IEC 60364-5-53:2019/AMD1:2020

IEC 60364-5-53 ®
Edition 4.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Low-voltage electrical installations –
Part 5-53: Selection and erection of electrical equipment – Devices
for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –
Partie 5-53: Choix et mise en oeuvre des matériels électriques – Dispositifs
de protection pour assurer la sécurité, le sectionnement, la coupure,
la commande et la surveillance

IEC 60364-5-53:2019-02/AMD1:2020-12(en-fr)

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IEC 60364-5-53 ®
Edition 4.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
A MENDMENT 1
AM ENDEMENT 1
Low-voltage electrical installations –

Part 5-53: Selection and erection of electrical equipment – Devices

for protection for safety, isolation, switching, control and monitoring

Installations électriques à basse tension –

Partie 5-53: Choix et mise en oeuvre des matériels électriques – Dispositifs

de protection pour assurer la sécurité, le sectionnement, la coupure,

la commande et la surveillance

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.01; 91.140.50 ISBN 978-2-8322-9008-8

– 2 – IEC 60364-5-53:2019/AMD1:2020
© IEC 2020
FOREWORD
This amendment has been prepared by IEC technical committee 64: Electrical installations and
protection against electric shock.
The text of this amendment is based on the following documents:
FDIS Report on voting
64/2457/FDIS 64/2465/RVD
Full information on the voting for the approval of this amendment can be found in the report on
voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the stability date indicated on the IEC website under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
_____________
531 Devices for protection against indirect contact by automatic disconnection
of supply
Replace the existing Clause 531, including its title, with the following new Clause 531:
531 Equipment for protection against electric shock
531.1 General
Clause 531 deals with requirements for the selection and erection of equipment for the following
protective measures in accordance with IEC 60364-4-41:
• automatic disconnection of supply,
• double or reinforced insulation,
• electrical separation,
• extra-low-voltage provided by SELV and PELV systems.
It also deals with requirements for the selection and erection of equipment for additional
protection.
© IEC 2020
531.2 Devices for automatic disconnection of supply
531.2.1 General
Devices used for automatic disconnection of supply shall be placed at the origin or upstream of
the circuit which is intended to be protected.
These devices shall be suitable for isolation in accordance with 536.
NOTE 1 Protective devices which require manual operation in order to achieve isolation are not excluded.
The following protective devices may be used:
– overcurrent protective devices in accordance with 531.2.2;
– residual current protective devices (RCDs) in accordance with 531.2.3.
Devices according to IEC 60947-2 identified with voltage value(s) followed by the symbol
(IEC 60417-6363:2016-07-16) or by the symbol shall not be used in IT systems for such
voltage(s) or above.
Devices according to IEC 60947-2 identified with the symbol  (IEC 60417-6363:2016-07-16)
or by the symbol  with no associated voltage value, shall not be used in IT systems.
NOTE 2 The symbol previously required will be progressively superseded by the preferred new symbol above.
531.2.2 Overcurrent protective devices
531.2.2.1 TN system
An overcurrent protective device shall be so selected that its operating characteristics meet the
following requirement:
U
o
I ≤
a
Z
s
where
I is the current in amperes (A) causing the automatic operation of the disconnecting device
a
within the time specified in IEC 60364-4-41:2005 and IEC 60364-4-41:2005/AMD1:2017,
411.3.2.2 or 411.3.2.3.
Z is the impedance in ohms (Ω) of the fault loop comprising
s
– the source,
– the line conductor up to the point of the fault, and
– the protective conductor between the point of the fault and the source;
U is the nominal AC or DC line-to-earth voltage in volts (V).
o
531.2.2.2 TT system
According to IEC 60364-4-41:2005 and IEC 60364-4-41:2005/AMD 1:2017, 411.5.2, RCDs shall
generally be used for protection against electric shock in TT systems.
Overcurrent protective devices may alternatively be used for this purpose, provided a suitably
low value of earth fault loop impedance is permanently and reliably ensured.

