IEEE STD C57.12.90 PDF

3 Park Avenue. New York, NY USA. IEEE Power and Energy Society. IEEE Std C™/Cor (Corrigendum to. The definition of constant k in Equation 2 (in ) and line terminal rated voltage in the last paragraph of are corrected in this corrigendum. Define IEEE Standard C means the IEEE Standard Test Code for Liquid – Immersed Distribution, Power, and Regulating Transformers, ;.

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Petersen Daidi Zhong Annette D. Typical phasor and zero-sequence impedance diagrams are shown in Figure 28 a and Figure 28 b. Circuits or groups of circuits of different voltage above ground shall be tested separately. This process will generally involve those connections ieed taps resulting in the highest losses.

This is equivalent to allowing sound reflection equivalent to 1.

While IEEE administers the process and establishes rules to promote fairness in the consensus development process, IEEE does not independently evaluate, test, or verify the accuracy of any of the information or the soundness of any judgments contained in its standards. The virtual front time of the chopped wave may be different than the virtual front during a full-wave test because of the presence of the chopping gap.

The use of a resistor in the chopping circuit may increase the time interval to the first voltage zero after the instant of chopping. The voltmeter shall be connected between the terminals of the energized windings.

Only the inherent generator and lead inductances should be in the circuit.

Definition of IEEE Standard C57.12.90

If conducting the test with temperatures outside the specified ranges is necessary, the empirical formula in Equation 3 may be used to correct the measured no-load losses to the reference temperature: Include the following information for the sound-measuring instruments: For these transformers, the measurements may, upon purchaser request, and as agreed upon, be made with the transformer on the highest sound producing tap position.

Because these factors vary from design to design and between transformers of the same design, it is not practical to specify an exact formula to account for temperature variation throughout the operating temperature range of transformers.

The temperature of the surrounding air shall be determined by at least three thermocouples or thermometers in containers spaced uniformly around the transformer under test. The no-load losses of the transformer corrected to a sine-wave basis shall be determined from the measured value using Equation 2: Such transformers are not considered as axial-split transformers and shall be short-circuit tested with the usual short-circuit test method. All resistance measurements shall be recorded at no longer than s intervals and no less than s intervals.


Short the line terminals and neutral of winding 2. In Figure 20, a bridge technique employs a precision, low-loss, high-voltage capacitor and precision current transformer.

No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Partial discharge acceptance criteria shall be based on each line terminal rated kV and above. Therefore, parts of the transformer cores will be either over-excited T2 or under-excited T1 and the no- load losses and noise will vary accordingly.

Windings 1 and 2 have the externally available neutrals, whereas Windings 3, 4, and so forth do not. In case of power limitations from the Laboratory, by agreement between the manufacturer and the purchaser, the test may be done by closing a breaker at the source terminal to apply energy to the previously short-circuited transformer, pre-set method. When the insulation resistance falls below prescribed values, it can, in most cases of good design and where no defect exists, be brought up to the required standard by cleaning and drying the apparatus.

Temperature correction shall be made as in 9. Voltage transformer ratios should yield approximately the same readings on the two voltmeters. The minimum test frequency to meet this condition is given in Equation They may be subtracted from the earlier wattmeter reading to obtain the no-load loss of the transformer under test.

The purpose is to bias the core in the opposite flux polarity to delay saturation during negative polarity full-wave test. The ratio of the load losses in kilowatts at the temperature of test to the impedance kilovoltampere at the temperature of test is the load loss power factor of the transformer during the test and is used for correction of phase-angle error as specified in this standard.

In order to achieve core saturation in a short time period, the dc power supply voltage should be large enough to saturate the cores in a short time. All measured zero-phase-sequence impedances should be expressed in percent and placed on a common kilovoltampere base. The sum of core and cooling system sound components is typically referred to as the no-load noise of a transformer.

The induced voltage test shall be the last dielectric test performed. The radio-noise meter shall be coupled to the line terminal s of the winding under test through the capacitance tap of the bushing s. This test shall be performed on a tap position as close as possible to the middle position, e.

The hot resistance-time data collected shall be fitted to an exponential decay curve using the method of least squares. The procedure for testing three-phase transformers is similar, except that all connections and measurements are three-phase instead of single-phase and a balanced three-phase source of power is used for the tests.


Simultaneous readings of wattmeter, voltmeter, and ammeter are recorded to determine load losses and impedance voltage. For delta-connected windings, the time can also be reduced by opening the delta connection.

The design-related factors include the type and thickness of core steel, the core configuration, the geometry of core joints, and the core flux density. The source shall be ungrounded to eliminate any system zero-sequence impedance that could influence the final calculation. The tap position of the windings of the same phase not being directly impulse tested shall follow the same basic rule described above and shall be set in order to obtain the maximum, minimum, and middle turn ratios, with one of these prescribed ratios for each of the individual phases.

The microphone shall be located on the measurement surface. Therefore, the no-load loss test is conducted with rated voltage impressed across the transformer terminals, using a voltage source at a frequency equal to the rated frequency of the transformer under test, unless otherwise specified. The constants in the equivalent circuit are as shown in Equation 22 through Equation Tests may be made at temperatures outside this range when suitable correction factors are available.

Short out one phase of the winding to create a virtual neutral for testing purposes. NOTE— For distribution and pad-mounted transformers up to kVA, where it may not be practical to wait for thermal equilibrium, the method used to determine the winding temperature should take into consideration the lack of thermal equilibrium and the effect of ohmic heating of the winding conductors by load current during the test.

Therefore, the insulation resistance may be useful to indicate whether the apparatus is in suitable condition for application of dielectric test. No temperature correction should be applied. A minus sign may be appropriate when a delta winding 3 or 4 is physically located within or between windings 1 and 2.

IEEE Standard C | legal definition of IEEE Standard C by

NOTE 2—When measurements are to be made using dc voltages exceeding the rms operating voltage of the winding involved or V for a solidly grounded wye windinga relief gap may be employed to protect the insulation. When fewer than three single-phase transformers are tested e. This standard is on a continuous revision cycle and is constantly being reviewed and updated.