The article is devoted to the operation logic modeling of relay protection and automation terminals in order to their verification, adjustment and further exploitation. The problem of adjusting protection terminals mutual interaction is unlikely to appear in real conditions due to wide variety of them. The authors propose a solution to this problem by creating a verified model based on a digital twin of an electric power network section created in the MatLab software package. This model helps to study the functioning of the researched protection settings in nominal, repair, emergency and post-emergency equipment operation modes. A model of the selected substation was created displaying all the properties that are significant for research of the original one. In addition, the requirements analysis for the main and backup protection operation settings of the three-winding transformers was carried out. The main unit is a differential transformer relay protection and the backup one is maximal current protection in amount of three units for every transformer winding circuit: higher, middle and lower transformer voltage branch. The model makes it possible to analyze the relay protection operation selectivity by checking the current settings which could be imported from XML documents unloaded from existing terminals and to evaluate the correctness of new calculated ones with the possibility of their manual input. As a result of the researched object modeling, a three-stage operation analysis of the differential and maximal current protections was carried out. It has shown relay protection selective operation both in the case of nominal and abnormal modes, including the event of the main transformer protection malfunction. This technique can be extended to the other electric power network.
modelling, digital model, equipment adjustment, relay protection and automation, digital substation, differential protection, maximal current protection