IEC 60331-1:2018

IEC 60331-1 ®
Edition 2.0 2018-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
GROUP SAFETY PUBLICATION
Tests for electric cables under fire conditions – Circuit integrity –
Part 1: Test method for fire with shock at a temperature of at least 830 °C for
cables of rated voltage up to and including 0,6/1,0 kV and with an overall
diameter exceeding 20 mm
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IEC 60331-1 ®
Edition 2.0 2018-03
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
GROUP SAFETY PUBLICATION
Tests for electric cables under fire conditions – Circuit integrity –

Part 1: Test method for fire with shock at a temperature of at least 830 °C for

cables of rated voltage up to and including 0,6/1,0 kV and with an overall

diameter exceeding 20 mm
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 13.220.40; 29.020; 29.060.20 ISBN 978-2-8322-5560-5

– 2 – IEC 60331-1:2018 RLV © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 Test conditions – Test environment . 8
5 Test apparatus . 9
5.1 Test equipment . 9
5.2 Test ladder and mounting . 12
5.3 Source of heat . 13
5.3.1 Burner . 13
5.3.2 Flow meters and flow rates . 14
5.3.3 Verification . 15
5.4 Shock producing device . 15
5.5 Positioning of source of heat . 16
5.6 Continuity checking arrangements for electric power and control cables with
rated voltage up to and including 600 V/1 000 V . 16
5.7 Fuses. 16
6 Test specimen (electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 16
6.1 Test specimen preparation . 16
6.2 Test specimen mounting . 17
6.2.1 Single core cables with concentric metal layer and multicore cables . 17
6.2.2 Single core cables without concentric metal layer . 19
7 Test procedure (electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 20
7.1 Test equipment and arrangement . 20
7.2 Electrical connections . 20
7.3 Flame and shock application . 22
7.4 Electrification . 22
8 Performance requirements (electric power and control cables with rated voltage
up to and including 600/1 000 V) . 23
8.1 Flame application time . 23
8.2 Acceptance criteria . 23
9 Retest procedure . 23
10 Test report(electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 23
11 Cable marking . 23
Annex A (normative) Verification procedure for the source of heat . 24
A.1 Measuring equipment . 24
A.2 Procedure . 24
A.3 Evaluation . 25
A.4 Further verification . 25
A.5 Verification report . 25
Annex B (informative) Guidance on the choice of recommended test apparatus (burner
and venturi) . 26

Influence of draughts in the test chamber .
Guidance on provision of a suitable test chamber .
Bibliography . 27

Figure 1 – Schematic diagram of test configuration . 10
Figure 2 – Plan view of fire test equipment . 11
Figure 3 – End elevation of fire test equipment (not to scale) . 12
Figure 4 – Typical rubber bush for supporting the test ladder . 13
Figure 5 – Burner face . 14
Figure 6 – Schematic diagram of an example of a burner control system using
rotameters . 15
Figure 7 – Example of method of mounting a larger diameter test specimen for test
(with a bending radius between approximately 200 and 400 mm) . 17
Figure 8 – Detailed section of adjustable position of vertical ladder elements for
mounting a smaller diameter test specimen for test (with a maximum bending radius of
approximately 200 mm) . 18
Figure 9 – Example of method of mounting test specimen with a bending radius in
normal use larger than approximately 400 mm . 19
Figure 10 – Method of mounting test specimen of a single core cable without
concentric metal layer . 20
Figure 11 – Basic circuit diagram – Electric power and control cables with rated
voltage up to and including 600 V/1 000 V . 22
Figure A.1 – Temperature measuring arrangement . 24

– 4 – IEC 60331-1:2018 RLV © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TESTS FOR ELECTRIC CABLES UNDER FIRE CONDITIONS –
CIRCUIT INTEGRITY –
Part 1: Test method for fire with shock at a temperature of at least
830 °C for cables of rated voltage up to and including 0,6/1,0 kV
and with an overall diameter exceeding 20 mm

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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International Standard IEC 60331-1 has been prepared by IEC technical committee 20:
Electric cables.
This second edition cancels and replaces the first edition published in 2009. It constitutes a
technical revision.
The significant technical changes with respect to the previous edition are as follows:
– extension of the scope to include metallic data and telecom cables and optical fibre
cables, although details for the specific point of failure, continuity checking arrangement,
test sample, test procedure and test report relevant to metallic data and telecom cables
and optical fibre cables are not given by IEC 60331-1;
– improved description of the test environment;
– modified steel test ladder with two extra vertical elements to accommodate the modified
testing of single core cables without concentric metal layer and the testing of cables with a
bending radius in normal use larger than approximately 400 mm;
– mandatory use of mass flow meters/controllers as the means of controlling accurately the
input flow rates of fuel and air to the burner;
– improved description of the information to be included in the test report.
The text of this International Standard is based on the following documents:
FDIS Report on voting
20/1781A/FDIS 20/1792/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
It has the status of a group safety publication in accordance with IEC Guide 104.
A list of all parts of the IEC 60331 series, published under the title: Tests for electric cables
under fire conditions – Circuit integrity, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – IEC 60331-1:2018 RLV © IEC 2018
INTRODUCTION
IEC 60331 consists of the following parts under the general title: Tests for electric cables
under fire conditions – Circuit integrity:
Part 1: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV and with an overall diameter exceeding 20 mm
Part 2: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV and with an overall diameter not exceeding 20 mm
Part 3: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV tested in a metal enclosure
Part 11: Apparatus – Fire alone at a flame temperature of at least 750 °C
Part 21: Procedures and requirements – Cables of rated voltage up to and including 0,6/1,0 kV
Part 23: Procedures and requirements – Electric data cables
Part 25: Procedures and requirements – Optical fibre cables
NOTE 1 Parts 21, 23 and 25 relate to fire-only conditions at a flame temperature of at least 750 °C.
NOTE 2 Parts 11, 21, 23 and 25 are no longer subject to maintenance. IEC 60331 Parts 1 and 2 are the
recommended test procedures
Since its first edition (1970), IEC 60331 has been extended and has introduced a range of test
apparatus in order that a test may be carried out on large and small power, control, data and
optical fibre cables.
Successful tests carried out in accordance with this standard will enable an identification to be
marked on the product.
TESTS FOR ELECTRIC CABLES UNDER FIRE CONDITIONS –
CIRCUIT INTEGRITY –
Part 1: Test method for fire with shock at a temperature of at least
830 °C for cables of rated voltage up to and including 0,6/1,0 kV
and with an overall diameter exceeding 20 mm

