SIST EN IEC 62271-208:2026

SLOVENSKI STANDARD
01-april-2026
Nadomešča:
SIST-TP CLC/TR 62271-208:2010
Visokonapetostne stikalne in krmilne naprave - 208. del: Metode za kvantifikacijo
elektromagnetnih polj v ustaljenem stanju z močjo in frekvenco, ki jih generirajo
visokonapetostne VN omrežne stikalne naprave in VN/NN montažne postaje, tako
za nazivno napetost nad 1 kV kot do vključno 52 kV (IEC 62271-208:2025)
High-voltage switchgear and controlgear - Part 208: Methods to quantify the steady
state, power-frequency electromagnetic fields generated by HV switchgear assemblies
and HV/LV prefabricated substations, both for rated voltages above 1 kV and up to and
including 52 kV (IEC 62271-208:2025)
Hochspannungs-Schaltgeräte und -Schaltanlagen – Teil 208: Methoden zur Bestimmung
der stationären, betriebsfrequenten elektromagnetischen Felder von HS-Schaltanlagen
und fabrikfertigen HS-/ NS-Stationen, beides für Bemessungsspannungen über 1 kV und
bis einschließlich 52 kV (IEC 62271-208:2025)
Appareillage à haute tension - Partie 208: Méthodes de quantification des champs
électromagnétiques à fréquence industrielle en régime établi générés par les ensembles
d'appareillages ht et les postes préfabriqués ht/BT, à la fois pour les tensions assignées
supérieures à 1 kv et inférieures ou égales à 52 kv (IEC 62271-208:2025)
Ta slovenski standard je istoveten z: EN IEC 62271-208:2026
ICS:
29.130.10 Visokonapetostne stikalne in High voltage switchgear and
krmilne naprave controlgear
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62271-208

NORME EUROPÉENNE
EUROPÄISCHE NORM February 2026
ICS 29.130.10 Supersedes CLC/TR 62271-208:2010
English Version
High-voltage switchgear and controlgear - Part 208: Methods to
quantify the steady state, power-frequency electromagnetic
fields generated by HV switchgear assemblies and HV/LV
prefabricated substations, both for rated voltages above 1 kV
and up to and including 52 kV
(IEC 62271-208:2025)
Appareillage à haute tension - Partie 208: Méthodes de Hochspannungs-Schaltgeräte und -Schaltanlagen - Teil
quantification des champs électromagnétiques à fréquence 208: Methoden zur Bestimmung der stationären,
industrielle en régime établi générés par les ensembles betriebsfrequenten elektromagnetischen Felder von HS-
d'appareillages HT et les postes préfabriqués HT/BT, à la Schaltanlagen und fabrikfertigen HS-/ NS-Stationen, beides
fois pour les tensions assignées supérieures à 1 kV et für Bemessungsspannungen über 1 kV und bis
inférieures ou égales à 52 kV einschließlich 52 kV
(IEC 62271-208:2025) (IEC 62271-208:2025)
This European Standard was approved by CENELEC on 2026-01-27. 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
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62271-208:2026 E

European foreword
The text of document 17C/977/FDIS, future edition 1 of IEC 62271-208, prepared by SC 17C
"Assemblies" of IEC/TC 17 "High-voltage switchgear and controlgear" was submitted to the IEC-
CENELEC parallel vote and approved by CENELEC as EN IEC 62271-208:2026.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-02-28
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-02-28
document have to be withdrawn
This document supersedes CLC/TR 62271-208:2010 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 62271-208:2025 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 62110 NOTE Approved as EN 62110
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 61000-6-2 - Electromagnetic compatibility (EMC) - Part EN IEC 61000-6-2 -
6-2: Generic standards - Immunity standard
for industrial environments
IEC 61786-1 - Measurement of DC magnetic, AC magnetic EN 61786-1 -
and AC electric fields from 1 Hz to 100 kHz
with regard to exposure of human beings -
Part 1: Requirements for measuring
instruments
IEC 61786-2 - Measurement of DC magnetic, AC magnetic - -
and AC electric fields from 1 Hz to 100 kHz
with regard to exposure of human beings -
Part 2: Basic standard for measurements
IEC 62271-200 - High-voltage switchgear and controlgear - EN IEC 62271-200 -
Part 200: AC metal-enclosed switchgear and
controlgear for rated voltages above 1 kV
and up to and including 52 kV
IEC 62271-201 - High-voltage switchgear and controlgear - EN 62271-201 -
Part 201: AC solid-insulation enclosed
switchgear and controlgear for rated
voltages above 1 kV and up to and including
52 kV
IEC 62271-202 - High-voltage switchgear and controlgear - EN IEC 62271-202 -
Part 202: AC prefabricated substations for
rated voltages above 1 kV and up to and
including 52 kV
IEC 62271-208 ®
Edition 1.0 2025-12
INTERNATIONAL
STANDARD
High-voltage switchgear and controlgear -
Part 208: Methods to quantify the steady state, power-frequency electromagnetic
fields generated by HV switchgear assemblies and HV/LV prefabricated
substations, both for rated voltages above 1 kV and up to and including 52 kV
ICS 29.130.10  ISBN 978-2-8327-0887-3

