The runaway speed of a hydraulic turbine is the speed?

Question

A. at full load.

B. at which cbe no damage to the runner

C. corresponding to maximum overload permissible

D. at which the turbine will run freely without load

Answer 1

D...At which it will run freely without load.

However, High speed turbines, Hydro, Steam or Gas Turbines, are fitted with an 'Overspeed Trip' mechanism that, should the 'Maximum Operating Speed' be exceeded by about 10%, (due to a sudden drop in load), the mechanism will safely shutdown the turbine thus preventing damage..

Overload tends to slow down a turbine.

Answer 2

The answer is neither, the runaway speed is speed with no load that the turbine will keep accelerating until it fails that is why most motors say do not connect to power without a load.