Interturn short circuit faults are the leading cause of power transformer failures. if not quickly detected, these faults usually develop into more serious faults that would result in irreversible damage to the transformer, unexpected outages and the consequential costs. this contribution is aimed at obtaining a better understanding of physical behavior of power transformers in the presence of interturn faults as well as extracting several features that would be useful to specify the faults. this research investigates the behavior of power transformersunder the occurrence of permanent winding insulation faults. for the study of these phenomena,a simple and efficient permeance-based electromagnetic transformermodel is used, which is based on the simultaneousconsideration of magnetic and electric equivalent circuits. to incorporate the internal faults in this model, a suitable equivalent circuit of the faulty winding is described. Permeance-based electromagnetic transformer model of power transformer has been developed to characterize the transient behavior of a real power transformer when the transformer is working under winding short circuit fault conditions. an experimental set-up consisting of the same transformer used to validate the simulation of the faulty transformer. the results of the experiments demonstrate the remarkable ability of the model to reproduce the real behavior of the transformer with interturn winding faults. the study characterizes the faultytransformer behavior under varying conditions of load and fault severity. To this end, the main objective of this research is to develop a new technique for detecting turn-to-turn short-circuit faults in one or two phases of power transformer. hence, modeling a turn to- turn short-circuit fault in more than one phase is the first novelty of this research for calculating phase currents under faulty conditions. This strategy uses the extracted features from the corresponding three-phase current pattern in 3-D space. Identification of faulty phases and of the severity of the fault is the outcome of this technique. this method just requires current sensors that are available in transformer protection facility to provide good controllability.experimental results are included to show the ability of the proposed strategy for detecting and locating phase/phases under different faults and load conditions. Keywords:Power transformer,Condition monitoring,Inter turn short circuit,Electromagnetic transformer model.