Desarrollo de una herramienta computacional para determinar el ajuste de bloqueo por corriente Inrush de la protección diferencial de transformadores de potencia.

Abstract

The energization of power transformers results in a transient magnetizing current known as Inrush current. This phenomenon may lead the differential protection 87T of the transformer into a misoperation. This is the reason why the differential protection has the blocking function which activates if the content of second harmonic to its fundamental component exceeds a preset percentage. In some circumstances, the content of second harmonic in Inrush currents is less than the preset percentage, consequently, the relay considers it as a fault current and disconnects the transformer during the energization. The present work aims to provide to protection engineering personal or Electrical Engineering students, a computational tool able to develop simulations with variations in those principal parameters which have more influence in Inrush current’s magnitude, duration and, second harmonic content. This is done to find the adequate scenario according to differential protection which is low second harmonic content and long duration. The tool developed in MATLAB is able to command simulations to ATP/EMTP and import the results in order to calculate the differential current and compare it with a differential relay operating characteristic. This is done to determine the duration time and de lower content of harmonics.