Analysis of transformer oil degradation due to thermal stress using optical spectroscopic techniques

Summary The power transformers are continuously under the impact of electrical and thermal stresses. These stresses are primarily responsible for the occurring incipient faults such as partial discharge, arcing, and pyrolysis. The incipient faults, if not taken care at the earliest, cause the insulating transformer oil to degrade and transformer failure over a period of time. Therefore, monitoring and diagnosing the power transformer have become an inevitable task for its effective functioning. In this proposed work, thermal analysis on different transformer oil samples has been performed by using optical methods such as ultraviolet‐visible spectroscopy, Fourier transform infrared spectroscopy and Nuclear magnetic resonance (NMR) spectroscopy. The obtained results with UV‐visible spectroscopy method exhibit proportional degradation of the oil samples with temperature rise. The Fourier transform infrared method identifies the dissolved gases (ie, CH 4 , C 2 H 6 ) released during the decomposition of hydro carbon present in the transformer oil. Finally, NMR spectroscopy method also confirmed that it has the potential to monitor the decomposed oil by investigating the region under an NMR signal which is proportional to the number of absorbing protons. The employed photo‐spectroscopic methods can be best alternative next to so called dissolved gas analysis method.