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Temperature match on
why do we take TNR Reference >= 100.3% as one of the permissive for temperature match on?

Hi everyone,

iam working on GE frame 9FA. my question is why do we take TNR Reference >= 100.3% as one of the permissive for temperature match on during unit cold startup in order to warmup our HRSG and steam bowl temperatures steadily so as to prevent the thermal stress? plz help me out some one

pawan,

When do you believe it should be possible to enable Temperature Matching? Before generator breaker closure?

The typical value of TNR when synchronization is started is 100.3%, and that's so that there is a positive watts flow when the generator breaker is closed. For a machine with 4% droop, and rated at approximately 200 MW, a TNR of 100.3% would correspond to a load (when synchronized) of ((0.3 /4)*200 = 15) 15 MW.

Please explain more about your situation and when you are trying to enable Temperature Matching (breaker open or breaker closed; what load--0.00 MW or 15 MW or ???).

I believe that the TNR "permissive" is to ensure that there is some positive load, not zero MW. Why it's 100.3% exactly, probably only GE knows for sure. So, it must be that you are trying to enable Temperature Matching below the load which corresponds to 100.3%.

Have you asked GE, or the packager of your turbine?

And, when did your plant start trying to do this? In other words, when did this "problem" start? Are you trying to enable Temperature Matching at lower loads than previously?

> When do you believe it should be possible to enable Temperature Matching? Before generator breaker closure?

> The typical value of TNR when synchronization is started is 100.3%, and that's so that there is a positive
> watts flow when the generator breaker is closed. For a machine with 4% droop, and rated at approximately 200 MW, a TNR of
> 100.3% would correspond to a load (when synchronized) of ((0.3 /4)*200 = 15) 15 MW.

> Please explain more about your situation and when you are trying to enable Temperature Matching (breaker
> open or breaker closed; what load--0.00 MW or 15 MW or ???).

> I believe that the TNR "permissive" is to ensure that there is some positive load, not zero MW. Why it's 100.3%
> exactly, probably only GE knows for sure. So, it must be that you are trying to enable Temperature Matching below the
> load which corresponds to 100.3%.

> Have you asked GE, or the packager of your turbine?

> And, when did your plant start trying to do this? In other words, when did this "problem" start? Are you trying to
> enable Temperature Matching at lower loads than previously?

Sir, we are enabling temperature match on after synchronising the GT machine with grid. After synchronising, the machine generates spinning reserve load, i.e about 23MW. Then after we are issuing Combined cycle mode selection in our GT HMI in order to open open our divertor damper towards HRSG. After that we are enabling TEMP MATCH ON by giving some temperature set point, say minimum 370 C. Before this everything happens, TNR> 100.3% is taken as a permissive to enable this TEMP MATCH ON. Some times this TNR will be forced as it gets below 100.3% if the grid frequency is maintaining in the lower side. In that case our C&I dept will force that logic ...

YEOWWWWW!!!!! Forcing TNR!!!! YIIIIIIKES!!!! It doesn't make any difference if the IT department or the Security department is forcing TNR--it shouldn't be forced.

I really sympathize with those who have to deal with "wild" grid frequencies, especially when you have HRSGs and Steam Turbines and you are trying to follow load and be "dispatched" on a daily basis. But, you should be working with the packager or OEM to find other ways to work around this condition other than forcing signals. The packagers or OEMs of these turbines need to understand the conditions they are being operated in and provide solutions to their Customers to allow them to be operated safely and sanely in what are usually very abnormal conditions, but which are increasingly more typical in some parts of the world.

I would like to know if using Temp Matching under these conditions actually improve the steam turbine start-up times or not. In other words, is it economically more advantageous to use Temp Matching under these grid frequency conditions as opposed to just trying to load the steam turbine manually as conditions permit.

Do you have the ability to bypass the steam turbine to the condenser during start-up while maintaining some steam flow through the admission piping to warm it up?

I would have to say if you are being called to come on line under low frequency conditions, then the grid regulators are in need of more generation and quickly, and if you are having to stop and hold for Temp Matching that you are not helping the grid regulators get more generation on line quickly to help restore frequency and maintain grid stability.

This may not be a problem you have much control over; if the grid regulators who are issuing the orders to come on line are not aware of your plant's loading rate because of the requirement to Temp Match to protect the steam turbine then that's certainly a problem that should be dealt with. Communication is key. Or, if you can find a way to load the gas turbine while bypassing steam to the condenser while waiting for the steam turbine warm-up permissives then you can make more money faster.?.?.? And help support grid stability in the process.?.!.?.!.?.!