IEC 60364-4-44:2024
(Amendment)Low-voltage electrical installations - Part 4-44: Protection for safety - Protection against voltage disturbances and electromagnetic disturbances
Low-voltage electrical installations - Part 4-44: Protection for safety - Protection against voltage disturbances and electromagnetic disturbances
IEC 60364-4-44:2024 provides requirements for the safety of electrical installations in the event of voltage disturbances and electromagnetic disturbances generated for different specified reasons. The requirements of this document are not intended to apply to systems for distribution of energy to the public, or power generation and transmission for such systems (see the scope of IEC 60364-1) although such disturbances can be conducted into or between electrical installations via these supply systems. This third edition cancels and replaces the second edition published in 2007, Amendment 1:2015 and Amendment 2:2018. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) the structure of the document has been updated in accordance with the ISO/IEC Directives, Part 2:2021: the terms, definitions and symbols have been regrouped under a new Subclause 440.3, the tables and figures have been renumbered;
b) Clause 443 has been amended to better introduce the DC SPD and to improve some of the wording.
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IEC 60364-4-44 ®
Edition 3.0 2024-12
REDLINE VERSION
INTERNATIONAL
STANDARD
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Low-voltage electrical installations –
Part 4-44: Protection for safety – Protection against voltage disturbances and
electromagnetic disturbances
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IEC 60364-4-44 ®
Edition 3.0 2024-12
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Low-voltage electrical installations –
Part 4-44: Protection for safety – Protection against voltage disturbances and
electromagnetic disturbances
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 91.140.50; 33.100.10; 33.100.20 ISBN 978-2-8327-0121-8
– 2 – IEC 60364-4-44:2024 RLV © IEC 2024
CONTENTS
FOREWORD . 5
INTRODUCTION . 2
440 Protection against voltage disturbances and electromagnetic disturbances. 8
440.1 Scope . 8
440.2 Normative references . 8
440.3 Terms, definitions and symbols . 10
440.3.1 Terms and definitions . 10
440.3.2 Symbols . 10
441 (Vacant) Void . 13
442 Protection of low-voltage installations against temporary overvoltages due to earth
faults in the high-voltage system and due to faults in the low-voltage system . 13
442.1 Field of application . 13
442.1.1 General . 13
442.1.2 General requirements . 13
442.2 Overvoltages in LV-systems during a high-voltage earth fault . 13
442.2.1 General . 13
442.2.2 Magnitude and duration of power-frequency fault voltage . 15
442.2.3 Magnitude and duration of power-frequency stress voltages . 16
442.2.4 Requirements for calculation of limits . 17
442.3 Power-frequency stress voltage in case of loss of the neutral conductor in a
TN and TT system . 17
442.4 Power-frequency stress voltage in the event of an earth fault in an IT system
with distributed neutral . 17
442.5 Power-frequency stress voltage in the event of a short-circuit between a line
conductor and the neutral conductor . 18
443 Protection against transient overvoltages of atmospheric origin or due to switching . 18
443.1 General . 18
443.2 Void . 19
443.3 Void . 19
443.4 Overvoltage control . 19
443.5 Risk assessment method . 19
443.6 Classification of rated impulse voltages (overvoltage categories) . 21
443.6.1 Purpose of classification of rated impulse voltages (overvoltage
categories) . 21
443.6.2 Rated impulse voltages of equipment and overvoltage categories . 22
444 Measures against electromagnetic influences . 24
444.1 General . 24
444.2 Void . 25
444.3 Void . 25
444.4 Mitigation of electromagnetic interference (EMI) . 25
444.4.1 General . 25
444.4.2 Sources of EMI . 25
444.4.3 Measures to reduce EMI . 25
444.4.4 TN-system . 27
444.4.5 TT system. 30
444.4.6 IT system . 31
444.4.7 Multiple-source supply . 32
444.4.8 Transfer of supply . 35
444.4.9 Services entering a building . 38
444.4.10 Separate buildings . 39
444.4.11 Inside buildings . 39
444.4.12 Protective devices . 41
444.4.13 Signal cables . 41
444.5 Earthing and equipotential bonding . 41
444.5.1 Interconnection of earth electrodes . 41
444.5.2 Interconnection of incoming networks and earthing arrangements . 41
444.5.3 Different structures for the network of equipotential conductors and
earthing conductors . 42
444.5.4 Equipotential bonding networks in buildings with several floors . 44
444.5.5 Functional earthing conductor . 45
444.5.6 Commercial or industrial buildings containing significant amounts of
information technology equipment . 46
444.5.7 Earthing arrangements and equipotential bonding of information
technology installations for functional purposes . 46
444.6 Segregation of circuits . 47
444.6.1 General . 47
444.6.2 Design requirements . 47
444.6.3 Conditions for zero segregation . 48
444.7 Cable management systems . 49
444.7.1 General . 49
444.7.2 Design guidelines . 49
444.7.3 Installation guidelines . 50
445 Protection against undervoltage. 52
Annex A (informative) Examples of calculated risk level CRL for the use of SPDs . 53
A.1 Example 1 – Building in rural environment . 53
A.2 Example 2 – Building in rural environment powered in HV . 53
A.3 Example 3 – Building in urban environment powered by overhead lines . 54
A.4 Example 4 – Building in urban environment powered by underground cables . 54
Annex B (informative) Guidance on overvoltage control by SPDs applied to overhead
lines . 55
Annex C (informative) List of notes concerning certain countries . 56
Bibliography . 58
Figure 1 – Representative schematic sketch diagram for possible connections to earth in
substation and LV-installation and occurring overvoltages in case of faults . 14
Figure 2 – Tolerable fault voltage due to an earth-fault in the HV system . 16
Figure 3 – Illustration of an installation showing the lengths to consider . 21
Figure 4 – By-pass conductor for screen reinforcement to provide a common
equipotential bonding system . 26
Figure 5 – Example of a substitute or by-pass equipotential bonding conductor in a TT-
system . 26
Figure 6 – Avoidance of neutral conductor currents in a bonded structure by using the
TN-S system from the origin of the public supply up to and including the final circuit
within a building . 28
Figure 7 – Avoidance of neutral conductor currents in a bonded structure by using a
TN-S system downstream of a consumer’s private supply transformer . 29
– 4 – IEC 60364-4-44:2024 RLV © IEC 2024
Figure 8 – TN-C-S system within an existing building installation . 30
Figure 9 – TT system within a building installation . 31
Figure 10 – IT system within a building installation . 32
Figure 11 – TN multiple-source power supply with a non-suitable multiple connection
between PEN and earth . 33
Figure 12 – TN multiple-source power supplies to an installation with connection to
earth
...
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