IEC 60079-7:2006

IEC 60079-7
Edition 4.0 2006-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 7: Equipment protection by increased safety "e"

Atmosphères explosives –
Partie 7: Protection de l'équipement par sécurité augmentée «e»

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by
any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.

IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
ƒ Catalogue des publications de la CEI: www.iec.ch/searchpub/cur_fut-f.htm
Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de référence,
texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou remplacées.
ƒ Just Published CEI: www.iec.ch/online_news/justpub
Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles
publications parues. Disponible en-ligne et aussi par email.
ƒ Electropedia: www.electropedia.org
Le premier dictionnaire en ligne au monde de termes électroniques et électriques. Il contient plus de 20 000 termes et
définitions en anglais et en français, ainsi que les termes équivalents dans les langues additionnelles. Egalement appelé
Vocabulaire Electrotechnique International en ligne.
ƒ Service Clients: www.iec.ch/webstore/custserv/custserv_entry-f.htm
Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du
Service clients ou contactez-nous:
Email: csc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC 60079-7
Edition 4.0 2006-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 7: Equipment protection by increased safety "e"

Atmosphères explosives –
Partie 7: Protection de l'équipement par sécurité augmentée «e»

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XC
CODE PRIX
ICS 29.260.20 ISBN 2-8318-8726-7

– 2 – 60079-7 © IEC:2006
CONTENTS
FOREWORD.5

1 Scope.7
2 Normative references .7
3 Terms and definitions .9
4 Constructional requirements for all electrical apparatus.12
4.1 General .12
4.2 Electrical connections.12
4.3 Clearances.15
4.4 Creepage distances.20
4.5 Solid electrical insulating materials.21
4.6 Windings .21
4.7 Temperature limitations .22
4.8 Wiring internal to apparatus.24
4.9 Degrees of protection provided by enclosures .24
4.10 Fasteners .24
5 Supplementary requirements for specific electrical apparatus.25
5.1 General .25
5.2 Rotating electrical machines.25
5.3 Luminaires .30
5.4 Caplights and handlights .34
5.5 Measuring instruments and instrument transformers.35
5.6 Transformers other than instrument transformers .35
5.7 Batteries.36
5.8 General purpose connection and junction boxes.42
5.9 Resistance heaters (other than trace heaters) .42
5.10 Other electrical apparatus .44
6 Type verifications and type tests .44
6.1 Dielectric strength .44
6.2 Rotating electrical machines.45
6.3 Luminaires designed for mains supply.47
6.4 Measuring instruments and instrument transformers.49
6.5 Transformers other than instrument transformers .50
6.6 Secondary batteries .50
6.7 General purpose connection and junction boxes.53
6.8 Resistance heating devices and resistance heating units .53
6.9 Terminal insulating material tests .54
7 Routine verifications and routine tests .55
7.1 Dielectric tests .55
7.2 Dielectric tests for batteries.55
7.3 Inter-turn overvoltage tests.56
8 Ex component certificates.56
8.1 General .56
8.2 Terminals .56

60079-7 © IEC:2006 – 3 –
9 Marking and instructions.56
9.1 General marking.56
9.2 Instructions for use.57
9.3 Warning markings .59

Annex A (normative) Cage motors − Methods of test and of calculation .60
Annex B (normative) Type tests for specific forms of resistance heating devices or
resistance heating units (other than trace heater) .62
Annex C (informative) Cage motors – Thermal protection in service.64
Annex D (informative) Resistance heating devices and units – Additional electrical
protection .65
Annex E (informative) Combinations of terminals and conductors for general purpose
connection and junction boxes .66
Annex F (informative) Dimensions of copper conductors .68
Annex G (informative) Potential stator winding discharge risk assessment – Ignition
risk factors.69
Annex H (normative) Test procedure for T8, T10 and T12 lamps.70
Annex I (Informative) Introduction of an alternative risk assessment method
encompassing ‘Equipment Protection Levels’ for Ex Equipment. .75

Bibliography.80

Figure 1 – Determination of creepage distances and clearances.20
Figure 2 – Minimum values of the time t of motors in relation to the starting current
E
ratio I /I .28
A N
Figure 3 – Arrangement for the luminaire vibration test .49
Figure A.1 – Diagram illustrating the determination of time t .61
E
Figure E.1 – Example of defined terminal/conductor arrangement table .67
Figure H.1 – Asymmetric pulse test circuit .71
Figure H.2 – Asymmetric power detection circuit.73
Figure H.3 – Flow Chart – Asymmetric power Test.74

