Transformer temperature rise test-Considering Solar radiation

[RasikaC]

Dear All,
If we have to consider the effect of solar radiation into account during the temperature rise test of a 250kVA hermetically sealed distribution transformer, how this can be done? Should we feed additional losses during the test? How to calculate these additional losses? Is there any international standard for this? Appreciate your kind guidance.

 

[prc]

No international standard on the subject. Solar radiation will not alter the thermal characteristics to that extent. Of course parts of tank side will be heated by solar radiation. But the extra heating will increase the oil movement inside and the effect can be ignored.

 

[bacon4life]

Assuming the transformer has 1% losses and has a surface area facing the sun of 1 square meter, the solar flux hitting the surface would be about half of the internal losses. On the next sunny day I want to go measure the temperature of transformers in the warehouse yard.

 

[HamburgerHelper]

If it matters, it is a little funny that so many are painted dark green.

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If you can't explain it to a six year old, you don't understand it yourself.

 

[prc]

Nearly 100 years back, GE Pittsfield engineers wrote a paper based on a series of experiments on distribution transformers painted with different colors kept under sun.They proved that color has little effect on radiation at the tank temperatures normally found in transformers. But recent years there were number of papers confirming solar radiation will increase temperatures and hence aging! I do not believe these computer models and research over computer screen. In one Gulf country they have built large tents over large power transformers (125 MVA) to protect from solar radiation! I asked some engineers in Saudi Arabia to check oil temperature during night and on day time with maximum radiation but at the same loading. They confirmed that there is no change in oil temperature under both conditions.