We are having 9FA Machines with Mark VI. Can someone please provide me with the droop characteristics for the machine and can two machines have different droop characteristics?

Given a choice shall we settle for two machines with slightly different droop characteristics or with similar droop characteristics but with different control constants?

Request your valuable suggestions in this regard.

 

Please explain what you believe droop does and how you believe a change in the droop characteristic would change a machine's behaviour.

 

Dear CSA, sorry for the late reply

1. Droop,I guess, is the differential between the reference speed and the actual speed when operating the machine in speed/load mode

2. Two newly commissioned machines of same make/model and working under similar ambient conditions with different droop settings (corrected by tweaking the control constants)can have so many implications (as I could perceive, and I may be wrong!!!), some of which are:

a)different fuel flow for similar load
b)difference in IGV or CPD calibration
c)difference in exhaust duct back pressure
d)difference in inlet air flow

 

Droop refers to the amount of load that a prime mover will "produce" for a given error in the difference between the turbine speed reference and the actual turbine speed. For example, a machine with 4% droop will change load by 25% of the machine's nameplate rating for each 1% error in the difference between the turbine speed reference and the actual turbine speed.

The error can occur because either the turbine speed reference changes as the actual turbine speed remains relatively constant ("normal" operation), or, because the actual turbine speed changes as the turbine speed reference remains relatively constant (caused by grid frequency excursion from nominal frequency).

I do not have any point of reference for your statement about two newly commissioned machines with different droop settings. There are lots of machines with different droop characteristics operating on the same grid. And they all operate just fine, thank you very much, without any tweaking.

If you're talking about the fact that two "identical" machines don't produce exactly the same amount of power for the same fuel flow rate and can have slightly different operating characteristics (IGV angle, CPD, exhaust duct backpressure), that's just the way machines work. The internal clearances of the machines are never identical. The orifices of the fuel nozzles are never exactly identical. The calibration of the IGV LVDTs is never exactly identical. The compressors are never equally clean (or dirty). The two machines are never started and stopped exactly the same number of times and at exactly the same rate. The two machines are never tripped the exactly same number of times from exactly the same load. And the two machines are never operated at exactly the same loads for exactly the same periods. There are just too many differences between the way the machines are operated, and this is in addition to the mechanical differences in machines. And droop doesn't have anything to do with these differences. Not a darned thing.

The amount of power produced by a generator being driven by a prime mover is directly proportional to the amount of torque being produced by the prime mover, which is a function of the fuel flow or the steam flow or whatever the source of energy that is being supplied to the prime mover. The amount of droop won't change the relationship between amount of energy required to produce the torque required to drive a particular load.

Droop also will not affect the IGV angle or CPD calibration or the difference in exhaust back pressure or any differences in air flow.

Droop only affects the amount of torque that is produced by the prime mover with respect to the difference between the amount of the turbine speed reference and the actual turbine speed.

And, again: There are many different machines with different droop characteristics all working together to drive a load that is larger than any single machine. That's the nature of a grid with many different generators--and their prime movers--to work together in a stable manner to drive a load that no single generator could drive by itself. And droop is how those prime movers work together to share in driving that large load without fighting each other. And it's also how they will all respond to grid frequency disturbances to help support the load.

But I still don't understand your query. At all. But I do believe that the droop characteristic of a machine, or any two machines, isn't going to solve your problem or problems or dilemma or question.

 

Thank you very much CSA for your detailed reply which helped me in understanding droop better. Let the thread be closed now.