Power system problems associated with low-head hydroelectric units

Large scale use of low-head hydroelectric units require their integration in an electric power system. Two of the associated problems -- namely, stability and operating reserve, are analyzed in this paper. Special features and operating characteristics of three types of turbines -- tube, bulb and straflo -- are also discussed here. Stability problems, resulting from different inertia (H) and damping (D) constants, associated with low-head units are analyzed. The effect of damping on generator rotor angle response characteristics is found to be quite conspicuous. The effect of the length of the penstock on the overall turbine-generator performance is discussed. For the purpose of analyzing the operating reserve, a group of low-head hydroelectric units operating under the umbrella of an electric utility is compared to a group of utilities operating in an integrated power pool. Availability and use of momentary, quick start and slow reserves in a subsystem containing low-head units are analyzed. It is found that some of these reserves must come from sources outside the subsystem. Consequences of such arrangements are discussed.