This thesis describes the properties and capabilities of the XGSLab software package and its modules. The goal was to independently calculate the magnetic field strength in this software package, study its applications and describe its use. The second chapter describes the properties of the electromagnetic field according to Maxwell’s equations in differential form. Furthermore, the magnetic field of an electric current and the quantities that describe it are explained in more detail. Then, the effects of magnetic fields on humans according to Directive 2013/35/EU of the European Parliament and of the Council are described. The main physical quantities and regulations that must be observed according to the Ordinance on Protection against Electromagnetic Fields are also listed. The tables give the limit values of magnetic field strength and magnetic flux density for public areas and areas of increased sensitivity. The third chapter contains a detailed description of the XGSLab software package: its modules GSA and GSA_FD for calculations of grounding systems, XGSA_FD for analysis of overhead and underground grounding systems in the frequency domain, XGSA_TD for analysis of overhead and underground grounding systems in the time domain and NETS for calculation and simulation of multi-conductor and multi-phase complex networks. The areas of application of this software package, its applications and capabilities are listed, starting from standard references, waveform, soil modeling, up to data analysis and display of results. At the end of this chapter, the calculation of the magnetic field strength is described and already solved examples of the distribution of magnetic induction in space for various elements of the power system in the XGSA_FD module are shown. The fourth chapter solves examples of the calculation of the magnetic field strength, or magnetic induction using the XGSLab software package for a three-phase overhead line and cable. All the steps necessary for successful execution of the calculation are listed and the obtained results are shown.