IEC 60255-1:2009

IEC 60255-1 ®
Edition 1.0 2009-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measuring relays and protection equipment –
Part 1: Common requirements
Relais de mesure et dispositifs de protection –
Partie 1: Exigences communes
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It also gives information on projects, withdrawn and replaced publications.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 60255-1 ®
Edition 1.0 2009-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Measuring relays and protection equipment –
Part 1: Common requirements
Relais de mesure et dispositifs de protection –
Partie 1: Exigences communes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 29.120.70 ISBN 978-2-88910-074-3
– 2 – 60255-1 © IEC:2009
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.9
2 Normative references .9
3 Terms and definitions .11
4 Environmental conditions.13
4.1 General .13
4.2 Normal environmental conditions.13
4.3 Special environmental conditions .14
4.4 Storage conditions .15
5 Ratings.15
5.1 General .15
5.2 Rated voltage.15
5.2.1 Input energizing voltage .15
5.2.2 Auxiliary energizing voltage .16
5.2.3 Rated insulation voltage .16
5.3 Rated current .16
5.3.1 Input energizing current.16
5.3.2 Auxiliary energizing current .17
5.4 Binary input and output .17
5.4.1 Binary input .17
5.4.2 Binary output .17
5.5 Transducer analogue input and output.17
5.5.1 Transducer analogue input .17
5.5.2 Transducer analogue output .17
5.6 Frequency .17
5.6.1 Rated frequency .17
5.6.2 Frequency operating range.17
5.7 Rated burden .17
5.8 Rated ambient temperature .17
6 Design and construction .18
6.1 Marking .18
6.2 Dimensions .18
6.3 Enclosure protection.18
6.4 Product safety requirements.18
6.5 Functional performance requirements.18
6.5.1 General .18
6.5.2 Intrinsic accuracy .18
6.5.3 Operating accuracy .19
6.5.4 Performance under dynamic system conditions .19
6.5.5 Performance under transient signal conditions.19
6.5.6 Multifunctional protection relay .19
6.5.7 Programmable logic.20
6.6 Communication protocols .20
6.7 Binary input and output .20

60255-1 © IEC:2009 – 3 –
6.7.1 Binary input .20
6.7.2 Binary output .20
6.8 Transducer analogue input and output.20
6.8.1 Transducer analogue input .20
6.8.2 Transducer analogue output .20
6.9 Input circuit for energizing quantities .20
6.9.1 Characteristic energizing quantity.20
6.9.2 Auxiliary energizing quantity.21
6.10 Burden tests.21
6.10.1 Burden for voltage transformers .21
6.10.2 Burden for current transformers.21
6.10.3 Burden for AC power supply .21
6.10.4 Burden for DC power supply.21
6.10.5 Burden for binary input .22
6.11 Contact performance .22
6.12 Climatic performance .23
6.12.1 General .23
6.12.2 Verification procedure.23
6.12.3 Climatic environmental tests.25
6.13 Mechanical requirements.31
6.13.1 Vibration response and endurance (sinusoidal) .31
6.13.2 Shock response, shock withstand and bump.31
6.13.3 Seismic .32
6.14 Pollution.32
6.15 Electromagnetic compatibility (EMC) .32
7 Tests .32
7.1 General .32
7.2 Test reference conditions .32
7.3 Test overview.33
7.4 Type test report content .34
8 Marking, labelling and packaging.35
9 Rules for transport, storage, installation, operation and maintenance .35
10 Product documentation.35
Annex A (informative) Type testing guidelines.37
Annex B (informative) Intrinsic, operating and overall system accuracy.40
Annex C (informative) Guidance on dependability.42
Bibliography.45

Figure 1 – Contact performance parameters .23
Figure A.1 – Definition of operate, transitional and quiescent states .38
Figure B.1 – Different kind of accuracies.40
Figure C.1 – Overview of fields that may be of interest for protection relays .42
Figure C.2 – Failure detection chart .43

