IEC TR 61916:2009

IEC/TR 61916 ®
Edition 2.0 2009-11
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Electrical accessories – Harmonization of general rules

Petit appareillage – Harmonisation des règles générales

IEC/TR 61916:2009
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IEC/TR 61916 ®
Edition 2.0 2009-11
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Electrical accessories – Harmonization of general rules

Petit appareillage – Harmonisation des règles générales

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
T
CODE PRIX
ICS 29.120 ISBN 978-2-88910-587-8
– 2 – TR 61916 © IEC:2009
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 General requirements .8
4 Resistance to heat.8
4.1 Requirements.8
4.2 Tests.9
5 Screws, current-carrying parts and connections (electrical and mechanical) .10
5.1 Definitions .10
5.1.1 Thread-forming screw.10
5.1.2 Thread-cutting screw .10
5.2 Requirements.11
5.3 Tests.13
6 Resistance to abnormal heat and to fire.14
6.1 Requirements.14
6.2 Glow-wire flammability test for end-products, IEC 60695-2-11.14
6.2.1 Purpose and principle.14
6.2.2 Test specimens .14
6.2.3 Test method .15
6.2.4 Relevance of test data.15
7 Resistance of insulating materials to tracking .15
7.1 Requirements.15
7.2 Tracking index test, IEC 60112.15
7.2.1 Purpose and principle.15
7.2.2 Definitions .16
7.2.3 Test method .16
7.2.4 Repeatability and reproducibility.16
7.2.5 Relevance of test data.16
8 Resistance to rusting.17
8.1 Requirements.17
8.2 Test.17
9 Legibility, durability and indelibility of marking .17
9.1 Requirements.18
9.2 Test.18
10 Screw-type terminals for connecting conductors .18
11 Criteria for tests in accessory standards .18
12 Tolerances .18
13 Mechanical strength .19
13.1 Impact .19
13.2 Free fall.19
14 Appropriate dimensioning of insulation distances.19
14.1 General information.19
14.2 What about the importance of pollution degrees (PDs) in IEC 60664-1 .20

TR 61916 © IEC:2009 – 3 –
14.2.1 How to read IEC 60664-1 table 2 and 7 for the dimensioning of
clearances.20
14.2.2 How to read IEC 60664-1 table 4 for the dimensioning of creepage
distances.21

Figure 1 – Thread-forming screw .10
Figure 2 – Thread-cutting screw.10

Table 1 – Torque per thread diameter .13

– 4 – TR 61916 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL ACCESSORIES –
HARMONIZATION OF GENERAL RULES

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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61916, which is a technical report, has been prepared by IEC technical committee 23:
Electrical accessories.
The second edition cancels and replaces the first edition published in 1998 and constitutes a
technical revision. The main technical changes with regard to the previous edition are as
follows:
– Updated reference standards.
– Introduction of appropriate dimensioning of insulation distances criteria.
– Interpretation on glow wire test.
– Indication of standard conditions for operation in service.

TR 61916 © IEC:2009 – 5 –
– Modification of Clauses 6 and 7 by including an explanatory introduction concerning how
to apply the relevant tests and a simple reference to the horizontal standard.
– Modification of Clause 12: Tolerances.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
23/469/DTR 23/478B/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
In this standard the following print types are used:
– requirements proper: in roman type;
– test specifications: in italic type;
– Explanatory matter: in smaller roman type.
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 – TR 61916 © IEC:2009
INTRODUCTION
The purpose of this Technical Report is to have harmonized rules on the same subjects in all
the Standards published by TC 23 and its subcommittees, in order to give coordinated
indications to subcommittees when making their standards.
These recommendations are meant as a guide. Consequently, subcommittees, according to
their own particularities, may use whole or part of the document which is not meant to be
compulsory.
In publishing these recommendations, TC 23 wishes to spread the information so that other
committees of the IEC may use these recommendations, if necessary.

