Aging of Cellulose at Transformer Service Temperatures. Part 1: Influence of Type of Oil and Air on the Degree of Polymerization of Pressboard, Dissolved Gases, and Furanic Compounds in Oil

摘要

A power transformer is expected to operate up to 40 years. With current cost-benefit calculations, the user is forced to perform maintenance that will bring a further extension of the transformer life. The maintenance can only be based on on-site and off-site monitoring with extended analytical and electrical tests, which can define the service condition of the transformer and predict its further life expectancy. The investment boom of the 1970s determines, to a large extent, the age distribution of transformers in service, and the percentage of transformers older than 30 years is increasing in both the utilities and industry. Highly loaded generator and furnace transformers show a more accelerated aging in comparison to grid units. It is not unusual that older transformers have 3 to 4% humidity in the solid insulation.