Abstract:

Aim at the dispersion characteristics and multi-modes of guided waves, which propagating in large generator stator insulation structure. In order to extract the insulation damage features and to effectively distinguish the wave packages of guided wave modes, and to achieve the goal of insulation damage detection. the numerical modeling and experimental methods were used to study on the excitation modes of guided waves. The guided wave propagation characteristic in stator insulation structure was analyzed. The optimization objective of guided waves excitation modes was presented. Before and after the presence of damage, the one-side excitation mode of guided waves, and the two-side in-phase excitation and anti-phase excitation modes were used to analyze the characteristics of guided wave mode utilizing finite element method (FEM). Moreover, under the different excitation modes, the wave package peak features were extracted and used to assess the effect of guided waves excitation by Hilbert transformation method. Finally, the effectiveness of different excitation modes were compared and verified through experimental. The numerical simulation and experimental results demonstrate that compared with the one-side excitation mode, the two-side in-phase excitation mode can strengthen S0 mode wave packages and the two-side anti-phase excitation mode can strengthen A0 mode wave packages, the guided waves modes were simplified using two-side excitation modes. Furthermore, under nondestructive and damage condition, the amplitude of A0 wave packages have obvious degree of reduced by the two-side anti-phase excitation mode, and the existence of stator insulation damage can be effectively identified by A0 mode wave package.

Key words: Stator insulation, damage detection, excitation mode, dispersive characteristics, multi-modes