1 Scope
This part of IEC 60331 specifies the test apparatus and procedure and gives the performance
requirements, including recommended flame application times, for low voltage power cables
of rated voltage up to and including 0,6/1,0 kV and control cables with a rated voltage which
are required to maintain circuit integrity when subject to fire and mechanical shock under
specified conditions. It is intended for use when testing cables of greater than 20 mm overall
diameter.
This part of IEC 60331 specifies the test method for cables which are required to maintain
circuit integrity when subject to fire and mechanical shock under specified conditions.
This document is applicable to cables of rated voltage not exceeding 600 V/1 000 V, including
those of rated voltage below 80 V, metallic data and telecom cables and optical fibre cables.
It is intended for use when testing cables of greater than 20 mm overall diameter.
NOTE Cables of smaller diameter should are intended to be tested using the apparatus,
procedure and requirements of IEC 60331-2.
This standard describes the means of test specimen preparation, the continuity checking
arrangements, the electrical testing procedure, the method of burning the cables and the
method of shock production, and gives requirements for evaluating test results.
This document includes details for the specific point of failure, continuity checking
arrangement, test sample, test procedure and test report relevant to electric power and
control cables with rated voltage up to and including 600 V/1 000 V. Details for the specific
point of failure, continuity checking arrangement, test sample, test procedure and test report
relevant to metallic data and telecom cables and optical fibre cables are not given by
IEC 60331-1.
NOTE Although the scope is restricted to cables with rated voltage up to and including 0,6/1,0
kV, the procedure may can be used, with the agreement of the manufacturer and the
purchaser, for cables with rated voltage up to and including 1,8/3 (3,3) kV, provided that
suitable fuses are used.
Annex A provides the method of verification of the burner and control system used for the
test.
Requirements are stated for an identification that may optionally be marked on the cable to
signify compliance with this document.
CAUTION – The test given in this standard may involve the use of dangerous voltages
and temperatures. Suitable precautions should be taken against the risk of shock,
burning, fire and explosion that may be involved, and against any noxious fumes that
may be produced.
– 8 – IEC 60331-1:2018 RLV © IEC 2018
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60584-1, Thermocouples – Part 1: Reference tables EMF specifications and tolerances
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
IEC Guide 104, The preparation of safety publications and the use of basic safety publications
and group safety publications
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
circuit integrity
ability of an electric cable to continue to operate in a designated manner whilst subjected to a
specified flame source for a specified period of time under specified conditions
3.2
draught-free environment
space in which the results of tests are not significantly affected by the local air speed
4 Test conditions – Test environment
The test shall be carried out in a draught-free environment within a suitable chamber, of
minimum volume 10 20 m , with facilities for disposing of any noxious gases resulting from
the burning. Sufficient ventilation shall be available to sustain the flame for the duration of the
test. Air inlets and the exhaust chimney should be located in such a way that the burner flame
remains stable during the verification procedure and test. If necessary, the burner shall be
shielded from any draughts by the use of draught shields. Windows may be installed in the
walls of the chamber in order to observe the behaviour of the cable during the test. Fume
exhaust should be achieved by means of natural draught through a chimney located at least
1 m from the burner. A damper may be used for adjustment of ventilation conditions.
NOTE Guidance on the choice of suitable chambers is given in Annex B.
NOTE Experience has shown a chamber similar to the "3 m cube" specified in IEC 61034-1 to be suitable.
The chamber and test apparatus shall be at a temperature of between 10 °C and 40 °C at the
start of each test.
The same ventilation and shielding conditions shall be used in the chamber during both the
verification and cable test procedures.

NOTE The test given in this standard may involve the use of dangerous voltages and temperatures. Suitable
precautions should be taken against the risk of shock, burning, fire and explosion that may be involved, and
against any noxious fumes that may be produced.
5 Test apparatus
5.1 Test equipment
The test equipment shall consist of the following:
a) a test ladder, on to which the test specimen is mounted, comprising a steel framework
fastened to a rigid support as described in 5.2;
b) a source of heat comprising a horizontally mounted ribbon burner as described in 5.3;
c) a shock-producing device as described in 5.4;
d) a test wall equipped with thermocouples for verification of the source of heat as described
in Annex A;
e) a continuity checking arrangement as described in 5.6;
f) fuses as described in 5.7.
A general arrangement of the test equipment is shown in Figure 1, Figure 2 and Figure 3.

– 10 – IEC 60331-1:2018 RLV © IEC 2018
Dimensions in millimetres
1 200 ±100
≈ 400
≈ 400
≈ 400
P
P
P
P
IEC
Key
1 shock producing device 5 fixed vertical elements of test ladder
2 steel test ladder 6 adjustable vertical elements of test ladder
3 rubber bush 7 rigid support framework
4 ribbon gas burner P plane of adjustment
Figure 1 – Schematic diagram of test configuration
600 ±50
Dimensions in millimetres
IEC
Key
1 entry for air 4 horizontal steel test ladder
2 rubber bush 5 entry for propane gas
3 rigid support framework
Figure 2 – Plan view of fire test equipment
1 200 ±100
– 12 – IEC 60331-1:2018 RLV © IEC 2018
Dimensions in millimetres
+5
60° 0
200 ±5
400 ±5
600 ±5
H ±2
IEC
Key
1 shock producing device H horizontal distance of metal enclosure centre line from burner face to
the centre of the test specimen
V
2 steel test ladder vertical distance of metal enclosure centre line from centre line of
burner to the centre of the test specimen
3 gas burner
4 centre line of burner face
Figure 3 – End elevation of fire test equipment (not to scale)
5.2 Test ladder and mounting
The test ladder shall consist of a steel framework as shown in Figure 1. The two four central
vertical elements of the ladder shall be adjustable in order to accommodate different sizes of
cable under test. The test ladder shall be (1 200 ± 100) mm long and (600 ± 50) mm high, and
the total mass of the test ladder shall be (18 24 ± 1) kg. Ballast, if required, shall be placed on
the steel supports.
NOTE 1 Angle iron approximately 45 mm wide and 6 mm thick, with suitable slots cut to allow for fixing of the
bolts or saddles, has been found to be a suitable material for construction of the ladder.
25,0 ±0,1
V ±2
600 ±50
Each horizontal element shall have a mounting hole not more than 200 mm from each end,
the exact position and diameter being determined by the particular supporting bush and
supporting framework used. The test ladder shall be fastened to a rigid support by four
bonded rubber bushes of hardness 50–60 Shore A fitted between the horizontal steel
elements of the ladder and the support framework, as shown in Figure 1 and Figure 2 so as to
allow movement under impact.
NOTE 2 A typical rubber bush, which has been found to be suitable, is shown in Figure 4.

