What does the furan test indicate about transformer oil?

The furan test indicates the presence of degradation products from the insulation paper in transformer oil. Specifically, it measures the concentration of furan compounds, which are byproducts of cellulose breakdown due to thermal and electrical stress. Elevated furan levels suggest insulation deterioration, potentially leading to reduced transformer reliability and increased risk of failure. Regular furan testing is essential for assessing the health of transformer insulation systems and planning maintenance actions.