IEEE C57.12.01-2020 pdf free download – IEEE Standard for General Requirements for Dry-Type Distributon and Power Transformers.
3. Definitions
For the purposes of this document, the fllowing terms and definitions apply. The IEEE Standards Dictionary’ Onine should be consulted for terms not defined in this clause. ” Standard transfomer terminology. which is available in IEEE Std C57.12.80,12 shall also apply.
reference temperature: Unless otherwise stated, the reference temperature shull be defined as 20 °C plus the Tated avernge winding rise. For multiple winding transformers that have more than one base rated average winding rise, the highest awerage winding rise shall be used to determine the reference temperature.
reference temperature for no-load Iosses The no-load lsses ofpower and dstribution tunsformers shall be determined based on a neference temperature at 20 °C?
4. Service conditions
4.1 Usual service conditions
4.1.1 General
Transformers conforming to this standard shall be suitable for operation at ruted kVA under the usual service conditions in 4.1.2 through 4.19. For umusual service conditions see Unusual service conditions in 4.2.
4.1.2 Temperature
4.1.2.1 Cooling alr temperature limlt
The temperature of the cooling air (ambient temperatur) shall not exeed 40 °C, and the avenge temperature of the cooling air for any 24-h period shall not exeed 30 °C.
The minimum ambieant temperuture shall not be lower than- 30 °C.
4.1.22 Cooling water temperature limit
When water ooled, the temperature of the cooling water (ambient temperature) shall not exceed 30 °C, and the avenage temperature of the cooling water for any 24-h period shall not exeed 25 °C. Minimum water temperature shall not be lower than 1 °C unless the cooling water includes antifeeze, which is suitable for -20 ^C operution.
4.1.3 Altitude
The atitude shall not exceed 1000 m 3300 ft).
4.1.4 Supply voltage The supply-voltage wave shape shall be approximately sinusoidal, and the phase voltage supplying a polyphase transformer shall be approximately equal in magnitude and of approximate equal time phase in displacement.
4.1.5 Load current The load current shall be approximately sinusoidal. The harmonic factor shall not exceed 0.05 per unit. Harmonic factor is defined in IEEE Std C57.12.80. Refer to IEEE Std C57.110 for information on establishing transformer capability when supplying nonsinusoidal load currents.
4.1.6 Operation above rated voltage or below rated frequency Transformers shall be capable of a) Operating continuously above rated voltage or below rated frequency, at maximum rated kilovolt- amperes for any tap, without exceeding limits of observable temperature rise when secondary voltage and volts per hertz does not exceed 105% of rated values, load power factor is 80% or higher, and frequency is at least 95% of rated value. b) Operating continuously above rated voltage or below rated frequency on any tap at no load, without exceeding limits of observable temperature rise when neither the voltage nor volts per hertz exceed 110% of rated values. IEEE C57.12.01 pdf download.