How to calculate GD2 of hydro generators for stable functioning of plant.?

Hello Prashant,

Are you asking in the context of Bentley HAMMER (for hydraulic transient simulations) or are you using different Bentley software? Can you tell us a bit more about what you need to simulate?

In HAMMER, you can model transients caused by sudden changes in turbine operation such as rapid closure or opening of the wicket gate. One of the parameters you need to define in order to model the turbine is the Moment of Inertia. I assume this is what you are referring to. Moment of Inertia for a turbine in HAMMER is defined as WR^2 (not GD2) where W is the weight of the turbine and R is the "radius of gyration". See more in the section "What value should I use for moment of inertia of a turbine?  Should I use WR^2 or GD^2?" in the following article: Modeling reference - Turbines

Turbine inertia can impact the transient response, but as for the part where you say "for stable functioning of plant", you might be referring to something else, so some clarification would help. Generally speaking the wicket gates would be closed fast enough to avoid "runaway speed" of the turbine impeller during load rejection situations (maybe this is what you mean by "stable functioning"?) but not too quickly so as to cause a damaging hydraulic transient. This is modeled by way of the "instant load rejection" Operating Case in the turbine properties along with the wicket gate closure pattern "Operating Rule". See more in the Modeling Reference article above.