Estudo de saturação de transformadores de corrente conforme a norma IEC 61869-2 utilizando o software ATPDraw

Abstract

Current transformer (CT) saturation in high-voltage power systems is a critical issue, as it directly affects the accuracy of protection devices, such as relays, which depend on correct measurements to perform their function. In short-circuit scenarios, CTs can saturate, compromising current measurement and potentially leading to operational failures, such as non-operation or improper operation of protections. Given this, the increasing demand for greater reliability and safety in electrical networks, coupled with the requirements of the National System Operator (ONS), makes it imperative to study and properly size CTs to avoid problems in critical situations. This work aims to analyze the behavior of CTs in a 500 kV substation under short-circuit conditions, focusing on their saturation, using analytical calculations based on IEC 61869-2 and simulations performed in ATPDraw software. The purpose is to verify how long the CT maintains its accuracy during a short circuit and assess whether the equipment meets the minimum requirements needed for the correct operation of protective relays. The methodology involved performing electromotive force (EMF) calculations, followed by computational simulations that reproduce short-circuit scenarios and observe the CT's secondary current and saturation state. This evaluation enables a comparison between the analytical and simulated results. The results showed that the analyzed CTs maintain their accuracy within the time limit adopted, ensuring the correct operation of protective relays during the short circuit. These results were validated by both the simulations and analytical calculations, demonstrating the reliability of the simulated model and its compliance with applicable standards. Based on these results, the calculated values can be sent to the manufacturer for CT sizing, ensuring that the equipment meets the ONS requirements and the operational conditions of the studied substation.