Why is acidity monitored in transformer oil diagnostics?

Acidity monitoring helps track oxidation of transformer oil. As oil ages, acidic compounds form that can attack paper insulation, reduce interfacial tension, and promote sludge formation. Rising acidity is an early warning of oil degradation and loss of oxidation stability. When trended together with interfacial tension, color, and dielectric loss, acidity helps determine whether oil treatment, regeneration, or replacement is required to protect insulation life and maintain reliable transformer operation.