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Conventional energy sytems in numbers
Mičánek, Jiří ; Paar, Martin (referee) ; Vyčítal, Václav (advisor)
Tato práce hodnotí možné budoucí energetické mixy pro Českou republiku. Uvádí údaje týkající se jednotlivých dostupných energetických zdrojů se zaměřením na výrobu elektřiny. Emise skleníkových plynů a další relevantní parametry jsou váženy a použity k hodnocení různých návrhů pomocí Pughovy matice, která umožňuje objektivně kvantifikovat scénáře. Pro zjištění názorů veřejnosti a ověření, zda se údaje dostupné prostřednictvím výzkumu shodují s jejími názory, je použit průzkum. Metodiky použité k hodnocení scénářů jsou podrobeny kritice a jsou uvedena doporučení, které z nich by měly být vyřazeny a jak zlepšit opakovanou analýzu.
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Impact of cross-country double earth faults on voltage condition in LV networks
Fojtášek, Jan ; Vyčítal, Václav (referee) ; Topolánek, David (advisor)
This master's thesis is focused on the influence of double earth fault on voltage ratios in the compensated network. This thesis is focuses on, in particular on the analysis of voltage ratios on the secondary sides of distribution transformers when this non-local fault occurs. The compensation of the non-local double earth fault using the symmetrical components method is performed and the performance of this method is verified. The analysis of the effect of double earth fault on the proposed power system is carried out in PSCAD software and further evaluated. This type of non-local fault is investigated while modifying the various parameters of the designed system. To differentiate the double earth fault from the two phase ground fault, the asymmetry on the LV sides of the distribution transformers is investigated. A locator is provided to locate the location of the double earth fault and the two-phase ground fault, which, combined with the asymmetry values, is able to determine both the location of the fault and the differentiation of the co-located fault from the non-co-located fault.
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Simulation of earthing system resistance measurement
Pirochta, Josef ; Topolánek, David (referee) ; Vyčítal, Václav (advisor)
In this bachelor thesis, the effect of different soil models and random wire placed underground on the results of earth resistance measurements using the 4-pole method was investigated. To determine this influence, simulations were performed in Ansys Electronics software, in which different soil models (with local inhomogeneity, horizontally divided soil and soil divided at an angle) were created. In these models, the measured earth was placed together with the measured random wire and its resistance was determined by simulating the measurements and with respect to the distant ground. The effect of the different soil models on the accuracy of the measurements was determined from the differences in the resistance of the earth random wire obtained by measurement and with respect to the distant ground. It was found by simulations that, of all the variants investigated, performing measurements in the presence of different soil models and a random wire can lead to a measurement error of up to 7,2 %.
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The measurements of earthing systems and the role of electrical soil resistivity
Capyk, Jan ; Jurák, Viktor (referee) ; Vyčítal, Václav (advisor)
The theoretical part of the thesis is focused on explaining the concept of soil resistivity, applicable methods of its measurement, comparison of two methods used to measure the resistance of the earth electrode and a description of the measuring device Metro PU 193 used for the practical part of the thesis. In the practical part, the reader is acquainted with the results of measuring soil resistivity and earth resistance in the field, with their evaluation with respect to various influencing factors and with designs of earth conductors for high voltage poles for which soil resistivity was measured. The thesis contains plotted graphs of various dependencies according to the results of measured values and compares them with theoretical assumptions.
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Unsymmetrical power flow calculation with the help of software applications
Ermolenko, Ilya ; Koudelka, Jan (referee) ; Vyčítal, Václav (advisor)
This work consists of four parts. The first part of the thesis provides a theoretical introduction to the power flow calculation problem. Furthermore, the analysis of power flow calculation as a linear and as a nonlinear problem is performed. In this thesis, Newton’s iteration method is used in the calculation of the nonlinear problem. The following describes possibilities for improving the power flow calculation by improving the Newton's iteration method and using non-standard methods. The second part describes the possibilities of power flow calculation using various software applications, such as Pandapower, Matpower, OpenDSS and PSS Sincal. In the third part of the thesis the selected software applications tool is used to test the possibility of unsymmetrical power flow calculation in the LV network for the state with and without the PEN conductor, and the calculation of the ground fault in the compensated network. In the fourth part of the work, the unsymmetrical power flow calculation is tested for a larger LV network, further is performed the evaluation of the influence of PEN conductor modeling on the calculation results compared to the calculations of a network without this conductor.
