Groundwall insulation damage localization of large generator stator bar using an active Lamb waves method

Condition monitoring of stator insulation is significant for reliable operation of large generators. However, locating groundwall insulation damage in a stator bar using existing methods is difficult. A new groundwall insulation damage localization method based on active Lamb waves is proposed in this study to address this issue. Two piezoelectric (PZT) transducers are mounted on the surface of a stator bar; one PZT works as an actuator to generate Lamb waves and the other works as a receiver to capture the propagated Lamb waves. The Hilbert transform associated with a cross-correlation function is then used to extract the time of flight of the damage-scattered wave. Consequently, a one-dimensional location model is established to determine the insulation damage position in stator bar. The proposed method has been experimentally verified by detecting insulation damages in both the slot and end-winding stator bars dismantled from a 18 kV/300 MW generator. Results show that the proposed method can effectively locate insulation damage in stator bars with high precision. In addition, the proposed method exhibits good noise robustness to avoid interference.