Table 1 – Creepage distances and clearances .16
Table 2 – Tracking resistance of insulating materials .20
Table 3 – Limiting temperatures for insulated windings .23
Table 4 – Potential air gap sparking risk assessment for cage rotor ignition risk factors.27
Table 5 – Minimum distance between lamp and protective cover .31
Table 6 – Creepage distances and clearances for screw lamp caps .31
Table 7 − Resistance to the effect of short-circuit currents.35
Table 8 – Explosion test mixtures .46
Table 9 – Insertion torque and minimum removal torque .47
Table 10 – Value for pull-out tests .55
Table 11 – Creepage distances and clearances for screw lamp caps .58
Table 12 − Text of warning markings .59

– 4 – 60079-7 © IEC:2006
Table F.1 – Standard cross-sections of copper conductors .68
Table G.1 – Potential stator winding discharge risk assessment – Ignition risk factors .69
Table I.1 – Traditional relationship of EPLs to Zones (no additional risk assessment) .77
Table I.2 – Description of risk of ignition protection provided .78

60079-7 © IEC:2006 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection
by increased safety "e"
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 60079-7 has been prepared by IEC technical committee 31:
Equipment for explosive atmospheres.
This fourth edition cancels and replaces the third edition published in 2001, and constitutes a
technical revision.
The significant changes with respect to the previous edition are listed below:
– requirements for electrical connections expanded and clarified,
– requirements for luminaire ballasts expanded and clarified,
– requirements for evaluation and testing of motor rotors clarified.

– 6 – 60079-7 © IEC:2006
The text of this standard is based on the following documents:
FDIS Report on voting
31/623/FDIS 31/639/RVD
Full information on the voting for the approval of this standard 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.
Cette publication a été rédigée selon les Directives ISO/CEI, Partie 2.
The list of all parts of IEC 60079 series, under the general title Explosive atmospheres, 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.
60079-7 © IEC:2006 – 7 –
EXPLOSIVE ATMOSPHERES –
Part 7: Equipment protection
by increased safety "e"
1 Scope
This part of IEC 60079 specifies the requirements for the design, construction, testing and
marking of electrical apparatus with type of protection increased safety "e" intended for use in
explosive gas atmospheres. This standard applies to electrical apparatus where the rated
voltage does not exceed 11 kV r.m.s. a.c. or d.c. Additional measures are applied to ensure that
the apparatus does not produce arcs, sparks, or excessive temperatures in normal operation
or under specified abnormal conditions.
This standard supplements and modifies the general requirements of IEC 60079-0. Where a
requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of
this standard takes precedence.
NOTE Increased safety "e" can provide Equipment Protection Levels (EPL) Mb or Gb. For further information,
see Annex I.
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 60034-1, Rotating electrical machines – Part 1: Rating and performance
IEC 60034-5, Rotating electrical machines – Part 5: Degrees of protection provided by the

internal design of rotating electrical machines (IP code) – Classification
IEC 60044-6, Instrument transformers – Part 6: Requirements for protective current trans-
formers for transient performance
IEC 60050(426), International Electrotechnical Vocabulary (IEV) – Chapter 426: Electrical
apparatus for explosive atmospheres
IEC 60061-1, Lamp caps and holders together with gauges for the control of
interchangeability and safety – Part 1: Lamp caps
IEC 60061-2, Lamp caps and holders together with gauges for the control of
interchangeability and safety – Part 2: Lampholders
IEC 60064, Tungsten filament lamps for domestic and similar general lighting purposes –
Performance requirements
IEC 60068-2-6, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal)

