Research The Partial Discharge Measurement On Stator Coils Of Large Turbine Generator

During the operation of turbine generators, partial discharge (PD) on stator coils is one ofthe aging factors. The research of partial discharge measurement on the windings of rotatingmachinery started in the1950s.The standards of online-PD measurement have beenformulated for windings of the large turbine generator. However, there are few papers abouthow to assess PD significance on stator coils and windings of generator, especially underoff-line conditions.According to GB/T20833-2007for PD measurement and evaluation on stator bars ofrotating machinery, this paper discusses the PD measurement methods and requirements.Comparing with different types of samples, both the main characteristics of the discharge andthe level of PD have been obtained. In the meanwhile, the regularity of PD characteristics hasbeen analyzed. Finally, this paper provides a review of the nature of PD, how it can bemeasured for stator coils and windings, and the discharge mode and assessment of groundwallinsulation.After measuring many turbine generator coils, most of them can’t meet the requirement ofGB/T20833, which require below200pC under phase voltage and500pC under line voltage.However, these generators have been running many years, which means the requirement fromGB/T20833doesn’t apply to turbine generator coils. Comparing the different discharge mode,different types and structures of the main insulation can affect the PD. When several coilparallel connected, the change of the PD signal transmission makes the principle ofmeasurement changed, which worthy of further study later.