Sensitivity of transformerʹs hottest-spot and equivalent aging to selected parameters

In 1995, IEEE released a revised Transformer Loading Guide which includes an Annex G that contains an additional set of transformer temperature equations that incorporate oil-flow phenomena, changing ambient air temperature, and account for the change in resistivity of the winding due to heating. These new equations involve empirical exponent variables that account for properties of the transformer. This paper investigates sensitivity of hottest-spot temperature and equivalent aging of transformers with respect to these variables. By varying these variables under various load conditions and by Monte Carlo simulation with different probability distributions of these variables, their importance in the transformer model and their influence in modeling accuracy pertaining to the Annex G equations have been obtained.