IEC 60076-21:2011
(Main)Power transformers - Part 21: Standard requirements, terminology, and test code for step-voltage regulators
Power transformers - Part 21: Standard requirements, terminology, and test code for step-voltage regulators
IEC 60076-21:2011/IEEE Std C57.15:2009 - Description of design types, tables of 50 Hz and 60 Hz ratings, supplementary ratings, construction, and available accessories are provided. Methods for performing routine and design tests applicable to liquid-immersed single and three-phase step-voltage regulators are described. Winding resistance measurements, polarity tests, insulation power factor and resistance tests, ratio tests, no load loss and excitation current measurements, impedance and load loss measurements, dielectric tests, temperature tests, routine and design impulse tests, short-circuit tests, control tests, calculated data, and certified test data are covered.
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Standards Content (Sample)
IEC 60076-21
Edition 1.0 2011-12
™
IEEE Std C57.15
INTERNATIONAL
STANDARD
Power transformers –
Part 21: Standard requirements, terminology, and test code for step-voltage
regulators
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IEC 60076-21
Edition 1.0 2011-12
™
IEEE Std C57.15
INTERNATIONAL
STANDARD
Power transformers –
Part 21: Standard requirements, terminology, and test code for step-voltage
regulators
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XD
ICS 29.180 ISBN 978-2-88912-848-8
– i – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
Contents
1. Overview . 1
1.1 Scope . 1
1.2 Purpose . 1
1.3 Word usage . 1
2. Normative references . 2
3. Definitions . 3
4. Service conditions . 9
4.1 Usual service conditions . 9
4.2 Loading at other than rated conditions .10
4.3 Unusual service conditions .10
4.4 Frequency .12
5. Rating data .12
5.1 Cooling classes of voltage regulators .12
5.2 Ratings .13
5.3 Supplementary continuous-current ratings .17
5.4 Taps .18
5.5 Operating voltage limits .18
5.6 Voltage supply ratios .20
5.7 Insulation levels .20
5.8 Losses .21
5.9 Short-circuit requirements .22
5.10 Tests .23
6. Construction .24
6.1 Bushings .24
6.2 Terminal markings .25
6.3 Diagram of connections .26
6.4 Nameplates .26
6.5 Tank construction .27
6.6 Components and accessories .31
7. Other requirements .32
7.1 Other supplementary continuous-current ratings .32
7.2 Other components and accessories .32
8. Test code.33
8.1 Resistance measurements .34
8.2 Polarity test .36
8.3 Ratio tests .37
8.4 No-load losses and excitation current .40
8.5 Load losses and impedance voltage .45
8.6 Dielectric tests .51
8.7 Temperature-rise tests .64
8.8 Short-circuit tests .73
8.9 Calculated data .77
9. Control systems .81
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
9.1 General .81
9.2 Control device construction .81
9.3 Control system requirements .82
9.4 Tests .83
Annex A (informative) Unusual temperature and altitude conditions .87
Annex B (informative) Field dielectric tests.89
Annex C (informative) Bibliography.90
Annex D (informative) IEEE List of Participants .92
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– iii – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 21: Standard requirements, terminology,
and test code for step-voltage regulators
FOREWORD
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International Standard IEC 60076-21/IEEE Std C57.15 has been processed through IEC
technical committee 14: Power transformers.
The text of this standard is based on the following documents:
IEEE Std FDIS Report on voting
C57.15-2009 14/688/FDIS 14/697/RVD
Full information on the voting for the approval of this standard can be found in the report
on voting indicated in the above table.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
A list of all the parts in the IEC 60076 series, published under the general title Power
transformers can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged
until the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the
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• withdrawn,
• replaced by a revised edition, or
• amended.
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– v – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
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Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– vii – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
IEEE Standard Requirements,
Terminology, and Test Code for
Step-Voltage Regulators
Sponsor
Transformers Committee
of the
IEEE Power & Energy Society
Approved 11 September 2009
IEEE-SA Standards Board
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
Abstract: Description of design types, tables of 50 Hz and 60 Hz ratings, supplementary ratings,
construction, and available accessories are provided. Methods for performing routine and design
tests applicable to liquid-immersed single and three-phase step-voltage regulators are described.
Winding resistance measurements, polarity tests, insulation power factor and resistance tests,
ratio tests, no load loss and excitation current measurements, impedance and load loss
measurements, dielectric tests, temperature tests, routine and design impulse tests, short-circuit
tests, control tests, calculated data, and certified test data are covered.
Keywords: control, design tests, position indicator, routine tests, series transformer, tap changer,
Type A, Type B, voltage regulator
•
National Electrical Safety Code and NESC are both registered trademarks and service marks of the Institute of Electrical
and Electronics Engineers, Inc.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– ix – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
IEEE Introduction
This introduction is not part of IEEE Std C57.15-2009, IEEE Standard Requirements, Terminology, and Test Code for
Step-Voltage Regulators.
