How is testing transformer oil used to predict insulation aging and failures?

Oil testing predicts failures by detecting changes that correlate with insulation stress and fault activity. DGA reveals developing electrical faults like partial discharge or arcing and thermal faults from overheating. Moisture trends show loss of dielectric margin and accelerated paper aging. Increasing acidity and decreasing interfacial tension indicate oxidation and sludge formation that impairs cooling, raising hot spot temperatures. Furan analysis links directly to paper depolymerization and loss of mechanical strength. By trending results and correlating with loading and temperature data, maintenance can be scheduled before breakdown.