IEC 60364-4-43:2008

Low-voltage electrical installations - Part 4-43: Protection for safety - Protection against overcurrent

IEC 60364-4-43:2008 provides requirements for the protection of live conductors from the effects of overcurrents. IEC 60364-4-43:2008 describes how live conductors are protected by one or more devices for the automatic disconnection of the supply in the event of overload (Clause 433) and short-circuit (Clause 434) except in cases where the overcurrent is limited in accordance with Clause 436 or where the conditions described in 433.3 (omission of devices for protection against overload) or 434.3 (omission of devices for protection against short-circuit) are met. Coordination of overload protection and short-circuit protection is also covered (Clause 435). This third edition cancels and replaces the second edition, published in 2001, and constitutes a technical revision. The main changes with respect to the previous edition are:
- Introduction of new informative Annexes B, C and D.
- Information concerning flexible cables added to Scope.
- Requirements added for overload detection for the neutral conductor for harmonic currents.
- Requirement that devices for protection against short-circuit current be capable of making as well as breaking short-circuit current added.
- Information added to clarify protection against overload current.
- Requirements where devices for protection against overload need not be provided expanded.
- Requirements where devices for protection against short-circuit need not be provided expanded.
- Requirements for short-circuit current ratings of busbar trunking systems added. The contents of the corrigendum of October 2008 have been included in this copy.

Installations électriques à basse tension - Partie 4-43: Protection pour assurer la sécurité - Protection contre les surintensités

La CEI 60364-4-43:2008 donne les exigences pour les protections des conducteurs contre les effets des surintensités. Cette norme décrit comment protéger les conducteurs par un appareil ou plus de déconnexion automatique de l'alimentation en cas de surcharge (Article 433) et court-circuit (Article 434), à l'exception où les surintensités sont limitées conformément à l'Article 436 ou si les conditions décrites en 433.3 (omission d'appareils de protection contre les surcharges) ou 434.3 (omission d'appareils de protection contre les courts-circuits) sont remplies. La coordination entre les protections contre les surintensités et les courts-circuits est aussi incluse (Article 435). Cette troisième édition annule et remplace la seconde édition, publiée en 2001, et constitue une révision technique. Les principales modifications par rapport à l'édition précédente sont les suivantes:
- Introduction des nouvelles Annexes B, C et D informatives.
- Ajout d'information dans le domaine d'application concernant les câbles souples.
- Ajout d'exigence pour la détection de surcharge dans le conducteur neutre en cas de courants harmoniques.
- Ajout d'exigence pour que les dispositifs de protection contre les court-circuits soient capables d'opérer aussi bien à l'ouverture qu'à la fermeture sur un courant de court-circuit.
- Développement des exigences où des dispositifs de protection contre les surcharges ne sont pas nécessaire.
- Développement des exigences où des dispositifs de protection contre les courts-circuits ne sont pas nécessaires.
- Ajout d'exigences pour les courants de court-circuit assignés des systèmes de canalisations préfabriquées. Le contenu du corrigendum d'octobre 2008 a été pris en considération dans cet exemplaire.

General Information

• Status: Published
• Publication Date: 12-Aug-2008
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 29.120.50 - Fuses and other overcurrent protection devices
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 64 - Electrical installations and protection against electric shock
• Drafting Committee: MT 2 - TC 64/MT 2
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 19-Jul-2023

Relations

• Corrected By: IEC 60364-4-43:2008/COR1:2008 - Corrigendum 1 - Low-voltage electrical installations - Part 4-43: Protection for safety - Protection against overcurrent
• Effective Date: 05-Sep-2023
• Revised: IEC 60364-4-43:2023 - Low-voltage electrical installations - Part 4-43: Protection for safety - Protection against overcurrent
• Effective Date: 05-Sep-2023
• Revises: IEC 60364-4-43:2001 - Electrical installations of buildings - Part 4-43: Protection for safety - Protection against overcurrent
• Effective Date: 05-Sep-2023
• Revises: IEC 60364-4-43:2001/COR1:2002 - Corrigendum 1 - Electrical installations of buildings - Part 4-43: Protection for safety - Protection against overcurrent
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60364-4-43
Edition 3.0 2008-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Low-voltage electrical installations –
Part 4-43: Protection for safety – Protection against overcurrent

