SIST EN IEC 60255-26:2025

SLOVENSKI STANDARD
01-junij-2025
Nadomešča:
SIST EN 60255-26:2014
SIST EN 60255-26:2014/AC:2014
Merilni releji in zaščitna oprema - 26. del: Zahteve za elektromagnetno združljivost
Measuring relays and protection equipment - Part 26: Electromagnetic compatibility
requirements
Messrelais und Schutzeinrichtungen - Teil 26: Anforderungen an die elektromagnetische
Verträglichkeit
Relais de mesure et dispositifs de protection - Partie 26: Exigences de compatibilité
électromagnétique
Ta slovenski standard je istoveten z: EN IEC 60255-26:2025
ICS:
29.120.70 Releji Relays
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60255-26

NORME EUROPÉENNE
EUROPÄISCHE NORM April 2025
ICS 29.120.70 Supersedes EN 60255-26:2013; EN 60255-
26:2013/AC:2013
English Version
Measuring relays and protection equipment - Part 26:
Electromagnetic compatibility requirements
(IEC 60255-26:2023)
Relais de mesure et dispositifs de protection - Partie 26: Messrelais und Schutzeinrichtungen - Teil 26:
Exigences de compatibilité électromagnétique Anforderungen an die elektromagnetische Verträglichkeit
(IEC 60255-26:2023) (IEC 60255-26:2023)
This European Standard was approved by CENELEC on 2024-10-16. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60255-26:2025 E

European foreword
The text of document 95/515/FDIS, future edition 4 of IEC 60255-26, prepared by TC 95 "Measuring
relays and protection equipment" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 60255-26:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-04-30
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-04-30
document have to be withdrawn
This document supersedes EN 60255-26:2013 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60255-26:2023 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 61000-4 series NOTE Approved as EN 61000-4 series
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60255-1 2022 Measuring relays and protection equipment EN IEC 60255-1 2023
- Part 1: Common requirements
IEC 61000-4-2 2008 Electromagnetic compatibility (EMC) - Part EN 61000-4-2 2009
4-2: Testing and measurement techniques
- Electrostatic discharge immunity test
IEC 61000-4-3 2020 Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-3 2020
4-3 : Testing and measurement techniques
- Radiated, radio-frequency,
electromagnetic field immunity test
IEC 61000-4-4 2012 Electromagnetic compatibility (EMC) - Part EN 61000-4-4 2012
4-4: Testing and measurement techniques
- Electrical fast transient/burst immunity
test
IEC 61000-4-5 2014 Electromagnetic compatibility (EMC) - Part EN 61000-4-5 2014
4-5: Testing and measurement techniques
- Surge immunity test
+ A1 2017 + A1 2017
IEC 61000-4-6 2013 Electromagnetic compatibility (EMC) - Part EN 61000-4-6 2014
4-6: Testing and measurement techniques
- Immunity to conducted disturbances,
induced by radio-frequency fields
- - + AC 2015
IEC 61000-4-8 2009 Electromagnetic compatibility (EMC) - Part EN 61000-4-8 2010
4-8: Testing and measurement techniques
- Power frequency magnetic field immunity
test
Publication Year Title EN/HD Year
IEC 61000-4-11 2020 Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-11 2020
4-11: Testing and measurement
techniques - Voltage dips, short
interruptions and voltage variations
immunity tests for equipment with input
current up to 16 A per phase
- - + AC 2020
- - + AC 2022
IEC 61000-4-16 2015 Electromagnetic compatibility (EMC) - Part EN 61000-4-16 2016
4-16: Testing and measurement
techniques - Test for immunity to
conducted, common mode disturbances in
the frequency range 0 Hz to 150 kHz
IEC 61000-4-17 1999 Electromagnetic compatibility (EMC) - Part EN 61000-4-17 1999
4-17: Testing and measurement
techniques - Ripple on d.c. input power
port immunity test
+ A1 2001 + A1 2004
+ A2 2008 + A2 2009
IEC 61000-4-18 2019 Electromagnetic compatibility (EMC) - Part EN IEC 61000-4-18 2019
4-18: Testing and measurement
techniques - Damped oscillatory wave
immunity test
IEC 61000-4-29 2000 Electromagnetic compatibility (EMC) - Part EN 61000-4-29 2000
4-29: Testing and measurement
techniques - Voltage dips, short
interruptions and voltage variations on d.c.
input power port immunity tests
CISPR 11 (mod) 2015 Industrial, scientific and medical equipment EN 55011 2016
- Radio-frequency disturbance
characteristics - Limits and methods of
measurement
+ A1 2016 + A1 2017
- - + A11 2020
+ A2 2019 + A2 2021
CISPR 32 2015 Electromagnetic compatibility of multimedia EN 55032 2015
equipment - Emission requirements
- - + AC 2016-07
+ A1 2019 + A1 2020
- - + A11 2020
IEC 60255-26 ®
Edition 4.0 2023-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measuring relays and protection equipment –

