Improved prediction of temperature distribution in power transformers.

In modern development of transformers there is a strong requirement for a save thermal calculation on the one hand and - on the other hand not to use more material and further resources than necessary. These aims can only be achieved by a precise calculation of the temperature distribution in the windings. The conventional way of calculating the temperature distribution is to calculate the bulk temperature of the oil in the winding channels by the known losses, the flow rate and the heat capacity of the oil. The temperature in the solid insulation is further calculated by an assumed heat transfer coefficient which is in reality known only very roughly. The topic of this article is a more precise alternative way of calculating the temperature distribution by first calculating the flow field by CFD (Computational Fluid Dynamics) models and therefore get a much more accurate value for the local heat-transfer coefficient between oil and solid insulation.