Dimensions in millimetres
30-40
IEC
Figure 4 – Typical rubber bush for supporting the test ladder
5.3 Source of heat
5.3.1 Burner
The source of heat shall be a ribbon type propane gas burner with a nominal burner face
length of 500 mm (outer distance between outer holes) with a venturi mixer. The nominal
burner face width shall be 10 mm. The face of the burner shall have three staggered rows of
drilled holes, nominally 1,32 mm in diameter and drilled at centres 3,2 mm from one another,
as shown in Figure 5.
A centre-feed burner is recommended.
Additionally, A row of small holes milled on each side of the burner plate, to serve as pilot
holes for keeping the flame burning, is permitted.
Guidance on the choice of a recommended burner system is given in Annex B.
20-30
– 14 – IEC 60331-1:2018 RLV © IEC 2018

Dimensions in millimetres
(Dimensions are approximate)
3,2
IEC
NOTE Round holes, 1,32 mm in diameter, on centres 3,2 mm from one another, staggered in three rows and
centred on the face of the burner. Nominal burner face length 500 mm.
Figure 5 – Burner face
5.3.2 Flow meters and flow rates
Mass flow meters/controllers should shall be used as the means of controlling accurately the
input flow rates of fuel and air to the burner.
NOTE Rotameter type flow meters may be used as an alternative, but are not recommended. Guidance on their
use, and the application of appropriate correction factors is given in IEC 60331-11:1999, Annex C.
NOTE Figure 6 shows an example of a rotameter type system.
For the purposes of this test, the air shall have a dew point not higher than 0 °C.
The mass flow rates used for the test shall be as follows:
– air: (160 ± 8) l/min at reference conditions (1 bar and 20 °C) or (3 267 ± 163)
mg/s ;
– propane: (10 ± 0,4) l/min at reference conditions (1 bar and 20 °C) or (319 ± 13) mg/s ;.
Propane: (320 ± 13) mg/s
NOTE 1 This is approximately equivalent to a volume flow rate of (10,0 ± 0,4) litres/min at reference conditions
(1 bar and 20 °C).
NOTE The purity of the propane is not defined. Industrial grades that contain impurities are
allowed provided that the calibration requirements are achieved.
Air: (3 270 ± 163) mg/s
NOTE 2 This is approximately equivalent to a volume flow rate of (160 ± 8) litres/min at reference conditions
(1 bar and 20 °C).
A schematic diagram of an example of a burner control system is given in Figure 6.

3,2
4,5
6A
IEC
Key
1 regulator  9 mass flow meters
2 piezoelectric igniter 10 venturi mixer
3 flame failure device 11 burner
4 control thermocouples 12 ball valve
5 propane cylinder 13 air flow
6 screw valve (6A = alternative position) 14 compressed air cylinder
7 pilot feed 15 screw valve on pilot feed
8 gas flow
Figure 6 – Schematic diagram of an example of a burner control
system using rotameters
5.3.3 Verification
The burner and control system shall be subject to verification following the procedure given in
Annex A.
5.4 Shock producing device
The shock-producing device shall consist of a mild steel round bar (25,0 ± 0,1) mm in
diameter and (600 ± 5) mm long. The bar shall be freely pivoted about an axis parallel to the
test ladder, which shall be in the same horizontal plane as, and (200 ± 5) mm away from, the
upper edge of the ladder. The axis shall divide the bar into two unequal lengths, the longer
length being (400 ± 5) mm which shall impact the ladder. The bar shall drop under its own

– 16 – IEC 60331-1:2018 RLV © IEC 2018
+5
weight from an angle of ° to the horizontal to strike the upper edge of the ladder at its
(60 )
midpoint as shown in Figure 1 and Figure 3.
5.5 Positioning of source of heat
The burner face shall be positioned in the test chamber so that it is at least 200 mm above the
floor of the chamber, or any solid mounting block, and at least 500 mm from any chamber
wall.
By reference to the centre point of the test specimen (cable) to be tested, the burner shall be
positioned centrally at a horizontal distance of (H ± 2) mm from the burner face to the centre
of the test specimen and at a vertical distance of (V ± 2) mm from the burner horizontal
central plane to the centre of the test specimen, as shown in Figure 3.
The exact burner location to be used during cable testing shall be determined using the
verification procedure given in Annex A, where the values of H and V to be used shall be
determined.
NOTE The burner should be rigidly fixed to the framework during testing so as to prevent
movement relative to the test specimen.
5.6 Continuity checking arrangements for electric power and control cables with
rated voltage up to and including 600 V/1 000 V
During the test, a current for continuity checking shall be passed through all conductors of the
test specimen. This shall be provided by a three-phase star connected or single-phase
transformer(s) of sufficient capacity to maintain the test voltage up to the maximum leakage
current allowable.
NOTE 1 Due Note should be taken of the fuse characteristics when determining the power rating of the
transformer.
This current shall be achieved by connecting, at the other end of the test specimen, a suitable
load and an indicating device (e.g. lamp) to each conductor, or group of conductors.
NOTE 2 A current of 0,25 A at the test voltage, through each conductor or group of conductors, has been found to
be suitable.
5.7 Fuses
Fuses used in the test procedure in Clause 7 shall be of type DII, complying with IEC 60269-3
Fuse System A-D Type DII, 2A. Alternatively, a circuit-breaker with equivalent characteristics
may be used.
Where a circuit-breaker is used, its equivalent characteristics shall be demonstrated by
reference to the characteristic curve shown in IEC 60269-3.
The test method using fuses shall be the reference method in the case of dispute.
6 Test specimen (electric power and control cables with rated voltage up to
and including 600 V/1 000 V)
6.1 Test specimen preparation
A cable sample at least 4,5 m long shall be available from the cable length for test. Each
individual test specimen to be tested shall consist of a piece of cable, taken from the cable
sample, not less than 1 500 mm long with approximately 100 mm of sheath or outer covering
removed at each end.
At each end of the test specimen each conductor shall be suitably prepared for electrical
connections, and, if there is more than one conductor, the exposed conductors shall be
spread apart to avoid contact with each other.
6.2 Test specimen mounting
6.2.1 Single core cables with concentric metal layer and multicore cables
The test specimen shall be bent to form an approximate arc of a circle. The internal radius of
the bend shall be the manufacturer’s declared minimum bending radius in normal use.
The test specimen shall be mounted centrally on the test ladder, as shown in Figure 7, using
metal clips which shall be earthed. Two U-bolts on the upper horizontal element of the ladder
are recommended, but P-clips made of metal strip (20 ± 2) mm wide for cables from 20 mm up
to 50 mm in diameter, and (30 ± 3) mm wide for larger cables shall be used on the two central
vertical elements. The P-clips shall be formed so as to have approximately the same diameter
as the test specimen under test.
If the test specimen is too small to be mounted on the central vertical elements when in the
position shown in Figure 7, the two central vertical elements shall be equally moved towards
the centre so that the specimen may be mounted as shown in Figure 8.
If the bending radius in normal use is too large to mount the cable as shown in Figure 7 on
the slots for the U-bolt (key 5 in Figure 7), the test specimen shall be mounted as shown in
Figure 9, using P-clips, which shall be earthed, on the four central vertical elements.
Dimensions in millimetres
(dimensions are approximate)
6 6
R
6 6
IEC
Key
1 U-bolt 5 slot for U-bolt
2 P-clip 6 slot for movement of adjustable vertical elements
3 adjustable vertical elements R minimum bending radius of cable in normal use
4 slot for P-clip fixing
Figure 7 – Example of method of mounting a larger diameter test specimen for test
(with a bending radius between approximately 200 and 400 mm)

