Abstract: Optimizing the closing rule of turbine wicket gates is crucial to the calculations of guaranteed regulation for hydropower stations. A reasonable closing rule can reduce water hammer pressure and limit hydro turbine unit speeds, providing an effective, economical measure. In this work, we develop a mathematical model for the transient process in a water diversion system of a hydropower station, conduct simulations of the process under the control conditions of the station, and examine the influence of closing rules of turbine wicket gates on the diversion system. Results show that quick-then-slow closure is an effective rule applicable to the hydropower stations where extreme water hammer pressure and extreme rotational speed occur in different working conditions. And for this type of hydropower stations, this rule can overcome the problem with the direct closing rule that cannot meet the requirement by guaranteed regulation.

Key words: hydraulic transient process, two-stage closing rule, unit rotation speed, volute pressure, calculation condition