Hydroelectric turbine setting – a rational approach

There are no standards for the setting of a hydraulic turbine with respect to the tailwater level. Manufacturers rely on hydraulic model data to determine the required protection against cavitation, and never publish these data. Utilities and consultants must then rely on the interpretation of published statistical data relating submergence to various turbine parameters. In this paper, an alternative approach is proposed wherein a general equation is developed relating the submergence of a stainless steel or cast steel runner to the number of runner blades, the plant capacity factor, the turbine throat velocity, the tailwater level above sea level, the water temperature, and the acceptable amount of cavitation. The equations have been tested on 39 different power plants having either horizontal or vertical axis Kaplan, propeller, or Francis turbines, both large and small. The equations are particularly useful for establishing the turbine diameter and setting during feasibility assessment, and for comparin...