Part 26: Electromagnetic compatibility requirements

Relais de mesure et dispositifs de protection –

Partie 26: Exigences de compatibilité électromagnétique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.120.70 ISBN 978-2-8322-6317-4

– 2 – IEC 60255-26:2023 © IEC 2023
CONTENTS
FOREWORD . 5
1 Scope . 7
1.1 General . 7
1.2 Emission . 7
1.3 Immunity . 7
2 Normative references . 7
3 Terms, definitions, and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 12
4 Electromagnetic environmental levels . 13
4.1 General . 13
4.2 Zone A, severe electromagnetic environment . 13
4.3 Zone B, typical electromagnetic environment . 14
5 Emission. 14
5.1 Radiated emission . 14
5.2 Conducted emission . 15
6 Immunity. 16
6.1 Immunity of enclosure . 16
6.2 Immunity of auxiliary power supply port . 17
6.3 Immunity of signal/control port and wired network port . 20
6.4 Immunity of input and output ports . 21
6.5 Immunity of earth port . 24
7 Test set-up and procedures . 24
7.1 General . 24
7.2 Emission . 25
7.2.1 General . 25
7.2.2 Radiated emission . 26
7.2.3 Conducted emission . 26
7.3 Immunity . 26
7.3.1 General . 26
7.3.2 Electrostatic discharge immunity test . 28
7.3.3 Radiated electromagnetic field immunity test . 29
7.3.4 Electrical fast transient/burst immunity test . 31
7.3.5 Damped oscillatory wave immunity test . 32
7.3.6 Surge immunity test . 33
7.3.7 Conducted RF immunity test . 35
7.3.8 Conducted power frequency immunity test on binary inputs . 37
7.3.9 Power frequency magnetic field immunity test . 38
7.3.10 Voltage dips and short interruptions test (AC or DC) . 38
7.3.11 Ripple on DC input power port immunity test . 39
7.3.12 Gradual shutdown / start-up tests . 40
8 Criteria for acceptance . 40
8.1 Emission . 40
8.2 Immunity . 41
9 Test report . 42
(normative) Power frequency immunity tests on binary inputs . 43

IEC 60255-26:2023 © IEC 2023 – 3 –
A.1 General . 43
A.2 Test classes . 43
A.3 Test equipment . 43
A.3.1 General . 43
A.3.2 Test generator . 43
A.3.3 Verification of the test generator . 44
A.3.4 Coupling networks . 44
A.4 Test set-up . 44
A.4.1 General . 44
A.4.2 Earthing connections . 44
A.4.3 Auxiliary equipment . 44
(informative) Background information for power frequency tests . 47
(informative) Background information about spot frequency tests . 48
(informative) EMC risk assessment . 50
D.1 EMC design risk assessment . 50
D.2 Product platform risk assessment . 52
(informative) Considerations regarding radio interfaces . 54
(informative) Immunity test to be considered in future . 55
Bibliography . 56

Figure 1 – Gradual shutdown / start-up test . 40
Figure A.1 – Example of Zone A differential mode tests . 45
Figure A.2 – Example of Zone B differential mode tests . 45
Figure A.3 – Example of Zone A and Zone B common mode tests . 46

Table 1 – Radiated emission tests – Enclosure port . 14
Table 2 – Required highest frequency for radiated measurement . 15
Table 3 – Conducted emission tests – AC and DC auxiliary power supply port . 15
Table 4 – Conducted emission tests – Wired network port . 15
Table 5 – Immunity tests – Enclosure port . 16
Table 6 – Immunity tests – Auxiliary power supply port . 17
Table 7 – Immunity tests – signal/control port and wired network port . 20
Table 8 – Immunity tests – Input and output port . 21
Table 9 – Immunity tests – Earth port . 24
Table 10 – Radiated emission test . 26
Table 11 – Conducted emission test . 26
Table 12 – Electrostatic discharge immunity test . 28
Table 13 – Radiated electromagnetic field immunity test (frequency sweep) . 29
Table 14 – Radiated electromagnetic field immunity test (spot frequencies) . 30
Table 15 – Electrical fast transient/burst immunity test . 31
Table 16 –Damped oscillatory wave immunity test . 32
Table 17 – Surge immunity test . 33
Table 18 – Conducted RF immunity test (frequency sweep) . 35
Table 19 – Conducted RF immunity test (spot frequencies) . 36
Table 20 – Conducted power frequency immunity test on binary inputs . 37

