Pressboard aging in different insulating liquids
There is a move in the industry to more and more alternative liquids because they have virtually no impact on the environment. But what happens in the transformer? We will focus on the different impacts each of these types of oil has on the pressboard in the transformer. To give the end-user a better practical guideline when they need to choose an insulating liquid.
Please note that this is experimental data and not industry-based data. The experiment was conducted on 9 different oils, a 3mm thick pressboard was aged in each of these liquids for a 12 month period at temperatures 120, 135, and 150⁰ Celsius in a vessel with an open as well as a closed expansion system. The load cycle has been simulated by decreasing the temperature to approximately 80⁰C for two hours per day.
Ester insulating oils
1. Transformer oil handbook – Nynas Naphthenics – 2004
3. Y Du et al “Moisture solubility of differently conditioned transformer oils.” IEEE transactions on Dielectrics and Electrical Insulation Vol 8 No 5 2001, pp 805-811
4. L Lundgaard et al ” Aging of Kraft Paper by Acid-Catalyzed Hydrolysis” IEEE Transactions on Dielectrics and Electrical Insulation, Vol 15, Issue 2, April 2008, pp540-546