IEC TS 62749:2020

Assessment of power quality - Characteristics of electricity supplied by public networks

IEC TS 62749:2020 specifies the expected characteristics of electricity at the SUPPLY TERMINALS of public low, medium and high voltage, 50 Hz or 60 Hz, networks.
NOTE 1 The boundaries between the various voltage levels can be different for different countries/regions. In the context of this TS, the following terms for system voltage are used:
- low voltage (LV) refers to less than or equal to 1 kV;
- medium voltage (MV) refers to between 1 kV and 35 kV;
- high voltage (HV) refers to between 35 kV and 230 kV.
While power quality is related to EMC in a number of ways this document is not an EMC publication. This second edition cancels and replaces the first edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) minimum number of remaining data for weekly analysis,
b) improvement of the compatibility between EN 50160 and IEC TS 62749,
c) further explanation of the conception of daily sliding window,
d) further explanation of the aggregation method used for events,
e) further explanation of the relation between Power Quality and EMC,
f) addition of a new definition of mains communicating system (MCS),
g) addition of a new Annex G: Other phenomena,
h) transfer of the main content of IEC TR 62510 to IEC TS 62749.

General Information

• Status: Published
• Publication Date: 10-Feb-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.220.99 - Other standards related to electricity and magnetism
• Technical Committee: TC 8 - System aspects of electrical energy supply
• Drafting Committee: WG 11 - TC 8/WG 11
• Current Stage: PPUB - Publication issued
• Start Date: 18-Feb-2020
• Completion Date: 11-Feb-2020

Relations

• Revises: IEC TS 62749:2015 - Assessment of power quality - Characteristics of electricity supplied by public networks
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TS 62749 ®
Edition 2.0 2020-02
TECHNICAL
SPECIFICATION
colour
inside
Assessment of power quality – Characteristics of electricity supplied by public
networks
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

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If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC TS 62749 ®
Edition 2.0 2020-02
TECHNICAL
SPECIFICATION
colour
inside
Assessment of power quality – Characteristics of electricity supplied by public

networks
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.99 ISBN 978-2-8322-7849-9

– 2 – IEC TS 62749:2020 © IEC 2020
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Recommended values for power quality indices . 17
4.1 General . 17
4.2 Frequency deviation . 19
4.3 Supply voltage deviation . 19
4.3.1 General . 19
4.3.2 Low voltage systems . 19
4.3.3 Medium voltage systems . 20
4.3.4 High voltage systems . 20
4.4 Voltage unbalance . 20
4.5 Flicker . 21
4.6 Harmonic and interharmonic voltage . 21
4.6.1 General . 21
4.6.2 Low voltage systems . 21
4.6.3 Medium voltage systems . 22
4.6.4 High voltage systems . 23
4.7 Voltage dip . 24
4.8 Voltage swell . 25
4.9 Voltage interruption . 25
4.10 Mains communicating voltage . 26
4.11 Rapid voltage change . 26
4.12 Transient overvoltage . 27
4.12.1 Low voltage systems . 27
4.12.2 Medium and high voltage systems . 27
5 Objectives and methods for power quality assessment . 27
5.1 General . 27
5.2 Site power quality assessment . 28
5.2.1 General . 28
5.2.2 Continuous phenomena . 28
5.2.3 For discontinuous phenomena (single event) . 30
5.3 System aspect power quality assessment . 31
5.3.1 General . 31
5.3.2 For continuous phenomena . 31
5.3.3 For discontinuous phenomena (events) . 31
Annex A (informative) Examples of profiles for power quality specification . 34
A.1 General . 34
A.2 LV and MV public distribution networks in European countries . 34
A.3 LV, MV and HV power supply system in China . 35
A.4 Example of a transmission system in Canada . 36
A.5 Examples of profiles in Australia . 37
Annex B (informative) Additional information on power quality assessments . 38

B.1 Weekly percentile values assessed on a daily sliding basis . 38
B.2 Example on system aspect continuous disturbance evaluation . 39
B.3 Aggregation method used for events . 39
B.3.1 General . 39
B.3.2 Time aggregation . 39
Annex C (informative) Main impact of poor power quality . 42
C.1 General . 42
C.2 Harmonic distortion . 42
C.3 Voltage unbalance . 42
C.4 Voltage deviation . 43
C.5 Frequency deviation . 43
C.6 Voltage fluctuation . 43
C.7 Flicker . 43
C.8 Voltage dip (or voltage sag) . 43
C.9 Transient overvoltages . 43
Annex D (informative) Power quality issues related to distributed generation and
micro-grids . 44
D.1 General . 44
D.2 Voltage deviation . 44
D.3 Harmonics . 44
D.4 DG magnetic bias (DC current injection) . 44
D.5 Voltage fluctuation and flicker . 45
D.6 High frequency conducted disturbances . 45
Annex E (informative) Methods to maintain and improve power quality . 46
E.1 General . 46
E.2 Voltage deviation . 46
E.3 Harmonics . 46
E.4 Flicker . 47
E.5 Voltage unbalance . 47
E.6 Voltage dip/swell/short time interruption . 48
Annex F (informative) Relation between power quality and EMC . 49
F.1 General . 49
F.2 Differences between power quality and compatibility levels . 49
F.3 Example of power quality level versus compatibility level . 50
Annex G (informative) Other phenomena . 53
G.1 General . 53
G.2 Level behaviour over time . 53
G.3 Duration . 53
G.4 Periodicity . 53
G.5 Bandwidth . 54
Annex H (informative) Role of stakeholders for power quality management –
Coordination of the parties involved . 55
H.1 General . 55
H.2 Network operator – Network user . 55
H.3 Network user – Equipment supplier . 55
H.4 Network operator – Equipment supplier . 56
Bibliography . 57

