Damage Detection of Large Generator Stator Insulation Using a Dual Excitation Guided Waves Method

The multi-modes and dispersion effects of the guided waves propagating in large generator stator insulation would decrease the signal-to-noise ratio (SNR) of guided waves detection signal. To improve the applicability of the guided wave detection method in the field environment, the excitation method of guided wave on stator insulation was studied in this paper. Firstly, the guided wave propagation characteristics in stator insulation structure were analyzed and the objective of optimized guided waves excitation modes was outlined. Then, the guided wave excitation experiments were conducted for three kinds of guided wave excitation modes, i.e., one-side excitation, two-side in-phase excitation and two-side anti-phase excitation. On that basis, the Hilbert transform was used to extract peak envelope of wave packet under different excitation modes of guided waves, and the excitation performance of guided waves was compared in experiments. The experimental results show that: the SO mode and AO mode wave packages can be strengthened by the two-side in-phase and anti-phase excitation, respectively. Compared with one-side excitation mode, the propagation modes of guided wave can be easier identified by two-side excitation mode. Moreover, the AO mode wave package is more suitable for damage detection of large generator stator insulation using the two-side anti-phase excitation mode.