The Working Group has undertaken the task to update this standard to:
a) Reflect the latest revisions of referenced documents IEEE Std C57.12.00™ [B13] and
IEEE Std C57.12.90™ [B16], and eliminate references to these standards in this standard
IEEE Std C57.15-2009 and duplicate applicable text.
b) Adapt the new IEEE approved format to ensure compatibility with the latest ISO and IEC
standards.
c) Include references to applicable IEC standards and keep IEEE standard references to a minimum.
This assists in setting up document as a possible candidate for a dual logo (IEC/IEEE).
d) Update tables of preferred ratings; include 50 Hz ratings. Ratings of 2.4 kV (45 BIL), 46 kV
(250 BIL), and 69 kV (350 BIL) have been removed from the three-phase 60 Hz voltage regulator
rating Table 5 (Table 4 in 1999 edition) due to historical inactivity of requests from users for
ratings.
e) Add bushing terminal connectors for current ratings of 669 A to 2000 A.
f) Clarify Type A and Type B designs and their resulting voltage regulation per extreme tap positions.
g) Review short-circuit requirements for distribution and substation applications and revise where
applicable.
Notice to users
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The numbers in brackets correspond to those of the bibliography in Annex C.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
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Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– 1 – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
POWER TRANSFORMERS –
Part 21: Standard requirements,
terminology, and test code for step-
voltage regulators
1. Overview
1.1 Scope
This standard describes electrical and mechanical requirements of liquid-immersed, single- and three-
phase, step-voltage regulators, not exceeding a regulation of 3000 kVA (for three-phase units) or 1000 kVA
(for single-phase units). This standard does not apply to load tap-changing power transformers.
1.2 Purpose
This standard is intended as a basis for the establishment of performance, limited electrical and mechanical
interchangeability, and general requirements of equipment described. It also assists in the proper selection
of such equipment.
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.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
2. Normative references
The following referenced documents are indispensable for the application of this standard (i.e., they must
be understood and used; therefore, each referenced document is cited in text and its relationship to this
standard is explained). For dated references, only the edition cited applies. For undated references, the
latest edition of the referenced document (including any amendments or corrigenda) applies.
Where references to both IEC and IEEE standards are made, users shall specify the standard they require,
and equipment shall be manufactured to meet that standard.
IEC 60068-2-1, Environmental testing—Part 2-1: Tests—Test A: Cold.
IEC 60068-2-2, Environmental testing—Part 2-2: Tests—Test B: Dry heat.
IEC 60068-2-30, Environmental testing—Part 2-30: Tests—Test Db: Damp heat, cyclic (12 h + 12 h
cycle).
IEC 60214-1, Tap-changers—Part 1: Performance requirements and test methods.
IEC 60255-5, Electrical Relays—Part 5: Insulation coordination for measuring relays and protection
equipment—Requirements and tests.
IEC 60255-21-1, Electrical Relays—Part 21: Vibration, shock, bump and seismic tests on measuring relays
and protection equipment—Section one: Vibration tests (sinusoidal).
IEC 60255-22-1, Measuring relays and protection equipment—Part 22-1: Electrical disturbance tests—
1 MHz burst immunity tests.
IEC 60255-22-2, Measuring relays and protection equipment—Part 22-2: Electrical disturbance tests—
Electrostatic discharge tests.
IEC 60255-22-3, Measuring relays and protection equipment—Part 22-3: Electrical disturbance tests—
Radiated electromagnetic field immunity.
IEC 60255-22-4, Measuring relays and protection equipment—Part 22-4: Electrical disturbance tests—
Electrical fast transient/burst immunity test.
IEC 60255-22-5, Measuring relays and protection equipment—Part 22-5: Electrical disturbance tests for
measuring relays and protection equipment—Surge immunity test.
IEC 60255-22-6, Electrical relays—Part 22-6: Electrical disturbance tests for measuring relays and
protection equipment—Immunity to conducted disturbances induced by radio frequency fields.
2, 3
IEEE Std 4™, IEEE Standard Techniques for High-Voltage Testing.
IEC publications are available from the Central Office of the International Electrotechnical Commission, 3, rue de Varembé, P.O.
Box 131, CH-1211, Geneva 20, Switzerland (http://www.iec.ch/). IEC publications are also available in the United States from the
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The IEEE standards or products referred to in Clause 2 are trademarks owned by the Institute of Electrical and Electronics Engineers,
Incorporated.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– 3 – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
IEEE Std C37.90.1™, IEEE Standard Surge Withstand Capability (SWC) Tests for Relays and Relay
Systems Associated with Electric Power Apparatus.
