PD Characteristics of Large Motor Typical Insulation Defects via PRPD and PSA Pattern

Many kinds of insulation defects will be generated in the main insulation of large motor during operation, and the characteristics of these defects cannot be fully reflected just by the phase resolved partial discharge (PRPD) pattern. To solve this problem, four typical insulation defects, e.g. internal small air gap, overlapping fault of end semiconductor and stress grading coating, coil wear in slot and surface contamination were simulated in the laboratory environment, and the partial discharge (PD) signals were collected in the electromagnetic shielding chamber. On this basis, the PRPD patterns and pulse sequence analysis (PSA) patterns were drawn respectively. Combined with the characteristics of PRPD and PSA patterns under different voltage levels, the PD characteristics of typical insulation defects were analyzed. The results show that these typical insulation defects can be accurately identified by considering the symmetry, amplitude and shape of PRPD patterns and the number, distribution and shape of discharge clusters in PSA patterns.