IEC 60076-21:2018
(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 60076-21:2018 describes electrical, mechanical and test requirements of liquid-immersed, single- and three-phase, 50 Hz and 60 Hz, self and forced-air cooled, distribution, overhead and substation, step-voltage regulators, 1 000 kVA (single-phase units) or 3 000 kVA (three-phase units) and smaller, 34 500 volts and below (2 400 V minimum) and their associated controls. Requirements, references and definitions relevant to either IEC or IEEE contexts are given and their use is described in Clause 4. This publication is published as an IEC/IEEE Dual Logo standard. This second edition cancels and replaces IEC 60076-21, published in 2011, and IEEE Std C57.15-2009. This edition includes the following significant technical changes with respect to IEC 6007621:2011/IEEE Std C57.15-2009:
a) updated list of normative and bibliography IEC and IEEE references and their associated text;
b) updated tables of preferred ratings for inclusion of maximum system voltage (Um), nominal system voltage and rated voltage (Ur);
c) inclusion of tables for optional fan-cooled ratings, external dielectric clearances and sound pressure levels;
d) revision of short-circuit requirements for distribution and substation voltage regulators;
e) inclusion of an universal interface between control enclosure and apparatus;
f) inclusion of tap-changer routine and type tests;
g) inclusion of audible sound pressure emissions test procedures;
h) inclusion of tank enclosure integrity type test procedures;
i) update of control environmental IEC reference test standard.
Keywords: step-voltage regulators
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IEC 60076-21 ®
Edition 2.0 2018-12
™
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 2.0 2018-12
IEEE Std C57.15™
INTERNATIONAL
STANDARD
Power transformers –
Part 21: Standard requirements, terminology, and test code for step-voltage
regulators
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-6260-3
– 2 – IEC 60076-21:2018
IEEE Std C57.15-2017
CONTENTS
FOREWORD . 9
1 Scope . 11
2 Normative references . 11
2.1 IEC references . 11
2.2 IEEE references . 11
2.3 SAE references . 12
3 Terms and definitions . 12
4 Use of normative references . 16
5 Service conditions . 17
5.1 Usual service conditions . 17
5.1.1 General . 17
5.1.2 Temperature . 17
5.1.3 Altitude . 17
5.1.4 Supply voltage . 17
5.1.5 Load current . 17
5.1.6 Outdoor operation . 17
5.1.7 Tank or enclosure finish. 17
5.2 Loading at other than rated conditions . 18
5.3 Unusual service conditions . 18
5.3.1 General . 18
5.3.2 Unusual temperature and altitude conditions . 18
5.3.3 Insulation at high altitude . 18
5.3.4 Other unusual service conditions . 19
6 Rating data . 20
6.1 Cooling classes of voltage regulators . 20
6.1.1 General . 20
6.1.2 Liquid-immersed (fire point ≤ 300 °C) air-cooled . 20
6.1.3 Liquid-immersed (fire point > 300 °C) air-cooled . 20
6.2 Ratings . 20
6.2.1 General . 20
6.2.2 Terms in which rating is expressed . 21
6.2.3 Preferred ratings . 21
6.2.4 Supplementary voltage ratings . 26
6.3 Supplementary continuous-current ratings . 27
6.3.1 General . 27
6.3.2 Optional forced-air ratings . 27
6.4 Taps . 28
6.5 Voltage supply ratios . 28
6.6 Insulation levels . 28
6.7 Losses . 29
6.7.1 General . 29
6.7.2 Total loss . 29
6.7.3 Tolerance for losses . 29
6.7.4 Determination of losses and excitation current . 29
6.8 Short-circuit requirements . 30
Published by IEC under licence from IEEE. © 2018 IEEE. All rights reserved.
IEEE Std C57.15-2017
6.8.1 General . 30
6.8.2 Mechanical capability demonstration . 31
6.8.3 Thermal capability of voltage regulators for short-circuit conditions . 31
6.9 Sound pressure level for liquid-immersed voltage regulators . 31
6.10 Tests . 32
6.10.1 General . 32
6.10.2 Routine tests . 32
6.10.3 Type tests . 32
7 Construction . 33
7.1 Bushings . 33
7.2 External dielectric clearances . 34
7.3 Terminal markings . 34
7.4 Diagram of connections . 35
7.5 Nameplates. 36
7.6 Tank construction . 37
7.6.1 General . 37
7.6.2 Pressure-relief valve . 37
7.6.3 Cover assembly . 37
7.6.4 Sudden pressure relay . 38
7.6.5 Lifting lugs . 38
7.6.6 Support lugs . 38
7.6.7 Substation bases . 40
7.6.8 Tank grounding provisions . 40
7.7 Components and accessories . 41
7.7.1 Components for full automatic control and operation. 41
7.7.2 Accessories for single-phase step-voltage regulators. 41
7.7.3 Accessories for three-phase step-voltage regulators . 42
8 Other requirements . 42
8.1 General . 42
8.2 Other components and accessories . 42
8.2.1 General . 42
8.2.2 Single- and three-phase voltage regulators . 42
8.2.3 Three-phase voltage regulators . 43
9 Test code . 43
9.1 General . 43
9.2 Resistance measurements . 43
9.2.1 General . 43
9.2.2 Determination of cold temperature . 43
9.2.3 Conversion of resistance measurements. 44
9.2.4 Resistance measurement methods . 44
9.3 Polarity test . 45
9.3.1 General . 45
9.3.2 Polarity by i
...
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