Demand for electric energy is growing from year to year, which brings higher electricity consumption as well. One of the most important conditions for electricity consumption is a properly planned distribution network.
The thesis consists of theoretical and practical part. The design of the distribution network is explained in the first part. The chapter contains the criteria for designing a medium voltage and low voltage network. Technical criteria for medium voltage and low voltage network are presented. The criteria presented in the medium voltage network include the criteria for assessing the power system reliability, the technical evaluation criteria (acceptable load, permissible voltage drops, transformer load) and the economic evaluation criteria. The presentation of low voltage networks includes limit voltage drops, reference impedances and transformer dimensioning. The section on network analysis follows. At the beginning of this thesis, a model of the power system is presented, which includes a line model, a transformer model, a load model and a generator model. Each example is described with words, formulas and a figure. Network analysis cannot be performed without iterative methods. Gauss, Gauss-Seidl, decoupled and fast decoupled methods are presented. The most suitable method for analysis in the distribution network is Newton-Raphson’s method. The presentation of Gredos and PISELJ software package follows. Both software packages are indispensable in the analysis and planning of the distribution network.
Finally, an example of voltage conditions in a low voltage network before and after the connection of a small solar power plant to the network is presented. At the beginning, general data on small solar power plants, a comparison of issued consents for production and the number of connected small solar power plants are presented. The impact of connecting a small solar power plant to the low voltage network is presented together with the process of issuing consent for the connection of a small solar power plant to the network. The selected example is presented in addition. The considered network is presented together with the results of measurements before and after the connection of a small solar power plant to the network. The last part of the thesis contains an analysis of the voltage conditions of the example case. The analysis of Elektro Ljubljana before the connection of a small solar power plant to the grid, the data on monitoring the temperature and power of solar radiation and the analysis of maximum and minimum voltages on a weekly basis are presented. Examples of operation of a small solar power plant in sunny and cloudy weather and the impact of operation on the maximum and minimum voltage conditions are presented.