Analysis of Insulation Diagnosis for Generator-Motor Stator Winding and Core in Pumped Storage Power Plants

摘要

Since the first pumped storage power plant started operation in South Korea in 1980, 14 generator-motor related failures have occurred, where two of these cases were stator winding failures. This study examines the stator winding failure cases of the "A" pumped storage power generator-motor, which has been operated for more than 30 years, and the "B" pumped storage power generator-motor, which has been operated for more than 20 years. The causes of the failures are analyzed, and their countermeasures are mentioned. Stator rewinding in the "A" pumped storage power plant was performed in 2010 after a winding meltdown caused by a short circuit at the upper side of the phase B stator winding. A ground fault occurred in the "B" pumped storage power plant because of a stator core damage in 2000, where the core clamping force was strengthened, and the stator winding with dielectric breakdown was replaced. Since then, the "A" and "B" pumped storage power plants have been in operation to date through periodic preventive maintenance. In addition to the insulation diagnostic tests of the "B" pumped storage generator-motor performed in the last two years, the correlation between the number as well as the severity of defects through observation of the ultraviolet (UV) rays generated at the winding terminal and the partial discharge (PD) test data were analyzed. Insulation refurbishment was completed for the maintenance of plant B generator-motor No. 2. The quality of the groundwall insulation of stator winding and stator core were also verified by analyzing the results of the off-line PD test and the EL-CID (ELectromagnetic Core Imperfection Detector) test, respectively, before and after the insulation refurbishment.