What does ethane presence in transformer oil indicate?

Ethane in transformer oil is one of the dissolved gases used in DGA interpretation. It commonly points to thermal fault activity at relatively lower temperatures compared with gases like acetylene, which is associated with high energy arcing. Ethane often appears alongside methane and ethylene, and the pattern and ratios help distinguish overheating of oil versus paper, contact issues, or other developing faults. Ethane alone is not a diagnosis, it must be interpreted with trends, load history, and other test results.