The transformer oil deterioration is averted by inspecting the oil twice a year with focus on parameters such as dielectric strength, water content, colour, acidity, sludge, flash point, DDA, IFT (interfacial tension) and resistivity of the oil.
At higher temperatures, organic compounds breakdown to form carbon compounds. Besides this, silica gel turns to pink colour from its original blue colour, owing to saturation of moisture and when the gel is not renewed it contaminates the oil.