Turbogenerator refurbishment with up-rating based on embedding stator damper winding and modern electromagnetic materials

40 MVA two-pole air cooled turbogenerator has been up-graded with stator refurbishment only. Generator active power has been increased from 32 MW to 42 MW with reference to 31% and apparent power has been increased for 23.5%, from 40 MVA to 49.4 MVA. It was necessary to redesign stator core and winding, to embed the stator damper winding and implement new magnetic and insulating materials in order to reach new higher power. Redesigned stator core needs to be of the same outside dimensions as the original one, and to be placed in the old stator casing. Refurbishment requirements with remaining the original machine parameters (but higher output) such as synchronous reactance, audible noise level, voltage and frequency regulation, reactive power and temperature rise in insulation class B have been achieved. Impact of embedding the stator damper winding has been determined by finite-element analysis since the other parameters of refurbished generator have been calculated using analytical and finite element modeling.