– 8 – 60079-7 © IEC:2006
IEC 60068-2-27:1987, Environmental testing – Part 2: Tests – Test Ea and guidance: Shock
IEC 60068-2-42, Environmental testing – Part 2-42: Tests – Test Kc: Sulphur dioxide test for
contacts and connections
IEC 60079-0:2004, Electrical apparatus for explosive gas atmospheres – Part 0: General
requirements
IEC 60079-1, Electrical apparatus for explosive gas atmospheres – Part 1: Flameproof
enclosures "d"
IEC 60079-11, Electrical apparatus for explosive gas atmospheres – Part 11: Equipment
protection by intrinsic safety "i"
IEC 60085, Electrical insulation – Thermal classification
IEC 60112, Method for the determination of the proof and the comparative tracking indices of
solid insulating materials
IEC 60228, Conductors of insulated cables
IEC 60238, Edison screw lampholders
IEC 60317-3:2004, Specifications for particular types of winding wires – Part 3: Polyester
enamelled round copper wires, class 155
IEC 60317-7:1990, Specifications for particular types of winding wires – Part 7: Polyimide
enamelled round copper wire, class 220
IEC 60317-8:1990, Specifications for particular types of winding wires – Part 8:
Polyesterimide enamelled round copper wire, class 180
IEC 60317-13:1990, Specifications for particular types of winding wires – Part 13: Polyester or
polyesterimide overcoated with polyamide-imide enamelled round copper wire, class 200
IEC 60364-3, Electrical installations of buildings – Part 5-55: Selection and erection of
electrical equipment – Other equipment
IEC 60400, Lampholders for tubular fluorescent lamps and starterholders
IEC 60432-1, Incandescent lamps – Safety specifications – Part 1: Tungsten filament lamps
for domestic and similar general lighting purposes
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1:1992, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements, and tests
IEC 60947-1, Low-voltage switchgear and controlgear – Part 1: General rules
IEC 60947-7-1, Low-voltage switchgear and controlgear – Part 7: Ancillary equipment –
Section 1: Terminal blocks for copper conductors

60079-7 © IEC:2006 – 9 –
IEC 60947-7-2, Low-voltage switchgear and controlgear – Part 2 – Ancillary equipment –
Section 1: Protective conductor terminal blocks for copper conductors
IEC 60999-1, Connecting devices – Electrical copper conductors – Safety requirements for
screw-type and screwless-type clamping units – Part 1: General requirements and particular
2 2
requirements for clamping units for conductors from 0,2 mm up to 35 mm (included)
IEC 60999-2, Connecting devices – Electrical copper conductors – Safety requirements for
screw-type and screwless-type clamping units – Part 2: Particular requirements for clamping
2 2
units for conductors above 35 mm up to 300 mm (included)
IEC 61195:1999, Double-capped fluorescent lamps – Safety specifications
IEC 61347-2-3:2000, Lamp controlgear – Part 2-3: Particular requirements for a.c. supplied
electronic ballasts for fluorescent lamps
Amendment 1(2004)
Amendment 2 (2006)
IEC 62086-1, Electrical apparatus for explosive gas atmospheres – Electrical resistance trace
heating – Part 1: General and testing requirements
ISO 2859-1, Sampling procedures for inspection by attributes – Part 1: Sampling schemes
indexed by acceptance quality limit (AQL) for lot-by-lot inspection
3 Terms and definitions
For the purposes of this document, the terms and definitions used in IEC 60079-0, together
with the following terms and definitions apply.
For the definitions of any other terms, particularly those of a more general nature, reference
should be made to IEC 60050(426) or other appropriate parts of the IEV (International
Electrotechnical Vocabulary).
3.1
clearance
shortest distance in air between two conductive parts
3.2
connections, factory
terminations intended for connection during a manufacturing process under controlled
conditions
3.3
connections, field-wiring
terminations intended for connection by the installer in the field
3.4
creepage distance
shortest distance along the surface of an electrically insulating material between two
conductive parts
– 10 – 60079-7 © IEC:2006
3.5
increased safety "e"
type of protection applied to electrical apparatus in which additional measures are applied so
as to give increased security against the possibility of excessive temperatures and of the
occurrence of arcs and sparks in normal service or under specified abnormal conditions
NOTE 1 This type of protection is denoted by "e". The “additional measures” are those required for compliance
with this standard.
NOTE 2 Apparatus producing arcs or sparks in normal service is excluded by this definition of increased safety.
3.6
initial starting current
I
A
highest r.m.s. value of current absorbed by an a.c. motor when at rest or by an a.c. magnet
with its armature clamped in the position of maximum air gap when supplied at rated voltage
and rated frequency
NOTE Transient phenomena are ignored.
3.7
limiting temperature
maximum permissible temperature for apparatus or parts of apparatus equal to the lower of
the two temperatures determined by
a) the danger of ignition of the explosive gas atmosphere,
b) the thermal stability of the materials used
NOTE This temperature may be the maximum surface temperature (see both 3.18 and Clause 5 of IEC 60079-0)
or a lower value (see 4.7).
3.8
normal service, motors
continuous operation at the nameplate rating (or set of ratings) including starting conditions
3.9
rated dynamic current
I
dyn
peak value of the current, the dynamic effect of which the electrical apparatus can sustain
without damage
3.10
rated short-time thermal current

