Large synchronous generator stator winding maintenance by on-line partial discharge testing (one case study)

Large synchronous generator failures due to insulation breakdown can cause catastrophic damages to the equipment, loss or de-rating of power output, lengthy forced outages and heavy costs to the operator. Therefore it is desirable to detect the onset of significant insulation deterioration and identify potential failures as early as possible. Faced with increasing pressure to increase unit availability yet reduce maintenance costs, operators are moving away from timebased maintenance practices to condition-based maintenance efforts. Operators of generators are using partial discharge analysis (PDA) systems to perform online condition monitoring of the stator insulation system. On-line partial discharge (PD) measurements have been recognized as an effective, reliable method of assessing stator insulation condition to forewarn plant personnel of possible machine failures. The measurements are obtained with the machine in normal operation and thus form an integral part of a condition-based maintenance program. Regular condition monitoring of the stator winding insulation can give users the confidence to safely operate machines, even ones that have suffered some degree of insulation degradation This paper presents one case study of how operators applied an on-line PD measurement system on a generator with insulation degradation to avoid substantial costs and forced outages. Long-term on-line PD monitoring has given the operators confidence to continue running machines that have the potential for insulation failures. The paper describes the interpretation of the PD data and how it contributed to the life extension of the stator winding.[1]

Large synchronous generator stator winding maintenance by on-line partial discharge testing (one case study) Keywords:

Synchronous generator , Partial discharge , Maintenance , On-line monitoring