IEC 62271-208:2025-12(en)
IEC 62271-208:2025 © IEC 2025
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Evaluation requirements . 8
4.1 General . 8
4.2 Methods of evaluation . 9
4.3 Evaluation of electric fields . 9
4.3.1 HV assemblies . 9
4.3.2 HV/LV prefabricated substations . 9
4.4 Evaluation of magnetic fields . 9
4.4.1 HV assemblies . 9
4.4.2 HV/LV prefabricated substations . 10
5 Measurements. 11
5.1 General . 11
5.2 Measuring instruments . 11
5.3 Measurement procedures . 12
5.3.1 General. 12
5.3.2 General. 12
5.3.3 Hot spot measurement procedure . 13
5.3.4 Isoline measurement procedure . 17
5.4 Measurement set-up . 18
5.4.1 General. 18
5.4.2 Hot spot measurement set-up. 18
5.4.3 Isoline measurement set-up . 20
5.4.4 External connections . 21
5.4.5 Additional provisions for HV/LV prefabricated substations . 22
6 Calculations . 22
6.1 General . 22
6.2 Software . 22
6.3 Calculation procedures . 23
6.4 Results . 23
6.5 Validation . 23
7 Documentation . 24
7.1 General . 24
7.2 Characteristics of the HV assembly or prefabricated substation . 24
7.3 Evaluation method . 24
7.4 Presentation of the measurement results . 24
7.5 Presentation of the calculation results . 25
Annex A (informative) Presentation of E- or B-field measurement data – Examples for
a typical HV/LV prefabricated substation . 26
A.1 Presentation of hot spot B-field measurement results . 26
A.1.1 General. 26
A.1.2 Hot spot locations . 27
A.1.3 Hot spot locations with its E- or B-field values . 27
IEC 62271-208:2025 © IEC 2025
A.1.4 Field variation around substation at hot spot locations . 28
A.1.5 Variation of the E- or B-field as a function of the distance . 28
A.1.6 Background fields . 29
A.2 Presentation of isoline E- or B-field measurement results . 29
A.2.1 Location of measurement points on isoline . 29
A.2.2 Background fields . 30
A.2.3 Example of an isoline measurement on a 1 600 kVA power transformer
substation . 31
Annex B (informative) Examples of analytical solutions to benchmark EMF
calculations . 32
B.1 Magnetic field . 32
B.2 Electric field . 41
Bibliography . 51

Figure 1 – Example of test circuits configuration to obtain the maximum external
magnetic field of a HV assembly or a prefabricated substation . 10
Figure 2 – Reference surface (RS) and measurement surface (MS) for equipment of
irregular shape . 13
Figure 3 – Scanning areas to find the hot spots . 14
Figure 4 – Determination of the field variation as a function of the distance from the hot
spot locations (perpendicular to the reference surface) . 15
Figure 5 – Height of measurement plane . 17
Figure 6 – Example of test circuit for electric and magnetic field measurement . 19
Figure 7 – Example of hot spot test set-up with measurement results. 20
Figure 8 – Example of isoline test set-up with measurement results . 21
Figure A.1 – Hot spot locations representing the field maxima . 27
Figure A.2 – Example diagram for the field variation at hot spots . 28
Figure A.3 – Graphical presentation of the field variation . 29
Figure A.4 – Graphical presentation of measurement points on isoline . 30
Figure A.5 – Isoline of 10 µT for a 1 600 kVA substation . 31
Figure B.1 – Schematic for 3-phase magnetic field calculation . 32
Figure B.2 – Variation of resultant magnetic field around 3-phase cable . 35
Figure B.3 – Maximum resultant magnetic field around 3-phase cable . 36
Figure B.4 – Schematic for 3-phase electric field calculation . 41
Figure B.5 – Variation of resultant electric field around 3-phase cable. 44
Figure B.6 – Maximum resultant electric field around 3-phase cable . 46

