This thesis consists of two parts. The first part of the task is the theoretical and the second the practical part. The theoretical part of the paper explains the concepts of project management, maintenance and overhauls. Under project management, the very concept of the project and the phases of the project life cycle are explained. Maintenance management is described and the division into preventive and corrective maintenance and the importance of reliability, availability and risk in the maintenance of the production plant is given, and the management of overhauls in the production plant is described. In the practical part of the paper, an insight into the project of overhaul of RHE Velebit is given and the works on aggregate 1 are described in detail, which include works on the engine-generator and on the pump-turbine. Finally, measurements and tests were performed to determine the correctness of the system and the success of the completed overhaul project of RHE Velebit. By applying the theoretical part of the paper to the practical part, the most appropriate management of the overhaul project of RHE Velebit was defined in order to increase efficiency.