overspeed limit for hydro generators

[edison123]

For a pelton wheel hydro generator, what is the speed limit to be set on mechanical and electrical overspeed protection ? What is the applicable standard ?

 

[itsmoked]

Doesn't it totally depend on the size of the wheel?
Are you talking a 6 inch one or a 6 foot one?

 

[edison123]

I didn't know the limit depended on the size.

The machine is 25 MW, 14 pole, 428 RPM with a 60 ton generator rotor and 15 ton turbine pelton runner

 

[RRaghunath]

In Hydro turbines, the runaway speeds are generally high, of the order of 180% for a 30MW Pelton turbine with 600rpm rated speed (typical).

The governor is expected to limit the speed rise on full load rejection to 110%. Hence, the trip setting for overspeed can be set to 110%, I think. Electrical overspeed setting is normally kept a little lower than the mechanical overspeed setting, say 108%, normally.

 

[edison123]

Thx Ragunath. That was the info I was looking for. Is there any standard that specifies this ?