Analysis and Investigation of the Main Causes in Overheating the Frontal Areas of Stators at Vertical Hydro-generators

Many Romanian hydroelectric power plants commissioned during 1970-1990 are nowadays confronted with overheating in front of the turbines' stator. For determining the main causes responsible of overheating during the functioning, the flowing rate, temperature, and the installed power were measured. These parameters were correlated with the water level from lake and the characteristics of the hydraulic machines. Ten of all tested turbines have a pronounced overheating in both modes of operation, inductive and capacitive. In these conditions, the turbine can not attend the secondary voltage control, neither at the power-frequency control. In the present paper from all the tested turbines confronted with the same problem, three turbines were selected. The obtained results for some aerodynamic and hydrodynamic parameters considered the main cause of improper functioning are analyzed. A new and unconventional solution for accomplishing the measurements was tested. The realized mathematical model establishes the necessary ventilation and the hydrodynamic parameters during the functioning. The obtained results were used as input data for the numerical model. The water level from the lake influences the proper functioning of the hydro-generators. The developed mathematical model enables the determination of the overheating causality. Some new solutions and constructive modifications are proposed, for improving the turbines operation. Finally, some conclusions and references are presented.