– 4 – IEC 60255-26:2023 © IEC 2023
Table 21 – Power frequency magnetic field immunity test . 38
Table 22 – Voltage dips and short interruptions test (AC or DC) . 38
Table 23 – Ripple on DC input power port immunity test . 39
Table 24 – Gradual shutdown and start-up test . 40
Table 25 – Acceptance criteria for immunity tests . 41
Table C.1 – Selection of spot frequencies . 48
Table D.1 – Risk assessment based on a hardware design modification . 51
Table D.2 – Risk assessment, selecting representative EUT configuration(s) . 52
Table E.1 – Listed standard with relevance . 54
Table F.1 – Immunity test to be considered in future . 55

IEC 60255-26:2023 © IEC 2023 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 26: Electromagnetic compatibility 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,
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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.
IEC 60255-26 has been prepared by IEC technical committee 95: Measuring relays and
protection equipment. It is an International Standard.
This fourth edition cancels and replaces the third edition published in 2013. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) update of normative references
b) introduction of a wired network port and signal/control port in accordance with CISPR 32;
c) introduction of low-power instrument transformer (LPIT) and battery monitor port;
d) expansion of the frequency range on radiated radio-frequency immunity test up to 6 GHz;
e) updated requirements on electrostatic discharge tests;
f) introduction of fast damped oscillatory wave test for Zone A applications;
g) specification of higher immunity requirements on power frequency magnetic field tests;

– 6 – IEC 60255-26:2023 © IEC 2023
h) update of the spot frequency test and addition of a new annex with background
information;
i) addition of details and further guidance on the relay settings;
j) additional test condition for AC voltage dips and interruptions;
k) addition of an annex about EMC risk assessments;
l) addition of an annex on radio interfaces.
The text of this International Standard is based on the following documents:
Draft Report on voting
95/515/FDIS 95/525/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all the parts in the IEC 60255 series, published 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 document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IEC 60255-26:2023 © IEC 2023 – 7 –
MEASURING RELAYS AND PROTECTION EQUIPMENT –

Part 26: Electromagnetic compatibility requirements

1 Scope
1.1 General
This part of IEC 60255 specifies the requirements for electromagnetic compatibility for
measuring relays and protection equipment. It is applicable to measuring relays and protection
equipment and combinations of devices to form schemes for power system protection including
the control, monitoring, communication and process interface equipment used with those
systems.
Tests specified in this document are not required for equipment not incorporating electronic
circuits, for example electromechanical relays.
The requirements specified in this document are applicable to measuring relays and protection
equipment in a condition representative of how new equipment is provided by the manufacturer.
All tests specified are type tests only.
1.2 Emission
This document specifies limits and test methods, for measuring relays and protection equipment
in relation to electromagnetic emissions which might cause interference in other equipment.
These emission limits represent electromagnetic compatibility requirements and have been
selected to ensure that the disturbances generated by measuring relays and protection
equipment, operated normally in substations and power plants, do not exceed a specified level
which could prevent other equipment from operating as intended.
Test requirements are specified for the enclosure, auxiliary power supply ports, input/output
ports, signal/control ports and wired network ports.
1.3 Immunity
This document specifies the immunity test requirements for measuring relays and protection
equipment in relation to continuous and transient, conducted and radiated disturbances,
including electrostatic discharges.
These test requirements represent the electromagnetic compatibility immunity requirements
and have been selected so as to ensure an adequate level of immunity for measuring relays
and protection equipment, operated normally in substations and power plants.
NOTE 1 Product safety considerations are not covered in this document.
NOTE 2 In special cases, situations will arise where the levels of disturbance could exceed the levels specified in
this document, for example where a hand-held transmitter or a mobile telephone is used close to measuring relays
and protection equipment. In these instances, special precautions and procedures could be needed.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.

