Sealed Vessel Tests for Determination of Arrhenius Curve Parameters

This paper reviews the natural ester aging data found in Annex B of IEEE C57.154 and adds new aging data that extends the original aging times. It presents the results from almost 3.5 years of accelerated aging tests, consisting of thermally upgraded Kraft paper in soybean oil and high oleic sunflower oil using both glass and steel aging vessels. Aging temperatures were 150°C, 160 °C, 170°C and 180 °C. Additional aging systems consisting of thermally upgraded Kraft paper in mineral oil were run as reference systems. The paper in mineral oil aged at rates consistent with the IEEE mineral oil unit life equation, sufficing the test validation criteria defined in IEEE C57.100. The natural ester data was consistent between the soybean oil and high oleic sunflower oils as well as between the glass and steel aging systems. The unit life coefficient is recalculated incorporating the new data, confirming the previously adopted values of thermal classes.