The restricted earth fault (REF) protection of power transformers are prone to maloperation during magnetizing inrush and severe external faults due to current transformer (CT) saturation. To tackle this issue, for the first time, an intelligent supervision method is designed in this paper which can significantly improve the immunity of this protection scheme. For this purpose, some decisive parameters used in some conventional methods are selected as distinguishing features. In the next step, a real power transformer is simulated under different operating conditions using PSCAD/EMTDC software. Then, three different intelligent classifiers are trained and tested using the simulation results and the most accurate and fast one is chosen to be used as the intelligent supervisory unit. Finally, a conventional relay performance is analyzed before/after being equipped with the new supervision unit. The obtained results show that by equipping the conventional REF protection scheme with it, a magnificent security against maloperation can be achieved while the imposed time delay is ignorable.
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