Development of complex relay protection models in the MATLAB software

Abstract

In the modern educational process, information technologies are actively used to realize the process of acquiring knowledge at a qualitatively new level, which is especially important for distance learning. The level of their development allows to develop mathematical models of any processes and phenomena. Relay protection schemes are chosen as the subject of research. Based on their functionality, virtual stands have been developed in the MATLAB software package, which allow the user to get closer to the real conditions of laboratory work. The program “Investigation of maximum current protection” allows to investigate the operation of circuit elements as a result of a two-phase short circuit in the electrical system that consists of the generator, power line and load. The symmetric method was used to create a mathematical model of short circuit. When you start the model, windows automatically appear, in which the graphs of the dependence of the currents flowing in each phase and the state of the elements from time to time are built in the form of animations. On the basis of previously developed algorithms of operation of the current relay RT-40 and the power direction relay RBM-178 the scheme “Research of the maximum directed current protection” is developed. The virtual stand considers a two-way power supply network, which includes: symmetrical three-phase AC sources, power lines, high-voltage switches, consumers and directional current protection. To ensure greater functionality, the introduction of the necessary parameters of the elements is provided. With the help of a group of switches, you can simulate a two- and three-phase short circuit in the circuit. When starting the model, the currents flowing in the line in normal, emergency and post-emergency modes are calculated. At the end of the simulation, graphs of the dependence of the currents flowing in each phase and the state of the elements over time appear. The program “Distance Protection Research” uses algorithms for calculating currents of two- and three-phase short circuits developed in previous stands. During the simulation, a panel with the main characteristics of the relay is provided for monitoring the results and recording them. There is a graph on the stand, which shows the angular characteristics and values of resistance at different points of the short circuit. The stands have light indication – lamps color – and visual indication – contacts status.