Oxidation stability of TUK and Nomex insulated power transformers

In the present paper, oxidation stability of thermally upgraded Kraft (TUK) and Nomex-410 insulated power transformers has been investigated at higher accelerated thermal stresses. Samples having a standard mass ratio of oil and paper insulations in accordance with IEEE Std. C57.154-2012 have been studied. These samples were stressed at higher temperatures between 180
⁰
C and 210
⁰
C. Subsequently, the aged samples were analyzed using ultra violet-visible spectroscopy test. It has been observed from the test results that the oil sample consisting of TUK has the higher absorption coefficient than that of the Nomex immersed oil sample. It indicates the sludge formation due to the oxidation effect in TUK transformers is high. Hence the degradation rate of TUK transformers is more at higher temperatures. Consequently, Nomex-410 insulated transformers have the better operating performance against the oxidation of the insulation at higher temperatures.