Table 1 – Normal environmental conditions.14

– 4 – 60255-1 © IEC:2009
Table 2 – Special environmental conditions .15
Table 3 – Dry heat test – operational .25
Table 4 – Cold test – Operational.26
Table 5 – Dry heat test, storage temperature .27
Table 6 – Cold test, storage temperature .28
Table 7 – Cyclic temperature test.29
Table 8 – Damp heat steady state test .30
Table 9 – Cyclic temperature with humidity test .31
Table 10 – Test reference conditions .32
Table 11 – Test overview .34
Table A.1 – Example of protection functions that may be used during tests .38
Table A.2 – Example of EMC test conditions for measuring inputs .39
Table C.1 – Definitions of symbols.43
Table C.2 – Meaning of terms defined in IEC 60050-191 for protection relays.43

60255-1 © IEC:2009 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 1: Common 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 60255-1 has been prepared by IEC technical committee 95:
Measuring relays and protection equipment.
This standard cancels and replaces the second edition of IEC 60255-6, published in 1988,
and constites a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
95/252FDIS 95/257/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.

– 6 – 60255-1 © IEC:2009
A list of all the parts in the IEC 60255 series, under the general title Measuring relays and
protection equipment, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

60255-1 © IEC:2009 – 7 –
INTRODUCTION
NUMBERING OF STANDARDS FALLING UNDER THE RESPONSIBILITY OF TC 95
In accordance with the decision taken at the technical committee 95 meeting in Paris on
2006-04-06 (item 12 of 95/191/RM) a new numbering system will be established of the
standards falling under the responsibility of TC 95. Numbering of the standards will follow the
following principle:
 common standards will start with IEC 60255 –;
 protection functional standards will start with IEC 60255-100 series;
 technical reports will start with IEC 60255-200 series.
The IEC 60255 series will consist of the following parts, under the general title Measuring
relays and protection equipment. Five parts (Parts 3, 8, 12, 13 and 16) will be renumbered
and Part 6 will be replaced by Part 1.
a) Common standards:
Part 1: Common requirements
Part 11: Interruptions to and alternating component (ripple) in d.c. auxiliary energizing
quantity of measuring relays
Part 21: Vibration, shock, bump and seismic tests
Part 22: Electrical disturbance tests
Part 24: Common format for transient data exchange (COMTRADE) for power systems
Part 25: Electromagnetic emission tests
Part 26: Electromagnetic compatibility requirements
Part 27: Product safety requirements

b) Protection functional standards:
121 Functional requirements for distance protection (revision of IEC 60255-16)
124 Functional requirements for volts per hertz protection
125 Functional requirements for synchronizing or synchronism-check
127 Functional requirements for over/under voltage protection (revision of IEC 60255-3)
(including the phase, neutral, residual and negative sequence)
132 Functional requirements for over/under power protection (revision of IEC 60255-12)
(including the real reactive and power factor)
140 Functional requirements for loss of excitation protection
149 Functional requirements for thermal protection (revision of IEC 60255-8)
151 Functional requirements for over/under current protection (revision of IEC 60255-3)
(including the phase, ground, residual and negative sequence)
160 Functional requirements for voltage or current unbalance protection
167 Functional requirements for directional current protection
178 Functional requirements for power swing/out-of-step protection
179 Functional requirements for reclosing
181 Functional requirements for frequency relay (including over/under, rate of change)

– 8 – 60255-1 © IEC:2009
185 Functional requirements for teleprotection function
187 Functional requirements for differential protection (revision of IEC 60255-13)
(including generator, transformer, busbar, line and restricted earth fault)
195 Functional requirements for synchrophasor measurement
NOTE 1 The functional standard for synchrophasor measurement may be developed from IEEE Std C37.118:1995
[1] .
NOTE 2 The last two digits of the part of the proposed functional standard new numbering correspond to device
function numbers as established in IEEE Std C37.2:1996[2].

c) Technical reports:
Part 200: Application guide for generator protection
Part 201: Application guide for motor protection
Part 202: Application guide for transformer protection
Part 203: Application guide for reactor protection
Part 204: Application guide for bus protection
Part 205: Application guide for line protection
Part 206: Application guide for breaker failure protection

—————————
Figures in square brackets refer to the bibliography.