TR 61916 © IEC:2009 – 7 –
ELECTRICAL ACCESSORIES –
HARMONIZATION OF GENERAL RULES

1 Scope
This technical report provides recommendations and test requirements applicable to electrical
accessories. It aims to harmonize general rules for the preparation of international standards
in this field. It gives to that effect recommendations which are intended to be used as a guide.
2 Normative references
The following referenced documents are indispensable for the application 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 60068-2-31: 2008, Environmental testing – Part 2-31: Tests. Test Ec: Rough handling shocks,
primarily for equipment-type specimens
IEC 60068-2-75: 1997, Environmental testing – Part 2: Tests – Test Eh: Hammer tests
IEC 60112:2003, Method for the determination of the proof and the comparative tracking
indices of solid insulating materials
IEC 60228:2004, Conductors of insulated cables
IEC 60664-1: 2007, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60664-4 :2005, Insulation coordination for equipment within low-voltage systems – Part 4:
Consideration of high-frequency voltage stress
IEC 60664-5:2007, Insulation coordination for equipment within low-voltage systems – Part 5:
Comprehensive method for determining clearances and creepage distances equal to or less
than 2 mm
IEC 60669-1:1998, Switches for household and similar fixed-electrical installations – Part 1:
General requirements
Amendment 1 (1999)
Amendment 2 (2006)
IEC 60695-2-10:2000, Fire hazard testing – Part 2-10: Glowing/hot-wire based test methods -
Glow-wire apparatus and common test procedure
IEC 60695-2-11:2000, Fire hazard testing – Part 2-11: Glowing/hot-wire based test methods -
Glow-wire flammability test method for end-products
IEC 60695-10-2:2003, Fire hazard testing - Part 10-2: Abnormal heat - Ball pressure test
IEC 60898-1:2002, Electrical accessories – Circuit breakers for overcurrent protection for
household and similar installations – Part 1: Circuit-breakers for a.c. operation
Amendment 1 (2002) and 2 (2003)
IEC 60998-1:2002, Connecting devices for low voltage circuits for household and similar
purposes – Part 1: General requirements

– 8 – TR 61916 © IEC:2009
IEC 60998-2-1:2002, Connecting devices for low-voltage circuits for household and similar
purposes – Part 2-1: Particular requirements for connecting devices as separate entities with
screw-type clamping units
IEC 60999 (all parts), Connecting devices – Electrical copper conductors – Safety
requirements for screw-type and screwless-type clamping units
IEC/TR 62062: 2002, Results of the Round Robin series of tests to evaluate proposed
amendment to IEC 60112
IEC Guide 104: The preparation of safety publications and the use of basic safety publications
and group safety publications
ISO 1456:2009, Metallic and other inorganic coatings – Electrodeposited coatings of nickel,
nickel plus chromium, copper plus nickel and of copper plus nickel plus chromium
ISO 2081:2008, Metallic and other inorganic coatings – Electroplated coatings of zinc with
supplementary treatments on iron or steel
ISO 2093:1986, Electroplated coatings of tin – Specification and test methods
3 General requirements
This guidance is applicable to the relevant clause(s) of a TC 23 standard covering general
requirements and/or scope.
Before tests, the specimen is stored for at least 24 h in an atmosphere having a temperature
between 15 °C and 35 °C and relative humidity between 45 % and 75 %, except for the test of
Clause 7 where IEC 60112 applies.
Accessories shall be so designed and constructed so that, in normal use, their performance is
reliable and safe for the user and the surroundings.
Standard conditions for operation in service for electrical accessories complying with the
existing standards should be suitable for use at ambient temperatures not normally exceeding
+ 40 ºC, but their average over a period of 24 h does not exceed +35 °C, with a lower limit of
the ambient air temperature of –5 °C.
4 Resistance to heat
This guidance is applicable to the relevant clause(s) of a TC 23 standard covering
requirements and tests to determine the resistance to heat of accessories.
NOTE These recommendations are in accordance with IEC 60669-1 (1998) + Amd. 1 (1999) + Amd. 2 (2006).
The text includes two subclauses:
– Requirements (4.1)
– Tests (4.2)
For editing purposes the order and the numbers may be altered if necessary.
4.1 Requirements
Accessories including enclosures, if any, shall be sufficiently resistant to heat.

