Bicen, Yunus2025-10-112025-10-1120252451-9049https://doi.org/10.1016/j.tsep.2025.103416https://hdl.handle.net/20.500.12684/21922The life of the insulation in oil-immersed transformers is greatly shortened over time by the rise in moisture content if dehydration is not carried out when necessary. This study demonstrates the superior aspects of the online dehydration system in hermetically sealed and free-breathing transformers using Kraft and thermally upgraded Kraft paper as the main insulation material. Twenty separate scenarios have been investigated, each with its own unique combination of insulation type, temperature, moisture, and oxygen level. The results demonstrate that using online dehydration systems can significantly increase life expectancy. The insulation life of hermetically sealed transformers, for instance, is increased by 1.9 times at 110 degrees C and further at lower temperatures. Online methods outperform conventional dehydration systems in terms of prolonging the insulation's lifespan. Theoretically, offline (traditional) dehydration techniques can extend insulation life by 2.5 times, however, online dehydration systems can improve this rate by up to 7.43 times. Dehydration systems have been shown to significantly increase insulating lifespan, particularly in transformers operating at low temperatures. Also, thermally upgraded paper is more sensitive to dehydration processes than Kraft paper. Given all of these results, online dehydration technologies have the potential to significantly improve transformer durability and reliability.en10.1016/j.tsep.2025.103416info:eu-repo/semantics/closedAccessAgingDehydrationInsulation lifespanLife extensionReliabilityTransformerMoistureArticle602-s2.0-85218173043WOS:001430467000001N/AQ1