Method for lifetime estimation of power transformer mineral oil

To reduce the test duration, this paper proposes a simpler method based on a single ageing test at a higher temperature and the activation energy of the oxidation reaction being determined from non-isothermal Differential Scanning Calorimetry (DSC) measurements. According to the proposed method, the plot ρ versus τ (ageing time) was drawn only for the accelerated ageing temperature T = 155 °C and the lifetime value (τx) for this temperature was experimentally obtained. In this case, the activation energy value Ea corresponding to oxidation reaction was determined (Ea = 102.4 kJ/mol). Based on both Ea and the τx at 155 °C, the lifetime at 80 °C (D2 = 1.86 × 105 h) was determined and compared with D1. The differences between D1 and D2 values are acceptable and the proposed method is effective in terms of costs and experimental time (the experimental time is reduced by a factor of 12-14) as compared to the present standardized method.