On-Line Partial Discharge Diagnosis on Stator Winding Insulation: Impacts of Voltage Distortion and Winding Temperature

Partial discharge (PD) magnitude and phase-resolved PD (PRPD) patterns are key indicators for on-line PD diagnosis for stator windings. These indicators can be influenced by generator operating conditions because generators are subjected to high temperatures and voltage distortion. This study investigates the impacts of voltage distortion and winding temperature on on-line PD diagnosis. We measure PDs in stator windings of a hydrogenerator. The voltage waveform and winding temperature varied with the load condition. Harmonic voltages of about 2–4 kHz are superimposed on the generator voltage. The temperature ranges from 27°C to 70°C. Although the superimposition of the harmonic voltages altered the PRPD pattern, its effect on PD magnitude remains negligible. In contrast, the shape of the PRPD pattern is independent of the temperature, whereas the PD magnitude decreases with the temperature. Based on these findings, we state notes for conducting on-line PD diagnosis under varying generator conditions.