IEEE C57.93-2007 pdf download IEEE Guide for Installation and Maintenance of Liquid-Immersed Power 1「ransformers
3. Liquid-immersed power transformers rated 501 kVA to 10 MVA (OA), or withprimary windings less than 69 kV
3.1 General
In general, these transformers can be either of the station or pad-mount configuration and may have load tapchanging (LTC) equipment. They normally have sealed liquid or inert gas insulation preservation systems, andmay have draw-lead-type high-voltage and bottom-connected low-voltage bushings. The radiators (if provided)may be welded directly to the tank
For outdoor applications, the insulating liquid normally is conventional mineral oil or synthetic oil. For specialapplications,or for use indoors, they may contain less flammable or non-flammable or biodegradableliquids.
Forced cooling (if present) normally uses fans.
Transformers in this size range are usually shipped filled with all their insulating fluid and do not have shippingbraces as such. Units rated 75-10 MVA feil/aif eeeled fOAH are sometimes shipped without liquid or witisome liquid removed and with the high-voltage bushings removed. Depending on shipping limitations, insulatingfluid may be delivered separately for installation on site.
In this size and voltage range, impact recorders are seldom may not be utilized and most shipments are made bytruck, directly to the site or a receiving facility, The presence of the manufacturer’s or the carrier’srepresentative (other than the driver) is seldom available upon receint of the transformer at the destination.
3.2 Inspection and receipt
Many transformers in this size and voltage range are shipped completely assembled, tested, and filled withinsulating liquid ready for immediate service.
Most of these transformers are reccived oil filled with a positive pressure in the main tank and with radiators (ifrequired) completely assembled. Unon receiving and before unloading, check for any visualUpon reeeipt; each transformer should be eheeked for evidenee of damage or leaks; and internat pressure should bemeasured: A positive or negative pressure indieates that the tank did not leak: Zere gauge ‘IEEE publications are available from the lnstitute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway, N)08854, USA
The IEEE products referred to in this clause are trademarks belonging to the Institute of Electrical and Electronics Eneineers, Inc damageto tank, radiators. bushings or any external accessories. Upon receipt, each transformer should be checked forevidence of damage or leaks, and the internalgas pressure should be measured. A positive or negative pressureindicates that the tank has noteak. Zero gauge pressure shouldvalve ordeveloped anybe investigated.A smalla plug fitting could be opened slightly to check for the internal gas pressure. The de-energized tap switch shouldbe operated and if necessary (provided that the bushings are installed or the winding leads are accessible), a ratiotest may be carried out to ensure that it is functional
If the transformer has been supplied with a series-parallel connection, the switch or other device thataccomplishes the change in connection should be checked to assure that it is in the correct position for theintended application voltage. Unless otherwise specified by the customer, if the series-parallel connection isocated in the HV winding. the connection should be set in the highest-voltage position. If series-parallelconnection is located in the LV winding, the connection should be set in the lowest-voltage position.
IEEE C57.93-2007 pdf download
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