Minimum Load of Gas Turbine

I Have a Question for Minimum Load of Gas Turbine. Why the Minimum Load of Gas Turbine as per GE instruction and recommendation no less than 2.5 Mw ?

any comment it will be help

 

I don't know what size of machine you have, but the normal setting for minimum (spinning reserve) load is 10% of rated output. With anything below that it is very difficult to maintain Power Factor and there is very good chance that you could trip the breaker on Reverse Power.

 

size of machine 25 mw.

no related with Gas Turbine this load?

 

> no related with Gas Turbine this load?

Sorry, I don't understand. Was this a question?

 

Bob,

We don't know enough about this gas turbine or exactly what "minimum load" he's referring to. Spinning Reserve is not "minimum load."

Some gas turbines have a minimum load for a particular fuel.

There's just too much we weren't told, and probably can never know....

 

Bob,
My question why the gas turbine recommendation no running less than 2.5 Mw.

it is related with fuel
or Excition
or Vibration

what ever the reason so that i know it is possible gas turbine can working with 1 mw for example.

 

There are three reasons that I know that determine minimum stable generation for any turbine generator.

1) As instructed by your Grid Codes - GE may not advise your based on this reason.

2) Minimum stable generation that the governing system is designed for. Some governors have less stable governing system at a very low loads. If your governor works fine at 10% of the rated capacity read 3 below.

3) If your GT operates under load set point, its load will be influenced by system frequency. If system frequency goes up above the referenced frequency of your GT, then your GT load reduces. Otherwise it increases. The governing equation is as follows:<pre>
P_new = P_previous + P_droop (1)

Where

P_new= New GT load (MW)

P_previous = Previous load (MW)

P_droop = Additional load due to frequency bias ( MW)

P_droop governing equation is as follows

P_droop = (F_ref-F_current)*B (2)

Where '

F_current =the actual frequency, current (Hz)

F_ref = the referenced frequency (Hz)

B = Frequency bias setting (MW/0.1Hz)

I don't want to detail it out the rest but let us take an example for your GT to work one example.

Rated capacity = 25MW

Droop percentage set point =5% (Or 2.5Hz of 50Hz) -I just made up the set point.

System frequency (Rated) =50Hz.

Normal frequency deviation =+/-0.2Hz above and below 50Hz.

For the droop set point of 5% your B is as follows

B= 25MW/2.5Hz= 10MW/Hz= 1MW/0.1Hz.

We wish to protect against Equation (1) from become negative. If your system frequency has the maximum value of +0.2Hz above the rated frequency, then

Max P_droop = (50-50.2)*1/0.1Hz= -2MW.</pre>
Theoretically your GT will never turn to reverse power if you set your minimum load is kept at 2MW if the maximum frequency deviation is +0.2Hz. If you set lower than that it will become negative. Your GT may trip on reverse power after sometime. However to have safety buffer you may want to set it at 2.5MW.

 

Guys,

Thanks a lot for the useful information. Can you share the full GE recommendation here ?

We have 3 Frame 5 GTs in our site and we will have a shutdown soon; therefore, the load will be 1-2 MWs. Is it ok to operate one turbine on that load, knowing that there is no connection between the plant grid and the main grid, and the load is mainly small motors; i.e. no significant reactive power to worry about the power factor? The duration of the shutdown is 48 hrs.

Thank you in advance.

 

Good day

Well
GT should be loaded at minimum load after get synchronized Ith either plant or grid...
You should consult OEM manuals as I don't have kind of information for GT frame 5..

Cheers
James

 

I advise you to have a search on house load. Concept

 

Guys,

Thanks a lot for the useful information. Can you share the full GE recommendation here ?

We have 3 Frame 5 GTs in our site and we will have a shutdown soon; therefore, the load will be 1-2 MWs. Is it ok to operate one turbine on that load, knowing that there is no connection between the plant grid and the main grid, and the load is mainly small motors; i.e. no significant reactive power to worry about the power factor? The duration of the shutdown is 48 hrs.

Thank you in advance.

Hello @Mohamedibr752,

Did you finally found the information that you looking for on such frame type ?

Thank you for updating us ,

Regards,
James