transformer temperature

[AYahya]

i have a two secondary’s transformer 132/6.3/6.3 kV 60/55MVA ONAF/ONAN
at 50% loading on both secondaries, the top oil temperature is 60 C, winding 62 C, ambient 27 C.
is this considered high temperature? IEC standard says that temperature rise is 60K, 65K

 

[ScottyUK]

Looks fine to me. Is the transformer working as ONAN or ONAF to achieve these temperatures?



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If we learn from our mistakes I'm getting a great education!

 

[TurbineGen]

We have run oil filled tranformers to 85-90 C for 40+ years with no problems. Your temperature is certainly acceptable. Are you running any of your cooling systems? 35C over ambient at only 50% loading seems a little higher than it should be to me if you are running the coolers.

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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[genhead]

As I understand it, the IEC standard will state the temperature rise, not the actual temperature limit. I don't recall what the base/ambient temperature is for the standard, but say the temperature rise was 60 degrees above an ambient temperature of 30 degrees, that would be a temperature limit of 90 degrees.

 

[dpc]

Not sure about IEC, but ANSI ratings are based on an AVERAGE ambient temperature of 30 deg C.

 

[AYahya]

this temperature is on ONAN.
IEC states that ambient temp -25 to +40 while not exceeding +30 on hottest month for air cooled trafo.
the trafo suppose to have maximum efficiency around 50% loading but the oil/wdg temp is 60/62 and the maximum is 90/95. What will be the temp in case of 80% loading?
is there a way to predict the temp at different loading points based on trafo data?

 

[Kiribanda]

Ayahya,

Yes, you are still within limits and no problem.

Ambient = 27 C

Per IEC-60076-2 allowable rise in oil = 60 C

Therefore allowable top oil temp = 27 + 60 = 87 C

Measured top oil temp = 60 C

Therefore no problem. You can load.

Similarly,

Ambient = 27 C

Per IEC 60076-2 allowable rise in wdg for ONAN/ONAF= 65 C

Therefore allowable wdg temp = 27 + 65 = 92 C

Measured wdg temp = 62 C

Therefore no problem. You can load.

Hope this helps.