Heat trap detection in the stator bar of large turbogenerators during the fault of cooling water channels blockage

Cooling water is used to remove the heat from stator bar of large turbogenerators and prevent additional temperature rise. Blockage of these channels leads to heat traps along the stator bar and its temperature failure. In addition, transposition of strands in a bar causes accumulation of heat in some parts of stator bar because of non-uniform arrangement of cooling channels especially when some of channels are blocked. In this paper, effect of cooling water channels blockage is studied using a precise thermal model. It is shown that such heat traps cause additional temperature rise in stator bars and this phenomenon can not be detected by thermal sensors of turbogenerator. Laboratory and onsite experimental data are presented to verify the simulation results. An operation program is proposed to work with generator in faulty cases.