A thermohydraulic modelling for the stator bars of large turbogenerators: development, validation by laboratory and on site tests

This paper presents a thermohydraulic model of stator bars in large turbogenerators. From the losses dissipated in a bar and considering the heat transfer by conduction and convection, it calculates the hot spot temperatures in it and the slot thermocouple temperature, for a clean or polluted stator. This model has been validated by laboratory tests made on individual bars and also by on site measurements made on a 900 MW turbogenerator. It shows the difficulty for the detection of hot spots by a slot thermocouple, and its systematic detection by the water temperature measurement at the bar outlet end. The modelling may be applicable for water-cooled machines ranging from 600 MW up to 1500 MW.