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Fault occurrence in electrical machines is avoidable but, quick fault detection can increase system reliability. According to studies of electrical power research institute (EPRI), most of the occurred faults in electrical motors are created in bushes (41%) and winding (37%). According to high probability of winding fault occurrence in motor, its fault diagnosis is so important. Source of this fault is often winding isolators. Inter-turn winding fault creates short circuit in phase winding and changes phase impedance. As a result, machine becomes unbalance. Rate of impedance reduction depends on intensity of fault. Prominent characteristic of winding fault is second harmonic creation in sequence components, motor currents, torque and speed. Therefore, the most common approaches rely on frequency analysis. In this paper, to diagnosis winding fault two approaches based on frequency analysis studied, MCSA and EPVA and to determine percentage of fault second harmonic of id has been used.