IEEE C57.12.00-2015 pdf free.IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers.
Transformers idcntilicd a… systcm tic transformers or auiotranskwmcrs shall be designed for step-down operation, or stcp-up operation, or both, as spccificd by the user.
4.1.9 Tank or enclosure finish
Tcmpcratw’c limits and tests shall be based on the use of a nonmetallic pigment surface paint Ii should be noted that metallic-flake paints, such as aluminum and zinc, have properties that increase the temperature nsc of transformers. ewepi in direct sunlight.
4.2 Loading at other-than-rated conditions
IEEE Sid C57.91”M 1H121 provides guidance fix loading at oihcr.than.ratcd conditions including the following:
a) Ambient temperatures higher or lower than the basi.. of rating
b) Short-time loading in excess of nameplate ICVA with normal life expectancy
C) Loading that results in reduced life expectancy.
IEEF Sid (57.91 lB 121 is an IEEE guide. and as such. it docs not specify mandatory requirements. It provides the best known gencral infornution for loading of transhirnien under various conditions based on typical winding insulation s stems. It is hascd upon the hcs* engineering information available at the time of preparation. The guide discusses limitations of ancillary components other than windings that may limit the capability of transformers. When specified. ancillary componcnls and other construction features (such as cables, bushings. tap changers. insulating liquid espanslon space. etc.) shall be supplied in a manner that will not limit the loading to less than the specified capability of the windmgs.
4.3 Unusual service conditions
Conditions other than those described in 4.1 arc considered untisual scrs ice conditions and, when prevalent. should be brought to the attention of those responsible for the design and application of the apparatus. litamples of some of these conditions are listed in 4.33.
4.3.1 Unusual ambient temperature and altitude conditions
Transformers may be used at higher or lower ambient temperatures or at higher altitudes than those specified in 4.1.3. but special consideration should be given to these applications. l1€I’E SW (57.91 1B121 provides informal ion on recommended practices.
4.3.2 Insulation at high altitude
The dielectric strength of transformers that depend in whole or partly upon air for insulation decreases as the altitude increases due io the effcct of decreased air density. When specified, transformers shall be designed with larger air spacing between terminals using the correction factors of Table I to obtain adequate air dielectric strength at altitudes above 1000 m (3300 9). Insulation level
The minimum insulation necessary at the required altitude can be obtained by dividing the standard insulation level at 1000 m (3300 9) by the appropnalc correction factor from Table 1.IEEE C57.12.00 pdf free download.