SIST EN 60255-27:2006

SLOVENSKI STANDARD
01-november-2006
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Measuring relays and protection equipment -- Part 27: Product safety requirements
Messrelais und Schutzeinrichtungen -- Teil 27: Anforderungen an die Produktsicherheit
Relais de mesure et dispositifs de protection -- Partie 27: Exigences de sécurité
Ta slovenski standard je istoveten z: EN 60255-27:2005
ICS:
29.120.70 Releji Relays
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN 60255-27
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2005

ICS 29.120.70
English version
Measuring relays and protection equipment
Part 27: Product safety requirements
(IEC 60255-27:2005)
Relais de mesure  Messrelais und Schutzeinrichtungen
et dispositifs de protection Teil 27: Anforderungen
Partie 27: Exigences de sécurité an die Produktsicherheit
(CEI 60255-27:2005) (IEC 60255-27:2005)

This European Standard was approved by CENELEC on 2005-11-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,
Switzerland and United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60255-27:2005 E
Foreword
The text of document 95/180/FDIS, future edition 1 of IEC 60255-27, prepared by IEC TC 95,
Measuring relays and protection equipment, was submitted to the IEC-CENELEC parallel vote and
was approved by CENELEC as EN 60255-27 on 2005-11-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2008-11-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60255-27:2005 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60068-3-4 NOTE Harmonized as EN 60068-3-4:2002 (not modified).
IEC 60112 NOTE Harmonized as EN 60112:2003 (not modified).
IEC 60255-5 NOTE Harmonized as EN 60255-5:2001 (not modified).
IEC 60695-2-13 NOTE Harmonized as EN 60695-2-13:2001 (not modified).
IEC 61010-1 NOTE Harmonized as EN 61010-1:2001 (not modified).
IEC 61508-1 NOTE Harmonized as EN 61508-1:2001 (not modified).
IEC 61558 NOTE Harmonized in EN 61558 series (modified).
IEC 61810-1 NOTE Harmonized as EN 61810-1:2004 (not modified).
__________
- 3 - EN 60255-27:2005
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE Where an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 60068-2-1 1990 Environmental testing EN 60068-2-1 1993
Part 2: Tests - Tests A: Cold
1)
IEC 60068-2-2 1974 Part 2-2: Tests - Tests B: Dry heat EN 60068-2-2 1993
A1 1993 A1 1993
A2 1994 A2 1994
2)
IEC 60068-2-30 1980 Part 2-30: Tests - Test Db and EN 60068-2-30 1999
guidance: Damp heat, cyclic (12 + 12-
hour cycle)
IEC 60068-2-78 2001 Part 2-78: Tests - Test Cab: Damp heat, EN 60068-2-78 2001
steady state
IEC 60085 2004 Electrical insulation - Thermal EN 60085 2004
classification
IEC 60127-1 1988 Miniature fuses
+ corr. March 1990 Part 1: Definitions for miniature fuses EN 60127-1 1991
and general requirements for miniature
fuse-links
IEC 60255-6 1988 Electrical relays EN 60255-6 1994
(mod) Part 6: Measuring relays and protection + corr. February 1995
equipment
IEC 60255-21-1 1988 Part 21: Vibration, shock, bump and EN 60255-21-1 1995
seismic tests on measuring relays and
protection equipment
Section 1: Vibration tests (sinusoidal)

IEC 60255-21-2 1988 Part 21: Vibration, shock, bump and EN 60255-21-2 1995
seismic tests on measuring relays and
protection equipment
Section 2: Shock and bump tests

1)
EN 60068-2-2 includes supplement A:1976 to IEC 60068-2-2.
2)
EN 60068-2-30 includes A1:1985 to IEC 60068-2-30.

