Power transformers are the vital equipment in the network of power generation, transmission and distribution. Mineral
oil in oil-filled transformers plays very important role as far as electrical insulation for the winding and cooling of the
transformer is concerned. As transformers are always under the influence of electrical and thermal stresses, incipient
faults like partial discharge, sparking and arcing take place. As a result, mineral oil deteriorates there by premature
failure of the transformer occurs causing huge losses in terms of revenue and assets. Therefore, the transformer health
condition has to be monitored continuously. The Dissolved Gas Analysis (DGA) is being extensively used for this
purpose, but it has some drawbacks like it needs carrier gas, regular instrument calibration, etc. To overcome these
drawbacks, Ultraviolet (UV) -Visible and Fourier Transform Infrared (FTIR) Spectro-photometric techniques are used as
diagnostic tools for investigating the degraded transformer oil affected by electrical, mechanical and thermal stresses.
The technique has several advantages over the conventional DGA technique.