An overview of water and relative saturation in power transformers

Water is known to play an important role in the life and operation of oil and paper insulated power transformers. Because the age of transformers in the electric utility industry continues to rise, water in transformers continues to be a significant problem today. The amount of water in the insulation system, coupled with loading and operating temperature data, can provide end-users with critical information for operating and maintaining service-aged transformers. This paper presents an overview of water and relative saturation, based on knowledge that have learnt from both research and practical experience on various issues caused by water contamination in aged transformers. Various methods available to calculate or estimate the overall wetness of the insulating system have been discussed.