– 18 – IEC 60331-1:2018 RLV © IEC 2018
Dimensions in millimetres
(dimensions are approximate)
1 1
7 7
45° 45°
6 6
IEC
Key
1 adjustable position of vertical elements 5 U-bolt
2 normal position of vertical elements 6 slot for movement of adjustable vertical
elements
3 lower horizontal element of test ladder 7 slot for P-clip fixing
4 additional clip to maintain cable arc (if 8 P-clip
required)
Figure 8 – Detailed section of adjustable position of vertical ladder elements
for mounting a smaller diameter test specimen for test (with a maximum
bending radius of approximately 200 mm)
Dimensions in millimetres
(dimensions are approximate)
1 200
IEC
Key
1 P-clip 3 slot for P-clip fixing
2 adjustable vertical elements 4 slot for movement of adjustable vertical elements
Figure 9 – Example of method of mounting test specimen with a bending radius
in normal use larger than approximately 400 mm
6.2.2 Single core cables without concentric metal layer
The test specimen shall be mounted straight centrally on the test ladder using four vertical
elements, as shown in Figure 10, using metal clips which shall be earthed to fix the cable to
these vertical elements.
The width of the metal clips shall be in accordance with 6.2.1.
NOTE Testing of a straight test specimen is appropriate for single core cables without concentric metal layer, as
bending will not affect the performance for this type of cable, as internal forces such as in multicore cables will not
occur.
The P-clips shall be formed so as to have approximately the same diameter as the test
specimen under test.
– 20 – IEC 60331-1:2018 RLV © IEC 2018
Dimensions in millimetres
(dimensions are approximate)
1 200
IEC
Key
1 P-clip 3 slot for P-clip fixing
2 adjustable vertical elements 4 slot for movement of adjustable vertical elements
Figure 10 – Method of mounting test specimen of a single core cable
without concentric metal layer
7 Test procedure (electric power and control cables with rated voltage up to
and including 600 V/1 000 V)
7.1 Test equipment and arrangement
The test procedure defined in this clause shall be carried out using the apparatus detailed in
Clause 5.
Mount the test specimen on the test ladder and adjust the burner to the correct position
relative to the test specimen in accordance with 5.5.
7.2 Electrical connections
At the transformer end of the test specimen, earth the neutral conductor, if present, and any
protective conductors. Any metal screens, drain wire or metallic layer shall be interconnected
and earthed. Connect the transformer(s) to the conductors, excluding any conductor which is
specifically identified as intended for use as a neutral or a protective conductor, as shown in
the circuit diagram in Figure 11. Where a metallic sheath, armour or screen acts as a neutral
or protective conductor, it shall be connected, as shown in the circuit diagram in Figure 11, as
for a neutral or protective conductor.
For single-, twin- or three-phase conductor cables, connect each phase conductor to a
separate phase of the transformer(s) output with a 2 A fuse or circuit-breaker with equivalent
characteristics in each phase.
For multicore cables that have four or more conductors (excluding any neutral or protective
conductors), the conductors shall be divided into three roughly equal groups, ensuring that
adjacent conductors are, as far as possible, in different groups.
For multipair cables, the conductors shall be divided into two equal groups, ensuring that the
a-core of each pair is connected to one phase and the b-core of each pair is connected to
another phase (L1 and L2 in Figure 11). Quads shall be treated as two pairs.
For multi-triple cables, the conductors shall be divided into three equal groups, ensuring that
the a-core of each triple is connected to one phase, the b-core of each triple to another phase
and the c-core of each triple to the third phase of the transformer (L1, L2 and L3 in Figure 11).
Connect the conductors of each group in series and connect each group to a separate phase
of the transformer output with a 2 A fuse or circuit-breaker with equivalent characteristics in
each phase.
NOTE The above test procedure connects the neutral conductor to earth. This may not be
appropriate if the cable is designed for use on a system where neutral is not earthed. If
required by the cable standard, it is permissible for the neutral conductor to be tested as if it
were a phase conductor. Where a metallic sheath, armour or screen acts as a neutral
conductor, it shall always be connected to earth. Any such variations in methodology should
be included in the test report.
NOTE For cable constructions not specifically identified above, the test voltage should be
applied, as far as is practicable, to ensure that adjacent conductors are connected to different
phases.
NOTE In certain cases, for example when testing a control cable using a three-phase
transformer, it may not be possible to apply a test voltage between conductors and from
conductor to earth equal to the rated voltage simultaneously. In such cases, either the test
voltage between conductors, or the test voltage from conductor to earth shall be equal to the
rated voltage, such that both the test voltage between conductors and the test voltage from
conductor to earth is equal to or higher than the rated voltage.
At the end of the test specimen remote from the transformer:
– connect each phase conductor, or group of conductors, to one terminal of the load and
indicating device (as described in 5.6), the other terminal being earthed;
– connect the neutral conductor and any protective conductor to one terminal of the load
and indicating device (as described in 5.6), the other terminal being connected to L1 (or
L2 or L3) at the transformer end (see Figure 11).

