Oil flow damage in Kraft paper 1: Thermal aging

Thermal aging was used as a tool to prepare samples of Kraft paper spanning its entire life cycle in a high voltage transformer, from new to end of life. After characterization of DP and mechanical properties, selected samples were exposed to oil flows mimicking ONAN, OFAF and reclamation conditions. Aging combined with high flow rates, led to significant surface roughening but despite this, no significant erosion was detected even under reclamation conditions. Whilst the tests need to be repeated at higher oil temperatures which more closely reflect conditions in plant, these preliminary findings indicate that the paper insulation component is unlikely to be damaged by normal reclamation activities, even in significantly aged assets.