IEEE C57.12.00-2015 pdf download

IEEE C57.12.00-2015 pdf download.IEEE Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers.
NOTE I In a transformcr with non-directed cooling, the ratcs of coolant flow through all thc windings vary with Lhc loading, and arc not directly controllcd by the pumps. The pumped insulating liquid flows frccly insidc thc tank and is not forced to flow through thc windings.
\OTF 2 In a transformcr dcsignatcd as having forccd dircctcd coolant circulation (second code lcttcr D, the ratc of coolant flow through thc main windings is dctcrmincd by the pumps and not by the loading minor fraction of thc coolant flow through the cooling equipment may be dircctcd outside the main windings to providc cooling for core and other parts. Regulating windings and or other windings having relatively low power may also have non-directed coolant circulation.
A transformer may be specified with more than one kVA rating (also referred to as cooling stages). The transformer nameplate shall list the rated kVA and cooling class designation for each rating. The ratings shall be listed in order of increasing kVA. The cooling class designations are normally listed in order with a diagonal slash separating each Ofle.
Exanipks:
ONANiONAF. The transformer has a set of fans that may be put in service as desired at high loading. The coolant circulation is by natural convection only.
()NANiOFAF. The coolant circulation is by natural convection only at base loading. However, the transformer has cooling equipment with pumps and fans to increase the power-carrying capacity at high loading.
Examples of the cooling class designations used in IEEE Std C57. 12.00-2006 and in previous revisions, with the corresponding new designations, are provided in Annex A.
5.2 Frequency
Unless otherwise specified. transformers shall be designed fur operation at a frequency of 60 Hz.
5.3 Phases
5.3.1 General
Transformers described in this standard are either single-phase or three-phase. Standard ratings are included in product standards for particular types of transformers. When specified, other phase arrangements may be provided.
5.3.2 Scott.connected or T-connected transformers
5.3.2.1 Phase transformation
These may be provided to accomplish three-phase to two-phase transformation, or vice versa, or to accomplish three-phase to three-phase transformation. Common arrangements used to accomplish such transformations are described here in 5.3.2.2. 5.3.2.3. and 5.3.2.4.
5.3.2.2 Dissimilar single-phase transformers
Two single-phase transformers are assembled in an enclosure, and permanently interconnected, with the
following characteristics:
a) Performance characteristics shall be based on hank operation of three-phase to iwo-phase transformation or vice versa.
b) The single-phase transformers may not be identical or interchangeable.
5.3.2.3 Three-legged core
Another arrangement uses a three-legged core with main and teaser coil assemblies located on the two outer legs.
and a center leg that has no coil assembly. This provides a common magnetic circuit for the two outer legs.
5.3.2.4 Identical single-phase transformers
When specified. two identical single-phase transformers shall be furnished.
a) The kVA rating of each transformer shall be half the bank output required. The racing of the individual units shall agree with the ratings established for single-phase transformers.
h) Performance characteristics (except heating) shall be based on single-phase operation.
c) The temperature rise shall be based on delivering the required bank capacity when transforming from three-phase to two-phase or from two-phase to three-phase. as specified.
d) Transformers shall be inwrch4ingeahle as main and teaser.
e) Regulating taps are not usually supplied on transformers for three-phase to two-phase or from two- phase to three-phase service. When taps are required. the teaser tap shall be 6.6° of the mean regulating taps (used here. mean refers to the midpoint of the range of regulating taps).
5.4 Rated kilovoltamperes
5.4.1 General
The rated kVA of a transformer shall be the output that can be delivered for the time specified at rated secondary voltage and rated frequency without exceeding the specified temperature-rise limitations under prescribed conditions of test, and within the limits of established standards.
5.4.2 Preferred continuous kVA ratings
Preferred continuous kVA ratings of single-phase and three-phase distribution and power transformers are based on an average winding rise of 65 °C. in accordance with 5.11.1.1 and are listed in Table 2.