisor)
First chapters of my bachelor´s thesis are focused on failures of networks, simple characteristics and description of their potential danger. Next chapters are thoroughly focused on the short-circuit, on the short-circuits graphs, on the circumstances which caused them and on their calculation. Next part is about the example, which is counted by the IEC 60909. First example is simple network. Second example is real distribution network 110kV. We are going to cogitate two involves for the real network and we are going to calculate symmetrical and asymmetrical short circuit current. There is summary of knowledge about the short-circuits and evaluation of the real distribution network at the end of my thesis.
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Stabilized operation of a 400 kV power line
Girga, Eduard ; Špaček, Jaroslav (referee) ; Blažek, Vladimír (advisor)
Electrical wiring 400 kV is the most used transfer wiring in the Czech Republic with length over three thousand kilometers. It is frequently used for running out significant output from the big power plants and for its significance in electrical engineering. Theoretical part of this thesis deals with the cross-section of mainly used methods for high and extra high stable wiring voltage solution. These methods can be generally dividend into precise and rough. Both of these methods will be analyzed in next chapters. Exact solution comes out from the presumption of equally spaced parameters. The rough solution uses substitution of double gates wiring, this method is accurate enough and accelerates the calculation. Former mentioned reasons explains it’s often use in technical practice. The electric line is substituted by T-cell, II-cell or Steinmetz cell according to length and required precision. Special method of rough solution is the broad method which enables to solve randomly knotted network by using II-cell to replace electric wiring between single knots. This method is mentioned in thesis for completeness; the network solved by me is not knotted. Part of the theoretical thesis is the analysis of specific transfer cases. In computing part will be mentioned not only the computation of stable wiring state with precise an rough method - with all former mentioned cell but the computation of specific transfer cases as well. In the end will be concluded all the counts from computing part and from precision view evaluated used methods of the stable wiring solution.
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Determination of Acoustic Properties of Sound-Absorbing Materials
Ďurica, Matej ; Řehák, Kamil (referee) ; Prokop, Aleš (advisor)
This diploma thesis is focused on experimental determination of acoustic absorption of four different material samples. The aims of the work include: research on the given issue, determination of the procedure for the performance of a technical experiment and modification of the measuring device for the determination of acoustic absorption. The performed experiments were evaluated and the results of the sound absorption coefficient were compared with the values given by the manufacturer. Sensitivity analyzes of the experiments were performed.
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Testing of a Prototype Device Using Electrochemical Impedance Spectroscopy (EIS)
Zsigmond, András ; Jaššo, Kamil (referee) ; Libich, Jiří (advisor)
.Tato diplomová práce se zabývá elektrochemickými procesy v lítium-iontových bateriích. Pro charakterizaci různých elektrochemických procesů se používá metoda nazývaná elektrochemická impedanční spektroskopie (EIS). V prvních kapitolách jsou popsány různé typy baterií a jejich rozdíly. Práce také obsahuje popis experimentálního zařízení používaného pro EIS. Součástí práce je také porovnání experimentálního zařízení a zařízení od společnosti BioLogic Science Instruments.
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Gel aprotic electrolytes with tetraalkylamonium salts
Michalec, Juraj ; Veselkova, Iuliia (referee) ; Sedlaříková, Marie (advisor)
The essence of this graduate thesis is to summarize knowledge about the aprotic gel electrolytes. In the graduate thesis, there are explained methods for mensuration electrochemical properties of the aprotic gel electrolytes. In the theoretical part, I focus on the knowledge related to gel polymeric electrolytes, their history, properties, mechanisms and application. In the experimental part, I describe the preparation of the samples of the gel polymeric electrolytes, in which I evaluate their properties, electrical conductivity and potencial window.
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Study of the influence of fillers and external conditions on the resistivity of cement composites
Kejda, Dalibor ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The progress of new materials is important for the construction industry. Modern materials include cement composites with reduced resistivity. This is achieved by adding suitable electrically conductive fillers. If there is enough of these fillers, the so-called percolation threshold occurs. Suitable fillers (Condufit C4 and Supragraphite C300) have been proposed. Recipes have been designed to be before and after the percolation threshold. The tests were performed on beams measuring 40x40x160 mm with built-in electrodes for measuring their resistivity. The aim of the work was the research of influencing external conditions on cement composites. The effect of temperature was verified. The lowest values of resistivity were evaluated at temperatures of 50 ° C and the resistivity increased with decreasing temperature. The effect of humidity on the resistivity was then verified. Reference samples and samples with a smaller proportion of graphite powder showed larger differences in resistivities with increasing humidity. The samples above the percolation threshold were not much affected by increasing humidity. Finally, the effect of loading on the resistivity of the samples was verified. Almost all samples with increasing compressive stress showed an increasing value of resistivity.
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Bioimpedance measurement
Pagáčová, Lenka ; Balogh, Jaroslav (referee) ; Sekora, Jiří (advisor)
The work deals with the body analysis using bioimpedance. The work included theory about bioimpedance and methods associated with the analysis. In the practical part is design of the device for measuring body composition including a software for the microcontroller. The assembled device was tested and compared with commercial product Tanita.
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Study of the dielectric properties of perovskite crystals
Mlčkovová, Hana ; Pospíšil, Jan (referee) ; Zmeškal, Oldřich (advisor)
The presented diploma thesis deals with the preparation of perovskite single crystals by inverse thermal crystallization and subsequent study of the basic properties of these hybrid organic-inorganic materials that can be used in various optoelectronic (photodetectors, transistors, lasers, LEDs) or photovoltaic applications. Their behavior in the electric field was studied by impedance spectroscopy. Impedance and capacitance-voltage (C-V) characteristics (frequency dependences) were measured in the dark and in the light. From the impedance dependences for measurements at 0 V voltage in the dark, the equivalent circuit was modeled and its parameters and dielectric constant were determined. From the C-V dependence, Mott-Schottky analysis determined the parameters – "flat-band" potential U_"fb" and charge carrier density N_"C-V" , the parameter – the so-called Warburg coefficient was found, which together with the parameter N_"C-V" was used to calculate the diffusion coefficient D.
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Computing directivity patterns in Comsol Multiphysics
Ryšánek, Martin ; Lukeš, Zbyněk (referee) ; Raida, Zbyněk (advisor)
The individual project – Computing directivity patterns in Comsol Multiphysics. In the first part, the theoretical background for monopole antennas is reviewed. The second part is focused on the analysis of several types of monopoles in COMSOL Multiphysics, and on the calculation of their radiation patterns and impedances. Finally, simulation results are presented and discussed.
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