“…The oil common incipient electrical faults are Partial discharge (PD), and arcing discharge of high and low energy (D2 and D1). While the thermal types of faults as high, medium and low (T3, T2, and T1) are types of thermal faults (S. S. M. Ghoneim, 2021, E. Bezerra, 2020, H. Salem, 2022, S. A.Ward, 2019, H. C. Chen, 2022. Hence, for improving the power system reliability and lowering the risk of transformer failure, it is crucial to identify the oil insulation levels with regular proactive and predicative maintenance program.…”