Turbine Max. Speed at 100% Load Dump test

[ilan7]

Hi to all
We installed a 2 MW turbine and Generator connected to the grid (6.4 KV, 60Hz). While performing a 100% load dump test, the max. Turbine speed was 21% over the normal speed (1,800 rpm). We have certified test reports from the generator and the turbine manufacturers for 130% speed 3 min. tests. Is there any regulation that specify the maximum speed in this case? We talking 2MW, 1,800 rpm Turbo-Gen. set.

 

[byrdj]

Is the turbine steam or combustion?
if steam:

ASME PTC20.1 & 0.2 (i don't think they are no longer in effect) can be used to define the terms and testing methods. However, the manufacture has to supply the key critera based on unit design. IEEE 122 is supose to provide requirements, but I have not read those standards.

The full load rejection critera in effect a decade ago for steam turbines, required the unit peak speed to be less than "Over speed trip" (provided by OEM, usually 110 to 115%) and have a "settle speed" between 100 and 107%(to carry house load).

 

[Tmoose]

I was real interested to hear your load dump results.

I think "Regulating" the overspeed would be tough.

Just starting on a High speed direct drive generator to replace a big heavy geared generator. We are designing our generator for 125% based on 120% Gas Turbine overspeed despite GT trip at something like 105% or 108%. We are required to have a shear type coupling. I'm thinking the turbine would really rev up if the coupling sheared and all the "flywheel" disappeared.
Structural integrity of the generator is one problem for us. Another limit I've run against in other applications is bearing seizure from cascading bearing thermal preload increases in the 1 to 15 minute range (bearings over 1,000,000 dn). Steel and hybrid precision angular contact spindle bearings.