IEEE Std C57.12.51 pdf free download

IEEE Std C57.12.51 pdf free download.Mechanical Interchangeability of Ventilated Dry-Type Transformers.
6.3 Nameplate
Nameplate requirements are described in IEEE Std C57.12.Ol. Nameplates should be located on the front wall
in Segment I as indicated in Figure 1.
6.4 Transformer connections
6.4.1 High-voltage line connections
High-voltage line connections may be located as per 10.1.
6.4.2 Low-voltage line connections
Low-voltage line connections may be located as per 10.2.
6.4.3 Neutral connections
The neutral may be either a blade connected directly to the ground or a terminal insulated for the appropriate low-frequency voltage insulation level per IEEE Std C57.12.0l.
When the neutral terminal is connected directly to the ground, provision may be made for disconnecting the winding neutral.
When a grounded-Y winding is involved, the connection from the neutral terminal to ground may be furnished by the manufacturer as a part of the associated equipment, such as switchgear or terminal compartments (see 10.1 and 10.2).
6.5 Tap changing
Facilities may be furnished for changing taps with the transfomwr dc-energized and should be physically marked and described on the nameplate, if applicable.
6.6 Lifting, jacking, and moving facilities
6.6.1 Safety factor
Lifting,jacking, and moving facilities shall be designed to provide a minimum safety factor of five. The safety factor is the ratio of the ultimate stress of the material used to the working stress. The working stress is the maximum combined stress developed in the lifting, jacking, or moving facilities by the static load of the component being lifted or moved.
6.6.2 Lifting facilities
A minimum of two lifting points shall be provided for lifting the complete transformer.
Lifting facilities should be designed for lifting using one lifting cable at each lifting point, and with a maximum cable angle of 30° with respect to the vertical. Lifting points should provide a balanced lift to help prevent overturning. The bearing surfaces of lifting facilities should be free from sharp edges and should be provided with a hole having a minimum diameter of 16 mm (0.625 in) for transformers < 500 kVA and 51 mm (2.00 in) for transformers> 500 kVA for guying purposes.
NOTE 1- Ikpcnding on the design and the manufacturer’s instructions, it may be necessary to have the cover in place when lifting, or it may be necessary to remove the cover to engage the lifting cables with the lifting facilities.
When this increased ambient temperature is specified, the kilovolt-ampere continuous rating should be based on not exceeding a 10 °C decrease in the average winding temperature rise, as measured by resistance. For example, the maximum temperature rise for a transformer using a 220 °C insulation system would be 140 °C.
9.2 Winding temperature rises
Winding temperature rise limits for continuously rated dry-type transformer windings arc listed in IEEE StdC57.12.O1.
9.3 Insulation system temperature class
Insulation system temperature classes arc listed in IEEE Std C57. 12.01.
9.4 High-voltage ratings and connections
9.4.1 High-voltage windings without taps
High-voltage windings may be furnished without taps.
9.4.2 Y-connected high-voltage windings and delta connected low-voltage windings
The neutral insulation levels are listed in IEEE Std C57. 12.01.
The angular displacement between high-voltage and low-voltage terminal voltages of a Y-A connected three- phase transformer is listed in IEEE Std C57. 12.01.
NOTE—See IEEE Std C57. I O5TM[I35] for problems that may result if the high-voltage neutral is grounded with the high- voltage Y-connected and the low-voltage A-connected.IEEE Std C57.12.51 pdf download.