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The framework for application of phase allocation of consumers
Franěk, Vít ; Koudelka, Jan (referee) ; Vyčítal, Václav (advisor)
The aim of this work is to introduce the issue of the smart grids concept, as well as the issue of phase identification sorting from implementation smart grids. The issue of phase identification sorting is described by several possible methods. The work continues by calculating the theoretical network and processing the values measured from the low voltage network and applying the phase identification method based on voltage events. Based on the results, a laboratory task proposal is prepared.
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Probabilistic Approach for Assessment of Earthing System Design
Vyčítal, Václav ; Gurecký, Jiří (referee) ; Procházka, Karel (referee) ; Toman, Petr (advisor)
This dissertation thesis deals with application of probabilistic approach to assessment of earthing system safety in distribution networks, especially for cases with common earthing of high and low voltage side of distribution transformers HV/LV. In these cases, the increased potential during fault might be transferred from high voltage to low voltage network and thus the individuals from public can be exposed to increased risk. Thus, for these cases were in this thesis defined expectable touch scenarios together with the resulting risk imposed on individuals from the public. Based on the results it seems that adoption of probabilistic approach for these cases of earthing systems might be more suitable compared to the conventional deterministic worst case approach. In accordance to the aims of the thesis, a thorough analysis of currently adopted probabilistic approaches was carried out as well and it was pointed out to some new possible simplifications in the adopted probabilistic based methodologies. For example, it seems that appropriate modelling of human body resistance by the full lognormal distribution is not completely necessary and similar results can be obtained when only the resistance for 50 % of population together with c3 and c4 fibrillation curves are used. Much of the work was also devoted to the determination of possible uncertainty of calculated risk of evaluated earthing system, especially due to inappropriate modelling of earthing system. The appropriateness of different earthing system modelling methods together with other parameters on the value of calculated risk was investigated through conducting sensitivity analysis. Based on the analysis results it seems, that due to using more, or less simplified modelling method, a possible underrating in the resulting risk of about 40 % (about half an order/decade) is expectable. On the other hand, the change of parameters related directly to calculation of fibrillation probability seems to exhibit greater change in calculated risk by up to units of orders/decades.
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Appropriateness of modelling the actual soil model as a uniform or horizontal two-layer soil model
Kuběna, Michael ; Topolánek, David (referee) ; Vyčítal, Václav (advisor)
The present thesis deals with soil resistivity and especially the suitability of replacing various soil models with a two-layer horizontal model. First, the factors that influence soil resistivity as well as the methodology of its measuring are described, and various soil models are introduced. Then, the Ansys program was used to create several soil models: a vertical model with perpendicular or oblique division, a model with a pronounced inhomogeneity and a three-layer model. In all of these models, a Wenner measurement simulation was performed, followed by a two-layer horizontal replacement model. Then the size of the error that was created by replacing the actual model with a two-layer horizontal model was examined.
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Modelling Of Electrical Installations
Earthing Systems In Ansoft Maxwell
Vycital, Vaclav
This paper discusses the possibilities of modelling of ES in Ansoft Maxwell software. The possible way of definition of the problem with possible modelling difficulties were discussed. The possible error in obtained results by choosing a value of radius of the earth model as well as choosing a value of target percent error in the software by the user is also discussed. The discussion is supplemented with a simplified sensitivity analysis of these input variables and the results are validated by comparing the results with results obtained from simplified analytical formulas.
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