Dynamical thermal model of oil transformer placed indoor

An important question in power utility is the estimation of additional heating of power transformers due to indoor placement. This depends dominantly on the size, type and position of ventilation jalousies, through which the air enters and exits the room. The heat transferred from the transformer cooling surfaces to the surrounding air is transferred outside the room by natural ventilation through the jalousies and by convection and conduction heat transfer through the room surfaces. Due to variable load of the transformer and variable ambient temperature, transient thermal processes appear and dynamic model is to be applied. The paper presents detailed dynamic thermal model of the transformer and the room, taking also into account the influence of wind velocity to convection heat transfer from outer room surfaces and the influence of sun radiation.