60255-1 © IEC:2009 – 9 –
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 1: Common requirements
1 Scope
This part of IEC 60255 specifies common rules and requirements applicable to measuring
relays and protection equipment including any combination of devices to form schemes for
power system protection such as control, monitoring and process interface equipment in order
to obtain uniformity of requirements and tests.
All measuring relays and protection equipment used for protection within the power system
environment are covered by this standard. Other standards in this series may define their own
requirements which in such cases shall take precedence.
For special applications (marine, aerospace, explosive atmospheres, computers, etc.), the
general requirements within this standard may need to be enhanced by additional special
requirements.
The requirements are applicable only to relays in new condition. All tests in this standard are
type tests, unless otherwise declared.
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 60044-1:1996, Instrument transformers – Part 1: Current transformers
IEC 60044-2:1997, Instrument transformers – Part 2: Inductive voltage transformers
IEC 60044-5:2004, Instrument transformers – Part 5: Capacitor voltage transformers
IEC 60044-7:1999, Instrument transformers – Part 7: Electronic voltage transformers
IEC 60044-8:2002, Instrument transformers – Part 8: Electronic current transformers
IEC 60050-191:1990, Internation Electrotechnical Vocabulary – Chapter 191: Dependability
and quality of service
IEC 60050-447:2009, International Electrotechnical Vocabulary – Part 447: Measuring relays
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
– 10 – 60255-1 © IEC:2009
IEC 60068-2-30:2005, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic
(12 h + 12 h cycle)
IEC 60068-2-78:2001, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,
steady state
IEC 60068-3-4:2001, Environmental testing – Part 3-4: Supporting documentation and
guidance – Damp heat tests
IEC 60255-11:2008, Measuring relays and protection equipment – Part 11: Voltage dips, short
interruptions, variations and ripple on auxiliary power supply port
IEC 60255-21-1:1988, Electrical relays – Part 21-1: Vibration, shock, bump and seismic tests
on measuring relays and protection equipment – Vibration tests (sinusoidal)
IEC 60255-21-2:1988, Electrical relays – Part 21-2: Vibration, shock, bump and seismic tests
on measuring relays and protection equipment – Shock and bump tests
IEC 60255-21-3:1993, Electrical relays – Part 21-3: Vibration, shock, bump and seismic tests
on measuring relays and protection equipment – Seismic tests
IEC 60255-22-2:2008, Measuring relays and protection equipment – Part 22-2: Electrical
disturbance tests – Electrostatic discharge tests
IEC 60255-22-4:2008, Measuring relays and protection equipment – Part 22-4: Electrical
disturbance tests – Electrical fast transient/burst immunity test
IEC 60255-22-5:2008, Measuring relays and protection equipment – Part 22-5: Electrical
disturbance tests – Surge immunity test
IEC 60255-22-7:2003, Electrical relays – Part 22-7: Electrical disturbance tests for measuring
relays and protection equipment – Power frequency immunity tests
IEC 60255-25:2000, Electrical relays – Part 25: Electromagnetic emission tests for measuring
relays and protection equipment
IEC 60255-26:2008, Measuring relays and protection equipment – Part 26: Electromagnetic
compatibility requirements
IEC 60255-27:2005, Measuring relays and protection equipment – Part 27: Product safety
equipment
IEC 60255-100 (all parts), Measuring relays and protection equipment – Parts 1XX: Protection
functional standards
IEC 60297-3-101:2004, Mechanical structures for electronic equipment – Dimensions of
mechanical structures of the 482,6 mm (19 in) series – Part 3-101: Subracks and associated
plug-in units
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)
IEC 60688, Electrical measuring transducers for converting a.c. electrical quantities to
analogue or digital signals
60255-1 © IEC:2009 – 11 –
IEC 60721-3-3, Classification of environmental conditions – Part 3-3: Classification of groups
of environmental parameters and their severities – Stationary use at weather-protected
locations
IEC/TR 61000-2-5:1995, Electromagnetic compatability (EMC) – Part 2: Environment –
Section 5: Classification of electromagnetic environments – Basic EMC publication
IEC 61810-1, Electromechanical elementary relays – Part 1: General requirements
IEC 61810-2, Electromechanical elementary relays – Part 2: Reliability
IEC 61850 (all parts), Communication networks and systems in substations
IEC 61850-9-2, Communication networks and systems in substations – Part 9-2: Specific
Communication Service Mapping (SCSM) – Sampled values over ISO/IEC 8802-3
3 Terms and definitions
For the purposes of this document, the terms and definitions of IEC 60050-447, as well as the
following, apply.
3.1
absolute error
difference between a measured operate value of the characteristic quantity or a measured
value of a specific time and its declared value (e.g. setting value).
3.2
alternating component
in d.c. expressed as a percentage of the difference between the maximum value U and the
max
minimum value U of a pulsating d.c. voltage to the mean value U of this voltage
min 0
U − U
max min
×100%
U
3.3
analogue inputs and outputs
current or voltage inputs/outputs whose values are directly proportional to physical measured
quantities i.e. transducer input
3.4
assigned error
error limits within which the manufacturer declares that any device of a given type will perform
under the reference conditions
3.5
binary inputs/outputs
inputs/outputs which have either an on or off state and can be either physical connections or
supplied via a communication port
3.6
dynamic performance
characteristics defining the ability of the relay to achieve the intended functions under fault
conditions (for example single phase to earth fault) and/or abnormal system conditions which
occur at the power system frequency (for example: power swings, harmonics, etc.)