TR 61916 © IEC:2009 – 9 –
Compliance is checked by the tests of 4.2.
4.2 Tests
Verification of resistance to heat
a) for surface mounting boxes, separable covers, separable cover plates and separable
frames by the test of 4.2.3;
b) for accessories, with the exception of the parts, if any, covered by 1), by the tests of 4.2.1,
4.2.2 and, with the exception for the accessories made from natural or synthetic rubber or
a mixture of both, by the test of 4.2.3.
± 2 °C.
4.2.1 The specimens are kept for 1 h in a heating cabinet at a temperature of 100 °C
During the test, they shall not undergo any change impairing their further use, and sealing
compound, if any, shall not flow to such an extent that live parts are exposed.
After the test and after the specimens have been allowed to cool down to approximately room
temperature, there shall be no access to live parts which are normally not accessible when
the specimens are mounted as in normal use, even if probe B of IEC 61032 is applied with a
force not exceeding 5 N.
After the test, markings shall still be legible.
Discoloration, blisters or slight displacement of the sealing compound is disregarded provided
that safety is not impaired within the meaning of the relevant standard.
4.2.2 Parts of insulating material necessary to retain current-carrying parts and parts of the
earthing circuit in position are subjected to a ball-pressure test according to IEC 60695-10-2,
except that the insulating parts necessary to retain the earthing terminals in a box shall be
tested instead to the test as specified in 4.2.3.
A current carrying part or a part of the earthing circuit retained by a mechanical means is
considered to be retained in position. The use of grease or the like is not considered to be
mechanical means.
In case of doubt, to determine whether an insulating material is necessary to retain current
carrying parts and parts of the earthing circuit in position, the specimen is examined without
conductors while held in all positions with the insulating material in question removed.
Before the test is started, the ball and the support on which the specimen shall be placed, are
brought to the temperature specified. The part under test shall be placed on a 3 mm thick
steel plate in direct contact with it, so as to be supported to withstand the test force.
NOTE When it is not possible to carry out the test on the specimens, the test should be carried out on a piece at
least 2 mm thick which is cut out of the specimen. If this is not possible, up to and including four layers, each cut
out of the same specimen, may be used, in which case the total thickness of the layers should be not less than 2,5 mm.
The test load and the supporting means shall be placed within the heating cabinet for a
sufficient time to ensure that they have attained the stabilized testing temperature before the
test commences.
The test is made in a heating cabinet at a temperature of 125 °C ± 2 °C.
+2
After 60 min, the ball is removed from the specimen which is then cooled and treated
− 0
according to Clause 7 of IEC 60695-10-2.

– 10 – TR 61916 © IEC:2009
The diameter of the impression caused by the ball is measured in accordance with
IEC 60695-10-2 and shall not exceed 2 mm.
4.2.3 Parts of insulating material not necessary to retain current-carrying parts and parts of
the earthing circuit in position, even though they are in contact with them, are subjected to a
± 2 °C or
ball pressure test in accordance with 4.2.2, but the test is made at a temperature of 70 °C
40 °C ± 2 °C plus the highest temperature rise determined for the relevant part during the test
of clause “Temperature rise test”, whichever is the higher.
5 Screws, current-carrying parts and connections (electrical and mechanical)
This guidance is applicable to the relevant clause(s) of a TC 23 standard covering the
requirements and tests of screws, current-carrying parts and connections (electrical and
mechanical) of accessories.
NOTE These recommendations are in accordance with IEC 60669-1 (1998) + Amd. 1 (1999) + Amd. 2 (2006).
The text includes three subclauses as follows:
– Definitions (5.1)
– Requirements (5.2)
– Tests (5.3)
For editing purposes, the order and numbers may be altered, if necessary.
5.1 Definitions
5.1.1 Thread-forming screw
A tapping screw having an uninterrupted thread which by screwing-in forms a thread by
displacing material in the cavity.
An example of a thread-forming screw is shown in Figure 1.

IEC  053/09
Figure 1 – Thread-forming screw
5.1.2 Thread-cutting screw
A screw having an interrupted thread which, by screwing-in, makes a thread by removing
material from the cavity.
An example of thread-cutting screw is shown in Figure 2.

