Tugai I. Subharmonic ferroresonance in high voltage electrical networks with effective grounded neutral

The оbject of research: the electromagnetic processes in high voltage electrical networks with effective grounded neutral. The purpose of research: development methods for the analysis of ferroresonance processes to prevent the initiation and progress of dangerous abnormal modes in high voltage electrical networks with effective grounded neutral. Methods of research: nonlinear dynamics methods, Galerkin method, numerical integration methods and mathematical modeling. Theoretical and practical results and innovations: the dangerous parameters domains of the ferroresonant circuit are first got using nonlinear dynamics methods; the mathematical models of the electrical network elements are improved by modeling hysteresis in the transformer core and the corona discharge on transmission lines and the substation buses; for the analysis of nonlinear oscillatory circuits the new combined method is developed, which allows to simultaneously check both necessary and sufficient conditions for the emergence and progress of ferroresonance; new software is developed to identify ferroresonance processes in high voltage electrical networks with effective grounded neutral. A subject degree of introduction: are used in the normative document of the Ministry of energy and coal industry of Ukraine and are introduced for mandatory use in all power systems of the National power company "Ukrenergo". Effectiveness of implantation: primary equipment accelerated wear of electric substation is reduced and the danger of damage to the voltage transformers is eliminated. Sphere of use: high voltage electrical networks with effective grounded neutral.