Governor class, steady state speed regulation and variation

[2012TECH]

ANSI B133.4 – 2.2.1 Steady State Speed Regulation or droop shall be capable of adjustment within range of 2 to 6% at rated speed.
Can someone explain what this mean?

 

[byrdj]

Doesn't ANSI provide definitions?
Stead State Speed regulation(SSSR)- the increase in turbine speed that result in control valves (CVs) going from full load to no load.
if a 60 htz system, and
SSSR set for 2%, an increase to 61.2 htz will force the unit from full load to no load,
or if
SSSR set for 5%, an increase to 63.0 htz will force the unit from full load to no load.
Now there may be some differences of where full load and no load CV position occures. the easiest approach is to use CV wide open and no load flow.

To measure an unit's response, the Droop is measured with the unit off line, unit running at a speed above rated (usually rated plus the expected SSSR%), isolated steam to the CVs and allow the speed to begin to decay. as the speed decays, the CVs will respond in an attempt to restore speed. the speed at which the CVs reach the full load lift would then be used to calculate the actual SSSR.

an example of such a calculation for a mechanical govenor and the errors that can occur is illustrated in my report of

http://www.slideshare.net/JosephFByrdJr/lynn-droop