– 22 – IEC 60331-1:2018 RLV © IEC 2018
3 6
2 5
L3 L3
L2 L2
L1
L1
N
PE
N
IEC
Key
L1, L2, L3 phase conductor (L2, L3 if present)
N neutral conductor (if present)
PE protective conductor (if present)
1 transformer 5 test conductor or group
2 fuse, 2 A 6 load an
...

IEC 60331-1 ®
Edition 2.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Tests for electric cables under fire conditions – circuit integrity –
Part 1: Test method for fire with shock at a temperature of at least 830 °C for
cables of rated voltage up to and including 0,6/1,0 kV and with an overall
diameter exceeding 20 mm
Essais pour câbles électriques soumis au feu – intégrité des circuits –
Partie 1: Méthode d'essai au feu avec chocs pour les câbles de tension assignée
au plus égale à 0,6/1,0 kV et de diamètre externe supérieur à 20 mm, à une
température d'au moins 830 °C
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IEC 60331-1 ®
Edition 2.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Tests for electric cables under fire conditions – circuit integrity –

Part 1: Test method for fire with shock at a temperature of at least 830 °C for

cables of rated voltage up to and including 0,6/1,0 kV and with an overall

diameter exceeding 20 mm
Essais pour câbles électriques soumis au feu – intégrité des circuits –

Partie 1: Méthode d'essai au feu avec chocs pour les câbles de tension assignée

au plus égale à 0,6/1,0 kV et de diamètre externe supérieur à 20 mm, à une

température d'au moins 830 °C
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.060.20 ISBN 978-2-8322-6153-8

– 2 – IEC 60331-1:2018 © IEC 2018
CONTENTS
CONTENTS . 2
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Test environment . 8
5 Test apparatus . 8
5.1 Test equipment . 8
5.2 Test ladder and mounting . 12
5.3 Source of heat . 13
5.3.1 Burner . 13
5.3.2 Flow meters and flow rates . 14
5.3.3 Verification . 15
5.4 Shock producing device . 15
5.5 Positioning of source of heat . 16
5.6 Continuity checking arrangements for electric power and control cables with
rated voltage up to and including 600 V/1 000 V . 16
5.7 Fuses. 16
6 Test specimen (electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 16
6.1 Test specimen preparation . 16
6.2 Test specimen mounting . 17
6.2.1 Single core cables with concentric metal layer and multicore cables . 17
6.2.2 Single core cables without concentric metal layer . 19
7 Test procedure (electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 20
7.1 Test equipment and arrangement . 20
7.2 Electrical connections . 20
7.3 Flame and shock application . 22
7.4 Electrification . 22
8 Performance requirements (electric power and control cables with rated voltage
up to and including 600/1 000 V) . 23
8.1 Flame application time . 23
8.2 Acceptance criteria . 23
9 Retest procedure . 23
10 Test report (electric power and control cables with rated voltage up to and
including 600 V/1 000 V) . 23
11 Cable marking . 23
Annex A (normative) Verification procedure for the source of heat . 24
A.1 Measuring equipment . 24
A.2 Procedure . 24
A.3 Evaluation . 25
A.4 Further verification . 25
A.5 Verification report . 25

Annex B (informative) Guidance on the choice of recommended test apparatus (burner
and venturi) . 26
Bibliography . 27

Figure 1 – Schematic diagram of test configuration . 10
Figure 2 – Plan view of fire test equipment . 11
Figure 3 – End elevation of fire test equipment (not to scale) . 12
Figure 4 – Typical rubber bush for supporting the test ladder . 13
Figure 5 – Burner face . 14
Figure 6 – Schematic diagram of an example of a burner control system . 15
Figure 7 – Example of method of mounting a larger diameter test specimen for test

(with a bending radius between approximately 200 and 400 mm) . 17
Figure 8 – Detailed section of adjustable position of vertical ladder elements for
mounting a smaller diameter test specimen for test (with a maximum bending radius of
approximately 200 mm) . 18
Figure 9 – Example of method of mounting test specimen with a bending radius in
normal use larger than approximately 400 mm . 19
Figure 10 – Method of mounting test specimen of a single core cable without
concentric metal layer . 20
Figure 11 – Basic circuit diagram – Electric power and control cables with rated
voltage up to and including 600 V/1 000 V . 22
Figure A.1 – Temperature measuring arrangement . 24

– 4 – IEC 60331-1:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TESTS FOR ELECTRIC CABLES UNDER FIRE CONDITIONS –
CIRCUIT INTEGRITY –
Part 1: Test method for fire with shock at a temperature of at least
830 °C for cables of rated voltage up to and including 0,6/1,0 kV
and with an overall diameter exceeding 20 mm