– 12 – 60255-1 © IEC:2009
3.7
equipment
single apparatus or set of devices or apparatuses, or a set of main devices of an installation,
or all devices necessary to perform a specific task
NOTE 1 Examples of equipment are a power transformer, the equipment of a substation, measuring equipment.
NOTE 2 For the purpose of this standard, equipment is a measuring relay and protection equipment.
3.8
equipment under test
EUT
equipment submitted to a test, including any accessories, unless otherwise specified
3.9
influence quantity
quantity not essential for the performance of a device but affecting its performance, e.g,
temperature, humidity, etc.
3.10
integrated protection relay
single apparatus taking a range of input measurements and performing a multitude of
protection functions on these measurements
3.11
intrinsic accuracy
quality which characterizes the ability of the device, when used under reference conditions, to
operate at values close to the true operating values of input energizing quantities and at times
close to the time setting values or to the absolute declared operating times
NOTE 1 See Annex B for additional information.
NOTE 2 Intrinsic accuracy depends only on uncertainty associated with the components of a measuring relay and
protection equipment under reference conditions.
NOTE 3 Accuracy is all the better when the operate value is closer to the corresponding true value and time
closer to time setting values or to the absolute declared time.
3.12
mean value of measurements
quotient of the algebraic sum of the measurements values by the number of measurements
NOTE Mean value may be expressed as an absolute value, a relative value or a percentage of its setting value.
3.13
normal use
use of the device installed and operated under normal service conditions, with all covers and
protective measures in place
3.14
operating accuracy
quality which characterizes the ability of the device, when submitted to influence quantities
within their tolerance ranges, to operate at values close to the true operating values of input
energizing quantities and at times close to the time setting values or to the absolute declared
operating times
NOTE 1 See Annex B for additional information.
NOTE 2 Operating accuracy of measuring relay and protection equipment depends on intrinsic accuracy and
uncertainty associated with the variation of performance of components due to influence quantities.

