The effect of catalysts in the form of a transformer copper winding with Kraft paper insulation on the lifetime of transformer oil was studied via ultraviolet-visible (UV-Vis) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. The tested naphthenic mineral oil was exposed to accelerated thermo-oxidative aging with limited access to air at temperatures of 110, 120, and 130 °C for times ranging from 24 to 2424 h in the presence and absence of catalysts. The UV-Vis technique focused on assessing the change in the color of the oil and quantified a 35%–45% reduction in oil lifetime, depending on the aging temperature, due to the influence of catalysts. The FT-IR analysis focused on the decrease in the spectral band at 3650 cm−1
, which corresponds to the low-temperature antioxidant present in the oil, and quantified the 35% reduction in the oil lifetime independent of the aging temperature. This high rate of reduction in the transformer oil lifetime points to the dominant catalytic role of the Kraft paper and copper during the aging process of the transformer insulation system.
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