I
th
r.m.s. value of the current required to heat up the conductor within 1 s from the temperature
reached in rated service at the maximum ambient temperature to a temperature not exceeding
the limiting temperature
3.11
rated voltage
value of voltage assigned by the manufacturer to a component, device or equipment and to
which operation and performance characteristics are referred

60079-7 © IEC:2006 – 11 –
3.12
resistance-heating devices and resistance-heating units
3.12.1
resistance-heating device
part of a resistance heating unit comprising one or more heating resistors, typically composed
of metallic conductors or an electrically conductive material suitably insulated and protected
3.12.2
resistance-heating unit
apparatus comprising an assembly of one or more resistance heating devices associated with
any devices necessary to ensure that the limiting temperature is not exceeded
NOTE It is not intended that the devices necessary to ensure that the limiting temperature is not exceeded should
have type of protection "e", or any type of protection when they are located outside the hazardous area.
3.12.3
workpiece
object to which a resistance-heating device or unit is applied
3.12.4
temperature self-limiting characteristic
characteristic whereby the thermal output of a resistance-heating device at its rated voltage
decreases as the temperature of its surroundings increases until the device reaches a
temperature at which its thermal output is reduced to a value at which there is no further rise
in temperature
NOTE The temperature of the surface of the element is then effectively that of its surroundings.
3.12.5
stabilized design
concept where the temperature of the resistance-heating device or unit will, by design and
use, stabilize below the limiting temperature, under the most unfavourable conditions, without
the need for a safety device to limit the temperature
3.13
short-circuit current
I
sc
maximum r.m.s. value of the short-circuit current to which the apparatus may be subjected in
service
NOTE This maximum value is recorded in the documentation according to Clause 24 of IEC 60079-0.
3.14
starting current ratio
I /I
A N
ratio between initial starting current I and rated current I
A N
3.15
time
t
E
time, in seconds, taken for an a.c. rotor or stator winding, when carrying the initial starting
current I , to be heated up to the limiting temperature from the temperature reached in rated
A
service at the maximum ambient temperature (see Figure A.1)

– 12 – 60079-7 © IEC:2006
3.16
trace heater
device designed for the purpose of producing heat on the principle of electrical resistance and
typically composed of one or more metallic conductors or an electrically conductive material
suitably electrically insulated and protected
3.17
working voltage
highest r.m.s. value of the a.c. or d.c. voltage across any particular insulation which can occur
when the equipment is supplied at rated voltage
NOTE 1 Transients are disregarded.
NOTE 2 Both open-circuit conditions and normal operating conditions are taken into account.
4 Constructional requirements for all electrical apparatus
4.1 General
The requirements of this clause apply, unless otherwise stated in Clause 5, to all electrical
apparatus with type of protection "e" and are themselves supplemented for certain electrical
apparatus by the supplementary requirements in Clause 5.
4.2 Electrical connections
4.2.1 General
Electrical connections are sub-divided into those for field-wiring and for factory wiring and into
permanent types and re-connectable / re-wirable types for convenience in detailing the
appropriate requirements.
Each type shall, as applicable:
a) be constructed in such a way that the conductors cannot slip out from their intended
location during tightening of a screw or after insertion;
b) provide a means to avoid loosening of the connection in service;
c) be such that contact is assured without damage to the conductors such that would impair
the ability of the conductors to fulfil their function, even if multi-stranded conductors are
used in connections intended for direct clamping of a single conductor;
d) provide a positive compression force to assure contact pressure in service;
e) be constructed in such a way that the contact they assure is not appreciably impaired by
temperature changes occurring in normal service;
f) except as permitted by the earth continuity test of IEC 60079-0, provide contact pressure
that is not applied through insulating materials;
g) not be specified to accommodate more than one individual conductor in a clamping point
unless specifically designed and assessed for doing so;
h) if intended for stranded conductors, employ a means to protect the conductors and
distribute the contact pressure evenly. The method of applying contact pressure shall be
capable, on installation, of reliably forming the stranded conductor into an effectively solid
shape that does not subsequently change in service. Alternatively, the method of applying
the contact pressure should be such that it is designed to accommodate any settlement of
the strands in service;
i) for screw connections, have a specified torque value;