IEEE Std C37.90.2™, IEEE Standard for Withstand Capability of Relay Systems to Radiated
Electromagnetic Interference from Transceivers.
IEEE Std C37.90.3™, IEEE Standard Electrostatic Discharge Tests for Protective Relays.
IEEE Std C57.12.31™, IEEE Standard for Pole-Mounted Equipment—Enclosure Integrity.
IEEE Std C57.91™, IEEE Guide for Loading Mineral-Oil-Immersed Transformers.
IEEE Std C57.98™, IEEE Guide for Transformer Impulse Tests.
IEEE Std C57.131™, IEEE Standard Requirements for Load Tap Changers.
3. Definitions
For the purposes of this document, the following terms and definitions apply. The IEEE Standards
Dictionary: Glossary of Terms & Definitions should be referenced for terms not defined in this clause.
ambient temperature: The temperature of the medium, such as air, water, or earth, into which the heat of
the equipment is dissipated.
NOTE 1— For self-ventilated equipment, the ambient temperature is the average temperature of the air in the
immediate neighborhood of the equipment.
NOTE 2— For air cooled equipment with forced ventilation, the ambient temperature is taken as that of the in-going
air.
angular displacement of a three-phase voltage regulator or bank of three single-phase voltage
regulators: (A) The time angle, expressed in degrees, between the line-to-neutral voltage of the reference
source voltage terminal and the line-to-neutral voltage of the corresponding load voltage terminal. (B) The
connection and arrangement of terminal markings for a three-phase voltage regulator or bank of three
single-phase voltage regulators in a wye connection has an angular displacement of zero degrees. (C) The
connection and arrangement of terminal markings for a three-phase voltage regulator or bank of three
single-phase voltage regulators in a delta connection has an angular displacement of zero degrees when the
voltage regulators are on the neutral tap position. When the voltage regulators are on a tap position other
than neutral, the angular displacement will be other than zero degrees. The angular displacement with the
voltage regulators connected in delta will be less than ±5° for a ±10% range of regulation.
autotransformer: A transformer in which at least two windings have a common section.
average winding temperature rise of a voltage regulator: The arithmetic difference between the average
winding temperature of the hottest winding and the ambient temperature.
common winding: That part of the autotransformer winding that is common to both the primary and
secondary circuits. Syn: shunt winding.
The IEEE Standards Dictionary: Glossary of Terms & Definitions is available at http://shop.ieee.org/.
Notes in text, tables, and figures of a standard are given for information only and do not contain requirements needed to implement
this standard.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
current transformer: An instrument transformer intended to have its primary winding connected in series
with the conductor carrying the current to be measured or controlled.
dielectric withstand voltage tests: Tests made to determine the ability of insulating materials and spacings
to withstand specified overvoltages for a specified time without flashover or puncture.
NOTE—The purpose of the tests is to determine the adequacy against breakdown of insulating materials and spacings
under normal or transient conditions.
excitation current: The current that flows in any winding used to excite the voltage regulator when all
other windings are open-circuited. It is usually expressed in percent of the rated current of the voltage
regulator.
impedance drop: The phasor sum of the resistance voltage drop and the reactance voltage drop.
NOTE—For voltage regulators, the resistance drop, the reactance drop, and the impedance drop are, respectively, the
sum of the primary and secondary drops reduced to the same terms. They are determined from the load-loss
measurements and are usually expressed in per unit or percent of the rated voltage of the voltage regulator. Since they
differ at different operating positions of the voltage regulator, two values of impedance shall be considered, in practice,
to be the tap positions that result in the minimum and the maximum impedance. Neutral position has the minimum
amount of impedance.
impedance voltage of a voltage regulator: The voltage required to circulate rated current through one
winding of the voltage regulator when another winding is short-circuited, with the respective windings
connected as for a rated voltage operation.
NOTE—Impedance voltage is usually referred to the series winding, and then that voltage is expressed in per unit, or
percent, of the rated voltage of the voltage regulator.
line-drop compensator: A device that causes the voltage regulating device to vary the output voltage by
an amount that compensates for the impedance voltage drop in the circuit between the voltage regulator and
a predetermined location on the circuit (sometimes referred to as the load center).
liquid: Refers to synthetic fluid, natural ester-based fluid, and mineral oil.