Publication Year Title EN/HD Year
IEC 60255-21-3 1993 Part 21: Vibration, shock, bump and EN 60255-21-3 1995
seismic tests on measuring relays and
protection equipment
Section 3: Seismic tests
IEC 60255-22-5 2002 Part 22-5: Electrical disturbance tests EN 60255-22-5 2002
for measuring relays and protection
equipment - Surge immunity test

IEC 60352-1 1997 Solderless connections EN 60352-1 1997
Part 1: Wrapped connections - General
requirements, test methods and
practical guidance
IEC 60352-2 1990 Part 2: Solderless crimped connections EN 60352-2 1994
- General requirements, test methods
and practical guidance
IEC 60417 data Graphical symbols for use on - -
base equipment
IEC 60529 1989 Degrees of protection provided by EN 60529 1991
enclosures (IP Code) + corr. May 1993
A1 1999 A1 2000
IEC 60664-1 1992 Insulation coordination for equipment
+ A1 2000 within low-voltage systems
+ A2 2002 Part 1: Principles, requirements and EN 60664-1 2003
tests
IEC 60664-3 2003 Part 3: Use of coating, potting or EN 60664-3 2003
moulding for protection against pollution

IEC/TS 60695-2-20 2004 Fire hazard testing - -
Part 2-20: Glowing/hot wire based test
methods - Hot-wire coil ignitability -
Apparatus, test method and guidance

IEC 60695-11-10 1999 Part 11-10: Test flames - 50 W EN 60695-11-10 1999
A1 2003 horizontal and vertical flame test A1 2003
methods
IEC 60825-1 1993 Safety of laser products EN 60825-1 1994
Part 1: Equipment classification, + corr. February 1995
A1 1997 requirements and user's guide A1 2002
A2 2001 A2 2001
+ corr. April 2004
IEC 60990 1999 Methods of measurement of touch EN 60990 1999
current and protective conductor current

IEC 61140 2001 Protection against electric shock - EN 61140 2002
Common aspects for installation and
equipment
- 5 - EN 60255-27:2005
Publication Year Title EN/HD Year
IEC 61180-1 1992 High-voltage test techniques for low- EN 61180-1 1994
voltage equipment
Part 1: Definitions, test and procedure
requirements
IEC 61180-2 1994 Part 2: Test equipment EN 61180-2 1994

IEC 62151 2000 Safety of equipment electrically - -
connected to a telecommunication
network
ISO 780 1997 Packaging - Pictorial marking for EN ISO 780 1999
handling of goods
ISO 7000 data Graphical symbols for use on - -
base equipment - Index and synopsis

NORME CEI
INTERNATIONALE
IEC
60255-27
INTERNATIONAL
Première édition
STANDARD
First edition
2005-11
Relais de mesure et dispositifs de protection –
Partie 27:
Exigences de sécurité
Measuring relays and protection equipment –
Part 27:
Product safety requirements
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For price, see current catalogue

60255-27  IEC:2005 – 3 –
CONTENTS
FOREWORD.9
INTRODUCTION.15
1 Scope and object.19
2 Normative references .19
3 Terms and definitions .23
4 General safety requirements.39
4.1 Earthing requirements (grounding, earthing and screening).39
5 Protection against electric shock .39
5.1 Requirements for protection against electric shock.39
5.2 Single-fault conditions .59
6 Mechanical aspects .67
6.1 Protection against mechanical hazards.67
6.2 Mechanical requirements.67
6.3 Mechanical security of terminations.69
7 Flammability and resistance to fire .69
7.1 General .69
7.2 General hazards from overheating and fire.73
7.3 Minimization of fire risk.75
7.4 Cabling and fusing .77
7.5 Flammability of materials and components .77
7.6 Fire ignition sources .83
7.7 Conditions for a fire enclosure.83
7.8 Requirements for primary circuits and circuits exceeding ELV limits .85
7.9 Fire enclosures and flame barriers .85
7.10 Assessment of the fire risk due to a single-fault condition.87
7.11 Limited-energy circuit .91
8 General and fundamental design requirements for safety .93
8.1 Climatic conditions for safety.93
8.2 Electrical connections.93
8.3 Components .95
8.4 Connection to communication networks.95
8.5 Connection to other equipment.95
8.6 Laser sources.97
8.7 Explosion .97
9 Marking, documentation and packaging .99
9.1 Marking .99
9.2 Documentation .113
9.3 Packaging .119
10 Type tests and routine tests .121
10.1 Safety type tests .123
10.2 Routine testing or sample testing .123
10.3 Conditions for testing .123
10.4 Verification procedure .125
10.5 Tests.125

