The task of the thesis was to model a high-voltage network and conduct a detailed analysis of the overvoltage protection of a power transformer due to a lightning strike using the EMTP-RV software package. When modeling the network, the principles and requirements of the profession were respected. The lightning strikes that were used to simulate a lightning strike are standardized values. The first, introductory chapter provides an overview of the thesis task and describes the software package in which the given problem will be solved. The considered scenario is also briefly outlined. The second chapter of the thesis provides an overview of all scenarios that are modeled in the EMTP-RV software package. It also describes the method of modeling lightning current using the Heidler function recommended by the HRN EN 62305 standard set. The third chapter of the thesis describes all the main elements of the equivalent circuit of the considered scenario in the EMTP-RV software package. An attempt was made to use ready-made elements that are available in the library of the relevant software package as much as possible. Some elements, such as surge arresters, are modeled using more complex methods that require combining multiple available blocks to obtain a functional block. The fourth chapter of the thesis provides a detailed insight into the behavior of the network due to lightning strikes on the protective cable at specific locations. Conclusions are drawn based on the analysis of where it is best to position the surge arresters themselves. At the end of this chapter, the spark gaps themselves on all thirty poles, which conducted the current, depending on the location and shape of the lightning, are also analyzed.