Periodic inspection of power transformers is important to prevent possible failures in power systems. One effective approach is transformer oil analysis. In recent years, the need for a fast, accurate and in situ method has been increased significantly. This research has employed laser-induced breakdown spectroscopy (LIBS) to analyze transformer oil and investigate its aging. For this purpose, changes in the intensity of molecular emissions (C2, CN and OH) and their correlation with aging processes have been used. Spectral investigation showed that Cu lines had been added to the spectra of aged samples. Additionally, the principle component analysis (PCA) method was used to check and compare the overall spectra. Finally, the results of Gas Chromatography (GC) and Acid Number (AN) tests were given to confirm the age of the samples
