Tube aging and oxidation of naphthenic and paraffinic transformer oils

The major components of the insulation system in oil-filled transformers and allied electrical equipment are paper, wire enamel, and the oil itself. The degradation of any one of these materials may affect the degradation and hence the performance of the others. The work reported here was undertaken in an attempt to assess the affect on the degradation of these components of a change from transformer oils derived from napthenic crude stocks to oils derived from paraffinic crude stocks. Oxidation of oil is the primary cause of degradation of oil during normal operation of transformers. The amount of oxygen remaining after manufacture or filling of transformers is usually limited. However, additional oxygen may reach the insulation system during servicing, through leaks or by diffusion through polymer seals or diaphragms. Particular attention has been paid to the comparative oxidation of naphthenic and paraffinic oils.