60255-27  IEC:2005 – 5 –
Annex A (normative) Isolation class requirements and example diagrams.151
Annex B (informative) Nominal voltages of supply systems .163
Annex C (normative) Rated impulse voltages.165
Annex D (normative) Guidance for the determination of clearance, creepage distance
and withstand voltages .167
Annex E (informative) Measurement of creepage distances and clearances.189
Annex F (normative) Standard test fingers .201
Annex G (informative) Guidance for impulse voltage test .205
Annex H (informative) Components.209
Annex I (informative) Safe maximum short-term voltage duration and capacitor size
under a single-fault condition .217
Annex J (informative) External wiring terminations.221
Annex K (informative) Examples of battery protection .225
Annex L (informative) Reasons why functional safety is excluded from the scope of
IEC 60255-27 .227

Figure 1 – Flow chart showing requirements for protection against the spread of fire .71
Figure 2 – Baffle .87
Figure 3 – Location and extent of a non-combustible flame barrier.87
Figure A.1 – Equipment with SELV input/output (I/O) .157
Figure D.1 – Guidance for determination of clearances, creepage distances and
withstand voltages .175
Figure F.1 – Rigid test finger.201
Figure F.2 – Jointed test finger .203
Figure G.1 – Impulse voltage test generator assembly schematic diagram.207
Figure I.1 – Maximum duration of short-term temporary accessible voltages under a
single-fault condition.217
Figure I.2 – Charged capacitance level under normal operational use and single-fault
condition.219
Figure K.1 – Non-rechargeable battery protection .225
Figure K.2 – Rechargeable battery protection .225
Figure L.1 – Simplified block diagram showing a protective relay which can actuate a
circuit-breaker to open it, the disconnected live line being subsequently rendered safe
by earthing.231
Figure L.2 – Live lines isolated by isolators mechanically or electro-mechanically
linked to the circuit-breaker, the disconnected live line being subsequently rendered
safe by earthing .231

Table 1 – Current levels in normal operational condition .45
Table 2 – Charge or energy of capacitance levels in normal operational condition .45
Table 3 – Current levels in single-fault condition.65
Table 4 – Maximum temperature in normal operational use and at an ambient
temperature of 40°C .73
Table 5 – Acceptable perforation in the bottom of an equipment case .87

60255-27  IEC:2005 – 7 –
Table 6 – Insulation material of windings .89
Table 7 – Limits of maximum available current.91
Table 8 – Overcurrent protective device.93
Table 9 – Symbols .109
Table 10 – Symbols for marking of test voltage(s).111
Table 11 – Overview of tests.121
Table 12 – Dry-heat test – Operational .125
Table 13 – Cold test – operational .127
Table 14 – Dry heat test, storage temperature .129
Table 15 – Cold test, storage temperature .129
Table 16 – Damp-heat test.131
Table 17 – Cyclic temperature with humidity test .131
Table 18 – Guidance for routine and sample dielectric voltage testing for safety –
informative.141
Table 19 – AC test voltages .143
Table A.1 – Circuit isolation class for product circuits/groups.151
Table A.2 – Insulation requirement between any two circuits .155
Table B.1 – Nominal voltages of a.c. or d.c. supply systems .163
Table C.1 – Rated impulse voltages (waveform: 1,2/50µs) .165
Table D.1 – Functional insulation, pollution degree 1, overvoltage category I.177
Table D.2 – Functional insulation, pollution degree 2, overvoltage category I.179
Table D.3 – Functional, basic or supplementary insulation, pollution degree 1,
overvoltage category II .179
Table D.4 – Functional, basic or supplementary insulation, pollution degree 2,
overvoltage category II .181
Table D.5 – Functional, basic or supplementary insulation, pollution degree 1,
overvoltage category III .181
Table D.6 – Functional, basic or supplementary insulation, pollution degree 2,
overvoltage category III .183
Table D.7 – Double or reinforced insulation, pollution degree 1, overvoltage category II .183
Table D.8 – Double or reinforced insulation, pollution degree 2, overvoltage category II .185
Table D.9 – Double or reinforced insulation, pollution degree 1, overvoltage category III .185
Table D.10 – Double or reinforced insulation, pollution degree 2, overvoltage category III .187
Table D.11 – Test voltage multiplication factor for proving the clearance in air .187
Table D.12 – Reduction of the pollution degree of internal environment through the use
of additional protection within the equipment .187
Table E.1 – Width X of groove as a function of pollution degree.189
Table G.1 – Components of the test generator.205
Table J.1 – Range of conductor sizes to be accepted by terminals.223
Table J.2 – Sizes of terminal studs or screws directly securing supply conductors .223

60255-27  IEC:2005 – 9 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 27: Product safety requirements

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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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 60255-27 has been prepared by IEC technical committee 95:
Measuring relays and protection equipment.
The text of this standard is based on the following documents:
FDIS Report on voting
95/180/FDIS 95/182/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.

