A New Simple Method to Avoid Maloperation of Transformer Restricted Earth Fault Relay during External Fault Events

< p>The restricted earth fault (REF) protection is provided for electrical power transformer in order to sense internal faults, mainly because it more sensitive than the main differential protection. However, The REF relay may maloperate when current (CT) saturation happens following a severe external fault. In this paper, new simple algorithm proposed scheme which realized by considering four fundamental conditions. These conditions are defined based on and neutral currents as well sum of phase currents. When these simultaneously satisfied, detects ground This implemented evaluated MATLAB program obtained result data from simulation real system using PSCAD/EMTDC software package. well-known Jiles-Atherton (JA) model used simulate transient behavior CTs. satisfactory results exhaustive investigation justify high security scheme.