Abstract
Mineral oil is the most popular insulating liquid for high voltage transformers due to its function as a cooling liquid and an electrical insulator. Kraft paper has been widely used as transformer solid insulation for a long time already. The degradation process of transformer paper due to thermal aging in mineral oil can change the physical and chemical structure of the cellulose paper. Fourier transform infrared (FTIR) spectroscopy analysis was used to identify changes in the chemical structure of transformer paper aged in mineral oil. FTIR results show that the intensity of the peak absorbance of the O–H functional group decreased with aging but the intensity of the peak absorbance of the C–H and C=O functional groups increased with aging. Changes in the chemical structure of the cellulose paper during thermal aging in mineral oil can be analyzed by an oxidation process of the cellulose paper and the reaction process between the carboxylic acids in the mineral oil and the hydroxyl groups on the cellulose. The correlation between the functional groups and the average number of chain scissions of transformer paper gives initial information that the transformer paper performance can be identified by using a spectroscopic technique as a non-destructive diagnostic technique.
Highlights
Operational conditions of the transformer such as increased loading and short-circuit power might affect the ability of the transformer to endure the mechanical, electrical, and thermal stresses that occur
This paper reports the chemical structures of transformer paper aged in mineral oil using Fourier transform infrared (FTIR) spectroscopy
The activation energy represents the energy that the molecule in the initial state of the process must about the thermal aging of transformer paper in mineral oil is shown in Equation (2) [33]: have before it can take part in the reaction
Summary
Operational conditions of the transformer such as increased loading and short-circuit power might affect the ability of the transformer to endure the mechanical, electrical, and thermal stresses that occur. The degradation process due to thermal aging can change the physical and chemical structure of transformer paper in mineral oil. For insulating liquid performance measurements, the combination of spectroscopy techniques and an artificial neural network is used to obtain the correlation between the spectral response and the chemical and physical properties of the oil. Several works have reported that this combined method has shown the possibility of using the spectroscopy technique for determining the degree of polymerization (DP) and water content of the transformer paper [6,16,17,18] Destructive methods such as viscometry have been widely used for the direct measurement of DP [6,19]. This paper reports the chemical structures of transformer paper aged in mineral oil using Fourier transform infrared (FTIR) spectroscopy. This study gives initial information that the condition of the cellulose paper as transformer solid insulation, which has a direct correlation with the life of the transformer, can be identified by using a spectroscopy technique
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