Prediction of Hottest Spot Temperature (HST

Abstract—The degradation of electrical insulation in trans-formers is more often due to thermal stress. In this paper, authors have attempted to work out a method of assessing the magnitude of temperature and the hottest region in the body of a large transformer with a reasonable degree of accuracy. A theoretical model has been developed based on boundary value problem of heat conduction in transformer winding using finite integral transform techniques. The model requires, in addition to electrical parameters of the transformer, information on the actual design data. The authors believe that this model predicts HST with precision and also indicates a possibility of online data acquisition. Index Terms—Finite transforms, H S location, heat transfer, IEEE loading guide, oil impregnated paper, prediction accuracy. NOMENCLATURE Diffusivity of insulation-conductor system. Roots of transcendental equation (14). Coefficient of volumetric expansion of oil. Roots of transcendental equation (13). Ultimate bottom oil rise over ambient at rated load Ultimate bottom oil rise over ambient. Characteristic dimension, used in the computatio