A hydro turbine on a dam with no penstocks can probably go from 0-100% in 5 to 10 seconds. The limit is pressure waves in the water conveyance system due to ch

A hydro turbine on a dam with no penstocks can probably go from 0-100% in 5 to 10 seconds. The limit is pressure waves in the water conveyance system due to changes in flow through the turbine. If the water conveyance system is only the width of the dam and encased in concrete it is going to have minimal transients compared to a 7km long steel or HDPE penstock on which the time from 0-100% is more like 2 minutes