This doctoral thesis describes an originally developed electromagnetic model for calculating the distribution of ground fault current in power plants, which is based on the application of the finite element technique to the integral formulation of the problem. The components of the electromagnetic model can be located in homogeneous soil or in air. The damping and phase rotation of the electromagnetic wave are approximately taken into account using the damping-phase factor. The developed electromagnetic model can take into account the complete electromagnetic coupling between the components of the electromagnetic model. All mutually electromagnetically coupled components of the electromagnetic model form one finite element. The components of the electromagnetic model are: the earthing switch of the considered transformer station, the earthing switches of neighboring transformer stations, power transformers, metal poles and earthing switches of overhead power lines, protective ropes and phase conductors of overhead power lines, metal screens and phase conductors of underground power cables, earthing conductors laid above underground cable lines and other conductive parts. Based on the known ground fault currents in the neighboring transformer stations, from which the transformer station affected by the ground fault is powered, one or more three-phase voltage sources are formed in each of the neighboring transformer stations. In this way, the power flows in the power system are taken into account. A particular part of the power system can be replaced by an impedance, which forms a separate finite element. Based on the developed theoretical basis, the computer program EMFCD has been developed, which is primarily intended for calculating the distribution of ground fault currents. However, this computer program can also be used for advanced analysis of current and voltage conditions on overhead and cable power lines.