IEC 61921:2017
(Main)Power capacitors - Low-voltage power factor correction banks
Power capacitors - Low-voltage power factor correction banks
IEC 61921:2017 is applicable to low-voltage AC shunt capacitor banks intended to be used for power factor correction purposes, possibly equipped with a built-in switchgear and controlgear apparatus capable of connecting to or disconnecting from the mains part(s) of the bank with the aim to correct its power factor. Low-voltage power factor correction banks if not otherwise indicated hereinafter and where applicable comply with the requirements of IEC 61439-1 and IEC 61439-2. This second edition cancels and replaces the first edition published in 2003. It constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: numerous changes regarding verification methods to align with IEC 61439-1; modification of marking; add routine verification of rated output; new Annex D with guidance on methods for temperature rise verification; update of normative references; general editorial review.
Keywords: low-voltage AC shunt capacitor banks
Condensateurs de puissance - Batteries de compensation du facteur de puissance basse tension
L'IEC 61921:2017 s’applique aux batteries de condensateurs shunt à basse tension en courant alternatif destinées à être utilisées pour la compensation du facteur de puissance, ces batteries comportant éventuellement des appareillages de connexion et de commande intégrés capables de mettre sous tension ou hors tension une ou des fractions de l’ensemble afin de compenser le facteur de puissance du réseau. Sauf indication contraire dans la présente norme et le cas échéant, les batteries de compensation du facteur de puissance basse tension satisfont aux exigences de l'IEC 61439‑1 et de l'IEC 61439-2. Cette deuxième édition annule et remplace la première édition parue en 2003. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: nombreuses modifications concernant l'alignement des méthodes de vérification sur l'IEC 61439-1; modification de marquage; ajout d'une vérification individuelle systématique de la puissance assignée; nouvelle Annexe D avec préconisations portant sur les méthodes de vérification de l'échauffement; actualisation des références normatives; révision rédactionnelle générale.
Mots clés: condensateurs shunt à basse tension en courant alternatif
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IEC 61921 ®
Edition 2.0 2017-06
REDLINE VERSION
INTERNATIONAL
STANDARD
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inside
Power capacitors – Low-voltage power factor correction banks
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
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About the IEC
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International Standards for all electrical, electronic and related technologies.
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IEC 61921 ®
Edition 2.0 2017-06
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Power capacitors – Low-voltage power factor correction banks
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.060.70 ISBN 978-2-8322-4505-7
– 2 – IEC 61921:2017 RLV © IEC 2017
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Marking of a capacitor bank . 8
5 Service conditions . 8
6 Guide for design, installation, operation and safety . 8
6.1 General . 8
6.2 Design . 9
6.2.1 Choice of rated voltage . 9
6.2.2 Switching and overload protection . 11
6.3 Installation and operation . 12
6.3.1 Electrical environment . 12
6.3.2 Secondary effects of the PFC system capacitor bank . 13
6.3.3 Overvoltages . 13
6.3.4 Overload currents . 13
6.4 Safety . 14
6.4.1 Discharging devices. 14
6.4.2 Discharging after disconnection . 15
6.4.3 Fire hazard in case of failure . 15
6.4.4 Human and property damage . 15
6.4.5 Busbar . 16
6.4.6 Connection of systems. 16
6 Electromagnetic compatibility .
6.1 Emission .
6.2 Immunity .
6.3 Assemblies incorporating electronic equipment .
7 Tests .
7.1 Classification of tests .
7.2 Type tests .
7.3 Routine tests.
7 Design verification . 19
7.1 General . 19
7.2 Strength of material and parts . 19
7.3 Verification of degree of protection of enclosures . 19
7.4 Verification of clearances and creepage distances . 19
7.5 Protection against electric shock and integrity of protective circuits . 19
7.6 Incorporation of switching devices and components . 19
7.7 Internal electrical circuits and connections . 19
7.8 Terminals for external conductors . 19
7.9 Verification of dielectric properties . 19
7.10 Verification of temperature-rise limits . 20
7.11 Verification of short-circuit withstand strength . 20
7.12 Electromagnetic compatibility . 20
7.13 Verification of mechanical operation. 20
8 Routine verification . 20
8.1 General . 20
8.2 Degree of protection of enclosures. 20
8.3 Clearances and creepage distances . 21
8.4 Protection against electric shock and integrity of protective circuits . 21
8.5 Incorporation of built-in components . 21
8.6 Internal electrical circuits and connections . 21
8.7 Terminals for external conductors . 21
8.8 Mechanical operation . 21
8.9 Dielectric properties . 21
8.10 Wiring, operational performance and function, including verification of rated
output . 21
Annex A (normative) Minimum and maximum cross-sections of copper conductors
suitable for connections . 23
Annex B (normative) Method of calculating the cross-sectional area of protective
conductors with regard to thermal stresses due to currents of short-duration .