60255-27  IEC:2005 – 11 –
IEC 60255 consists of the following parts, under the general title Measuring relays and
protection equipment:
Part 3: Single input energizing quantity measuring relays with dependent or independent
time
Part 5: Insulation coordination for measuring relays and protection equipment –
Requirements and tests
Part 6: Measuring relays and protection equipment
Part 8: Thermal electrical relays
Part 11: Interruptions to and alternating component (ripple) in d.c. auxiliary energizing
quantity of measuring relays
Part 12: Directional relays and power relays with two input energizing quantities
Part 13: Biased (percentage) differential relays
Part 16: Impedance measuring relays
Part 21-1: Vibration, shock, bump and seismic tests on measuring relays and protection
equipment – Section One: Vibration tests (sinusoidal)
Part 21-2: Vibration, shock, bump and seismic tests on measuring relays and protection
equipment – Section Two: Shock and bump tests
Part 21-3: Vibration, shock, bump and seismic tests on measuring relays and protection
equipment – Section 3: Seismic tests
Part 22-1: Electrical disturbance tests for measuring relays and protection equipment –
1 MHz burst immunity tests
Part 22-2: Electrical disturbance tests for measuring relays and protection equipment –
Section 2: Electrostatic discharge tests
Part 22-3: Electrical disturbance tests for measuring relays and protection equipment –
Radiated electromagnetic field disturbance tests
Part 22-4: Electrical disturbance tests for measuring relays and protection equipment –
Electrical fast transient/burst immunity test
Part 22-5: Electrical disturbance tests for measuring relays and protection equipment –
Surge immunity test
Part 22-6: Electrical disturbance tests for measuring relays and protection equipment –
Immunity to conducted disturbances induced by radiofrequency fields
Part 22-7: Electrical disturbance tests for measuring relays and protection equipment –
Power frequency immunity tests
Part 24: Common format for transient data exchange (COMTRADE) for power systems
Part 25: Electromagnetic emission tests for measuring relays and protection equipment
Part 26: Electromagnetic compatibility requirements for measuring relays and protection
equipment
Part 27: Product safety requirements

60255-27  IEC:2005 – 13 –
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.
60255-27  IEC:2005 – 15 –
INTRODUCTION
In order to demonstrate that equipment is safe, it was previously necessary to refer to general
safety standards such as IEC 61010-1 in addition to IEC 60664-1.
These general safety standards specify requirements for general product types or product
families in order to reduce the risk of fire, electric shock or injury to the user. The product
types do not include measuring relays and protection equipment. These standards also take
into account single-fault conditions. This product safety standard takes precedence over
general standards for matters of safety.
Reference to all these various standards created confusion due to conflicting requirements,
for example, different clearances, creepage distances and test voltages etc., for the same
rated voltages.
The aim of this standard is
• to remove confusion due to conflicting requirements between existing standards;
• to achieve a uniform approach throughout the international industry for measuring relays
and protection equipment.
This product safety standard for measuring relays and protection equipment takes the general
standards and IEC 60664-1 as the base, defining those issues specific to measuring relays
and protection equipment, taking into account all the requirements of IEC 60255-5.
The main clause headings of this standard are:
1. Scope
2. Normative references
3. Definitions
4. General safety requirements
5. Protection against electric shock
6. Mechanical aspects
7. Flammability and resistance to fire
8. General and fundamental design requirements for safety
9. Marking, documentation and packaging
10. Type tests and routine tests
A list of the normative and informative tests is provided in Table 11.
The equipment will normally be installed in a restricted access area within a power station,
substation or industrial/retail environment. The environmental conditions specified for the
equipment in the IEC 60255 series of standards apply. The standard considers the normal
conditions of corrosion caused by humidity but does not cover corrosion by atmospheric
pollution.
It is assumed that access to the equipment in normal service is restricted to personnel aware
of working procedures necessary to ensure safety. However, service personnel should be
protected against unexpected hazards.

