Diagnosis of faults in induction generators under fluctuating load conditions through the instantaneous frequency of the fault components

This paper introduces a methodology for improving the reliability of diagnosis of different types of faults in wound rotor induction generators which works under variable load conditions; the method is based on the extraction of the Instantaneous Frequency of the fault related components of stator and rotor currents during speed transients, caused by load changes. It is shown that under these conditions, the Instantaneous Frequency plots of the fault components versus the slip are straight lines with a specific slope and offset for each kind of fault. In addition, neither of these patterns are dependent on the machine features, nor the way in which the load changes. Besides, the practical methodology of this technique is introduced for diagnosing two different kinds of fault: stator winding asymmetry and rotor winding asymmetry. The approach is validated by laboratory tests, for both types of faults.