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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60331-1 has been prepared by IEC technical committee 20:
Electric cables.
This bilingual version (2018-11) corresponds to the monolingual English version, published in
2018-03.
This second edition cancels and replaces the first edition published in 2009. It constitutes a
technical revision.
The significant technical changes with respect to the previous edition are as follows:
– extension of the scope to include metallic data and telecom cables and optical fibre
cables, although details for the specific point of failure, continuity checking arrangement,
test sample, test procedure and test report relevant to metallic data and telecom cables
and optical fibre cables are not given by IEC 60331-1;
– improved description of the test environment;
– modified steel test ladder with two extra vertical elements to accommodate the modified
testing of single core cables without concentric metal layer and the testing of cables with a
bending radius in normal use larger than approximately 400 mm;
– mandatory use of mass flow meters/controllers as the means of controlling accurately the
input flow rates of fuel and air to the burner;
– improved description of the information to be included in the test report.
The text of this International Standard is based on the following documents:
FDIS Report on voting
20/1781A/FDIS 20/1792/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
The French version of this document has not been voted upon.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
It has the status of a group safety publication in accordance with IEC Guide 104.
A list of all parts of the IEC 60331 series, published under the title: Tests for electric cables
under fire conditions – Circuit integrity, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site 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.
– 6 – IEC 60331-1:2018 © IEC 2018
INTRODUCTION
IEC 60331 consists of the following parts under the general title: Tests for electric cables
under fire conditions – Circuit integrity:
Part 1: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV and with an overall diameter exceeding 20 mm
Part 2: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV and with an overall diameter not exceeding 20 mm
Part 3: Test method for fire with shock at a temperature of at least 830 °C for cables of rated
voltage up to and including 0,6/1,0 kV tested in a metal enclosure
Part 11: Apparatus – Fire alone at a flame temperature of at least 750 °C
Part 21: Procedures and requirements – Cables of rated voltage up to and including 0,6/1,0 kV
Part 23: Procedures and requirements – Electric data cables
Part 25: Procedures and requirements – Optical fibre cables
NOTE 1 Parts 21, 23 and 25 relate to fire-only conditions at a flame temperature of at least 750 °C.
NOTE 2 Parts 11, 21, 23 and 25 are no longer subject to maintenance. IEC 60331 Parts 1 and 2 are the
recommended test procedures.
Since its first edition (1970), IEC 60331 has been extended and has introduced a range of test
apparatus in order that a test may be carried out on large and small power, control, data and
optical fibre cables.
Successful tests carried out in accordance with this standard will enable an identification to be
marked on the product.
TESTS FOR ELECTRIC CABLES UNDER FIRE CONDITIONS –
CIRCUIT INTEGRITY –
Part 1: Test method for fire with shock at a temperature of at least
830 °C for cables of rated voltage up to and including 0,6/1,0 kV
and with an overall diameter exceeding 20 mm

1 Scope
This part of IEC 60331 specifies the test method for cables which are required to maintain
circuit integrity when subject to fire and mechanical shock under specified conditions.
This document is applicable to cables of rated voltage not exceeding 600 V/1 000 V, including
those of rated voltage below 80 V, metallic data and telecom cables and optical fibre cables.
It is intended for use when testing cables of greater than 20 mm overall diameter.
Cables of smaller diameter are intended to be tested using the apparatus, procedure and
requirements of IEC 60331-2.
This document includes details for the specific point of failure, continuity checking
arrangement, test sample, test procedure and test report relevant to electric power and
control cables with rated voltage up to and including 600 V/1 000 V. Details for the specific
point of failure, continuity checking arrangement, test sample, test procedure and test report
relevant to metallic data and telecom cables and optical fibre cables are not given by
IEC 60331-1.
Although the scope is restricted to cables with rated voltage up to and including 0,6/1,0 kV,
the procedure can be used, with the agreement of the manufacturer and the purchaser, for
cables with rated voltage up to and including 1,8/3 (3,3) kV, provided that suitable fuses are
used.
Annex A provides the method of verification of the burner and control system used for the
test.
Requirements are stated for an identification that may optionally be marked on the cable to
signify compliance with this document.
CAUTION – The test given in this standard may involve the use of dangerous voltages
and temperatures. Suitable precautions should be taken against the risk of shock,
burning, fire and explosion that may be involved, and against any noxious fumes that
may be produced.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60584-1, Thermocouples – Part 1: EMF specifications and tolerances

– 8 – IEC 60331-1:2018 © IEC 2018
IEC 60269-3, Low-voltage fuses – Part 3: Supplementary requirements for fuses for use by
unskilled persons (fuses mainly for household and similar applications) – Examples of
standardized systems of fuses A to F
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
circuit integrity
ability of an electric cable to continue to operate in a designated manner whilst subjected to a
specified flame source for a specified period of time under specified conditions
3.2
draught-free environment
space in which the results of tests are not significantly affected by the local air speed
4 Test environment
The test shall be carried out in a draught-free environment within a suitable chamber, of
minimum volume 20 m , with facilities for disposing of any noxious gases resulting from the
burning. Sufficient ventilation shall be available to sustain the flame for the duration of the
test. Air inlets and the exhaust chimney should be located in such a way that the burner flame
remains stable during the verification procedure and test. If necessary, the burner shall be
shielded from any draughts by the use of draught shields. Windows may be installed in the
walls of the chamber in order to observe the behaviour of the cable during the test. Fume
exhaust should be achieved by means of natural draught through a chimney located at least
1 m from the burner. A damper may be used for adjustment of ventilation conditions.
NOTE Experience has shown a chamber similar to the "3 m cube" specified in IEC 61034-1 to be suitable.
The chamber and test apparatus shall be at a temperature of between 10 °C and 40 °C at the
start of each test.
The same ventilation and shielding conditions shall be used in the chamber during both the
verification and cable test procedures.
5 Test apparatus
5.1 Test equipment
The test equipment shall consist of the following:
a) a test ladder, on to which the test specimen is mounted, comprising a steel framework
fastened to a rigid support as described in 5.2;
b) a source of heat comprising a horizontally mounted ribbon burner as described in 5.3;
c) a shock-producing device as described in 5.4;
d) a test wall equipped with thermocouples for verification of the source of heat as described
in Annex A;
e) a continuity checking arrangement as described in 5.6;
f) fuses as described in 5.7.
A general arrangement of the test equipment is shown in Figure 1, Figure 2 and Figure 3.

– 10 – IEC 60331-1:2018 © IEC 2018
Dimensions in millimetres
1 200 ±100
≈ 400
≈ 400
≈ 400
P
P
P
P
IEC
Key
1 shock producing device 5 fixed vertical elements of test ladder
2 steel test ladder 6 adjustable vertical elements of test ladder
3 rubber bush 7 rigid support framework
4 ribbon gas burner P plane of adjustment
Figure 1 – Schematic diagram of test configuration
600 ±50
Dimensions in millimetres
IEC
Key
1 entry for air 4 horizontal steel test ladder
2 rubber bush 5 entry for propane gas
3 rigid support framework
Figure 2 – Plan view of fire test equipment
1 200 ±100
– 12 – IEC 60331-1:2018 © IEC 2018
Dimensions in millimetres
+5
60° 0
200 ±5
400 ±5
600 ±5
H ±2
IEC
Key
1 shock producing device H horizontal distance from burner face to the centre of the test specimen
2 steel test ladder V vertical distance from centre line of burner to the centre of the test
specimen
3 gas burner
4 centre line of burner face
Figure 3 – End elevation of fire test equipment (not to scale)
5.2 Test ladder and mounting
The test ladder shall consist of a steel framework as shown in Figure 1. The four central
vertical elements of the ladder shall be adjustable in order to accommodate different sizes of
cable under test. The test ladder shall be (1 200 ± 100) mm long and (600 ± 50) mm high, and
the total mass of the test ladder shall be (24 ± 1) kg. Ballast, if required, shall be placed on
the steel supports.
NOTE 1 Angle iron approximately 45 mm wide and 6 mm thick, with suitable slots cut to allow for fixing of the
bolts or saddles, has been found to be a suitable material for construction of the ladder.
25,0 ±0,1
V ±2
600 ±50
Each horizontal element shall have a mounting hole not more than 200 mm from each end,
the exact position and diameter being determined by the particular supporting bush and
supporting framework used. The test ladder shall be fastened to a rigid support by four
bonded rubber bushes of hardness 50–60 Shore A fitted between the horizontal steel
elements of the ladder and the support framework, as shown in Figure 1 and Figure 2 so as to
allow movement under impact.
NOTE 2 A typical rubber bush, which has been found to be suitable, is shown in Figure 4.

