Optimum Timing of Stator Winding Maintenance Based on a Combination of On-Line Partial Discharge Measurements and Visual Inspections

For how long can a generator be operated before the risk of an earth fault reaches to an in-acceptable level? And what are the necessary diagnostic tools? A promising answer to these vital questions for power producers is provided in this paper. It is shown how on-line PD analysis and visual inspections are combined to form an efficient tool for predictive maintenance. On-line partial discharge pattern measurements were used to identify potential problems in the machine insulation. Subsequent visual inspections served to verify the findings and determine the location and severity of these defects. Partial discharge measurements were used in order to verify the efficiency of the corrective action and have shown to be an effective quality assurance tool. Examples of real world experience are provided