In this paper, a model of a disc type winding for a transformer with directed oil flow is presented which utilizes a network of oil flow paths. Along each path segment, oil velocities and temperature rises are computed. The model includes temperature dependent oil density, resistivity, and oil viscosity and temperature and velocity dependent heat transfer and friction coefficients. Because of the non-linearity, an iterative solution is necessary. Temperature and oil velocities are computed and compared with experiment values. From this, the average winding temperature rise and the hot spot temperature can be determined. The model assumes the oil flows in definite paths and ignores local circulation, since we assume the oil flow is guided by means of oil flow washers, this assumption should be fairly accurate. The disc type winding is assumed to be subdivided into directed oil flow cooling paths.

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