This study deals with the analysis of partial discharge characteristics of aged and aged with copper extra virgin olive oil. To confirm long-term reliability of transformers, it is essential to recognize the degradation characteristics of insulating oil in long-term operations, which are the dominant factors of the transformer dielectric strengths. This study is to identify how the PD characteristics of this oil changes and deteriorates with increasing age and what are the impacts on the electrical characteristics. The changes in the PD pattern and PD pulse due to the degradation of oil have been investigated with an innovative PD detection system PDBASEII. The Phase Resolved Partial Discharge (PRPD) pattern, time domain and frequency domain characteristics of PD pulses of vegetable oil was measured and they were compared with the mineral oil.