Phase resolved partial discharge patterns of typical defects from generator stators with different size of samples

Partial discharge (PD) is a common fault in power equipment, which poses a serious threat to the safe operation of large generators. This study is to analyze the phase resolved partial discharge (PRPD) mode of large generator stator in detail, and to explore the characteristics of different typical insulation defects in PRPD mode. In this study, typical defect types of stator bar are made, including delamination defects between the conductor and insulation, delamination defects between insulation and insulation, defects in the slot, and defects at the end. Voltage withstand tests were carried out at 20 kV, and PRPD patterns with 1, 10, 100, 1000 superposition groups of different defects were obtained. Main conclusions can be drawn as follows: (1) Unique shapes in patterns are evident at different superposition group sizes. As for delamination defects between the conductor and insulation, unique cluster can be clearly seen in low-number superposition groups but another unique cluster can be clearly seen in high-number superposition groups. (2) The PRPD patterns of different superposition groups of the same defect type can be well separated by t-SNE. As for defects in slot, the silhouette coefficients and rand coefficients gradually increase. (3) The more superimposed groups are, the better the PRPD patterns of different defect types can be distinguished. As for defects at the end, the discreteness gradually increases and the densities gradually decreases as the superposition groups increase.