Dimensions in millimetres
30-40
IEC
Figure 4 – Typical rubber bush for supporting the test ladder
5.3 Source of heat
5.3.1 Burner
The source of heat shall be a ribbon type propane gas burner with a nominal burner face
length of 500 mm (outer distance between outer holes) with a venturi mixer. The nominal
burner face width shall be 10 mm. The face of the burner shall have three staggered rows of
drilled holes, nominally 1,32 mm in diameter and drilled at centres 3,2 mm from one another,
as shown in Figure 5.
A centre-feed burner is recommended.
A row of small holes milled on each side of the burner plate, to serve as pilot holes for
keeping the flame burning, is permitted.
Guidance on the choice of a recommended burner system is given in Annex B.
20-30
– 14 – IEC 60331-1:2018 © IEC 2018

Dimensions in millimetres
(Dimensions are approximate)
3,2
IEC
NOTE Round holes, 1,32 mm in diameter, on centres 3,2 mm from one another, staggered in three rows and
centred on the face of the burner. Nominal burner face length 500 mm.
Figure 5 – Burner face
5.3.2 Flow meters and flow rates
Mass flow meters/controllers shall be used as the means of controlling accurately the input
flow rates of fuel and air to the burner.
For the purposes of this test, the air shall have a dew point not higher than 0 °C.
The mass flow rates used for the test shall be as follows:
Propane: (320 ± 13) mg/s
NOTE 1 This is approximately equivalent to a volume flow rate of (10,0 ± 0,4) litres/min at reference conditions
(1 bar and 20 °C).
The purity of the propane is not defined. Industrial grades that contain impurities are allowed
provided that the calibration requirements are achieved.
Air: (3 270 ± 163) mg/s
NOTE 2 This is approximately equivalent to a volume flow rate of (160 ± 8) litres/min at reference conditions
(1 bar and 20 °C).
A schematic diagram of an example of a burner control system is given in Figure 6.
3,2
4,5
6A
1 12
IEC
Key
1 regulator  9 mass flow meters
2 piezoelectric igniter 10 venturi mixer
3 flame failure device 11 burner
4 control thermocouples 12 ball valve
5 propane cylinder 13 air flow
6 screw valve (6A = alternative position) 14 compressed air cylinder
7 pilot feed 15 screw valve on pilot feed
8 gas flow
Figure 6 – Schematic diagram of an example of a burner control system
5.3.3 Verification
The burner and control system shall be subject to verification following the procedure given in
Annex A.
5.4 Shock producing device
The shock-producing device shall consist of a mild steel round bar (25,0 ± 0,1) mm in
diameter and (600 ± 5) mm long. The bar shall be freely pivoted about an axis parallel to the
test ladder, which shall be in the same horizontal plane as, and (200 ± 5) mm away from, the
upper edge of the ladder. The axis shall divide the bar into two unequal lengths, the longer
length being (400 ± 5) mm which shall impact the ladder. The bar shall drop under its own
+5
weight from an angle of (60 ) ° to the horizontal to strike the upper edge of the ladder at its
midpoint as shown in Figure 1 and Figure 3.

– 16 – IEC 60331-1:2018 © IEC 2018
5.5 Positioning of source of heat
The burner face shall be positioned in the test chamber so that it is at least 200 mm above the
floor of the chamber, or any solid mounting block, and at least 500 mm from any chamber
wall.
By reference to the centre point of the test specimen (cable) to be tested, the burner shall be
positioned centrally at a horizontal distance of (H ± 2) mm from the burner face to the centre
of the test specimen and at a vertical distance of (V ± 2) mm from the burner horizontal
central plane to the centre of the test specimen, as shown in Figure 3.
The exact burner location to be used during cable testing shall be determined using the
verification procedure given in Annex A, where the values of H and V to be used shall be
determined.
The burner should be rigidly fixed to the framework during testing so as to prevent movement
relative to the test specimen.
5.6 Continuity checking arrangements for electric power and control cables with
rated voltage up to and including 600 V/1 000 V
During the test, a current for continuity checking shall be passed through all conductors of the
test specimen. This shall be provided by a three-phase star connected or single-phase
transformer(s) of sufficient capacity to maintain the test voltage up to the maximum leakage
current allowable.
NOTE 1 Note the fuse characteristics when determining the power rating of the transformer.
This current shall be achieved by connecting, at the other end of the test specimen, a suitable
load and an indicating device (e.g. lamp) to each conductor, or group of conductors.
NOTE 2 A current of 0,25 A at the test voltage, through each conductor or group of conductors, has been found to
be suitable.
5.7 Fuses
Fuses used in the test procedure in Clause 7 shall comply with IEC 60269-3 Fuse System A-D
Type DII, 2A. Alternatively, a circuit-breaker with equivalent characteristics may be used.
Where a circuit-breaker is used, its equivalent characteristics shall be demonstrated by
reference to the characteristic curve shown in IEC 60269-3.
The test method using fuses shall be the reference method in the case of dispute.
6 Test specimen (electric power and control cables with rated voltage up to
and including 600 V/1 000 V)
6.1 Test specimen preparation
A cable sample at least 4,5 m long shall be available from the cable length for test. Each
individual test specimen to be tested shall consist of a piece of cable, taken from the cable
sample, not less than 1 500 mm long with approximately 100 mm of sheath or outer covering
removed at each end.
At each end of the test specimen each conductor shall be suitably prepared for electrical
connections, and, if there is more than one conductor, the exposed conductors shall be
spread apart to avoid contact with each other.

