Estudo para implementação da protecção diferencial (87) de um novo transformador de potência na subestação eléctrica de Chibata

Abstract

The power transformer is the most crucial element in an electrical substation, playing a fundamental role in converting voltage levels for the efficient distribution of energy. Therefore, it is essential to ensure that it is protected against any failures, whether internal or external, that may compromise its operation and the safety of the system. This project focuses primarily on the implementation of effective differential protection for a 200MVA step-down transformer on the primary and secondary sides, and 53.3MVA on the tertiary side, with a voltage of 210/113.5/18.6kV at the Chibata electrical substation. The current transformers (CTs) used in the differential relay were sized, selecting CTs with ratios of RTC1=200, RTC2=400, and RTC3=400. The slope was determined to be 116.11%. The selection of equipment was also carried out. Selected CTs include Model: CG-245 for the 210kV winding, Model: CG-145 for the 113.5kV winding, and Model: CXD-24 for the 18.6kV winding. The digital differential relay selected is Model: SEL-787. The selected circuit breakers are Model: LW43-256 for the 210kV winding of the transformer, Model: LW36-126 for the 113.5kV winding, and Model: Evolis-24 for the 18.6kV winding. These are the proposed equipment to be used in the project.