Effect of Oxidation of Aged Power Transformer Insulating Oil on UV-Vis Spectra

Abstract

Optical spectroscopy is a major rising condition monitoring tool used to assess the status of the insulating oil in power transformer with a non-destructive approach. Accelerated thermal ageing studies have been discussed considering the effect of temperature on the oil condition. These studies didn't perfectly reflect what is happening in a real in-service power transformer due to the absence of copper catalyst in the ageing process. This paper discusses the effect of oxidation for a more precise simulation of the in-service ageing process of insulating oil. The optical results when copper catalyst is included in the accelerated thermal ageing process are compared with previously obtained results of accelerated thermal ageing to deduce the change that took place in the UV-Vis spectra. Dielectric dissipation factor is assessed to correlate between the optical spectra and transformer oil characteristic parameters. Dissolved decay products were calculated for the samples containing copper catalyst with the same ageing days compared to only thermally accelerated aged samples without the addition of copper catalyst. Dissolved decay products were correlated to both ageing days and dielectric dissipation factor. It was found that the copper catalyst caused a great difference in the obtained UV-Vis spectra.