Using partial discharge measurement technology to implement predictive maintenance in high voltage motor and generator stator windings

Partial discharge (PD) tests can determine which motor and generator stator windings are experiencing insulation problems. A deteriorated winding has a PD activity which can be 30 times or more higher than a winding in good condition. This great difference in PD activity enables even nonspecialized maintenance personnel to identify the few motors or generators in a company which need further investigation and/or maintenance. After implementing on-line partial discharge tests companies can often confidently extend the outage between major machine inspections. This saves on outage costs and reduces the risk of a stator fault due to human error during maintenance. Finally, on older machines, if there has been no increase in partial discharge activity over time, then the life of the stator winding can be confidently extended, saving a considerable capital expenditure. The PD tests discussed cost virtually nothing to perform, once the sensors are installed, since existing company staff can do the tests in about 30 minutes during normal motor or generator operation.