IEC  054/09
Figure 2 – Thread-cutting screw

TR 61916 © IEC:2009 – 11 –
5.2 Requirements
5.2.1 Connections, electrical or mechanical, using screws and nuts, shall withstand the
mechanical stresses occurring in normal use.
Screws and nuts which transmit contact pressure shall be of metal and shall be in
engagement with a metal thread. Screws and nuts which are operated when mounting an
accessory during installation, and/or which are likely to be operated during the life of the
accessory, shall be in engagement with a metal thread.
Screws for connecting external conductors shall not be tapping screws.
Screws and nuts operated when mounting the accessory during installation, and/or which are
likely to be operated during the life of the accessory, shall not be of the thread cutting type.
NOTE 1 Screws and nuts which are operated when mounting the accessory include screws for fixing cover of
cover plates, etc., but not connecting means for screwed conduits and screws for fixing the base of the accessory.
Compliance is checked by inspection and by the test of 5.3.
NOTE 2 Attention is drawn to the fact that screwed connections also have to comply with the requirements
applicable to the accessory.
5.2.2 For screws in engagement with a thread of insulating material and screws of insulating
material, which are used for the installation of the accessory and/or which are likely to be
operated during the life of the accessory, correct introduction of the screw into the screw hole
or nut shall be ensured.
Screws of insulating materials shall not be used in cases when the replacement with metal
screws could impair the insulation of the accessory.
Compliance is checked by inspection and by manual test.
NOTE The requirements with regard to correct introduction are met if introduction of the screw in a slanting
manner is prevented, for example by guiding the screw by the part to be fixed, by a recess in the female thread or
by the use of a screw with the leading thread removed.
5.2.3 Screws and rivets, intended to be used for electrical connections and screws and
rivets intended to be used for mechanical connection, shall be locked against loosening or
turning.
Compliance is checked by inspection and manual test.
NOTE Spring washers may provide satisfactory locking. For rivets, a non-circular shank or an appropriate notch
may be sufficient. Sealing compound which softens on heating provides satisfactory locking only for screw
connections not subjected to torsion in normal use.
5.2.4 Electrical connections shall be so designed that contact pressure is not transmitted
through insulating material other than ceramic, pure mica or other material with
characteristics no less suitable, unless there is sufficient resiliency in the metallic parts to
compensate for any possible shrinkage or yielding of the insulating material.
Compliance is checked by inspection.
NOTE The suitability of the material is considered as regards the stability of the dimensions.
5.2.5 Current-carrying parts, including those of terminals (also earthing terminals), shall be
of a metal having, under the conditions occurring in the equipment, mechanical strength,
electrical conductivity and resistance to corrosion adequate for their intended use.
Compliance is checked by inspection and, if necessary, by chemical analysis.

– 12 – TR 61916 © IEC:2009
Examples of suitable metals, when used within a permissible temperature range and under
normal conditions of chemical pollution are:
– copper;
– an alloy containing at least 58 % copper for parts that are worked cold or at-least 50 %
copper for other parts;
– stainless steel containing at least 13 % chromium and not more than 0,09 % carbon;
– steel provided with an electroplated coating of zinc according to ISO 2081, the coating
having a thickness of at least:
• 5 μm (ISO service condition 1) for ordinary equipment
• 8 μm (ISO service condition 2) for drip-proof and splash-proof equipment
• 12 μm (ISO service condition 3) for jet-proof and watertight equipment;
– steel provided with an electroplated coating of nickel and chromium according to ISO
1456, the coating having a thickness of at least:
• 10 μm (ISO service condition 1) for ordinary equipment
• 20 μm (ISO service condition 2) for drip-proof and splash-proof equipment
• 30 μm (ISO service condition 3) for jet-proof and watertight equipment;
– steel provided with an electroplated coating of tin, according to ISO 2093, the coating
having a thickness equal to at least that specified for:
• 12 μm (ISO service condition 1) for ordinary equipment
• 20 μm (ISO service condition 2) for drip-proof and splash-proof equipment
• 30 μm(ISO service condition 3) for jet-proof and watertight equipment
Parts which may be subjected to mechanical wear, shall not be made of steel provided
with an electroplated coating;
– steel provided with an electroplated coating of zinc is only permitted for prime current-
carrying parts if no fixed connection is intended to be made. For connection, an
electroplated coating of zinc is permissible only on parts which do not participate directly
in current transmission, such as screws or washers used for certain types of terminals in
which they transmit only the contact pressure.
NOTE 1 This requirement is not intended to apply to contacts, magnetic circuits, heating elements, bimetallic
components, shunts, parts of electronic devices, etc.
NOTE 2 Screws, nuts, washers, clamping plates and similar parts of terminals are not regarded as current-
carrying parts.
NOTE 3 New requirements to be verified by a test for determining the resistance to corrosion are under
consideration. These requirements should permit other materials to be used if suitably coated.
Under moist conditions, metals having a great difference of electrochemical potential with
respect to each other, shall not be used in contact with each other.
Compliance is checked by inspection.
5.2.6 Thread-forming screws and thread-cutting screws shall not be used for the connection
of current-carrying parts. Thread-forming screws and thread cutting screws may be used to
provide earthing continuity, provided that it is not necessary to disturb the connection in
normal use and at least two screws are used for each connection.
Compliance is checked by inspection.
NOTE The use of thread-forming screws without displacing of material which are operated when mounting the
accessory are under consideration.