6.2 Test specimen mounting
6.2.1 Single core cables with concentric metal layer and multicore cables
The test specimen shall be bent to form an approximate arc of a circle. The internal radius of
the bend shall be the manufacturer’s declared minimum bending radius in normal use.
The test specimen shall be mounted centrally on the test ladder, as shown in Figure 7, using
metal clips which shall be earthed. Two U-bolts on the upper horizontal element of the ladder
are recommended, but P-clips made of metal strip (20 ± 2) mm wide for cables from 20 mm up
to 50 mm in diameter, and (30 ± 3) mm wide for larger cables shall be used on the two central
vertical elements. The P-clips shall be formed so as to have approximately the same diameter
as the test specimen under test.
If the test specimen is too small to be mounted on the central vertical elements when in the
position shown in Figure 7, the two central vertical elements shall be equally moved towards
the centre so that the specimen may be mounted as shown in Figure 8.
If the bending radius in normal use is too large to mount the cable as shown in Figure 7 on
the slots for the U-bolt (key 5 in Figure 7), the test specimen shall be mounted as shown in
Figure 9, using P-clips, which shall be earthed, on the four central vertical elements.
Dimensions in millimetres
(dimensions are approximate)
5 5
1 1
R
2 2
6 6
IEC
Key
1 U-bolt 5 slot for U-bolt
2 P-clip 6 slot for movement of adjustable vertical elements
3 adjustable vertical elements R minimum bending radius of cable in normal use
4 slot for P-clip fixing
Figure 7 – Example of method of mounting a larger diameter test specimen for test
(with a bending radius between approximately 200 and 400 mm)

– 18 – IEC 60331-1:2018 © IEC 2018
Dimensions in millimetres
(dimensions are approximate)
1 1
2 2
7 7
45°
45°
6 6
IEC
Key
1 adjustable position of vertical elements 5 U-bolt
2 normal position of vertical elements 6 slot for movement of adjustable vertical
elements
3 lower horizontal element of test ladder 7 slot for P-clip fixing
4 additional clip to maintain cable arc (if 8 P-clip
required)
Figure 8 – Detailed section of adjustable position of vertical ladder elements
for mounting a smaller diameter test specimen for test (with a maximum
bending radius of approximately 200 mm)
Dimensions in millimetres
(dimensions are approximate)
1 200
IEC
Key
1 P-clip 3 slot for P-clip fixing
2 adjustable vertical elements 4 slot for movement of adjustable vertical elements
Figure 9 – Example of method of mounting test specimen with a bending radius
in normal use larger than approximately 400 mm
6.2.2 Single core cables without concentric metal layer
The test specimen shall be mounted straight centrally on the test ladder using four vertical
elements, as shown in Figure 10, using metal clips which shall be earthed to fix the cable to
these vertical elements.
The width of the metal clips shall be in accordance with 6.2.1.
NOTE Testing of a straight test specimen is appropriate for single core cables without concentric metal layer, as
bending will not affect the performance for this type of cable, as internal forces such as in multicore cables will not
occur.
The P-clips shall be formed so as to have approximately the same diameter as the test
specimen under test.
– 20 – IEC 60331-1:2018 © IEC 2018
Dimensions in millimetres
(dimensions are approximate)
1 200
IEC
Key
1 P-clip 3 slot for P-clip fixing
2 adjustable vertical elements 4 slot for movement of adjustable vertical elements
Figure 10 – Method of mounting test specimen of a single core cable
without concentric metal layer
7 Test procedure (electric power and control cables with rated voltage up to
and including 600 V/1 000 V)
7.1 Test equipment and arrangement
The test procedure defined in this clause shall be carried out using the apparatus detailed in
Clause 5.
Mount the test specimen on the test ladder and adjust the burner to the correct position
relative to the test specimen in accordance with 5.5.
7.2 Electrical connections
At the transformer end of the test specimen, earth the neutral conductor, if present, and any
protective conductors. Any metal screens, drain wire or metal layer shall be interconnected
and earthed. Connect the transformer(s) to the conductors, excluding any conductor which is
specifically identified as intended for use as a neutral or a protective conductor, as shown in
the circuit diagram in Figure 11. Where a metal sheath, armour or screen acts as a neutral or
protective conductor, it shall be connected, as shown in the circuit diagram in Figure 11, as
for a neutral or protective conductor.
For single-, twin- or three-phase conductor cables, connect each phase conductor to a
separate phase of the transformer(s) output with a 2 A fuse or circuit-breaker with equivalent
characteristics in each phase.
For multicore cables that have four or more conductors (excluding any neutral or protective
conductors), the conductors shall be divided into three roughly equal groups, ensuring that
adjacent conductors are, as far as possible, in different groups.
For multipair cables, the conductors shall be divided into two equal groups, ensuring that the
a-core of each pair is connected to one phase and the b-core of each pair is connected to
another phase (L1 and L2 in Figure 11). Quads shall be treated as two pairs.
For multi-triple cables, the conductors shall be divided into three equal groups, ensuring that
the a-core of each triple is connected to one phase, the b-core of each triple to another phase
and the c-core of each triple to the third phase of the transformer (L1, L2 and L3 in Figure 11).
Connect the conductors of each group in series and connect each group to a separate phase
of the transformer output with a 2 A fuse or circuit-breaker with equivalent characteristics in
each phase.
The above test procedure connects the neutral conductor to earth. This may not be
appropriate if the cable is designed for use on a system where neutral is not earthed. If
required by the cable standard, it is permissible for the neutral conductor to be tested as if it
were a phase conductor. Where a metal sheath, armour or screen acts as a neutral
conductor, it shall always be connected to earth. Any such variations in methodology should
be included in the test report.
For cable constructions not specifically identified above, the test voltage should be applied, as
far as is practicable, to ensure that adjacent conductors are connected to different phases.
In certain cases, for example when testing a control cable using a three-phase transformer, it
may not be possible to apply a test voltage between conductors and from conductor to earth
equal to the rated voltage simultaneously. In such cases, either the test voltage between
conductors, or the test voltage from conductor to earth shall be equal to the rated voltage,
such that both the test voltage between conductors and the test voltage from conductor to
earth is equal to or higher than the rated voltage.
At the end of the test specimen remote from the
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