What does furan oil analysis reveal about transformer insulation?

Furan analysis reveals the condition of cellulose paper insulation by measuring furanic compounds dissolved in oil. Higher furan levels indicate paper depolymerization and thermal aging, often linked to overheating, moisture, or long term stress. Because paper degradation is irreversible, furan trending helps estimate remaining life and risk. It is especially valuable when DGA suggests thermal faults or when loading history is aggressive.