IEEE STANDARD FOR POWER TRANSFOEMR-LIQUID (OIL) TEMPERATURE LIMIT AND WINDING TEMPERATURE LIMIT

[subash148]

I am trying to review estimated temperature rise calculation for 260 MVA GSU transformer. Following is the transformer data.

260 MVA, 14.4 kV/242 kV,3-Phase, Percentage Impedence= 14.9 %

As per IEEE C57.12.00-2010, Section-5.11.1.1(Winding Tempertaure Rise): The average winding temperature rise above ambient temperature shall not exceed 65 degree celcius at rated KVA. Also, the maximum (hottest-spot) winding temperature rise above ambient temperature shall not exceed 80 degree celcius at rated KVA.

Is there any IEEE standard where in some situation winding hottest spot temperature limit is considered at 120 degree celcius. This number (120 degree celcius) is shown in the calculation i am reviewing.

As per IEEE C57.12.00-2010- Section 5.11.1.4 (Liquid Temeparture Rise)- The insulating liquid temperature rise above ambient temperature shall not exceed 65 degree celcius when measured near the top of the main tank.

Is there any IEEE standard where in some situation top oil temeparure limit is considered at 105 degree celcius. This number (105 degree celcius) is shown in the calculation i am reviewing.

SG

 

[dpc]

Make sure you are clear on the difference between the actual temperature and the temperature RISE. The ambient temperature must be added to the temperature rise to determine the actual temperature.

 

[stevenal]

See 4.1.2.1 and 4.2 and 4.3.

 

[prc]

As per IEEE standard for transformers, maximum ambient temperature considered is 40C. 105 &120 C that you see in the calculations are the absolute temperatures,adding the 65&80C temperature rises to maximum ambient temperature.

 

[subash148]

Hi PRC,
Thanks for the response. I aboslutely agree with what you just mentioned above. IEEE standard also says " the average temperature of the cooling air for any 24 h period shall not exceed 30C. Since transformer run continiously, now in my temperature rise calculation, do i need to add 40 C (maximum ambient temperature of cooling air) or 30C( average temperature of the cooling air for any 24 h period)to 65 C(top oil temperature rise limit over ambient) and 80C(winding hottest-spot temperature rise over ambient)?

Please clarify?

SG

 

[prc]

I dont know what type of calculations you are doing and for what purpose.In case the ambient temperature for the area you are considering is more than any of it (ie average and maximum) then the average rise and hot spot shall be reduced to that extent.Both parameters are to be met.