Application of guided waves and probability imaging approach for insulation damage detection of large generator stator bar

Damage Identification of Large Generator Stator Insulation Based on PZT Sensor Systems and Hybrid Features of Lamb Waves

“…To compare the proposed hierarchical PDI method using hybrid features of Lamb wave with the basic PDI method in [ 20 ], the location identification errors of the two methods are compared under a noisy environment (noise type: factory noise, SNR: 20 db). According to the comparative results, as listed in Table 2 , the proposed PDI method shows a higher location identification precision of insulation damage under noise environment.…”

“…The material parameters of stator insulation were tested as: Young’s modulus of 35 Gpa, density of 1720 kg/m 3 and Poisson’s ratio of 0.2. Based on these parameters, the dispersive curves for Lamb wave propagation in stator insulation can be acquired by solving the Rayleigh-Lamb Equations [ 20 , 26 ]. In accordance with [ 20 ], the excitation signal in the experiment adopted a five-cycle Hanning-windowed sinusoidal toneburst with a central frequency of 15 kHz.…”

“…Based on these parameters, the dispersive curves for Lamb wave propagation in stator insulation can be acquired by solving the Rayleigh-Lamb Equations [ 20 , 26 ]. In accordance with [ 20 ], the excitation signal in the experiment adopted a five-cycle Hanning-windowed sinusoidal toneburst with a central frequency of 15 kHz. The AFG3022B generates the preset toneburst excitation signal, followed by the 7602 M for power amplification.…”

“…As discussed in Section 2.4 , the ToF of damage scatter wave is a vital feature to indicate damage position, but it is prone to pollution by many factors. To evaluate the proposed WT-based ToF extraction method, the procedure of extracting ToF from Lamb wave signals by WT and Hilbert transform (HT) [ 20 ] method are first described. Figure 4 a shows the time domain waveforms of Lamb wave signals in healthy and damaged states, respectively.…”

“…Due to the merits of Lamb wave on SHM of composite, the Lamb wave tomography method shows a potential solution for intuitively detecting stator insulation damages [ 20 ]. However, the stator insulation of large generators is mostly composed of mica tapes and epoxy resins, which can be regarded as composite materials with bar-like structures [ 4 ].…”