The behavior of different transformer oils relating to the generation of fault gases after electrical flashovers

Abstract Dissolved gas analysis is a common technique in the supervision and maintenance of transformers. It can give hints on defects and faults in oil-immersed transformers by determination and quantification of gases arising in consequence of thermal or electrical stress. Different algorithms for the assessment of transformers, which employ data obtained from dissolved gas analysis, have been published so far. However, only few investigations, dealing with the influence of the oil’s composition towards the oil’s tendency of releasing gases, exist. This research study presents a comparison of three commercially available transformer oils of different composition regarding that aspect. The results indicate that an oil with high percentages of paraffinic hydrocarbons forms gases to a lesser extent than naphthenic oils when it is exposed to electrical stress. This phenomenon can be explained either by a variable solubility of gases in the medium oil, or by the presumption that cyclic hydrocarbons are the main producers of gases.