Análise da capacidade de condução de cabos de média tensão em redes subterrâneas: estudo de caso em um parque fotovoltaico

Abstract

The expansion of the renewable energy sector, particularly the generation of electricity through photovoltaic solar sources, has shown significant growth worldwide. The expansion of this sector is not limited solely to distributed generation, but also includes large scale projects known as centralized generation, in which electricity produced is sold to large industries and electric utilities. Consequently, investments are made in equipment and systems that increase the reliability of these projects to ensure the fulfillment of bilateral contracts for the purchase and sale of electricity. With this purpose, underground medium voltage networks are presented as a solution to increase reliability. The reliability is related to the expected lifespan of underground cables and the number of failures during that period. One of the main factors contributing to the reduction of underground cable lifespan is the overload to which the cables are subjected. In this context, this study presents the main methodologies for determining the current carrying capacity or ampacity of underground medium voltage cables, with a special focus on the methodologies presented in the ABNT NBR 14039:2021 and IEC 60287 series standards. Additionally, a case study was conducted on a 121.68 MVA photovoltaic plant to verify the carrying capacity and temperature of the layers of medium voltage cables during peak generation periods. The results were obtained using the IEC 60287 series for the worst thermal scenarios to which the medium-voltage cables are subjected. It was found that one of the analyzed sections experiences cable overloads, which can compromise the reliability and availability rate of the project.