Installations électriques à basse tension –
Partie 4-43: Protection pour assurer la sécurité – Protection contre les
surintensités
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IEC 60364-4-43
Edition 3.0 2008-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Low-voltage electrical installations –
Part 4-43: Protection for safety – Protection against overcurrent

Installations électriques à basse tension –
Partie 4-43: Protection pour assurer la sécurité – Protection contre les
surintensités
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
V
CODE PRIX
ICS 29.120.50; 91.140.50 ISBN 2-8318- 8318-9922-2
– 2 – 60364-4-43 © IEC:2008
CONTENTS
FOREWORD.4

43 Protection against overcurrent.6
430.1 Scope.6
430.2 Normative references.6
430.3 General requirements.7
431 Requirements according to the nature of the circuits.7
431.1 Protection of line conductors .7
431.2 Protection of the neutral conductor .7
431.3 Disconnection and reconnection of the neutral conductor in multi-phase
systems .8
432 Nature of protective devices .8
432.1 Devices providing protection against both overload current and short-circuit
current.8
432.2 Devices ensuring protection against overload current only.9
432.3 Devices ensuring protection against short-circuit current only.9
432.4 Characteristics of protective devices.9
433 Protection against overload current .9
433.1 Coordination between conductors and overload protective devices.9
433.2 Position of devices for overload protection.10
433.3 Omission of devices for protection against overload .10
433.4 Overload protection of conductors in parallel .11
434 Protection against short-circuit currents .12
434.1 Determination of prospective short-circuit currents .12
434.2 Position of devices for short-circuit protection.12
434.3 Omission of devices for protection against short-circuit .12
434.4 Short-circuit protection of conductors in parallel .13
434.5 Characteristics of short-circuit protective devices .13
435 Coordination of overload and short-circuit protection .15
435.1 Protection afforded by one device.15
435.2 Protection afforded by separate devices .15
436 Limitation of overcurrent by characteristics of supply .15

Annex A (informative) Protection of conductors in parallel against overcurrent.16
Annex B (informative) Conditions 1 and 2 of 433.1.21
Annex C (informative) Position or omission of devices for overload protection .22
Annex D (informative) Position or omission of devices for short-circuit protection .25
Annex E (informative) List of notes concerning certain countries.28

Bibliography.30

Figure A.1 – Circuit in which an overload protective device is provided for each of the
m conductors in parallel.18
Figure A.2 – Circuit in which a single overload protective device is provided for the m
conductors in parallel.18

60364-4-43 © IEC:2008 – 3 –
Figure A.3 – Current flow at the beginning of the fault.19
Figure A.4 – Current flow after operation of the protective device cs.19
Figure A.5 – Illustration of linked protective device .20
Figure B.1 – Illustration of conditions 1 and 2 of 433.1.21
Figure C.1 – Overload protective device (P ) NOT at the origin of branch circuit (B)
(refer to 433.2.2a)).22
Figure C.2 – Overload protective device (P ) installed within 3 m of the origin of the
branch circuit (B) (refer to 433.2.2b)) .23
Figure C.3 – Illustration of cases where overload protection may be omitted (refer to
433.3.1a), b) and d)).23
Figure C.4 – Illustration of cases where overload protection may be omitted in an IT
system .24
Figure D.1 – Limited change of position of short-circuit protective device (P ) on a
branch circuit (refer to 434.2.1).25
Figure D.2 – Short-circuit protective device P installed at a point on the supply side of
the origin of a branch circuit (refer to 434.2.2) .26
Figure D.3 – Situation where the short-circuit protective device may be omitted for
some applications (refer to 434.3).27

Table 43A – Values of k for conductors.14

– 4 – 60364-4-43 © IEC:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE ELECTRICAL INSTALLATIONS –

Part 4-43: Protection for safety –
Protection against overcurrent

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