Introduction
Transformers are essential components of a power transmission and distribution system. Their condition is critical to the safety and reliability of the system. Thermal and electrical faults that develop in an oil-filled power transformer are always associated with the formation of dissolved gases in the oil, including carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethylene (C2H4), acetylene (C2H2), ethane (C2H6), and hydrogen (H2) [1]–[3]. Using dissolved gas analysis (DGA), it is possible to distinguish different types of faults such as overheating, partial discharge, and arcing [4]–[8]. Following several decades of testing and monitoring oil-filled transformers, DGA has been accepted worldwide as an effective diagnostic method for the detection of incipient transformer faults [9]–[11].