The synchronous generator is a principal elements of the power generation cycle. Its operational condition affects the electricity supply reliability and the system stability. Withgenerators, protection and monitoring equipment are employed routinely to prevent damage. Rotor winding short circuits occur relatively frequently and if continuous, can lead to high temperatures and excessive vibration of the rotor resulting in damage to the generator if the fault is not cleared. To detect shorted turns in the rotor windings, several methods have been used for many years; for example, the airgap search coil technique, the monitoring of circulating stator current in double circuit machines measurement the rotor shaft voltage and the recurrent surge oscillograph (RSO) method, refs [1 -3] For stator winding shorts in double circuit machines circuits, measurement of the differential current between parallel connected half phases is used.Single winding stators present a more intractable problem, although it has been observed that there are some harmonic changes in line current under such conditions.
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