Average Degree of Polymerization Dependence of Insulating Paper Rupture in Bending Test about Thermally Upgraded Kraft Paper Wrapped Copper Windings

Abstract

The bending test was conducted to establish a guideline for a transformer life, which uses the thermally upgraded Kraft paper (TUK) wrapped copper windings. Test samples were prepared with different degrees of deterioration by heat treatment. The breaking strength of the insulation paper shows that the average degree of polymerization, which corresponds to a load capacity of 1200kgf/cm² was approximately 300. However, it was shown that the TUK windings had a smaller load capacity than the regular Kraft windings in the DP range of 500 to 900. The tensile properties of the insulating paper were tested and considered that the decrease in breaking elongation not the strength causes the difference in load capacity between the two.