Annex B (informative) Formulae for capacitors and installations . 26
B.1 Computation of the output of three-phase capacitors from three single-phase
capacitance measurements . 26
B.2 Resonance frequency . 26
B.3 Voltage rise . 26
B.4 Inrush transient current . 27
B.4.1 Switching in of a single capacitor . 27
B.4.2 Switching of capacitors in parallel with energized capacitor(s) . 27
B.4.3 Discharge resistance in single-phase units or in one-phase or
polyphase units . 27
Annex C (informative) Typical examples of assemblies .
Annex C (informative) Definition of similar designs for capacitor bank . 28
Annex D (informative) Methods for connecting additional capacitors for performing
temperature rise test . 29
Bibliography . 30
Figure D.1 – Configurations for temperature rise test . 29
– 4 – IEC 61921:2017 RLV © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER CAPACITORS –
LOW-VOLTAGE POWER FACTOR CORRECTION BANKS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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...
IEC 61921 ®
Edition 2.0 2017-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Power capacitors – Low-voltage power factor correction banks
Condensateurs de puissance – Batteries de compensation du facteur de
puissance basse tension
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
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Switzerland www.iec.ch
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 corrigenda or an amendment might have been published.
IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 16 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.
IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and
CISPR.
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IEC 61921 ®
Edition 2.0 2017-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Power capacitors – Low-voltage power factor correction banks
Condensateurs de puissance – Batteries de compensation du facteur de
puissance basse tension
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.060.70 ISBN 978-2-8322-4423-4
– 2 – IEC 61921:2017 © IEC 2017
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Marking of a capacitor bank . 7
5 Service conditions . 8
6 Guide for design, installation, operation and safety . 8
6.1 General . 8
6.2 Design . 8
6.2.1 Choice of rated voltage . 8
6.2.2 Switching and overload protection . 9
6.3 Installation and operation . 10
6.3.1 Electrical environment . 10
6.3.2 Secondary effects of the capacitor bank . 10
6.3.3 Overvoltages . 10
6.3.4 Overload currents . 10
6.4 Safety . 11
6.4.1 Discharging devices. 11
6.4.2 Discharging after disconnection . 11
6.4.3 Fire hazard in case of failure . 12
6.4.4 Human and property damage . 12
6.4.5 Busbar . 12
6.4.6 Connection of systems. 12
7 Design verification . 12
7.1 General . 12
7.2 Strength of material and parts . 12
7.3 Verification of degree of protection of enclosures . 12
7.4 Verification of clearances and creepage distances . 12
7.5 Protection against electric shock and integrity of protective circuits . 13
7.6 Incorporation of switching devices and components . 13
7.7 Internal electrical circuits and connections . 13
7.8 Terminals for external conductors . 13
7.9 Verification of dielectric properties . 13
7.10 Verification of temperature-rise limits . 13
7.11 Verification of short-circuit withstand strength . 13
7.12 Electromagnetic compatibility . 13
7.13 Verification of mechanical operation. 14
8 Routine verification . 14
8.1 General . 14
8.2 Degree of protection of enclosures. 14
8.3 Clearances and creepage distances . 14
8.4 Protection against electric shock and integrity of protective circuits . 14
8.5 Incorporation of built-in components . 14
8.6 Internal electrical circuits and connections . 14
8.7 Terminals for external conductors . 14
8.8 Mechanical operation . 14
8.9 Dielectric properties . 14
8.10 Wiring, operational performance and function, including verification of rated
output . 15
Annex A (normative) Minimum and maximum cross-sections of copper conductors
suitable for connections . 16
Annex B (informative) Formulae for capacitors and installations . 17
B.1 Computation of the output of three-phase capacitors from three single-phase
capacitance measurements . 17
B.2 Resonance frequency . 17
B.3 Voltage rise . 17
B.4 Inrush transient current . 18
B.4.1 Switching in of a single capacitor . 18
B.4.2 Switching of capacitors in parallel with energized capacitor(s) . 18
B.4.3 Discharge resistance in single-phase units or in one-phase or
polyphase units . 18
Annex C (informative) Definition of similar designs for capacitor bank . 19
Annex D (informative) Methods for connecting additional capacitors for performing
temperature rise test . 20
Bibliography . 21
Figure D.1 – Configurations for temperature rise test . 20
– 4 – IEC 61921:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER CAPACITORS –
LOW-VOLTAGE POWER FACTOR CORRECTION BANKS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning s
...
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