1.1 This standard specifies rating and symbols, requirements, marking, tolerances and tests for power transformers (including, .auto-transformers) rated at 1 kVA and above for single-phase transformers and at 5 kVA
and above for three-phase transformers with the system highest voltage not exceeding 245 kV.
1.2 Service conditions
This standard gives requirements for transformers for use under the following conditions
1.2.1 Altitude
Power transformers in this standard are intended for use at a height above sea level not exceeding 1 000 m. If intended for use at altitudes in excess of this height above sea level, the transformers shall, in addition, comply with the requirements of clauses 4.2.3 and 4.3.3.
1.2.2 Temperature of cooling medium
1.2.2.1 For water-cooled apparatus, the temperature of the cooling water shall not exceed 25℃ at the inlet.
1.2.2.2 For air-cooled apparatus, the air temperature shall not exceed 40℃ and, in any local, not exceed 30℃ average in any one year.
1.2.3 Wave shape of supply voltage
The wave shape of the supply voltage shall be approximately sinusoidal.
1.2.4 Symmetry of polyphase supply voltages
For polyphase transformers, the supply voltages shall be approximately symmetrical.
1.3 This standard gives fundamental requirements:
Where the service calls for higher values of the given requirement and / or additional specification, the special requirements for such transformers are a matter for agreement between the manufacturer and the purchaser.