| Title |
Analysis of Insulation Characteristics After Cleaning and Maintenance Work in High Voltage Motor Stator Windings |
| Authors |
구자영(Ja-Young Koo) ; 곽준호(Jun-Ho Kwak) ; 김희동(Hee-Dong Kim) |
| DOI |
https://doi.org/10.5370/KIEE.2025.74.1.198 |
| Keywords |
stator winding; HV motor; contamination; OCP; cleaning work; VPI; PD; UV; maintenance work; surface discharge; ECP |
| Abstract |
The stator winding of a long-term-operated high-voltage (HV) motor is subject to tracking owing to the accumulation of foreign substances, such as dust, on the surface of the end-winding. Insufficient space for phase-to-phase windings leads to damage caused by discharge. In this study, severe contamination inside the stator winding of a weather protected (WPII) of HV motor (3,700 kW, 13.2 kV) that had been in operation for approximately 15 years resulted in the detection of damage to the outer corona protection (OCP) in the slot end after cleaning work, as observed through visual inspection. After completing the conductive paint application process and global VPI(Vacuum Pressure Impregnation) re-impregnation of the stator windings, partial discharge (PD) and ultraviolet (UV) tests were conducted. After cleaning work, the PD were measured at 66,500 pC and 354,000 pC at the phase voltage (7.62 kV) and 1.25 times the phase voltage (9.53 kV), respectively. After maintenance work, the PD magnitudes significantly decreased to 20,900 pC, 26,500 pC, and 34,500 pC at the voltages of 7.62 kV, 9.53 kV, and rated voltage (13.2 kV), respectively. PD patterns were observed at 7.62 kV and 9.53 kV, with the surface discharges accompanied by 1∼2 arcs. At 13.2 kV, surface discharge with almost no arcs was observed. After cleaning work, the UV count was measured at 32,760 when the alternating current (AC) voltage was increased. The occurrence location was confirmed to be in the damaged area of the OCP. After maintenance work, UV counts were measured at the end of the end-winding corona protection (ECP) rather than at the slot end. |