Uma análise da proteção de sobrecorrente com restrição por tensão (51V) em contexto da minigeração distribuída

Abstract

The increasing integration of distributed minigeneration into distribution networks changes the behavior of power systems during faults and creates new challenges for overcurrent protection. In installations with inverter-based sources, the limitation of the current supplied by power converters may hinder the operation of conventional protection functions, requiring the assessment of alternatives that consider additional electrical quantities. In this context, this study analyzes the application of ANSI function 51V, voltage-restrained overcurrent protection, in networks with distributed generation connected at medium voltage. The study comprises an overview of the protection functions associated with the connection of generating facilities, a literature review concerning the application of function 51V, and an analysis of the technical documents adopted by Brazilian distribution utilities. Additionally, simulations were performed in MATLAB/Simulink to evaluate voltage and current behavior under different fault conditions, as well as the sensitivity of functions 51 and 51V. The results showed that the combined analysis of these quantities provides a more comprehensive characterization of fault conditions. In cases where the current contribution from the generating facility remained limited, conventional function 51 showed difficulty in reaching its operating threshold, whereas voltage restraint reduced the operating threshold of function 51V and enabled the identification of conditions not detected through overcurrent alone. Nevertheless, its response remained dependent on voltage-sag severity, fault characteristics, and the selected settings. Accordingly, function 51V proved to be a complementary alternative for improving protection sensitivity in networks with inverter-based generation, especially when fault current is limited by power converters. However, its application requires system-specific studies and coordination with other protection functions.