Application of wavelet transform to discriminate induction motor stator winding short circuit faults from incipient insulation failures

Stator winding insulation faults in induction motor can be classified in two categories namely, direct inter-turn short circuit faults and incipient insulation failures. Both these two types of faults, when involving less number of turns, may remain undetected by normal protection schemes since such minor faults do not hamper normal operation of the motor. However, if these faults are not caught early they can lead to major failures in stator winding. The fault detection problem becomes more complicated when direct inter-turn short circuit faults and incipient insulation failures exhibit similar fault current magnitudes. The present contribution reports experimental results on an induction motor where both these two types of faults have been emulated. Park's Transformation has been used to extract AC components of the Park's Vector Modulus (PVM) of three phase line currents under different operating conditions of the motor. Continuous Wavelet Transform (CWT) has been used to extract several features from the non-stationary AC components of PVM. These features have been used to discriminate stator winding inter-turn faults from equivalent incipient insulation failures.