Research on oxidation stability of insulating oil containing trace water based on infrared spectral analysis

Key words:  trace water  infrared spectrum  insulating oil  oxidation stability  total acid number

Abstract:

The acid value of insulating oil will change when it was polluted by trace water, and the oxidation stability can be influenced, so it is necessary to investigate the intrinsic relationship between trace water and the acid value of oil for the safe and reliable operation of insulating oil. Firstly, a series of oil samples with different content of trace-water were prepared, and the thermal oxidation experiments of the oil samples with 164 hours were conducted. Then, the experiments of mid-infrared spectrum scanning and total acid number (TAN) were conducted for the oil samples, and the changes of absorbance values at the wave-number of 3650 cm-1(phenolic hydroxyl group of T501) and 1700 cm-1 (carbonyl group of organic carboxylic acids) were analyzed before and after thermal oxidation experiments, the relationship of total acid number with water content was obtained. Finally, the multiple linear regression(MLR) calculating model was established. The results show that the goodness of fitting model is 0.9792, the residual sum of square is 1.1726×10-6, and the error is from -2.50% to 3.77% between the calculated values and the measured values according to the model. This model can reflect the relationships of TAN and the status of oxidation stability of insulating oil with different trace-water contents accurately.