الفهرس 
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Abstract
one of the major faults in transformer is thermal degradation of the oil and paper insulation in the trasformer. dissolved gas-in-oil analysis (DGA) is a sensitive and reliable technique for the detection of incipient fault condition within oil-immersed transformers by presence of certain key gases is monitored and quatified.
there are a number of methods developed for analyzing these gases and interpreting their significance: key gas, rogers ratios, doernenburg, logarothmic nomogragh, IEC Ratio, basic ratios and duval triangle etc. this present work investiates the accuracy and consistency of these methods in interpreting the transformer condition. in addition, the degradation of paper insulation evolves furan compounds, which will reduce the life of transformers, and prediction of furan content in transformer oil has been proposed.