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IEC 60076-2-2011 pdf download

IEC 60076-2-2011 pdf download.Power transformers – Part 2: Temperature rise for liquid-immersed transformers.
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60076-1, Power transformers — Part 1: General
IEC 60076-8:1997, Power transformers — Part 8: Application guide
IEC 60085:2007, Electrical insulation — Thermal evaluation and designation
IEC 61 181:2007, Mineral oil-filled electrical equipment — Application of dissolved gas analysis (0 GA) to factory tests on electrical equipment
IEC Guide 115:2007, Application of uncertainty of measurement to conformity assessment activities in the electrotechnical sector
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60076-1 and the following apply.
external cooling medium
the medium external to the transformer cooling system (air or water) into which the heat produced by the transformer losses is transferred
3.2 internal cooling medium
the liquid in contact with the windings and other transformer parts by means of which the heat produced by the losses is transferred to the external cooling medium
NOTE The liquid can be mineral oil or other natural and synthetic liquid.
3.3 temperature rise
the difference between the temperature of the part under consideration (for example, the average winding temperature) and the temperature of the external cooling medium
4 Cooling methods
4.1 ldentification symbols
Transformers shall be identified according to the cooling method employed. For liquid-immersed transformers, this identification is expressed by a four-letter code as described below.
First letter: Internal cooling medium:
O: mineral oil or synthetic insulating liquid with fire point S 300 °C;
4.2 Transformers with alternative cooling methods
A transformer may be specified with alternative cooling methods. In this case, the specification and the rating plate shall then carry information about the power values at which the transformer fulfils the temperature rise limits when these alternatives apply, see
IEC 60076-1.
The power value for the alternative cooling methods with the highest cooling capacity is the rated power of the transformer (or of an individual winding of a multi-winding transformer, see IEC 60076-1). The alternatives cooling methods are conventionally listed in rising order of cooling capacity.
• ONAN/ONAF. The transformer has a set of fans which may be put into service as desired at high loading. The insulating liquid circulation is by thermosiphon effect only, in both cases.
• ONAN/OFAF. The transformer has cooling equipment with pumps and fans but is also specified with a reduced rated power under natural cooling (for example. in case of failure or reduction of auxiliary power).
5 Normal cooling conditions
5.1 Air-cooled transformers
Normal ambient temperature limits for power transformers are given in IEC 60076-1.IEC 60076-2 pdf free download.

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