A Study of Pressboard Monodimensional Impregnation with Transformer Oil and Its Influence on Dielectric Strength

The knowledge of the impregnation mechanism of porous solid insulation seems useful to ascertain the reaching of optimum insulating properties, but the problem has been scarcely dealt with in the literature, perhaps because of the high analytical difficulties resulting if a theoretical approach accounting for all the relevant phenomena is taken. A simplified mathematical model of pressboard monodimensional impregnation with transformer oil is presented, and a method for an experimental evaluation of model parameters is developed. Results of a set of experimental tests carried out by different methods and under different conditions are reported together with experimental tests of breakdown strength during impregnation, and a satisfactory agreement with the model previsions is noted. Finally, plots of approximate values of model parameters for different pressboards are given.