What are the technical aspects of transformer oil colour?

The technical aspects of transformer oil color primarily relate to its purity and condition. New, high-quality transformer oil typically appears clear and light yellow. Darkening or discoloration can indicate the presence of contaminants, oxidation, or thermal degradation. Color changes are assessed using ASTM D1500 standards, which classify oil color on a scale from 0.5 to 8. Regular monitoring of oil color helps in evaluating the health of the transformer and determining maintenance needs.