Effect of ageing in transformer oil using UV-visible spectrophotometeric technique

Abstract

In power systems, varieties of insulation materials are used to protect the high voltage power apparatus such as transformer, switchgear, current transformer, potential transformer etc. One of the most common liquid insulating materials used as a dielectric medium in transformers is the transformer oil. The transformer oil is degraded due to the combination of the ageing processes such as partial discharge (PDs), electrical arcing, and thermal ageing while it is under operation during its long period of service. In this work, the effects of different ageing processes on the optical absorption properties of insulating oil of a model transformer is studied using a UV-visible spectrophotometer diagnostic method which is presently becoming a popular method to identify the ageing of the insulating oil of high voltage transformers. It is found that the aged transformer oils exhibit optical absorption in 200–400 nm wavelength regions. The optical quality of the transformer oil is mostly degraded due to PDs, and sharp and prominent absorption peaks appear at 293 nm, 306 nm, and 324 nm wavelengths, for sample which is aged due to PDs. For other aged samples, the peak at 306 nm is absent and the optical absorption characteristics are almost similar to that of the new transformer oil.