IEC 60076-21:2018

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

General Information

• Status: Published
• Publication Date: 06-Dec-2018
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.180 - Transformers. Reactors
• ICS: 33.160.40 - Video systems
• Technical Committee: TC 14 - Power transformers
• Current Stage: PPUB - Publication issued
• Completion Date: 07-Dec-2018

Standards Content (Sample)

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
IEC 60076-21:2018-12(en) IEEE Std C57.15-2017
---------------------- Page: 1 ----------------------
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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

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 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.
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IEC 60076-21:2018 – 3 –
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 inductive kick ............................................................................... 46

9.3.3 Polarity by ratio meter.................................................................................... 46

9.4 Ratio test .............................................................................................................. 46

9.4.1 General ......................................................................................................... 46

9.4.2 Taps .............................................................................................................. 46

Published by IEC under licence from IEEE. © 2018 IEEE. All rights reserved.
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– 4 – IEC 60076-21:2018
IEEE Std C57.15-2017

9.4.3 Voltage and frequency ................................................................................... 47

9.4.4 Three-phase voltage regulators ..................................................................... 47

9.4.5 Tolerance for ratio ......................................................................................... 47

9.4.6 Ratio test methods ......................................................................................... 47

9.5 No-load loss and excitation current ....................................................................... 49

9.5.1 General ......................................................................................................... 49

9.5.2 No-load loss test ............................................................................................ 50

9.5.3 Waveform correction of no-load loss .............................................................. 51

9.5.4 Test methods for three-phase voltage regulators ........................................... 52

9.5.5 Determination of excitation (no-load) current ................................................. 52

9.5.6 Measurements ............................................................................................... 53

9.5.7 Correction of loss measurement due to metering phase-angle errors ............. 53

9.6 Load loss and impedance voltage ......................................................................... 54

9.6.1 General ......................................................................................................... 54

9.6.2 Factors affecting the values of load loss and impedance voltage ................... 55

9.6.3 Tests for measuring load loss and impedance voltage ................................... 56

9.6.4 Calculation of load loss and impedance voltage from test data ...................... 58

9.7 Dielectric tests ...................................................................................................... 60

9.7.1 General ......................................................................................................... 60

9.7.2 Lightning impulse type test ............................................................................ 61

9.7.3 Lightning impulse routine test ........................................................................ 67

9.7.4 Applied-voltage test ....................................................................................... 69

9.7.5 Induced-voltage test ...................................................................................... 69

9.7.6 Insulation power factor tests .......................................................................... 71

9.7.7 Insulation resistance tests ............................................................................. 72

9.8 On-load tap-changer routine tests ......................................................................... 73

9.8.1 General ......................................................................................................... 73

9.8.2 Mechanical test ............................................................................................. 74

9.8.3 Auxiliary circuits insulation test ...................................................................... 74

9.9 Control system routine tests .................................................................................. 74

9.9.1 Applied voltage .............................................................................................. 74

9.9.2 Operation ...................................................................................................... 74

9.10 Temperature-rise test ............................................................................................ 74

9.10.1 General ......................................................................................................... 74

9.10.2 Test methods ................................................................................................. 75

9.10.3 Resistance measurements ............................................................................. 78

9.10.4 Temperature measurements .......................................................................... 79

9.10.5 Correction of temperature-rise test results ..................................................... 82

9.11 Short-circuit test ................................................................................................... 83

9.11.1 General ......................................................................................................... 83

9.11.2 Test connections ........................................................................................... 83

9.11.3 Test requirements .......................................................................................... 84

9.11.4 Test procedure .............................................................................................. 84

9.11.5 Proof of satisfactory performance .................................................................. 86

9.12 Determination of sound level ................................................................................. 87

9.12.1 General ......................................................................................................... 87

9.12.2 Applicability ................................................................................................... 88

Published by IEC under licence from IEEE. © 2018 IEEE. All rights reserved.
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IEC 60076-21:2018 – 5 –
IEEE Std C57.15-2017

9.12.3 Instrumentation .............................................................................................. 88

9.12.4 Test conditions .............................................................................................. 88

9.12.5 Microphone positions ..................................................................................... 90

9.12.6 Sound level measurements ............................................................................ 91

9.12.7 Determination of sound level of a voltage regulator ....................................... 95

9.12.8 Presentation of results ................................................................................... 97

9.13 Calculated data ..................................................................................................... 98