– 8 – IEC 60255-26:2023 © IEC 2023
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60255-1:2022, Measuring relays and protection equipment – Part 1: Common requirements
IEC 61000-4-2:2008, Electromagnetic compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test
IEC 61000-4-3:2020, Electromagnetic compatibility (EMC) – Part 4-3: Testing and
measurement techniques – Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-4:2012, Electromagnetic compatibility (EMC) – Part 4-4: Testing and
measurement techniques – Electrical fast transient/burst immunity test
IEC 61000-4-5:2014, Electromagnetic compatibility (EMC) – Part 4-5: Testing and
measurement techniques – Surge immunity test
IEC 61000-4-5:2014/AMD1:2017
IEC 61000-4-6:2013, Electromagnetic compatibility (EMC) – Part 4-6: Testing and
measurement techniques – Immunity to conducted disturbances, induced by radio-frequency
fields
IEC 61000-4-8:2009, Electromagnetic compatibility (EMC) – Part 4-8: Testing and
measurement techniques – Power frequency magnetic field immunity test
IEC 61000-4-11:2020, Electromagnetic compatibility (EMC) – Part 4-11: Testing and
measurement techniques – Voltage dips, short interruptions and voltage variations immunity
tests for equipment with input current up to 16 A per phase
IEC 61000-4-16:2015, Electromagnetic compatibility (EMC) – Part 4-16: Testing and
measurement techniques – Test for immunity to conducted, common mode disturbances in the
frequency range 0 Hz to 150 kHz
IEC 61000-4-17:1999, Electromagnetic compatibility (EMC) – Part 4-17: Testing and
measurement techniques – Ripple on d.c. input power port immunity test
IEC 61000-4-17:1999/AMD1:2001
IEC 61000-4-17:1999/AMD2:2008
IEC 61000-4-18:2019, Electromagnetic compatibility (EMC) – Part 4-18: Testing and
measurement techniques – Damped oscillatory wave immunity test
IEC 61000-4-29:2000, Electromagnetic compatibility (EMC) – Part 4-29: Testing and
measurement techniques – Voltage dips, short interruptions and voltage variations on d.c. input
power port immunity tests
CISPR 11:2015, Industrial, scientific and medical equipment – Radio-frequency disturbance
characteristics – Limits and methods of measurement
CISPR 11:2015/AMD1:2016
CISPR 11:2015/AMD2:2019
CISPR 32:2015, Electromagnetic compatibility of multimedia equipment – Emission
requirements
CISPR 32:2015/AMD1:2019
IEC 60255-26:2023 © IEC 2023 – 9 –
3 Terms, definitions, and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
analogue output port
port that generates an analogue output signal to drive actuators, analogue panel meters, etc.
Note 1 to entry: Typically a current or voltage less than or equal to 20 mA or 10 V DC respectively.
[SOURCE: IEC 60255-1:2022, 3.1.3]
3.1.2
auxiliary equipment
AE
equipment necessary to provide the equipment under test (EUT) with the signals required for
normal operation and to verify the performance of the EUT
3.1.3
auxiliary power supply port
AC or DC auxiliary energizing input
Note 1 to entry: Some modern relays have a single auxiliary power supply port that can be energized with both AC
and/or DC.
3.1.4
battery monitor port
port intended for connection to the station battery for the purpose of battery voltage monitoring
[SOURCE: IEC 60255-1:2022, 3.1.6]
3.1.5
binary input port
port intended for inputs which have an on or off state given by direct connection to an energizing
quantity without any communications protocol
[SOURCE: IEC 60255-1:2022, 3.1.7]
3.1.6
binary output port
port intended for outputs which have an on or off state given by direct connection to an
energizing quantity without any communications protocol
[SOURCE: IEC 60255-1:2022, 3.1.8]
3.1.7
common mode
CM
mode between each active conductor and a specified reference, usually earth or ground
reference plane
– 10 – IEC 60255-26:2023 © IEC 2023
3.1.8
cabinet
free-standing and self-supporting enclosure for housing electrical and/or electronic equipment
Note 1 to entry: A cabinet is usually fitted with doors and/or side panels, which may or may not be removable.
[SOURCE: IEC 60050-581:2008, 581-25-02]
3.1.9
coupling network
electrical circuit or device for the purpose of transferring energy from one circuit to another with
a defined impedance
3.1.10
coupling/decoupling network
CDN
electrical circuit incorporating the functions of both the coupling and decoupling networks
3.1.11
decoupling network
electrical circuit for the purpose of preventing test voltages applied to the EUT from affecting
other devices, equipment, or systems which are not under test
3.1.12
differential mode
DM
mode between any two of a specified set of active conductors
3.1.13
earth port
point where a cable intended for connection to earth for functional or safety purposes can be
connected
3.1.14
enclosure port
physical boundary of the EUT through which electromagnetic fields can radiate or impinge
[SOURCE: IEC 60050-445:2010, 445-07-04, modified – The term "time relay" has been
replaced by "EUT" and "can" has been replaced by "may".]
3.1.15
equipment under test
EUT
equipment submitted to a test, including any accessories such as communication modules,
plug-in power supplies, etc. unless otherwise specified
[SOURCE: IEC 60255-1:2022, 3.1.15]
3.1.16
highest internal frequency
F
X
highest fundamental frequency generated or used within the EUT or highest frequency at which
it operates
Note 1 to entry: This includes frequencies which are solely used within an integrated circuit.

