IV valve "reference" is the "desired" valve signal that is summed with regulated speed error to derive the EsubL-IV signal to the IV flow control loops (there is a loop for each servo controled IV). the referance is ganged with the CV reference so that a CV referance for 0% CV will povide 100% IV referance. the gain of SE is such that a 2 to 3 % over speed will close the IVs. the IV referance can be reduced to perform reheater safety valve testing.
Some times some people interchange the phrase "referance" for "EsubL-IV". Also "CV reference" can be confused with "load set" and when there is no loading rate control the two are the same
Thanks, Byrdj, your right the IV valves will try and control speed in a pre emergency overspeed situation but I forget to add that this mark vi control system is for a G.E. reverse flow turbine we roll up and load the unit to approx 30% megawatt load on the intercept valves then place the turbine in foward flow IE: Steam flow through the main steam stop valves and control valves this is where the IV reference comes in it determines through some cal if the turbine will stay in foward flow this is what I don't understand thanks
If you don't mind I will guess at how the normal system could be used to roll on the IVs.
As stated the CV reference and IV reference are ganged together, in fact they are same value, the CV reference is summed with a set 100% bias to derive the IV reference. a 0% CV reference will will have the IV's 100% open, and a -30% CV reference will have the IV's at 0% open.
Thus set the CV referance to -30% and speed error will control the IVs near 0% open to roll the unit. once "at set speed" rated, the CV referance will be increased, increasing the IV referencae to synch and load the unit. as the IVs open and increase load, the CV referance will be approaching 0%, once IVs are at 100%, the CVs will be opening and continue to increase load.
That would be my guess.
Sounds like an interesting system, much more so than the straight forward speed control units I put into service 20 years ago.
