|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
Electricity Load Forecasting Using Auto-Regressive and Artificial Neural Network Model
Vyčítal, Václav
In this paper a short review of two forecasting models Autoregressive and Artificial neural network is presented. Both models were used to demonstrate its superior performance in load forecasting issues. In the third section the results of load forecasting experiment are given. For obtained forecasted results mean absolute percentage error for autoregressive model was 0.644 % and for artificial neural network model 2.31 %. In this paper error distribution for both models is also shown.
|
|
|
Determination of electromagnetic field distribution around underground power cable
Gromotovič, Ivan ; Paar, Martin (referee) ; Vyčítal, Václav (advisor)
The thesis deals with the distribution of the electromagnetic field around the conductor in the way of laying the conductors. The paper describes the structure of the cables and their lettering. More detailed is described the underground cable and various ways of protecting the conductor against mechanical damage are shown. The functions of the locator of underground lines on the electromagnetic field principle are briefly described . In the practical part, in simulation software Ansys Maxwell has been designed models to simulate the layout of the underground line. The output of the thesis is the comparison of the results created by the simulations.
|
|
|
Development of the tool for application of the method for localization of unsymmetrical faults
Pospíšil, Tomáš ; Vyčítal, Václav (referee) ; Topolánek, David (advisor)
In resonant earthed distribution systems, the capacitive current of the system is compensated by grounding via a arc suppression coil. The level of fault current is then very small and independent on the fault location which greatly complicates the rapid finding of the fault site. At this moment there is no method to be used to directly locate the site of a single-phase fault in the distribution network, new methods and solutions are being constantly sought to address the shortcomings of the existent localization methods. The diploma thesis deals with the design of a universal software tool that allows to apply a new method of locating an asymmetric fault in the distribution network. The tool is created in a MATLAB environment and utilizes the negative sequence voltage measured on the low-voltage sides of the distribution transformers and the negative sequence current measured behind the power transformer. By using the proposed tool, it is possible to read the parameters of any part of the distribution system that the user enters together with the measured values of the voltage and current into the initialization file. After the specified network parameters are loaded, a numerical model is created, which is then used for the method. In the work is described in detail the way of entering the parameters of the network into the initialization file, the method of automatic assembling of the numerical model based on the entered data and the possibility of customizing the calculation parameters. At the end of the thesis, the functionality of the proposed software tool is verified on data from simulation of the test network.
|
|
|
Measurement of electrical soil resistivity
Matyska, Stanislav ; Topolánek, David (referee) ; Vyčítal, Václav (advisor)
This master’s thesis deals with the measurement of the electrical soil resistivity. In the theoretical part there are described the methods by which the soil resistivity is measured – especially the Wenner’s method, which was used for the practical measurements. Then there is also described the one-layered and the two-layered model of this method. Furthermore, there is described the procedure for the measurement of soil resistivity using the OMICRON CPC 100 and PU 193 instruments used in the measurement. To verify the modeling of a two-layered soil model, the theoretical part of the thesis describes the soil modeling process using the program Ansys. As for the practical part of the thesis, the measurements were carried out in three localities: Brno – Královo Pole; Hrušovany nad Jevišovkou – Pravice; Hustopeče nad Bečvou – Vysoká. The measured values were processed using the Matlab’s graphical user interface (GUI) that was developed within this thesis. From these values, at least one two-layered soil model was created for each location and both meters – a total of 12 models were created. For these models, measurements were simulated in Ansys. The results of the simulations were then compared with the measured values. The aim of this thesis is to compare the measured data with the data obtained by the simulations and subsequently to describe the suitability / unsuitability of the substitution of the one-layered soil model for the two-layered one for given measurements.
|
guest ::
RSS feed.