Thermo-Oxidative Stability of Mineral Naphthenic Insulating Oils: Combined Effect of Antioxidants and Metal Passivator
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- 作者：R. Crisó ; stomo Rabelo Neto ; Daniel O. Lima ; Thauzer D. S. Pinheiro ; Rô ; mulo F. Almeida ; Tereza N. Castro Dantas ; Michelle S. G. Dantas ; M. Adelina S. Araú ; jo ; Cé ; lio L. Cavalcan
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2004
- 出版时间：November 10, 2004
- 年：2004
- 卷：43
- 期：23
- 页码：7428 - 7434
- 全文大小：201K
- 年卷期：v.43,no.23(November 10, 2004)
- ISSN：1520-5045
文摘
The oxidation of mineral oils is the most important cause of poor power transformer performance.High voltages, high temperatures, and the presence of oxygen and metallic surfaces are some ofthe factors that may trigger oxidation reactions. The use of antioxidant additives and metalpassivators in insulating oils has the purpose of improving their performance, by increasingtheir stability to oxidation so as to ensure a more reliable operation of the transformer. Thiswork presents a kinetic experimental study of the oxidation reactions of a naphthenic mineraloil (with and without additives) as a function of temperature. Oil samples were doped withphenolic antioxidants (AOX), a metal passivator (MPA), and combinations of these (AOX andMPA) in order to verify the efficiency of such additives in increasing thermo-oxidative stability.All doped and nondoped oil samples were submitted to an accelerated oxidation test accordingto modified ASTM D-2440 method. The level of degradation was assessed by monitoring thearea under the carbonyl band (around 1713 cm-1) in the FTIR spectrum and comparing it tothat obtained for the new nonoxidized oil. The results obtained for the oxidation of nondoped oilsamples showed that the kinetic behavior may be well represented by a first-order homogeneousreaction rate law, with energy of activation around 10 kcal/mol. Our results also show thathindered phenolic antioxidants significantly reduce the formation of oxidation products. Theaddition of a metal passivator, even at very low levels (8 ppm), causes a synergetic effect withall antioxidants tested, leading to a significant improvement in the resistance of the oil againstoxidation.