IEC 60255-26:2023 © IEC 2023 – 11 –
3.1.17
input port
port through which the EUT is energized or controlled in order to perform its function(s)
EXAMPLE 1 Analogue current transformer (LPCT/CT) input, analogue voltage transformer (LPVT or VT) input,
binary input, battery monitor input, etc.
[SOURCE: IEC 60255-1:2022, 3.1.18]
3.1.18
low-power instrument transformer
LPIT
arrangement, consisting of one or more current or voltage transformer(s) which may be
connected to transmitting systems and secondary converters, all intended to transmit a
low-power analogue or digital output signal to measuring instruments, meters and protective or
control devices or similar apparatus
EXAMPLE An arrangement consisting of three current sensors, three voltage sensors connected to one merging
unit delivering one digital output is considered an LPIT.
Note 1 to entry: LPITs are commonly called non-conventional instrument transformers (NCIT).
Note 2 to entry: The output power produced by these devices is typically lower or equal to 1 VA.
[SOURCE: IEC 61869-6:2016, 3.1.601]
3.1.19
low-power current transformer
LPCT
low-power instrument transformer for current measurement
[SOURCE: IEC 61869-6:2016, 3.1.602]
3.1.20
low-power voltage transformer
LPVT
low-power instrument transformer for voltage measurement
[SOURCE: IEC 61869-6:2016, 3.1.603]
3.1.21
output contact
arrangement of contact members, with their insulation, which close or open their contact circuit
by their relative movement
[SOURCE: IEC 60050-444:2002, 444-04-03, modified – The term "contact" has been replaced
by "output contact", the domain "for elementary relays" and the figure have been omitted.]
3.1.22
output port
port through which the EUT produces predetermined changes
[SOURCE: IEC 60255-1:2022, 3.1.27]
3.1.23
port
particular interface of the specified EUT with the external electromagnetic environment

