This paper deals with the use of an Extended Kalman Filter (EKF) for on-line detection of inter-turn short-circuits in stator windings of Permanent Magnet Synchronous Generator (PMSG). Inter-turn short-circuits are among the most critical faults occurring in the PMSG. Indeed, due to the permanent rotor flux, the short-circuit current is maintained as long as the machine is rotating. This faulty current may induce critical effects as much for the machine itself as for its environment. Thus, with regard to safety considerations, corrective actions (such as mechanical disconnect of the PMSG) have to be considered to reduce the fault incidence. In this work, focus is made on an important stage of the whole safety process, i.e the detection stage. Usually employed for sensorless or adaptative control, an EKF is used for detection purpose. Through the EKF estimated parameters, an indicator for interturn short-circuits is build. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed approach.