Transformer Cooling Type Designation

[KLG]

Hello. I am looking for some help witht the description of Power Transformer cooling type designations.
I am looking at two transformers with similiar characteristics.
The first is a 115 KVA 3 phase transformer with the following MVA and cooling designations:
15/20/25 MVA (oil filled with cooling radiators/fins)
ONAN/ONAF/ONAF
Now I believe that these designations are as follows:
ONAN - oil natural, air natural; indicating that both the air and oil are allowed to flow and release heat through natural convection.
ONAF - oil natural, air forced (with fans running); forced air flow over the cooling fins and radiators.

The second transformer has the following rating 115 kVAC, 3 ph:
15/20/25 MVA (oil filled with cooling radiators/fins)
ONS/ONP/ONPP
ONS -?
ONP -?
ONPP -?
I think that these are similar designation but I am not completely sure (or even the French designation?). Could somone either explan these designations or point me to a good information source?
Thanks,

 

[rbulsara]

On your first transformer, Did you mean the last of the options being OFAF (Forced oil and forced air)i.e. both oil and air are moved by force. Oil is pump circulated.

I don't know about the markings on your second transformer, but they should mean the same I guess.

 

[busbar]

IEEE Std C57.12.00-2000 Liquid-Immersed Distribution, Power and Regulating Transformers §5.1 ‘Cooling classes of transformers’ [noted as consistent with IEC 60076-2: 1993] does not list a “P” desgnation .

 

[electricpete]

fwiw, Google search for "ONS/ONP" gives a bunch of transformer hits. Still don't know what it means.

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