NOTE—Some synthetic fluids may be unsuitable for use in the arcing environment of a step-voltage regulator.
liquid-immersed self-cooled (Class KNAN): A voltage regulator having its core and coil immersed in a
liquid with fire point > 300 °C and cooled by the natural circulation of air over the cooling surfaces.
liquid-immersed self-cooled (Class ONAN): A voltage regulator having its core and coil immersed in a
liquid with fire point ≤ 300 °C and cooled by the natural circulation of air over the cooling surfaces.
liquid-immersed self-cooled/forced-air-cooled (Classes KNAN/KNAF and KNAN/KNAF/KNAF): A
voltage regulator having its core and coils immersed in liquid with fire point > 300 °C and having a self-
cooled rating with cooling obtained by the natural circulation of air over the cooling surface and a forced-
air-cooled rating with cooling obtained by the forced circulation of air over this same cooling surface.
liquid-immersed self-cooled/forced-air-cooled (Classes ONAN/ONAF and ONAN/ONAF/ONAF): A
voltage regulator having its core and coils immersed in liquid with fire point ≤ 300 °C and having a self-
cooled rating with cooling obtained by the natural circulation of air over the cooling surface and a forced-
air-cooled rating with cooling obtained by the forced circulation of air over this same cooling surface.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
– 5 – IEC 60076-21:2011(E)
IEEE Std C57.15-2009
liquid-immersed self-cooled/forced-air-cooled/forced-liquid-cooled (Class KNAN/KNAF/KFAF): A
voltage regulator having its core and coils immersed in liquid with fire point > 300 °C and having a self-
cooled rating with cooling obtained by the natural circulation of air over the cooling surface; a forced-air-
cooled rating with cooling obtained by the forced circulation of air over this same air cooling surface; and a
forced-liquid-cooled rating with cooling obtained by the forced circulation of liquid over the core and coils
and adjacent to this same cooling surface over which the cooling air is being forced-circulated.
liquid-immersed self-cooled/forced-air-cooled/forced-liquid-cooled (Class ONAN/ONAF/OFAF): A
voltage regulator having its core and coils immersed in liquid with fire point ≤ 300 °C and having a self-
cooled rating with cooling obtained by the natural circulation of air over the cooling surface; a forced-air-
cooled rating with cooling obtained by the forced circulation of air over this same air cooling surface; and a
forced-liquid-cooled rating with cooling obtained by the forced circulation of liquid over the core and coils
and adjacent to this same cooling surface over which the cooling air is being forced-circulated.
liquid-immersed voltage regulator: A voltage regulator in which the core and coils are immersed in an
insulating liquid.
liquid-immersed water-cooled (Class KNWF): A voltage regulator having its core and coils immersed in
a liquid with fire point > 300 °C and cooled by the natural circulation of the liquid over the water-cooled
surface.
liquid-immersed water-cooled (Class ONWF): A voltage regulator having its core and coils immersed in
a liquid with fire point ≤ 300 °C and cooled by the natural circulation of the liquid over the water-cooled
surface.
liquid-immersed water-cooled/self-cooled (Class KNWF/KNAN): A voltage regulator having its core
and coils immersed in liquid with fire point > 300 °C and having a water-cooled rating with cooling
obtained by the natural circulation of liquid over the water-cooled surface, and a self-cooled rating with
cooling obtained by the natural circulation of air over the air-cooled surface.
liquid-immersed water-cooled/self-cooled (Class ONWF/ONAN): A voltage regulator having its core
and coils immersed in liquid with fire point ≤ 300 °C and having a water-cooled rating with cooling
obtained by the natural circulation of liquid over the water-cooled surface, and a self-cooled rating with
cooling obtained by the natural circulation of air over the air-cooled surface.
load losses: Those losses that are incident to the carrying of a specified load. Load losses include I R loss
in the current carrying parts (windings, leads, busbars, bushings), eddy losses in conductors due to eddy
currents and circulating currents (if any) in parallel windings or in parallel winding strands, and stray loss
induced by leakage flux in the tank, core clamps, or other structural parts.
load tap changer: A selector switch device, which may include current interrupting contactors, used to
change voltage regulator taps with the voltage regulator energized and carrying full load.
no-load (excitation) losses: Those losses that are incident to the excitation of the voltage regulator. No-
load (excitation) losses include core loss, dielectric loss, conductor loss in the winding due to exciting
current, and conductor loss due to circulating current in parallel windings. These losses change with the
excitation voltage.
Published by the IEC under licence from IEEE. © 2009 IEEE. All rights reserved.
IEEE Std C57.15-2009
nominal system voltage: A nominal value assigned to a system or circuit of a given voltage for the
purpose of convenient designation. The term nominal voltage designates the line-to-line voltage, as
distinguished from the line-to-neutral voltage. It applies to all parts of the system or circuit. The system
voltage by which the system is designated and to which certain operating characteristics of the system are
related. (The nominal voltage of a system is near the voltage level at which the system normally operates
and provides a per-unit base voltage for system study purposes. To allow for o
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