TR 61916 © IEC:2009 – 13 –
5.3 Tests
Compliance with the requirements of 5.2.1 is checked by inspection and by the following test.
The screws and nuts are tightened and loosened:
– 10 times for metal screws in engagement with a thread of insulating material and for
screws of insulating material;
– 5 times in all other cases.
Screws or nuts in engagement with a thread of insulating material and screw of insulating
material are completely removed and re-inserted each time.
The test is made by means of a suitable test screwdriver or spanner applying a torque as
shown in T able 1.
The shape of the blade of the test screwdriver shall suit the head of the screw for screws and
nuts which are operated when mounting and connecting up the device by the following test.
The screws and nuts shall be tightened smoothly. In the case of a test on terminals, the
conductor is moved each time the screw or nut is loosened.
Table 1 – Torque per thread diameter
Torque
Nominal diameter of thread Nm
mm I II III IV V
Up to and including 2,8 0,2 – 0,4 0,4 –
over 2,8 up to and including 3,0 0,25 – 0,5 0,5 –
over 3,0 up to and including 3,2 0,3 – 0,6 0,6 –
over 3,2 up to and including 3,6 0,4 – 0,8 0,8 –
over 3,6 up to and including 4,1 0,7 1,2 1,2 1,2 1,2
over 4,1 up to and including 4,7 0,8 1,2 1,8 1,8 1,8
over 4,7 up to and including 5,3 0,8 1,4 2,0 2,0 2,0
over 5,3 up to and including 6,0 1,2 1,8 2,5 3,0 3,0
over 6,0 up to and including 8,0 2,5 2,5 3,5 6,0 4,0
over 8,0 up to and including 10,0 – 3,5 4,0 10,0 6,0
over 10,0 up to and including 12,0 – 4,0 – – 8,0
over 12,0 up to and including 15,0 – 5,0 – – 10,0

Column I applies to screws without head if the screw when tightened does not protrude from
the hole, and to other screws which cannot be tightened by means of a screwdriver with a
blade wider than the diameter of the screw.
Column II applies to nuts of mantle terminals which are tightened by means of a screwdriver.
Column III applies to other screw which are tightened by means of a screwdriver.
Column IV applies to screws and nuts other than nuts of mantle terminals which are tightened
by means other than a screwdriver
Column V applies to nuts of mantle terminals which are tightened by means other than a
screwdriver.
– 14 – TR 61916 © IEC:2009
NOTE For mantle screws, the specific nominal diameter is that of the slotted stud.
For screw with a nominal diameter over 5,3 mm and having a head with a slot, the test is
made twice, first applying to the hexagonal head the torque specified in column IV, and then
on another set of specimens applying the torque specified in column III by means of a
screwdriver.
For smaller screws having a hexagonal head with a slot, only the test with the screwdriver is
made.
During the test, the screwed connection shall not work loose and there shall be no damage,
such as breakage of screws or damage to the head slots, threads, washers or stirrups, that
will impair the further use of the accessory.
6 Resistance to abnormal heat and to fire
This guidance is applicable to the relevant clause(s) of a TC 23 standard covering
requirements and tests to determine the resistance to abnormal heat and to fire of the
insulating parts of accessories. Subclauses 6.1 and 6.2 are meant to give to Subcommittees
information on how to use IEC 60695-2-10 and IEC 60695-2-11.
6.1 Requirements
Parts of insulating material of electrotechnical equipment which might be exposed to
excessive thermal stress due to electric effects and the deterioration of which might impair the
safety of the equipment shall not be unduly affected by heat and by fire generated within the
equipment.
For certain accessories (e.g. switches, plugs, or others) the requirements apply to all parts of
the insulating material, whereas for other accessories (e.g. circuit breakers), which have their
insulating material submitted to severe resistance to fire tests, the requirements apply only to
the external parts of the insulating material.
Parts of insulating material or of other solid combustible material which are liable to propagate
flames inside the equipment may be ignited by glowing wires or glowing elements. Under
certain conditions, for example a fault current flowing through a wire, overloading of
components, and bad connections, certain elements may attain a temperature such that they
will ignite parts in their vicinity.
NOTE In some subcommittees, only external parts are taken into account.
Compliance is checked by the glow-wire test according to 6.2.
6.2 Glow-wire flammability test for end-products, IEC 60695-2-11
6.2.1 Purpose and principle
The glow-wire is a specified loop of resistance wire, which is electrically heated to a specified
temperature. The test apparatus is described in IEC 60695-2-10.
The purpose of IEC 60695-2-11 is to ensure that, under defined conditions, the glow-wire
does not cause ignition of parts, and that a part, if ignited, has a limited duration of burning
without spreading fire by flames or by burning or glowing particles falling from the test
specimen.
6.2.2 Test specimens
The test specimen should be a complete end-product chosen so that the conditions of the test
will not be significantly different from those occurring in normal use.

