My gas turbine is 30MW MK-4. I can control the MW from 5MW to 24MW. but if i set the load setter to 30MW (in AUTO mode), the load doesn't increase over 24MW and at 24 MW it changes to MANUAL mode. On the other hand i cant increase the MW to 30MW manually as well.

Please, help me .....what is the problem and solution?

 

Hi,
What is the control mode, when the load is 24 MW (Load /temperature)?

Once the unit reached temperature control, it can't produce additional load.

Do you have strainer in the gas line? If yes inspect for the cleaning.

Do you have normal hydraulic pressure?

take care
G.Rajesh

 

It is quite unlikely any person can help you out. The information given is very little to come up with meaningful conclusion.

I think this is the best I can do from the given scenario. The load never increase to 24MW because the control limits it to 24MW. Why? Many possible reasons that nobody can tell you without having detail information.

Let me play dice for this one. I think your controller has found out that for the given ambient temperature the maximum GT output has been reached. In order to increase the load by says additional 1MW you have to increase the machine RPM says by 10rpm (Example only). But then the controller already sees that your machine has already operated at 3300RPM, i.e. the maximum RPM (example only) it can go. It fuel controller never defines anything above 3300rpm!

Don't confuse grid frequency and supposed to be equivalent prime mover's frequency. The prime mover does not know what is load. It just knows what RPM it shaft should rotate to get the desired load. Then it feeds this requirement to the desired fuel controller. In the case of the controller sees the RPM is already reached the maximum designed RPM then it will assume maximum GT output has already been reached. Whether in auto or in manual the same thing holds.

Why? We keep "why" part later. You have to confirm this is the case.

How? I don't expect it is going to be an easy job but it is doable. I have done it once two years ago. The plant owner had tried for 3 years to determine why one of its GT was 3MW lower than the other similar unit in the plant. The fuel flow has not yet reached to the rated maximum. The exhaust temperature was still many degrees lower than the rated. But the fuel control valve just didn't respond (manually or in auto) to the raise command.

After about two days studying the logic control I found out that the controller saw that the GT had already achieved the maximum RPM at 2850RPM, due to faulty of one the input data, i.e. compressor inlet temperature. The plant engineers had confirm this is the case after they went through load trending based on 3 months historical data.

 

Please take the time to answer G.Rajesh's questions; they are prescient and germain to the problem.

However, as Namatimangan08 has said, without being about to see the sequencing running in the Mark IV at your site it's probably going to be very difficult to say what is limiting the load. You say you can "manually" increase the load, so it's not hitting temperature control when the load is being limited while trying to load under Preselected Load Control. I also presume you are changing the setpoint on the Mark IV, and not via some external load control system sending discrete raises/lowers or a mA signal to the Mark IV.

What Process- and Diagnostic Alarms are present when the load is being limited?