60079-7 © IEC:2006 – 13 –
j) for screwless connections intended for class 5 and/or class 6 fine-stranded conductors
according to IEC 60228, the fine-stranded wire shall be equipped with a ferrule or the
termination shall have a method to open the clamping mechanism so that the conductors
are not damaged during the installation of the conductor.
NOTE 1 The use of aluminium wire may cause difficulties by compromising critical creepage and clearance
distances when anti-oxidant materials are applied. The connection of aluminium wire to terminals may be
accomplished by the use of suitable bi-metallic connection devices providing a copper connection to the terminal.
NOTE 2 Special precautions against vibration and mechanical shock may be required.
NOTE 3 Special precautions against electrolytic corrosion should be considered.
NOTE 4 Special precautions against corrosion should be considered where ferrous materials are used.
NOTE 5 The limiting temperature of the insulation of terminal blocks and accessories will usually be based on the
limiting temperature of the insulation in accordance with item a) of 4.7.2 but the limiting temperature allocated to
erminal when used in equipment will also depend on the maximum cable insulation temperature rating of the
the t
cable which is to be connected.
4.2.2 Field wiring connections
4.2.2.1 General
Terminals for field wiring shall be generously dimensioned to permit the effective connection
of conductors of cross-section equal to at least that corresponding to the rated current of the
electrical apparatus.
Connections shall be located in a position such that where required to be inspected in service
they are reasonably accessible.
The number and size of conductors that can be safely connected shall be specified in the
descriptive documentation according to IEC 60079-0.
4.2.2.2 Connections made using terminals complying with IEC 60947-7-1,
IEC 60947-7-2, IEC 60999-1, or IEC 60999-2
Such terminals are intended for the connection of copper conductors with the insulation
locally removed and without the addition of intermediate parts other than those replicating the
form of a bare conductor, such as a ferrule.
Terminals shall be subject to the terminal insulation material tests of 6.9.
Terminals shall be capable of being fixed in their mountings.
The temperature rise of the conductor bar shall not exceed 45 K at a test current of 110 % of
rated current according to the method of the temperature-rise test of IEC 60947-7-1.
NOTE 1 This test relates to the absolute maximum current rating of the terminal when tested without any
enclosure. For practical purposes, when terminals are used in multiple within enclosures, it will be necessary to
establish reduced current ratings according to the particular circumstances. See 5.8, 6.7 and Annex E.
Terminals for connecting conductors of rated cross-section not exceeding 4 mm (12 AWG)
shall also be suitable for the effective connection of conductors at least two ISO wire sizes
smaller if not otherwise specified in the certificate. See Annex F.
NOTE 2 Subclause 4.2.2.2 is primarily intended to give requirements for terminals as components. When mounted
in equipment any consequent limitations given in this standard apply.

– 14 – 60079-7 © IEC:2006
4.2.2.3 Field wiring connection facilities integral to “e” apparatus or components
Terminals shall meet the requirements of 4.2.2.2, where applicable.
Temperatures for the verification of the thermal stability of materials shall be determined
using a test sample configured to represent the complete apparatus, from a heating
perspective, in accordance with IEC 60079-0.
4.2.2.4 Connections designed to be used with cable lugs and similar devices
Such connections shall be fixed in their mountings.
A means of securing the cable to prevent rotation or movement shall be provided to avoid
either loosening or compromising creepage and clearance. Alternatively, it shall be
demonstrated that such rotation or movement is not reasonably foreseeable.
4.2.2.5 Connections using permanent arrangements
These connections are typically tails with crimping or soldering facilities that are intended to
be connected during installation using appropriate connection methods.
Either a means of fixing the completed connections to a suitable location is to be provided or
the completed connections are to be provided with means of reliably insulating them to the
requirements of this standard.
If the method of connection is by soldering, a method of providing mechanical support of the
completed connection shall be provided. The security of the joint shall not be permitted to rely
solely on the solder.
4.2.3 Factory connections
4.2.3.1 General
Factory connections shall be either fixed in a specific location or be provided with means of
meeting the creepage and clearance requirements of this standard.
4.2.3.2 Field wiring connection methods used for factory connections
Any of the connection methods suitable for use as field wiring connections may be used for a
factory connection, except in this case, the terminal insulation material tests of 6.9 need not
be conducted.
4.2.3.3 Permanent connections
Permanent connections shall only be made by
a) crimping,
b) brazing,
c) welding,
d) soldering, provided that the conductors are not supported by the soldered connection
alone.
60079-7 © IEC:2006 – 15 –
4.2.3.4 Pluggable connections
These connections are designed to be readily connected or disconnected during assembly,
maintenance, or repair.
NOTE Typical examples are plug-in components, and card edge connectors.
Pluggable connections shall provide the following:
a) each connection shall employ at least two contact arrangements where the effectiveness
of each is substantially independent of the other;
b) each connection or group of connections shall be provided with a mechanical retaining
device, which, excluding internal friction, provides a force resisting separation of at least
30 N. Where a group of individual connections is mechanically linked and the separable
component weighs more than 0,25 kg or carries more than 10 cables, special
consideration shall be given to the security of the connection;
c) for a lightweight connecting component relying on friction to remain in place and not
attached in any way outside of the connection points, the separating force in Newtons
shall be greater than 200 times the weight of the component and a mechanical retaining
device is not required. The force shall be applied gradually near the centre of the
component;
d) if the factory connection may remain energised when separated, it shall be provided with
an interlock to prevent separation when energised or shall be marked in accordance with
item b) of Table 12. For small items, adjacent marking can be provided.
4.2.3.5 Terminal bridging connections
These connections are designed to be made one-time only and not connected or
disconnected during maintenance or repair.
A terminal bridging connection shall have a separating force in Newtons that is greater than
200 times the weight of the component. The force shall be applied gradually near the centre
of the component.
4.3 Clearances
Clearances between bare conductive parts at different potentials shall be as given in Table 1
with a minimum value for external connections of 3 mm.
Spacings at wiring terminals shall be evaluated with the conductor size that produces the
minimum clearance.
NOTE For requirements for lamps with screw caps, see 5.3.3.1.
Clearances shall be determined as a function of the working voltage. Where the apparatus is
intended for more than one rated voltage or for a range of rated voltage, the value of working
voltage to be used shall be based on the highest value of rated voltage. In determining the
clearances, examples 1 to 11 (inclusive) in Figure 1 illustrate the features to be taken into
account and the appropriate clearances.

