PD measurements on rotating machines help to identify problems such as slot discharges, loose wedges (bar vibrations), cracked and broken conductors, end winding surface contamination, insulation degradation, and collector ring and brush sparking, for example. To prepare for PD measurements, the rotating machine, such as turbine generator, hydro, or a large motor is brought off-line and deenergized, and coupling capacitors are installed for permanent access. Subsequently, time-based PD measurements using the ICM system or permanent on-line monitoring utilising the ICM monitor are available through connection to the installed coupling capacitors.
