1. A method for identifying a type of abnormality in an insulation system of a power transformer, comprising: measuring dielectric losses in a section of the insulation system; calculating theoretical dielectric losses for the section based on the material properties, geometry, and temperature of the section; generating a graphical representation of a percent difference between the measured and calculated dielectric losses; and comparing a shape of the graphical representation with a shape of one or more graphical representations of a percent difference between measured and theoretical dielectric losses in one or more other sections of insulation each known to have a specific type of abnormality.