– 4 – IEC TS 62749:2020 © IEC 2020
Figure 1 – Mains communicating voltages recommended values in percent of U used
N
in public LV networks (or U in public MV networks) . 26
c
Figure 2 – Example for illustrating voltage THD assessment result trends . 30
Figure 3 – Example showing information of single event assessment . 31
th
...

IEC TS 62749 ®
Edition 2.0 2020-02
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Assessment of power quality – Characteristics of electricity supplied by public
networks
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé [e-mail]
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: [e-mail].
IEC TS 62749 ®
Edition 2.0 2020-02
REDLINE VERSION
TECHNICAL
SPECIFICATION
colour
inside
Assessment of power quality – Characteristics of electricity supplied by public

networks
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.99 ISBN 978-2-8322-7880-2

– 2 – IEC TS 62749:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 10
4 Recommended values for power quality indices . 18
4.1 General . 18
4.2 Frequency deviation . 20
4.3 Supply voltage deviation . 20
4.3.1 General . 20
4.3.2 Low voltage systems . 20
4.3.3 Medium voltage systems . 21
4.3.4 High voltage systems . 21
4.4 Voltage unbalance . 21
4.5 Flicker . 22
4.6 Harmonic and interharmonic voltage . 22
4.6.1 General . 22
4.6.2 Low voltage systems . 22
4.6.3 Medium voltage systems . 23
4.6.4 High voltage systems . 24
4.7 Voltage dip . 25
4.8 Voltage swell . 26
4.9 Voltage interruption . 26
4.10 Mains signalling communicating voltage . 27
4.11 Rapid voltage change . 27
4.12 Transient overvoltage . 28
4.12.1 Low voltage systems . 28
4.12.2 Medium and high voltage systems . 28
5 Objectives and methods for power quality assessment . 28
5.1 General . 28
5.2 Site power quality assessment . 29
5.2.1 General . 29
5.2.2 Continuous phenomena . 29
5.2.3 For discontinuous phenomena (single event) . 31
5.3 System aspect power quality assessment . 32
5.3.1 General . 32
5.3.2 For continuous phenomena . 32
5.3.3 For discontinuous phenomena (events) . 33
Annex A (informative) Examples of profiles for power quality specification . 35
A.1 General . 35
A.2 LV and MV public distribution networks in European countries . 35
A.3 LV, MV and HV power supply system in China . 36
A.4 Example of a transmission system in Canada . 37
A.5 Examples of profiles in Australia . 38
Annex B (informative) Additional information on power quality assessments . 39

B.1 Weekly percentile values assessed on a daily sliding basis . 39
B.2 Example on system aspect continuous disturbance evaluation . 40
B.3 Aggregation method used for events . 40
B.3.1 General . 40
B.3.2 Time aggregation . 40
Annex C (informative) Main impact of poor power quality . 43
C.1 General . 43
C.2 Harmonic distortion . 43
C.3 Voltage unbalance . 44
C.4 Voltage deviation . 44
C.5 Frequency deviation . 44
C.6 Voltage fluctuation . 44
C.7 Flicker . 44
C.8 Voltage dip (or voltage sag) . 44
C.9 Transient overvoltages . 45
Annex D (informative) Power quality issues related to distributed generation and
micro-grids . 46
D.1 General . 46
D.2 Voltage deviation . 46
D.3 Harmonics . 46
D.4 DG magnetic bias (DC current injection) . 46
D.5 Voltage fluctuation and flicker . 47
D.6 High frequency conducted disturbances . 47
Annex E (informative) Methods to maintain and improve power quality . 48
E.1 General . 48
E.2 Voltage deviation . 48
E.3 Harmonics . 48
E.4 Flicker . 49
E.5 Voltage unbalance . 49
E.6 Voltage dip/swell/short time interruption . 50
Annex F (informative) Relation between power quality and EMC . 51
F.1 General . 51
F.2 Differences between power quality and compatibility levels . 51
F.3 Example of power quality level versus compatibility level . 52
Annex G (informative) Other phenomena . 55
G.1 General . 55
G.2 Level behaviour over time . 55
G.3 Duration . 55
G.4 Periodicity . 55
G.5 Bandwidth . 56
Annex H (informative) Role of stakeholders for power quality management –
Coordination of the parties involved . 57
H.1 General . 57
H.2 Network operator – Network user . 57
H.3 Network user – Equipment supplier . 57
H.4 Network operator – Equipment supplier . 58
Bibliography . 59

– 4 – IEC TS 62749:2020 RLV © IEC 2020
Figure 1 – Signal Mains communicating voltages recommended values in percent of
U used in public LV networks (or U in public MV networks) . 27
N c
Figure 2 – Example for illustrating voltage THD assessment result trends . 31
Figure 3 – Example showing information of single event assessmen
...