– 16 – 60079-7 © IEC:2006
Table 1 – Creepage distances and clearances
Minimum creepage distance
Voltage
(see Note 1)
mm
Minimum clearance
U a.c. or d.c.
.
r.m.s
Material group mm
V
I II IIIa
10 (see Note 3) 1,6 1,6 1,6 1,6
12,5 1,6 1,6 1,6 1,6
16 1,6 1,6 1,6 1,6
20 1,6 1,6 1,6 1,6
25 1,7 1,7 1,7 1,7
32 1,8 1,8 1,8 1,8
40 1,9 2,4 3,0 1,9
50 2,1 2,6 3,4 2,1
63 2,1 2,6 3,4 2,1
80 2,2 2,8 3,6 2,2
100 2,4 3,0 3,8 2,4
125 2,5 3,2 4,0 2,5
160 3,2 4,0 5,0 3,2
200 4,0 5,0 6,3 4,0
250 5,0 6,3 8,0 5,0
320 6,3 8,0 10,0 6,0
400 8,0 10,0 12,5 6,0
500 10 12,5 16 8,0
630 12 16 20 10
800 16 20 25 12
1 000 20 25 32 14
1 250 22 26 32 18
1600 23 27 32 20
2 000 25 28 32 23
2 500 32 36 40 29
3 200 40 45 50 36
4 000 50 56 63 44
5 000 63 71 80 50
6 300 80 90 100 60
8 000 100 110 125 80
10 000 125 140 160 100
NOTE 1 Voltages shown are derived from IEC 60664-1 and are based on the rationalization of supply voltages
given in Table 3b of IEC 60664-1. When determining the required values for creepage and clearance, the voltage
value in the table may be increased by a factor of 1,1 in order to recognize the range of rated voltages in common
use.
NOTE 2 The creepage distance and clearance values shown are based on a maximum supply voltage tolerance of
±10 %.
NOTE 3 At 10 V and below, the value of CTI is not relevant and materials not meeting the requirement for material
group IIIa may be acceptable.
60079-7 © IEC:2006 – 17 –
NOTE These examples are identical with those given in IEC 60664-1.
Example 1
IEC 1808/01
Condition: Path under consideration includes a parallel- Rule: Creepage distance and clearance are measured
or converging-sided groove of any depth with a width directly across the groove as shown.
less than X mm.
Example 2
IEC 1809/01
Condition: Path under consideration includes a parallel- Rule: Clearance is the "line of sight" distance. Creepage
sided groove of any depth d equal to or more than X mm. path follows the contour of the groove.

Example 3
IEC 1810/01
Condition: Path under consideration includes a V-shaped Rule: Clearance is the "line of sight" distance. Creepage
groove with a width greater than X mm.
path follows the contour of the groove but "short circuits"
the bottom of the groove by X mm link.

Example 4
IEC 1811/01
Condition: Path under consideration includes a rib. Rule: Clearance is the shortest direct air path over the
top of the rib. Creepage path f
...