Assessment and Analysis of the Reliability of Insulation System for High-Voltage Induction Motors Based on the Partial Discharge Level

The object of the paper is an experimental study and analysis of the reliability of the stator winding insulation of high voltage induction motors that have been in continuous operation for more than 30 years. The analysis is based on experimental results of measurements of the dissipation factor values and partial discharges, performed on a number of induction motors in several consecutive years. They give an information to asses the current condition of the stator insulation, the trend of insulations deterioration and allow forecasting its residual life.