Why is transformer oil acidity test important for aging assessment?

Acidity indicates oxidation byproducts that can increase dielectric losses, reduce resistivity, and promote sludge formation. As acidity rises, oil becomes more polar and can accelerate paper degradation and reduce cooling effectiveness by fouling surfaces. Trending acidity helps decide when filtration is not enough and when regeneration or oil replacement is needed. It also supports root cause analysis by revealing whether oxidation control is failing due to oxygen ingress, depleted inhibitor, overheating, or long service intervals.