Extension of generator lifetime by winding renewal

Two hydro generators were chosen to renew the stator winding. The motivation of this investment was an expertise about the condition of the generators. Beside technical diagnosis the operational dates and maintenance history was taken into account as well as the age of these generators. The stator windings were replaced with an insulation system that had the benefit of a 10 % power increase. The aged generator bars were tested in laboratory with the focus on the residual lifetime. Voltage endurance tests and optical investigations were done and statistically analysed. The result of these investigations confirmed the decision of the renewal of the stator winding.