60255-1 © IEC:2009 – 13 –
NOTE 3 Accuracy increases (or it is higher) when the operate value is closer to the corresponding true value and
time closer to time setting values or to the absolute declared time.
3.15
overall system accuracy
accuracy of a protection system, considering intrinsic accuracy and operating accuracy of the
device, to which is added uncertainties and variations due to external sensors accuracy and
to external wires
NOTE See Annex B for additional information.
3.16
primary relay
measuring relay directly energized by the current or voltage in a main circuit, without any
intermediate instrument transformer, shunt or transducer or with a built-in instrument
transformer
3.17
product family
range of products based on a common hardware and/or software platform
3.18
routine test
conformity test made on each individual device during or after manufacture
3.19
secondary relay
measuring relay energized by the quantity (e.g. electric current or voltage) derived from an
instrument transformer or transducer
3.20
shunt relay
measuring relay energized by the current derived from a shunt in a main circuit
3.21
transient response
reaction of the device under transient system conditions which do not occur at the power
system frequency (for example magnetizing inrush, capacitive voltage transformer transients,
etc.).
3.22
type test
test of one or more devices made to a given design, to check if these devices comply with the
requirements of the standard concerned.
4 Environmental conditions
4.1 General
This clause specifies environmental conditions for weather-protected equipment during
stationary use, maintenance and repair.
4.2 Normal environmental conditions
Measuring relays and protection equipment are intended to be used in the normal service
conditions listed in Table 1.
– 14 – 60255-1 © IEC:2009
Table 1 – Normal environmental conditions
Environmental parameters Conditions

a
Upper limit ≤ +55 °C
Ambient air temperature
e
Lower limit ≥ –10 °C
Solar radiations Negligible
Altitude ≤ 2 000 m
Air pollution by dust, salt, smoke, corrosive/flammable gas,
b
No significant air pollution
vapours
c
Relative humidity: 24 h average From 5 % to 95 %
According to IEC 60255-21 series
Vibration, earth tremors
environment Class 0 or Class 1
Electromagnetic environment defined by
Electromagnetic disturbances immunity test levels of IEC 60255-26,

d
Class B
a
The ambient air temperature is the maximum or minimum temperature around the enclosure of the
protection relay. Depending on the type of climate and the type of weather-protected location where a
measuring relay and protection equipment is mounted, temperature limits may be more or less severe.
Consequently, the equipment should be capable of operating under one of the preferred standard
temperature ranges listed in 5.8.
b
These conditions correspond to maximum values given for classes 3C1 and 3S1 in IEC 60721-3-3.
c
No condensation or ice is considered.
d
This is in line with basic standard IEC/TR 61000-2-5, classification of electronic environments, for a
location class type 5 listing attributes for a heavy industrial location, a generating station or a switch-
yard.
e
Display may become dark or un-readable at low temperature; however, this condition does not affect the
proper operation of the protection or other functions.

4.3 Special environmental conditions
When equipment is used under conditions different from the normal environmental conditions
given in Table 1, the user shall refer to Table 2. In this case, there shall be an agreement
between the manufacturer and the user.

60255-1 © IEC:2009 – 15 –
Table 2 – Special environmental conditions
Environmental parameters Conditions

a
Ambient air temperature Upper limit > +55 °C

g
Lower limit < –10 °C
b
Altitude > 2 000 m
Location in urban areas with industrial
Air pollution by dust, salt, smoke, corrosive/flammable
activities and without special precautions to
gas, vapours
c
minimize the presence of sand or dust

d
Relative humidity: 24 h average > 95 %
According to IEC 60255-21 series
Vibration, seismic conditions
e
environment, Class 2
Electromagnetic environment defined by
Electromagnetic disturbances
f
immunity test levels of IEC 60255-26
a
The ambient air temperature is the maximum or minimum temperature around the enclosure of the
protection relay.
b
For altitudes higher than 2 000 m users shall refer to IEC 60664-1.

c
These conditions correspond to maximum values given for classes 3C2 and 3S2 in IEC 60721-3-3.

d
In Tropical indoor conditions, the average value of relative humidity measured during a period of 24 h
can be 98 %.
e
This severity class concerns measuring relays and protection equipment for which a very high margin
of security in service is required, or where the seismic shock level is very high.

f
Special environmental conditions for electromagnetic disturbances imply that the measuring relay and
protection equipment is submitted to severity class A of IEC 60255-22-4, suitable for typical industrial
environment, and/or to severity class A of IEC 60255-22-7. Applicable to substations with high earth
fault currents and where wiring practice allows the d.c. status inputs to be wired in open loops (go
and return wire in different multicore cable).

g
Display may become dark or un-readable at low temperature; however, this condition does not affect
the proper operation of the protection or other functions.

