Transformer MVA rating IEEE vs. IEC 1

[cuky2000]

There are difference between IEEE STD and IEC STD associated to power transformer rating as shown on the table below.
For a 100MVA unit with 30 degree C average ambient temperature in 24 hrs. What should be the maximum rating if specified per IEEE or the same maximum rating if designed based on the IEC std.?

 

[cranky108]

I don't know, as some of your temps appear to be in Kelvin.

 

[cuky2000]

Hi Cranky108, for temperature rise, the diferencial in Kevin or Celsius is the same.
The Celsius and Kelvin scales increase by the same increments, meaning that to increase the temperature by 1°C results in the same increase of 1 K. The major difference is that when water freezes, a Celsius thermometer will read 0°C, and a Kelvin thermometer will read 273.15 K.

 

[7anoter4]

If the transformer is built as per IEEE/ANSI or NEMA instructions -certain materials and dimensions-if the ambient temperature is lower you may overload in a way the transformer without reducing its life.
The same, on a transformer built as per IEC standard you have to reduce the load if the ambient is upper.
The calculation has to follow IEEE std. C57.91
and IEC 60076-2 and IEC 60354, in my opinion.

 

[dpc]

I'm not sure what "Life ambient temperature" means. For ANSI, my understanding is that the rating is based on a 30 deg C max ambient average over 24 hours.