It is well known that the paper and oil used in transformers Degrade with time at rates which depend on the temperature and the amount of air and water present [1, 2]. Various devices such as completely sealing the units, using nitrogen blankets and using flexible membranes, have been suggested as means of improving the lifetime of the oil. In addition, thermally upgraded papers have been devised and have been available for some years. Some supply authorities and transformer manufacturers have been using some or all of these devices with varying degrees of success. Many others have taken the stance of cautious awareness. In the absence of any evidence that normal papers are inadequate, they have continued to use them in transformers fitted with conservators. As part of this current overall package of research, paper aging was re-examined with a view to reassessing the need for change, either in the materials or practices Used or in the preservation systems
