Quantification of changes in surface texture of thermally-aged kraft paper using orthogonal wavelets

Samples of plain Kraft cellulose paper, normally used in power transformer winding turn insulation, were thermally aged in controlled laboratory experiments to obtain a sample set with varying levels of thermal deterioration. Microscopy images from the samples were analyzed using a texture analysis method where wavelet energies at different decomposition levels were calculated. Analysis of our results indicates that as the paper fibers breakdown, the wavelet energies of the texture details are reduced in value in proportion to this deterioration in the paper.