Hello,

I work in a power plant in Nigeria. We lost 4 of our gas turbines of 20MW capacity each due to an external factor. Unfortunately, for close to 5 hours, we could not run them up as the units enter temperature control during run-up. This same issue happens to the 4 units at the same time. What could be the reason for this?

 

So if I understand correctly, you were trying to increase load on these turbines but they were entering exhaust temperature control at a load much lower than expected?

For all of the turbines to react this way, I would look to see if there were any changes to the exhaust temperature control logic or changes to the IGV settings.

Other causes could be lower than usual turbine speed (low grid frequency) or hotter than usual ambient air conditions.

 

It would REALLY be helpful if we knew:

1) Fuel being burned when the units tripped

2) Fuel being burned during re-start attempts

3) Turbine manufacturer and model

4) Age of turbines

5) Type of combustion system (conventional (diffusion flame); emissions reducing combustion system (DLN (Dry Low NOx))

6) Turbine control system used on the four machines

7) Alarms annunciated during the run-ups that failed (ALL alarms, Process and Diagnostic if the turbine control system is so configured)

8) Do the machines exhaust to atmosphere or into an HRSG ("boiler")

9) How many times was START pushed during the five hours?

10) What was done during the five hours to try to understand the issue(s)?

11) If the machines can exhaust into an HRSG is there a damper tin the exhaust duct hat can be used to choose between atmosphere and HRSG (often called a "diverter damper")? And if the machines have a diverter damper, what position were the dampers in before the trips and during the machine re-starts?

12) Were any of the exhaust thermocouples providing readings that are much higher or lower than the other exhaust thermocouples during the run-ups?

Good try, but even the experts need actionable data and information. We can't come up with a concrete solution or more than @MattyIce offered with the information provided in the original post EVEN if we knew about the machines and the control system(s) and the specifics of the situation. Even if we're on the Internet/World Wide Web. Even if we provide information for free. (A paid consultant would ask similar questions based on the information provided--and charge a LOT more money.)