– 12 – IEC 60255-26:2023 © IEC 2023

3.1.24
rated value
value of a quantity used for specification purposes, established for a specified set of operating
conditions of a component, device, equipment, or system
[SOURCE: IEC 60050-447:2020, 447-03-11]
3.1.25
signal/control port
port intended for the interconnection of components of an EUT, or between an EUT and local
AE and used in accordance with relevant functional specifications (for example, for the
maximum length of cable connected to it)
Note 1 to entry: Examples include EIA-232, Universal Serial Bus (USB), High-Definition Multimedia Interface ®
), IEEE Standard 1394 ("FireWire"), IRIG-B Interface.
(HDMI
3.1.26
small equipment
equipment, either positioned on a tabletop or standing on the floor which, including its cables,
fits in a cylindrical test volume of 1,2 m in diameter and 1,5 m above the ground plane
Note 1 to entry: For small equipment, emission testing at distances under 10 m is accepted.
3.1.27
wired network port
port for the connection of voice, data and signalling transfers intended to interconnect widely
dispersed systems by direct connection to a single-user or multi-user communication network
Note 1 to entry: Examples of these ports include CATV, PSTN, ISDN, xDSL, LAN, EIA-485 and similar networks.
Note 2 to entry: These ports may support screened or unscreened cables and may also carry AC or DC power (e.g.
PoE) where this is an integral part of the telecommunication specification.
Note 3 to entry: A port generally intended for interconnection of components of a system under test (e.g. EIA-232,
IEEE Standard 1284 (parallel printer), Universal Serial Bus (USB), IEEE Standard 1394 ("Fire Wire"), etc.) and used
in accordance with its functional specifications (e.g. for the maximum length of cable connected to it), is not
considered to be a wired network port.
3.2 Abbreviated terms
AAN Asymmetric artificial network
AE Auxiliary equipment
AMN Artificial mains network
CATV Communal (broadcasting) antenna/cable TV network
CDN Coupling/decoupling network
CCC Capacitive coupling clamp
CM Common mode
CVP Capacitive voltage probe
DM Differential mode
IEC 60255-26:2023 © IEC 2023 – 13 –
EMC Electromagnetic compatibility
ESD Electrostatic discharge
EUT Equipment under test
FW Firmware
HW Hardware
IED Intelligent electronic device
ISDN Integrated services digital network
LAN Local area network
LPCT Low-power current transformer
LPIT Low-power instrument transformer
LPVT Low-power voltage transformer
PCBA Printed circuit board assembly
PCB Printed circuit board
PSTN Public switched telephone network
RF Radio frequency
RTD Resistance temperature detector
UFA Uniform field area
USB Universal serial bus
xDSL Generic term for all types of DSL (digital subscriber line) technology
4 Electromagnetic environmental levels
4.1 General
The environmental levels shall be selected in accordance with the most realistic installation and
environmental conditions in which the EUT is expected to operate.
Based on common installation practices, the recommended selection of test levels is given in
4.2 and 4.3.
4.2 Zone A, severe electromagnetic environment
The installation is characterized by the following attributes:
• no suppression of electrical fast transients/bursts in the power supply and control and power
circuits which are switched by relays and high-power contactors;
• no separation of the industrial circuits from other circuits associated with environments of
higher severity levels;
• no separation between power supply, control, signal and communication cables;
• use of common multi-core cables for control and signal lines;
• interconnections that are running as outdoor cables along with power cables, even to the
high voltage equipment; a special case of this environment is when the electronic equipment
is connected to the telecommunication network within a densely populated area. There is
no systematically constructed grounding network outside the electronic equipment, and the
grounding system consists only of pipes, cables, etc.
The outdoor area of industrial process equipment, power stations, open-air HV substation
switchyards and gas insulated switchgear may be representative of this environment.

– 14 – IEC 60255-26:2023 © IEC 2023
4.3 Zone B, typical electromagnetic environment
The installation is characterized by the following attributes:
• no suppression of electrical fast transients/bursts in the power supply and control circuits
which are switched by relays;
• poor separation of the industrial circuits from other circuits associated with environments of
higher severity levels;
• dedicated cables for power supply, control, signal and communication lines;
• poor separation between power supply, control, signal and communication cables;
• the interconnection cables can be partly outdoor cables, but close to the grounding network;
• availability of earthing system represented by conductive pipes, ground conductors in the
cable trays (connected to the protective earth system) and by a ground mesh.
The area of industrial process equipment, power plants and the relay room of open-air HV
substations may be representative of this environment.
Measuring relays and protection equipment shall meet Class A emission limits for both
environmental conditions (Zone A and Zone B).
5 Emission
5.1 Radiated emission
Table 1 – Radiated emission tests – Enclosure port
Reference Test
standard procedure
Environmental
Item Frequency range Limits (reference to
phenomena
this
document)
40 dB (µV/m) quasi-peak
at 10 m
30 MHz to 230 MHz
50 dB (µV/m) quasi-peak
Radiated
at 3 m
emission
1.1 CISPR 11 See 7.2.2
a
47 dB (µV/m) quasi-peak
(below 1 GHz)
at 10 m
230 MHz to 1 000 MHz
57 dB (µV/m) quasi-peak
at 3 m
56 dB (µV/m) average
at 3 m
1 GHz to 3 GHz
76 dB (µV/m) peak
Radiated
at 3 m
1.2 emission CISPR 32 See 7.2.2
60 dB (µV/m) average
(above 1 GHz)
at 3 m
3 GHz to 6 GHz
80 dB (µV/m) peak
at 3 m
a
Measuring relays and protection equipment are apparatus which satisfy the class A limits. Limits can be
measured at a nominal distance of 3 m or 10 m or 30 m. A measuring distance less than 10 m is allowed only
for equipment which complie
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