A comparison of bubble evolution temperature in aramid and cellulose paper

The paper deals with the problem of the bubble effect in transformer winding insulation. The bubble effect should be understood as the release of water vapor from insulation. The main goal of the research was to compare the initiation temperature of bubble evolution in aramid and cellulose paper depending on the water content. Cellulose and aramid paper samples of different water content were prepared for the research study. The obtained results confirmed that aramid paper is less hygroscopic than cellulose paper. It was also proven that the initiation temperature of bubble evolution is lower for aramid paper than for cellulose paper with the same water content. However, the initiation temperature of bubble evolution is very similar for aramid and cellulose paper conditioned at the same relative humidity.