The detection of stator and rotor winding short circuits in synchronous generators by analysing excitation current harmonics

The synchronous generator is a principal elements of the power generation cycle. Its operational condition affects the electricity supply reliability and the power system stability. With modern generators, 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 method. Here, a novel method which looks at the harmonic components present in the generator excitation current is proposed to detect both stator and rotor winding shorts. Analytical justification of the method is given together with experimental results obtained using two synchronous machines of different ratings, both of which have single circuit stator windings and four pole salient rotors