9.13.1 Reference temperature .................................................................................. 98

9.13.2 Loss and excitation current ............................................................................ 99

9.13.3 Efficiency ....................................................................................................... 99

9.13.4 Calculation of winding temperature during a short-circuit ............................... 99

9.13.5 Certified test data ........................................................................................ 101

10 Component tests ......................................................................................................... 102

10.1 General ............................................................................................................... 102

10.2 Enclosure integrity .............................................................................................. 102

10.2.1 General ....................................................................................................... 102

10.2.2 Static pressure ............................................................................................ 102

10.2.3 Dynamic pressure ........................................................................................ 103

10.2.4 Type test for fault current capability of a voltage regulator enclosure ........... 103

10.3 On-load tap-changer ........................................................................................... 104

10.3.1 General ....................................................................................................... 104

10.3.2 Type tests .................................................................................................... 104

10.4 Control system .................................................................................................... 109

10.4.1 General ....................................................................................................... 109

10.4.2 Control device construction.......................................................................... 110

10.4.3 Accuracy ..................................................................................................... 110

10.4.4 Type tests .................................................................................................... 112

11 Universal interface ....................................................................................................... 116

11.1 Connection between control enclosure and apparatus ......................................... 116

11.2 Universal interface connector .............................................................................. 117

Annex A (informative) Unusual temperature and altitude conditions ................................... 120

A.1 Unusual temperatures and altitude service conditions ......................................... 120

A.2 Effects of altitude on temperature-rise ................................................................ 120

A.3 Operation at rated kVA ....................................................................................... 120

A.4 Operation at less than rated kVA ........................................................................ 120

Annex B (informative) Field dielectric tests ........................................................................ 121

B.1 Tests on bushings ............................................................................................... 121

B.2 Dielectric tests in the field ................................................................................... 121

Annex C (informative) Step-voltage regulator construction ................................................. 122

C.1 General ............................................................................................................... 122

C.2 Type A ................................................................................................................ 123

C.3 Type B ................................................................................................................ 123

C.4 Series transformer construction .......................................................................... 124

C.5 Reactor circuit .................................................................................................... 124

C.6 Equalizer winding ................................................................................................ 124

Annex D (informative) Hazards of Bypass off Neutral ......................................................... 126

Published by IEC under licence from IEEE. © 2018 IEEE. All rights reserved.
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– 6 – IEC 60076-21:2018
IEEE Std C57.15-2017

Annex E (informative) Overloading of step-voltage regulators ............................................ 130

Annex F (informative) Power capacitor and distributed generation compatibility ................. 134

F.1 Power capacitor application issues ..................................................................... 134

F.1.1 General ....................................................................................................... 134

F.1.2 Power circuit for consideration ..................................................................... 134

F.1.3 Voltage regulator incorporating line-drop compensation (LDC) in the

control ......................................................................................................... 134

F.1.4 Voltage regulator incorporating line current compensation (LCC) in the

control ......................................................................................................... 137

F.2 Distributed generation application issues ............................................................ 137

F.2.1 General ....................................................................................................... 137

F.2.2 Control operation with power reversal recognition ........................................ 138

F.2.3 Power circuit for consideration ..................................................................... 139

F.2.4 Distributed generator alternatives ................................................................ 139

F.2.5 P-Q summary .............................................................................................. 140

F.2.6 Example system with distribution generation (DG) ....................................... 140

F.2.7 Expanded example, distributed generation mode ......................................... 142

F.2.8 Caveats ....................................................................................................... 142

F.2.9 Conclusions ................................................................................................. 142

Bibliography ........................................................................................................................ 143

Figure 1 – Single-phase voltage regulators ........................................................................... 35

Figure 2 – Three-phase voltage regulators with two arrangements of bushings ..................... 35

Figure 3 – Type-B support lugs ............................................................................................. 39

Figure 4 – Type-C support lugs ............................................................................................. 40

Figure 5 – Connections for voltmeter-ammeter method of resistance measurement .............. 44

Figure 6 – Voltage regulator connected for polarity testing – Voltage regulator in

Neutral pos
...