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Generator over temperature protection

Generator over temperature protection

Generator over temperature protection

(OP)
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
flashover

Flashover

RE: Generator over temperature protection

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.\\\

RE: Generator over temperature protection

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.

RE: Generator over temperature protection

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".

 1.   50.0% GE Generator Fleet Experience and Available Refurb
GE Generator Fleet Experience and Available Refurbishment Options Alex Lemberg GE Energy Services Atlanta, GA Karl Tornroos GE Energy Services Atlanta, GA g GE Energy © 2004 General Electric Company. GE Generator Fleet Experience and Avail .....
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger4223.pdf

  
 2.   50.0% GER 4212 - GE Generator Rotor Design, Operational Issues, and Refurbishment Options
GE Power Systems GER- 4212 (08/ 01) i GE Generator Rotor Design, Operational Issues, and Refurbishment Options Contents Overview . .1 Function of a Generator Rotor . .1 Types of Generator Rotors .
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger4212.pdf

  
 3.   50.0% GER 3809 - Generator Rotor Thermal Sensitivity: Theory and Experience
1 General Generator Rotor Vibration . 1 Generator Rotor Thermal Sensitivity . 3 Causes of Thermal Sensitivity.
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger3809.pdf

  
 4.   50.0% GER 4203 - GE Generator Technology Update
GE Power Systems GE Generator Technology Update Christian L. Vandervort Edward L. Kudlacik GE Power Systems Schenectady, NY GER- 4203 g Contents Abstract . 1 Design for Six Sigma Process.
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger4203.pdf

  
 5.   50.0%  1 In- Situ Inspection Supports Condition- Based M
1 In- Situ Inspection Supports Condition- Based Maintenance . 1 In- Situ Inspection A Critical Part of Generator Maintenance Cost Reduction . 1 In- Situ Inspection Technologies .
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger3954b.pdf

  
 6.   50.0% GER 3751A - Understanding, Diagnosing, and Repairing Leaks in Water-Cooled Generator Stator Windings
1 Leaks in Stator Hydraulic Components and Connections. 2 Leaks in the Stator Bar . 3 Leaks in the Clip- to- Strand Connection .
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger3751a.pdf

  
 7.   50.0% GER3688B - GE Generators - An Overview
AIR- COOLED GENERATORS Air- cooled generators are produced in two basic configurations: open ventilated (OV) and totallyenclosed water- to- air- cooled (TEWAC) . GER- 3688B Design Option Design Option 6A3 6A3 6OHz 5oHz 6OHZ 6OHZ Generator .....
http://www.gepower.com/prod_serv/products/tech_docs/en/downloads/ger3688b.pdf

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

saludos.
a.

RE: Generator over temperature protection

(OP)
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
Flashover

Flashover

RE: Generator over temperature protection

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).

RE: Generator over temperature protection

(OP)
Many thanks to all

Flashover

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