60255-27  IEC:2005 – 17 –
This standard applies to equipment designed to be safe at least under the following
environmental conditions:
• indoor use;
• altitude up to 2 000 m;
• external operating temperature range, in accordance with IEC 60255-6;
• maximum external relative humidity 93 %, non-condensing;
• supply fluctuations in accordance with IEC 60255-6;
• applicable supply overvoltage category;
• external pollution degree 1 and external pollution degree 2.

60255-27  IEC:2005 – 19 –
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 27: Product safety requirements

1 Scope and object
This International Standard describes the product safety requirements for measuring relays
and protection equipment having a rated a.c. voltage up to 1 000 V with a rated frequency up
to 65 Hz, or a rated d.c. voltage up to 1 500 V. Above these limits, IEC 60664-1 should be
used for the determination of clearance, creepage distance and withstand test voltage.
This standard details essential safety requirements to minimize the risk of fire and hazards
caused by electric shock or injury to the user.
This standard does not cover the safety requirements of installations. It does cover all the
ways in which the equipment may be mounted and used in cubicles, racks and panels, and
also re-testing. This standard also applies to auxiliary devices such as shunts, series
resistors, transformers, etc., solely used and tested together with measuring relays and
protection equipment.
Ancillary equipment used in conjunction with measuring relays and protection equipment may
need to comply with additional safety requirements.
This standard is intended to describe only product safety requirements; therefore, functional
performance of the equipment is not covered.
Functional safety requirements, including EMC functional safety, are not covered by this
standard. Functional safety risk analysis is not within the scope of this product safety
standard.
This standard does not specify individual equipments or implementations of circuits and
components.
The object of this standard is to have a comprehensive standard that covers all aspects of
product safety and the related type and routine tests, for measuring relays and protection
equipment.
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 60068-2-1:1990, Environmental testing − Part 2: Tests – Test A: Cold
IEC 60068-2-2:1974, Environmental testing – Part 2: Tests – Tests B: Dry heat
Amendment 1 (1993)
Amendment 2 (1994)
60255-27  IEC:2005 – 21 –
IEC 60068-2-30:1980, Environmental testing – Part 2: Tests – Test Db and guidance: Damp
heat, cyclic (12 + 12-hour cycle)
IEC 60068-2-78:2001, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,
steady state
IEC 60085: 2004, Electrical insulation – Thermal classification
IEC 60127-1:1988, Miniature fuses – Part 1: Definitions for miniature fuses and general
requirements for miniature fuse-links
IEC 60255-6:1988, Electrical relays – Part 6: Measuring relays and protection equipment
IEC 60255-21-1:1988, Electrical relays – Part 21: Vibration, shock, bump and seismic tests on
measuring relays and protection equipment – Section One: Vibration tests (sinusoidal)
IEC 60255-21-2:1988, Electrical relays – Part 21: Vibration, shock, bump and seismic tests on
measuring relays and protection equipment – Section Two: Shock and bump tests
IEC 60255-21-3:1993, Electrical relays – Part 21: Vibration, shock, bump and seismic tests on
measuring relays and protection equipment – Section 3: Seismic tests
IEC 60255-22-5:2002, Electrical relays – Part 22-5: Electrical disturbance tests for measuring
relays and protection equipment – Surge immunity test
IEC 60352-1:1997, Solderless connections – Part 1: Wrapped connections – General
requirements, test methods and practical guidance
IEC 60352-2:1990, Solderless connections – Part 2: Solderless crimped connections –
General requirements, test methods and practical guidance.
IEC 60417-DB:2005, Graphical symbols for use on equipment
IEC 60529: 1989, Degrees of protection provided by enclosures (IP Code)
Amendment 1 (1999)
IEC 60664-1:1992, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests.
Amendment 1 (2000)
Amendment 2 (2002)
IEC 60664-3:2003, Insulation coordination for equipment within low-voltage systems – Part 3:
Use of coating, potting or moulding for protection against pollution
IEC 60695-2-20:2004, Fire hazard testing – Part 2-20: Glowing/hot-wire based test methods –
Hot-wire coil ignitability – Apparatus, test method and guidance
IEC 60695-11-10:1999, Fire hazard testing – Part 11-10:Test flames, 50 W horizontal and
vertical flame test methods.
Amendment 1 (2003)
___________
“DB” refers to IEC on-line data base.
There exists a consolidated edition 2.1 (2001) that includes edition 2.0 and its amendment 1.
There exists a consolidated edition 1.2 (2002) that includes edition 1.0 and its amendments 1 and 2.

