Non-stationary thermal model of indoor transformer stations

The paper presents a thermal model of an indoor transformer station. The model includes generation of heat and its transfer from the transformer active parts to the surrounding air, natural air ventilation through ventilation holes, and convection and conduction transfer of heat through room parts. All parameters of the model are discussed and the procedure, based on measurements, for the determination of natural air ventilation parameters is described. The model is tested using measurements on a typical indoor 10 kV/0.4 kV transformer station. The results of the proposed thermal model and those of a simplified approach from Standards are compared.