Transformer de-rating for high ambient temps, which ANSI C57 standard? 1

[Latango]

Have done quite a few different searches here, and can't pin down which standard I need to get. I cannot find, in Australia, a standard that guides de-rating factors for higher-than-nameplate ambient temps. That is, if I have a 60 - 65 transformer (oil - winding), that is designed for 40 degree ambient, how much do I de-rate it for use in 50 degree ambient? I realise it won't be 100% accurate, but dpc mentioned in this post ANSI C57, and there are a lot of them.

I don't have access to load / no load losses for the transformer unfortunately, so there isn't any way to be accurate.

It's only a baby (500kVA) but it's always good to add some knowledge that can be extrapolated to other jobs.

Thanks in advance

Mat

 

[prc]

As per ANSI C57.12.00-2006, the average winding temperature rise of 65C and hot spot winding temperature rise of 80C is specified based on a maximum ambient air temp of 40C and average daily ambient temperature of 30C( 24 hour period)

For ambient conditions other than above, C57.12.91-2011 Loading guide, recommends as below for ambient temperatures from -30C to 50C.

Clause 6.3 &Table 3, for every degree reduction in average ambient temperature the rating can be increased by 1% of kVA rating and for every one degree rise in average ambient temperature, the load shall be decreased by 1.5 % of kVA rating. This is approximate variation in rating and for detailed calculation reference may be made to other clauses in C57.12.91

 

[Latango]

Exactly what I was after, prc. Thanks a lot for that, now to see if I can buy a pdf online somewhere.

Cheers,

Mat

 

[jghrist]

http://www.techstreet.com/cgi-bin/detail?vendor_id=5297