TR 61916 © IEC:2009 – 15 –
6.2.3 Test method
The tip of the heated glow-wire is brought into contact with a test specimen for a specific
period of time and a range of observations and measurements are made, depending upon the
particular test procedure.
The tip of the glow-wire is applied horizontally to the part of the test specimen which is likely
to be subjected to thermal stresses in normal use.
6.2.4 Relevance of test data
This test identifies a pass/fail criterion at a temperature specified by the relevant product
committee. The main use of the test by electrotechnical committees is to ensure the suitability
of insulating materials in contact with live parts or electrical connections that might overheat
due to a fault. The aim is to ensure that possible ignition of the insulating material does not
cause a fire to spread from the product.
Overheating of the electrical connection may cause ignition in the product but, on removal of
the fault current, an insulating material which has passed the test would be expected to self-
extinguish. Therefore, although the product may have been rendered unusable, flame spread
is unlikely to have occurred and so the user and other property will not have been put at risk
from fire.
As well as checking the integrity of the supporting insulating material, the test also records
whether flaming or molten droplets fall onto a specified surface below. In a large product this
would be assessed by placing below the test specimen a sample of the material that would, in
normal use, be subjected to the droplets. If this layer was not damaged and contained the
molten material then this would be considered satisfactory. When there is no surface to trap
the droplets, and they were likely to escape from the product (for example onto a flammable
surface) then a standard sheet of wrapping tissue on a wooden board is used.
This test also records whether or not the material ignites and can provide further data by
measuring the flame height. Flame height is difficult to measure and so some product
committees note that ignition has occurred and then assume a standardized zone above the
area of the live part or electrical connection to carry out further tests. This is known as
consequential testing and it may be carried out using the needle flame test.
7 Resistance of insulating materials to tracking
This guidance is applicable to the relevant clause(s) of a TC 23 standard covering
requirements and tests to determine the resistance of insulating material to tracking.
Subclauses 7.1 and 7.2 are meant to give to Subcommittees information on how to use
IEC 60112.
7.1 Requirements
For accessories other than ordinary ones (generally higher than IPX0) where tracking paths
can be formed across insulating material, this material shall be resistant to tracking. For
materials other than ceramics, compliance is checked by the test of IEC 60112.
7.2 Tracking index test, IEC 60112
7.2.1 Purpose and principle
IEC 60112 specifies the method of test for the determination of the proof and comparative
tracking indices of solid insulating materials on pieces taken from parts of equipment and on
plaques of material using alternating voltages. The standard also provides for the
determination of erosion when required.

– 16 – TR 61916 © IEC:2009
7.2.2 Definitions
7.2.2.1
tracking
the progressive formation of conducting paths, which are produced on the surface of a solid
insulating material, due to the combined effects of electric stress and electrolytic
contamination on this surface
7.2.2.2
electrical erosion
the wearing away of insulating material by action of electrical discharges
7.2.2.3
Comparative tracking index (CTI)
the numerical value of the maximum voltage in volts at which a material withstands 50 drops
without tracking
NOTE The value of each test voltage and the CTI should be divisible by 25.
7.2.2.4
Proof tracking index (PTI)
the numerical value of the proof voltage in volts at which a material withstands 50 drops
without tracking
7.2.2.5
test specimen
the test specimen should be flat, at least 3 mm thick, and have an area sufficient to ensure
that during the test no liquid flows over the edges of the test specimen. 20 mm × 20 mm is
recommended as a minimum size
7.2.3 Test method
The upper surface of the test specimen is supported in an approximately horizontal plane and
subjected to an electrical stress via two platinum electrodes, 4 mm apart, using an a.c.
voltage of between 100 V and 600 V. The surface between the electrodes is subjected to a
succession of drops of electrolyte either until an over-current device operates, or until ignition
and a persistent flame occurs, or until the test period has elapsed.
The individual tests are of short duration (less than 1 h) with up to 50 or 100 drops of about
20 mg of electrolyte falling at 30 s intervals. The number of drops needed to cause failure
usually increases with decreasing applied voltage and, below a critical value, tracking ceases
to occur.
During the test, the specimen may also erode or soften, thereby allowing the electrodes to
penetrate it. If required, erosion is measured. If a hole is formed, this is reported.
7.2.4 Repeatability and reproducibility
Data are reported in IEC/TR 62062
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