Master’s thesis deals with computation of steady state and short-circuit conditions in 110 kV nodal area of Čebín. The first part of thesis is theoretical. There is described computation of steady state and short-circuit conditions. There is description of 110 kV nodal area of Čebín too. There are made computations in the practical part. Two types of operation of transformers T401 and T402 are evaluated. The transformers operate independent at first, then they are connected in parallel. Voltage conditions in substations, load of lines and transformers, power losses and short-circuit resistance of substations in 110 kV nodal area of Čebín are evaluated based on the computations. There are compared the both types of operation of transformers in the end of practical part.

The dissertation describes several types of low and high voltage distribution networks including their implementation in specified location with regards to the reliability and quality of electric power supply. The distributions networks are classified according to ways of cable routing, distribution line voltage levels as well as according to types of network interconnections. The high and low voltage distribution networks are further categorized based on used cable types, where, more attention is paid to insulated lines used in the Czech Republic, low voltage lines called „AES“ and „PAS“ high voltage lines used more and more during the distribution network reconstruction. Attention is also given to the description of used methodology for the calculation of network performance stability. An individual part of the dissertation is devoted to a low voltage distribution network proposal in the village of Kovalovice. Based on performed analysis of distribution network conditions, several reconstruction versions were proposed with the help of „KASI“ software, the description of which is also included. The proposed versions are further analysed for both, technical and economical aspects and is selected most suitable version of the distribution network.

This diploma thesis is concerned with reconstruction of distribution network in Hruba Vrbka. The diploma thesis is divided in two parts. For better understanding to this issue, the first theoretical part is shortly dedicated to the history of electrical power system, to the several types of distribution network of low voltage and high voltage and their utilization in the area, considering the reliability and the quality of delivery of the electric energy. In this thesis there is mentioned division of distribution grids according to placing of cable lines, according to voltage and according to type of grid connection. Next part of this work is dedicated to the description of overhead lines and cable lines and their characteristics. For the proper concept of the grid we should know some characteristics of the electric line’s proposal: mechanical strength, warming, voltage drop, efficiency, degree of safety and provision of delivery. In the end of the theoretical part there are described methods for calculation of grid’s steady state as a linear task and also non-linear task, elimination of the balancing node, the iterative method, the reduction of external power take-off nodes and the solution of the steady state of the network through the direct current model. The second part of the diploma thesis is concerned with the calculation of the steady state in the village Hruba Vrbka. In this part is also described the KASI program which was used for the calculation of the grid’s steady state. Firstly low voltage grid’s balance in Hruba Vrbka was found out and evaluated and then there were proposed some solutions of the reconstruction for the grid improving. The suggested options of the reconstruction are considered from technical and economical point of view and the best solution is chosen. For this solution there is suggested the protection through program SICHR 9. In the end of this diploma thesis there is checked the load of the high voltage line.

This Master´s thesis deals with problematics related to the connection of new decentralized power sources into electrical power grid. Due to advantageous legislative support of these new, especially photovoltaic power sources, a massive amount of these sources have been connected into the power grid between years 2009 and 2010. For theoretical understanding of processes during a steady-state, the initial parts of this paper are focused on a procedure which solves steady-state on every power line mentioned. When we speak of decentralized power sources connection, it is necessary to mention the connected legislative. National distribution grid operators in collaboration with national regulatory commission have decided on a legislative document Rules of distribution grid operation, which puts a set of demands and requirements on applicants wishing to connect a new power source to the grid. The text of this thesis is focused mainly on demands required after the latest change in 1/2010. Practical part of this work deals with verification of new power source influence on a related power grid and meeting the legislatively required demands. The most important demands are voltage change due to new power source operation and its transfer to other voltage levels, higher harmonics injection, power output fluctuation and last, not least, changes in load flow directions. For reasons previously mentioned an analysis is made and possibilities of reducing or removing of these influences are introduced. To achieve these goals, two computer programs, Siemens Sinaut Spectrum and NetCalc are used.

This Master's thesis is focused on connecting of new power sources into electrical network, particularly, the steady state and allowed voltage variation in network nodes, which occur in steady state before and after connection of a new power source into distribution network, with regard to valid legislation. The new power source in question is the new wind farm Drahany with active power of 45 MW, which should be connected into distribution network 110kV, operated by distribution company E.ON. The aim of this work is to find the most suitable connection point of a wind farm into distribution network, considering transmission capacity of individual electric lines and voltage variations in network nodes, as well as Drahany wind farm's investor's expenses on construction of a connection line to connection point and the distribution network's operator's expenses on modification of the connection point. Also, methods of calculating of electric networks in steady state are described in this paper, particularly, linear calculations, because these are needed for the calculations in E-vlivy program, in which the possible options of Drahany wind farm's connection into network 110 kV, in various places, were modeled. The description of the E-Vlivy program is also included in this paper. The E.ON company's materials form the basis for this Master's thesis, which will later serve as one of the documents needed for Drahany wind farm’s connection point evaluation into distribution network 110 kV.