– 4 – IEC 60364-5-53:2019/AMD1:2020
© IEC 2020
Where, exceptionally, an overcurrent protective device is used for this purpose, it shall be so
selected that its operating characteristics meet the following requirement.
U
o
I ≤
a
Z
s
where
is the current in amperes (A) causing the automatic operation of the disconnecting device
I
a
within the time specified in IEC 60364-4-41:2005 and IEC 60364-4-41:2005/AMD1:2017,
411.3.2.2 or 411.3.2.4;
Z is the impedance in ohms (Ω) of the fault loop comprising
s
– the source,
– the line conductor up to the point of the fault,
– the protective conductor of the exposed-conductive-parts,
– the earthing conductor,
– the earth electrode of the installation, and
– the earth electrode of the source;
U is the nominal AC or DC line-to-earth voltage in volts (V).
o
531.2.2.3 IT system
Devices shall be suitable for IT systems in accordance with the manufacturer instructions.
The overcurrent protective devices shall be so selected that their operating characteristics
comply with the following requirement:
a) Where exposed-conductive-parts are interconnected by a protective conductor collectively
earthed to the same earthing arrangement, the following conditions shall be fulfilled:
• where the neutral or mid-point conductor is not distributed:
U
I ≤
a
2Z
s
• or where the neutral or mid-point conductor is distributed:
U
o
I ≤
a
'
2Z
s
where
U is the nominal AC or DC voltage in volts (V) between line conductors;
U is the nominal AC or DC voltage in volts (V) between line conductor and neutral or
o
mid-point conductor, as appropriate;
Z is the impedance in ohms (Ω) of the fault loop comprising the line conductor and the
s
protective conductor of the circuit;
Z' is the impedance in ohms (Ω) of the fault loop comprising the neutral or mid-point
s
conductor and the protective conductor of the circuit;
I is the current in amperes (A) causing operation of the protective device within the
a
time required for TN systems in IEC 60364-4-41:2005 and IEC 60364-4-
41:2005/AMD1:2017, 411.3.2.2 or 411.3.2.3.

© IEC 2020
NOTE The factor 2 in both formulas takes into account that in the event of the simultaneous occurrence of two
faults, the faults may exist in different circuits.
b) Where the exposed-conductive-parts are earthed in groups or individually, the following
condition applies:
• In alternating current
I ≤
a
R
A
where
R is the sum of the resistances in ohms (Ω) of the earth electrode and the protective
A
conductor to the exposed-conductive-parts;
I is the current in amperes (A) causing automatic disconnection of the protective
a
device in a time complying to that for TT systems in IEC 60364-4-41:2005 and
IEC 60364-4-41: 2005/AMD1:2017, 411.3.2.2 or 411.3.2.4.
In direct current, in accordance with IEC 60364-4-41:2005 and IEC 60364-4-41:2005/
AMD1:2017, 411.6.2, no requirement is needed.
531.2.3 Residual current protective devices
531.2.3.1 General conditions of installation
An RCD shall disconnect all live conductors in the circuit protected, except as permitted in
531.2.3.5.1.
For a multiphase supplied installation, where there is subdivision into single phase final circuits,
protection by individual RCDs is recommended. Where time delayed RCDs (CBRs (circuit
breaker incorporating residual current protection), and MRCD (modular residual current device)
in conjunction with circuit-breakers, according to IEC 60947-2) are used, the setting of the time
delay shall be in accordance with IEC 60364-4-41:2005 and IEC 60364-4-41:2005/
AMD1:2017, 411.3.2.
Where a modular RCD is used, an MRCD according to IEC 60947-2:2016, Annex M shall be
selected and used in conjunction with a circuit breaker in accordance with IEC 60947-2.
A protective conductor shall not pass through the sensor of an MRCD. However, where such
passing is unavoidable, for example in case of armoured cables, the protective conductor alone
shall be passed again through the sensor but in the reverse direction. The protective conductor
shall be insulated and shall not be earthed between the first and the second passing.
531.2.3.2 Unwanted tripping
To reduce the risk of unwanted tripping, the following shall be considered:
• subdivision of electrical circuits with individual associated RCDs so that the accumulated
protective conductor currents and/or leakage currents likely to occur during normal
op
...