60255-27  IEC:2005 – 23 –
IEC 60825-1:1993, Safety of laser products – Part 1: Equipment class, requirements and
user's guide
Amendment 1 (1997)
Amendment 2 (2001)
IEC 60990:1999, Methods of measurement of touch current and protective conductor current
IEC 61140:2001, Protection against electric shock – Common aspects for installation and
equipment
IEC 61180-1:1992, High-voltage test technique for low-voltage equipment – Part 1:
Definitions, test and procedure requirements.
IEC 61180-2:1994, High-voltage test technique for low-voltage equipment – Part 2: Test
equipment.
IEC 62151:2000, Safety of equipment electrically connected to a telecommunication network
ISO 780:1997, Packaging – Pictorial marking for handling of goods
ISO 7000-DB:2005 , Graphical symbols for use on equipment – Index and synopsis
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE For definitions of general terms not defined in this standard, reference should be made to IEC 60664-1,
1.3, and IEC 60050 (151-448).
3.1
accessible (of a part)
part which can be touched in normal operational use with a standard rigid or jointed test finger
as specified in Annex F
[IEV 442-01-15, modified]
NOTE 1 Accessible in normal operational use applies mainly to the front of the equipment only, for the purposes
of this standard.
NOTE 2 A communication circuit/network, which may be connected and taken outside of the cubicle housing, the
equipment, or on the front of the panel without the need to open a cover or flap to access it, should be considered
to be accessible, i.e. should be PEB, PELV, SELV or equivalent.
3.2
adjacent circuits
electric circuits which are separated from the considered circuit by the necessary basic or
double/reinforced insulation. Circuits which are separated by far more than double or
reinforced insulation are not considered to be adjacent
3.3
ambient temperature
temperature, determined under prescribed conditions, of the air surrounding the complete
equipment
[IEV 441-11-13, modified]
NOTE 1 For equipment installed inside an enclosure, it is the temperature of the air outside the enclosure.
NOTE 2 The ambient temperature is measured at half the distance from any neighbouring equipment, but not
more than 300 mm distance from the equipment case, at middle height of the equipment, protected from direct heat
radiation from the equipment.
___________
There exists a consolidated edition 1.2 (2001) that includes edition 1.0 and its amendments 1 and 2.
“DB” refers to ISO on-line data base.

60255-27  IEC:2005 – 25 –
3.4
barrier
part providing protection against direct contact from any usual direction of access
[IEV 826-12-23]
NOTE Barriers may provide protection against the spread of fire (see Clause 7).
3.5
basic insulation
insulation of hazardous live parts to provide basic protection
[IEV 826-12-14, modified]
NOTE This concept does not apply to insulation used exclusively for functional purposes.
3.6
bounding surface
outer surface of the equipment case, considered as though metal foil were pressed into
contact with accessible surfaces of insulating material
3.7
Class I equipment
equipment with basic insulation as provision for basic protection against electric shock and
protective bonding as provision for fault protection, such that conductive parts on the outside
of the equipment case, cannot become live in the event of a failure of the basic insulation
3.8
Class II equipment
equipment with
• basic insulation as provision for basic protection against electric shock, and
• supplementary insulation as provision for fault protection; or
• in which basic protection and fault protection are provided by reinforced insulation
NOTE There should be no provision for a protective conductor or reliance upon installation conditions for safety
purposes. It is, however, permissible to connect an earth/ground conductor to Class II equipment for functional (for
example, EMC) purposes.
3.9
Class III equipment
equipment, or parts of an equipment, in which protection against electric shock relies upon
supply from SELV or PELV circuits and in which hazardous voltages are not generated
3.10
clearance
shortest distance, measured in air, between two conductive parts, or between a conductive
part and the outer bounding surface of the equipment, whether conductive or not

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3.11
comparative tracking index
(CTI abbreviation)
numerical value of the maximum voltage in volts which a material can withstand without
tracking under specified test conditions
[IEV 212-01-44]
3.12
communication circuit/network
circuit/network for receiving and/or transmitting, digital or analogue signals. It may
communicate with other circuits via optical, magnetic or electromagnetic radiation means, or
metallic connections
3.13
creepage distance
shortest distance along the surface of a solid insulating material between two conductive
parts, or between a conductive part and the b
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