Protecção diferencial de um Transformador de potência na subestação eléctrica da Matola

Abstract

The power transformer is the main component of an electrical substation, being extremely important to protect it against all types of internal defects or external that may occur. The project's main focus is to ensure the differential protection to a step-down transformer of 160MVA 275/66KV in the Matola electrical substation. It presents the main internal protections in a power transformer, with emphasis on gas and pressure relays and the Buchholz relay, analyzes the operation of instrument transformers (transformers of potential and current), and its application in the measurement and protection of equipment of the electrical system. Evaluates the operating conditions of the differential relay under influence of maneuvers and operations in the electrical system that introduce errors in the actuation of the differential relay 87, identifying methods to eliminate or attenuate its influence, the CTs used in the differential relay were dimensioned, selecting CTs with ratios of 400/5 and 2400/5, the percentage deviation of relay 87 was determined and the operating curve was chosen, with a slope of 20%. And the choice was made of the equipment, selecting the CTs, Model: CA-300 For the high side transformer voltage 275kV, Model: CXG-72 For the Medium voltage side 66kV from the transformer, and the digital differential relay Model: SEL-787, these are the equipment proposed to be used in the project. (TRADUÇÃO NOSSA)