Evaluación del impacto de la saturación de transformadores de corriente en la actuación de protecciones diferenciales de transformador considerando corrientes de INRUSH y fallas externas

Abstract

The technical project prior to obtaining the title of electrical engineer, presents a heuristic methodology evaluates the impact of TC saturation on the operation of the 87T differential relay through detailed simulations carried out in ATPDraw or DIgSILENT, following international standards including IEC 61869-2, IEC 61869-1, IEEE C57.13, and IEEE C37.91. Three critical scenarios are studied: internal faults, external faults with TC saturation, and magnetizing inrush. The simulation models incorporate nonlinear TC magnetization curves, a realistic power transformer model, and a differential relay equipped with dual-slope restraint characteristics and harmonic blocking, based on the methodology proposed by Guzmán et al. The results show that conventional differential relays are highly vulnerable to mis-operations under TC saturation and inrush conditions, whereas modern numerical relays employ dual-slope restraint and second-harmonic blocking maintain stable and selective operation. Additionally, TC with higher accuracy classes such as 10P20 and TPY, characterized by a higher knee point voltage, significantly reduce transformation errors during external fault conditions.