Rehabilitation of Water Flooded Hydro Generator

Rehabilitation of water flooded hydro generators ensures improved performance and enhanced service life. Water ingress into the insulation system of the winding not only negatively impacts the dielectric strength, it inhibits the power production. It is difficult mission to clean the muck and dry up the wet insulation to uphold the rated potential of the machine. If it is an old hydro generator with aged insulation system, renovation is time consuming which may take months as most of the insulation materials are hygroscopic. In this paper, refurbishment approach is put forward for a water flooded 50 years old hydro generator of 40 MW, 11kV rating where the asphalt insulation system was extremely soaked in rain water and unattended for an year. The task begins with condition assessment study followed by drying techniques to remove moisture in order to improve the dielectric strength. Analysis of insulation resistance test results which is considered as the criterion factor that influences the method of drying is presented. The better way to raise up the winding is the oven drying process of individual coils through which the dielectric properties are assured at minimal expenditure and in less time. This work promises guiding instruction for accidentally water immersed windings of old hydro generators.