Partial Discharge Characteristics of Spherical Metal Particle in Mineral Oil and PFAE Under AC Voltage

This paper reported the partial discharge of free spherical metal particle in mineral oil and Palm Fatty Acid Ester Oil (PFAE) under quasi-uniform field of AC applied voltage in transformer. The partial discharge inception voltage (PDIV) for the single particle was measured to be 11kV and 15kV for PFAE and mineral, respectively. The Phase-Resolved Partial Discharge (PRPD) pattern for both oils shows that during early stage of applied voltage, the PDs are mostly occur at the adjacent of zero cross point. PRPD pattern under increment of applied voltage in mineral oil has shown a slow scattering distribution with larger number of PD compared to PFAE. PDs in mineral oil start to scatter at 21kV and concentrate at 90 degrees and 270 degrees of positive and negative half cycle, respectively. Meanwhile, PDs in PFAE shows to scatter at 15kV and with increasing voltage, the PDs show to distribute around 100 degrees in positive half cycle and 290 degrees in negative half cycle. At 21kV, mineral oil has shown to have approximately 1.5 times more number of PDs compared to PFAE. The observation on spherical metal particle movement revealed that there were different stages of motion process involved in these two different oils.