Plis V. Improvement of testing methods of asynchronous electric motor protection devices

The dissertation is dedicated to improving methods for testing and setting up digital relay protection terminals (RPT) to confirm their correct functioning. The developed methods allow for convenient testing of real microprocessor RPTs in laboratory conditions, considering the specifics of the protected element. The introduction substantiates the relevance, purpose, and objectives of the research, and outlines the scientific novelty, practical significance, and the list of implementations of the dissertation results. The first chapter analyzes publications related to existing testing systems and complexes for testing and verifying the correct setting of microprocessor RPTs. Identified deficiencies and problems are discussed. The development stages of relay protection systems (RPS) are considered; modern directions for managing the modes of power systems (PS); issues with using microprocessor-based RPS and solutions to these problems are outlined. Comprehensive technical re-equipment and reconstruction of relay protection and automation systems (RPA) aimed at maximizing the automation of dispatcher operations are impossible without the use of microprocessor devices. The second chapter analyzes mathematical models and software packages for calculating electromagnetic and electromechanical transient processes in the power supply system (PSS). The mathematical model of the asynchronous motor (AM) has been improved, taking into account the nonlinearities of the motor. A comprehensive mathematical model of the electrical system for analyzing transient processes of the protected object has been developed, which considers the distortion of the current waveform in the secondary circuit of current transformers (CT) due to their saturation. The third chapter describes the used experimental hardware-software stand, which allows for testing real microprocessor RPTs, considering the specifics of the protected element. The stand enables the automation of the protection testing process in characteristic operating modes of the object by supplying analog and discrete signals corresponding to normal and emergency operating modes, and due to the feedback presence. The fourth chapter analyzes the functional capabilities of RPS devices based on electromechanical relays and microprocessor devices. The requirements for RPS of electric motors and the possibilities of their implementation using microprocessor RPTs are considered. The fifth chapter develops a method for verifying the correct functioning of RPTs and creates a testing algorithm. The research is carried out by jointly using the developed mathematical models, their software implementations, and the experimental stand. Repeated testing of the protection terminal allows for judging the correctness of the algorithms' operation and the accuracy of the protection settings calculation. The theoretical positions and practical research of the dissertation are used in the educational process of the Department of Power Supply and Energy Management of the National University "Odessa Polytechnic" and at enterprises in southern Ukraine.