IEEE C57.12.90-2006 Test Code for Liquid-Immersed Transformers (series 1)

I have obtained a photocopy of the IEEE Standard C57.12.90-2006 Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers. I am posting part by part of the standard and the posts will serve as my reference notes.

IEEE Standard Test Code
For Liquid-Immersed Distribution,
Power, and Regulating Transformers

1. Overview

1.1 Scope

This standard describes methods for performing tests specified in IEEE Std C57.12.00tm-2006 and other standards applicable to liquid-immersed distribution, power, and regulating transformers. It is intended for use as a basis for performance, safety, and proper testing of such transformers.

This standard applies to all liquid-immersed transformers, except instrument transformers, step-voltage and induction voltage regulators, arc furnace transformers, rectifier transformers, specialty transformers, grounding transformers, and mine transformers.

Transformer requirements and specific test criteria are not a part of this standard, but they are contained in appropriate standards, such as IEEE Std C57.12.00-2006, ANSI C57.12.10.1998, ANSI C57.12.20-1997, and ANSI C57.12.40-1994, or in user specifications.

1.2 Purpose

The purpose of this standard is to provide test procedure information.

1.3 Word usage

When this standard is used on a mandatory basis, the word shall indicates mandatory requirements. The words should or may refer to matters that are recommended or permitted but not mandatory.

2. Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For updated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.
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3. Definitions

For the purposes of this document, the following terms and definitions apply, IEEE, Std C57.12.80-2002 and The Authoritative Dictionary of IEEE Standards Terms [B5]5 should be referenced for terms not defined in this clause.

3.1 actual time to crest: The time interval from the start of the transient to the time when the maximum amplitude is reached.

3.2 ambient sound pressure level: The sound pressure level measured at the test facility or the substation without the transformer energized.

3.3 A-weighted sound level: Loudness that is measured with a sound level meter using the A-weighted response filter that is built into the meter circuitry. The A-weighting filter is commonly used to measure community noise and it simulates the frequency response of the human ear.

3.4 C-weighted sound level: Loudness that is measured with sound level meter using the C-weighted filter that is built into the sound level meter. The C-weighting has only little dependence on frequency over the greater part of the audible frequency range.

3.5 efficiency (of a transformer): The ratio of the useful power output of a transformer to the total power input.

3.6 guard: One or more conducting elements arranged and connected on an electrical instrument or measuring circuit so as to divert unwanted currents from the measuring means.

3.7 semi-reverberant facility: A room with a solid floor and an undetermined amount of sound-absorbing materials on the walls and ceiling.

3.8 sound pressure level Lp in decibels: Twenty times the logarithm to the base ten of the ratio of the measured sound pressure (P) to a reference pressure (Po) of 20 µPa or


Lp= 20 x log10(P/Po)

3.9 sound power level Lw in decibels: Ten times the logarithm to the base ten of the emitted sound power (w) to a reference power of 10-12 W (wo) or

LW= 10 x log10(w/wo)

3.10 time to first voltage zero on the tail of the wave: The time interval from the start of the transient to the time when the first voltage zero occurs on the tail of the wave.

3.11 total losses: The sum of the no-load losses and the load losses.

4. General

4.1 Types of tests

Various types of tests (routine, design, conformance, and other) are defined in IEEE Std. C57.12.80-2002.

4.2 Test requirements

A general summary of test requirements is included in Table 21 of IEEE Std C57.12.00.2006 and indicates which tests are normally considered routing, design, or other, by size.

4.3 Test sequence

See 10.1.5.1 for the sequence of dielectric tests when lightning impulse or switching impulse tests are specified.

NOTE – To minimize potential damage to the transformer during testing the resistance, polarity, phase relation, ratio, no-load loss and excitation current, impedance, and load loss tests (and temperature-rise tests, when applicable) should precede dielectric tests. Using this sequence, the beginning tests involve voltages and currents, which are usually reduced as compared with rated values, thus rendering to minimize damaging effects to the transformer.

4.4 Instrumentation

Although the figures in this standard show conventional meters, adequate digital readout measuring devices and digital sampling techniques with computer calculations are considered to be satisfactory alternatives.

Source: IEEE C57.12.90-2006 Test Code for Liquid-Immersed Distribution, Power and Regulating Transformers