Temperature Rise of an Oil-Filled Transformer with Varying Load

An oil-filled transformer is modeled as a fifth order system and a systematic procedure for the determination of the eight thermal conductances of its analogous circuit, based on measurement of the driving-point and transfer thermal impedances, is developed. It is shown that provided the matrix of these impedances is made entirely consistent with the analogous circuit model, it may be inverted to give the thermal conductance matrix directly. Since these conductances are not constant, this must be done for several conditions of controlled loss so that each may be obtained as a function of the mean temperature rise of the oil.