4.4 Storage conditions
Measuring relays and protection equipment are intended to be stored in their supplied
packaging. The temperature range of storage shall be chosen from the ranges given in 5.8
and stated by the manufacturer.
5 Ratings
5.1 General
The rated values listed below are preferred values for specification purposes. Other values
may be adopted according to conditions of operation and use.
5.2 Rated voltage
5.2.1 Input energizing voltage
5.2.1.1 Primary relay
Manufacturer shall declare rated values for a.c. or d.c.

– 16 – 60255-1 © IEC:2009
5.2.1.2 Secondary relay
The preferred rated values of a.c. voltages, in r.m.s. value, are in line with IEC 60044-2 and
IEC 60044-5 and are given below, together with those values multiplied by 1/3 or 3 or 1/ 3.
100 V; 110 V; 115 V; 120 V; 200 V; 220 V; 230 V
For equipment compatible with electronic voltage transformers (e.g. low power analogue VT),
the preferred values shall be those stated in IEC 60044-7.
5.2.1.3 Shunt relay
The preferred rated values of d.c. voltages are given below:
30 mV; 45 mV; 50 mV; 60 mV; 75 mV; 100 mV; 150 mV; 200 mV; 300 mV; 600 mV.
5.2.2 Auxiliary energizing voltage
5.2.2.1 AC voltage
The preferred rated values of a.c. voltages, in r.m.s value, are given below, together with
those values multiplied by 3 or 1/ 3:
100 V; 110 V; 115 V; 120 V; 200 V; 230 V
5.2.2.2 DC voltage
The preferred rated values of d.c. voltages are given below:
12 V; 24 V; 48 V; 60 V; 110 V; 125 V; 220 V; 250 V.
5.2.2.3 Operating range
The preferred operating range is 80 % to 110 % of the rated voltage.
5.2.3 Rated insulation voltage
The rated insulation voltage of one or all of the circuits of the equipment shall be chosen from
the values stated in IEC 60255-27.
5.3 Rated current
5.3.1 Input energizing current
5.3.1.1 Primary relay
Manufacturer shall declare rated values for a.c. or d.c. currents.
5.3.1.2 Secondary relay
The preferred rated values of a.c. currents, in r.m.s value, are in line with IEC 60044-1 and
are 1 A or 5 A.
For equipment compatible with electronic current transformers (e.g. low power analogue CT),
the preferred values shall be those stated in IEC 60044-8.

60255-1 © IEC:2009 – 17 –
5.3.2 Auxiliary energizing current
The manufacturer shall declare rated values for a.c. currents.
5.4 Binary input and output
5.4.1 Binary input
The manufacturer shall declare the ratings.
5.4.2 Binary output
The manufacturer shall declare the ratings.
5.5 Transducer analogue input and output
5.5.1 Transducer analogue input
The manufacturer shall declare the ratings.
5.5.2 Transducer analogue output
The manufacturer shall declare the ratings.
5.6 Frequency
5.6.1 Rated frequency
The standard values of the rated frequency are as follows:
16,7 Hz; 50 Hz; 60 Hz.
5.6.2 Frequency operating range
The preferred frequency operating range of the equipment shall be specified according to one
of the following ranges:
–5 % to +5 %; –5 % to +10 %; –10 % to +5 % or –10 % to +10 % of the rated frequency.
For protection equipment designed to operate over a wide frequency range, e.g. generator
protection then this frequency range shall be specified.
5.7 Rated burden
The burden for the voltage transformers, current transformers (at rated quantity), power
supply (a.c. including power factor/d.c.) at quiescent state and maximum load and for other
energized circuits shall be specified.
The maximum start-up inrush current of the power supply circuits shall also be stated.
5.8 Rated ambient temperature
Unless otherwise stated, the preferred rated ambi
...