In the distribution network 110 kV of E.ON Company there are the nodal areas of Čebin substation and Sokolnice substation which are operated separately at the present time. There is one 400/110 kV transformer for each nodal area. In case of fault on one of these transformers or on busbar in which the set transformer is working, it comes to an outage of electric supply in the set nodal area. This problem has to be solved with help of the parallel operation of nodal areas of Čebín substation and Sokolnice substation. The main and also the practical task of this work is to design the bridge connection appropriate for parallel operation of nodal areas (supply transformers 400/110 kV). With help of a computing program there were made calculations of steady state and short-circuit conditions in distribution network 110 kV for separated and parallel operation of nodal areas. Voltage conditions, load of transformers (400/110 kV and 110/vn kV) and conditions on 110 kV lines are evaluated and controlled as the result of steady state calculations. Based on short-circuit conditions there is controlled the short-circuit resistance of the substations. Finally there are compared advantages and disadvantages of separated and parallel operations of nodal areas. If necessary, technical arrangements required for introduction of parallel operation of nodal areas of Čebín substation and Sokolnice substation will be designed. The theoretical part of the work deals with calculation of steady state with help of iterative methods, namely Newton´s and Gauss-Seidel methods. There are further described the method of calculating short-circuit currents, characteristic values and time behaviours of short-circuit current.

The theoretical part of this thesis deals with distribution networks in terms of distribution according to different criteria, describes the main elements of electric distribution networks and their qualities. The following describes the methods of calculating the steady state of electrical networks. These methods are nowadays used as basics for computer programs. In the penultimate chapter of the theoretical part are summarized the principles for the development of present networks and construction of new electrical networks. The aim of practical part of the thesis is to assess the current condition of the network 22 kV in the city of Brno and assess the condition after installation of 110/22 kV transformation in Brno-Sever switching substation. After evaluating the results of steady state electrical network and identifying certain problems is the following aim a proposal of solving problems that emerged in the network. The result should be operational, functional and reliable electric distribution network. This thesis used to calculate the steady state electrical networks by software PAS DAISY Off-Line Bizon V4.

Master’s thesis deals with computation of steady state and short-circuit conditions in the 110 kV distribution network in the nodal area of Čebín. Computations are done during independent operation and bridge operation of transformers T401, T402 in transformation station Čebín with proposed configuration of network. Additional computations of steady state during specific operating conditions such as (T401 outage, disconnection of line 5553) were done during network operation in bridge operation of T401, T402. Voltage conditions in substations, load of 110kV lines and 400/110 kV, 110/HV kV transformers are evaluated based on the computations of steady state. Short-circuit resistance of substations is being evaluated with the aid of calculations of short-circuit conditions. There is a comparison and processed results of computations during independent operation, bridge operation, special operational states and proposed technical measures of operation in bridge operation in the end of the thesis. Theoretical part of the master’s thesis deals with the description of 110 kV distribution networks, theory of calculation of the steady state of electric system with the aid of Newton iterative method a calculation of single-phase and three-phase short-circuit current with the aid of method of symmetrical components.

This thesis can be divided into five main parts. The first part deals with theoretical analysis of power flow calculation in power network during steady state condition. Load flow calculation is presented here as a linear and nonlinear problem. Newton iteration method is proposed for solving power flow as nonlinear problem. The second part of this thesis deals with the analysis of short-circuit calculation in accordance with valid International Standard IEC 60909. The equivalent voltage source method is adopted in case of the short-circuit calculation. For the calculation of unbalanced short-circuit currents, the symmetrical components method is also presented. The last three parts of this paper are focused on calculations of power flow and short-circuit conditions in power grid Sokolnice. So in the third part is the description of nodal area Sokolnice with its substations and the calculation of load flow and short-circuit conditions for two different power supply options. For each supply option is also considered an abnormal (fault) grid condition. (overall there are solved four different options) The fourth part of this thesis deals with the result analysis and also the results of different power supply options are compared. In the last part there are presented necessary technical improvements for fault-free operation of power grid Sokolnice based on the result of power flow and short-circuit conditions in that grid.