Generator over temperature protection

[Flashover]

Hi all,

I have a problem on site. Ths gas turbine must be capeable of running continously in Augmented mode, hence higher output. however the generator is rated to run at class B temperature with class F insulation. the higher throughput means the generator now operates above class B (close to class F). the contractor wishes to solve this problem by increasing the cooler size on the generator......... this worries me
So my questions are:-
1)what is the standard alarm level for over temperature on the generator coils? really i am looking for setting examples from other Gas turbine plants.
2)secondly the best way of measuring stator coil temperatures this value, direct measurment or resistance measurment?

Thanking you kindly
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[jbartos]

1)what is the standard alarm level for over temperature on the generator coils? really i am looking for setting examples from other Gas turbine plants.
///The most prudent temperature settings are those that are in the generator manuals. The manufacturer tech support should be contacted for deviations in temperature set points. Other Gas turbine plants are not really good examples to follow since they may have some special conditions that allows different temperature settings.\\2)secondly the best way of measuring stator coil temperatures this value, direct measurment or resistance measurment?
///Traditionally, on-line measurements are via temperature sensors. These sensors vary in the principle of operation and quality.\\

 

[DougMSOE]

We have about 18 GT in our fleet. Typically the stator coil alarms are set at 10 to 15 (at most) degrees BELOW the class F rating.
Secondly, in your instruction book for this machine it should have a 20C and or a 40C resistance measurement for the different phases. Use this value and calculate the stator coil copper temperature.

 

[abeltio]

What is the Generator make?
The manufacturer's (e.g. GE) have programs to re-rate the generator and see how much more juice u can get safely with the current configuration.

This is with a search done withing gepower.com for "generator uprates".

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Regarding the measurement the usual std is RTD's embedded in the stator.

saludos.
a.

 

[Flashover]

Many thanks for all the replies
Very simply for a TEWAC Generator with ETD winding temp measurement I want to know what is the correct setting for the alarm and trip signal for Class B temp rise.

IEC 34-1 deals with this as far as I know as follows for Class B :

40C (Max Ambient) + 85K (Temp Rise) + 10K (Asymmetry) - 5K
(15.75kV Gen Voltage) = 130C (max operating temp).

However the allowance for asymmetry of 10K is the maximum allowed and therefore 5K is a more reasonable value giving a max operating temp at MCR of 125C for Class B insulation.

The alarm setting would then be typically 130C with the trip at 135C.
Obviously the figures would be higher if based on Class F.

any comments?
many thanks
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[edison123]

ETD's is the easier and recommended way of measuring winding temp without going off-line to measure the actual winding resistances.

For class F machines, the maximum operating temp is = 40 deg C (ambient) + 100 deg C (rise) = 140 deg C. For machines over 11 KV to 17 KV, max temp rise shall be reduced by 1 deg C for each 1 KV above 11 KV.

However, continuous operation at these high temps will reduce the residual life of the winding considerably. I would recommend the maximum temp not exceeding 120 deg C (115 deg C alarm and 120 deg C trip). If it is a new machine, then the supplier must stick to his GTP's and see to that the machine supplied is actually rated for the promised capacity.

If it is an old one that you now trying run at higher load, a more efficent cooling system may only be the way to reduce your winding temp.

For every 10 deg C temp rise in the operating winding temp, the residual life of winding insulation is estimated to come down by 50%. (This applies to people also, so, stay cool always).

 

[jbartos]

Suggestion: Visit

http://www.gepower.com/prod_serv/products/tech_docs/en/generators.htm

for more info. Most references have already been posted by Albeltio posting

 

[Flashover]

Many thanks to all


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