Table A.1 – Listing of the hot spot coordinates . 28
Table A.2 – Variation of field values for one hot spot . 29
Table A.3 – Background fields . 29
Table A.4 – Listing of the location (coordinates) of the measurement points . 30
Table A.5 – Background fields . 31
Table B.1 – Values of H [A/m] for spatial angles θ and time angles ωt . 35
res
Table B.2 – Values of maximum H [A/m] for spatial angles θ. 37
res
Table B.3 – Values of E [V/m] for spatial angles θ and time angles ωt . 45
res
Table B.4 – Values of maximum E for spatial angles θ . 46
IEC 62271-208:2025 © IEC 2025
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
High-voltage switchgear and controlgear -
Part 208: Methods to quantify the steady state, power-frequency
electromagnetic fields generated by HV switchgear assemblies and HV/LV
prefabricated substations, both for rated voltages above 1 kV and up to
and including 52 kV
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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 62271-208 document has been prepared by subcommittee 17C: High-voltage switchgear
and controlgear assemblies, of IEC technical committee 17: Switchgear and controlgear.
This first edition cancels and replaces the first edition of IEC TR 62271-208, published in 2009.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the isoline measurement procedure is introduced and compared to the hot spot one when it
is required as a measurement for the characterization of a generated electromagnetic field.
IEC 62271-208:2025 © IEC 2025
The text of this International Standard is based on the following documents:
Draft Report on voting
17C/977/FDIS 17C/983/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 62271 series, under the general title High-voltage switchgear
and controlgear, 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, or
– revised.
IEC 62271-208:2025 © IEC 2025
INTRODUCTION
Manufacturers of electricity supply equipment can be asked to provide information about the
electromagnetic field characteristics to enable the user to
• assess the electromagnetic field conditions to assist with planning, installation, operating
instructions and service,
• take measures to meet requirements or regulations on electromagnetic fields,
• compare different products as far as their level of electromagnetic fields is concerned.
The purpose of this document is to describe a methodology for the evaluation (measurement or
calculation) of generated electromagnetic fields. In particular, if a measurement is required, hot
spot and isolines procedures are introduced and described.
The electromagnetic field characteristic of the equipment comprises the values of the electric
and the magnetic fields around its accessible surfaces.
The electromagnetic field characteristic defined in this document refers to a single product as
defined in the scope. In real installations, several field sources can superimpose, so the
resulting electromagnetic fields on site can differ significantly from the single product
characteristics.
This document does not define a mandatory test for the products mentioned in the scope.
Neither the establishment of limits for the electromagnetic fields generated by equipment, nor
the establishment of assessment methods for the human exposure to electromagnetic fields are
within the content or intent of this document.

IEC 62271-208:2025 © IEC 2025
1 Scope
This part of IEC 62271 gives practical guidance for the evaluation and documentation of the
external steady state power-frequency electromagnetic fields which are generated by HV
switchgear and controlgear assemblies and prefabricated substations. Basic requirements to
measure or calculate the electric and magnetic fields are summarised for assemblies covered
by IEC 62271-200 and IEC 62271-201, and for prefabricated substations covered by
IEC 62271-202.
NOTE 1 The methods described in this document refer to three-phase equipment. However, the methodology can
be used correspondingly for any single- or multi-phase equipment covered by this document.
This document applies to equipment rated for voltages above 1 kV up to and including 52 kV
and power-frequencies from 15 Hz to 60 Hz. The electromagnetic fields which are generated
by harmonics or transients are not considered in this document. However, the methods
described are equally applicable to the harmonic fields of the power-frequency.
Detailed generic information on requirements and measurements of low-frequency
electromagnetic fields is given in IEC 61786-1 and IEC 61786-2.
This document covers evaluation under factory or laboratory conditions before installation. The
electric and the magnetic fields can be evaluated either by measurements or by calculations.
NOTE 2 Where practicable, the methods described in this document can also be used for installations on site.
It is not within the scope of this document to specify limit values of electromagnetic fields or
methods for the assessment of human exposure.
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.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61000-6-2, Electromagnetic compatibility (EMC) - Part 6-2: Generic standards - Immunity
for industrial environments
IEC 61786-1, Measurement of DC magnetic, AC magnetic and AC electric fields from 1 Hz to
100 kHz with regard to exposure of human beings - Part 1: Requirements for measuring
instruments
IEC 61786-2, Measurement of DC magnetic, AC magnetic and AC electric fields from 1 Hz to
100 kHz with regard to exposure of human beings - Part 2: Basic standard for measurements
IEC 62271-200, High-voltage switchgear and controlgear - Part 200: AC metal-enclosed
switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
IEC 62271-201, High-voltage switchgear and controlgear - Part 201: AC solid-insulation-
enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including
52 kV
IEC 62271-202, High-voltage switchgear and controlgear - Part 202: AC prefabricated
substations for rated voltages above 1 kV and up to and including 52 kV
IEC 62271-208:2025 © IEC 2025
3 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
electromagnetic field
EMF
field, determined by a set of four interrelated vector quantities, that characterizes, together with
the electric current density and the volumic electric charge, the electric and magnetic conditions
of a material medium or of a vacuum
Note 1 to entry: The four interrelated vector quantities, which obey Maxwell’s equations, are by convention:
• the electric field strength E,
• the electric flux density D,
• the magnetic field strength H,
• the magnetic flux density B.
Note 2 to entry: This definition of electromagnetic field is valid in so far as certain quantum aspects of
electromagnetic phenomena can be neglected.
Note 3 to entry: An electromagnetic field can include static components, i.e. an electrostatic field and a
magnetostatic field, and time-varying components representing electromagnetic waves.
[SOURCE: IEC 60050-121:2021 [1],121-11-61]
3.2
electric field characteristic
values (RMS) and spatial distribution of the electric field strength (E) expressed in kV/m at rated
voltage and frequency around all accessible surfaces of the equipment
Note 1 to entry: The electric field characteristic is the resultant of the RMS values of the three orthogonal vector
components.
3.3
magnetic field characteristic
values (RMS) and spatial distribution of the magnetic field strength (H) expressed in A/m or the
magnetic flux density (B) expressed in µT, at rated continuous current and frequency around all
accessible surfaces of the equipment
Note 1 to entry: The magnetic field characteristic is the resultant of the RMS values of the three orthogonal vector
components.
Note 2 to entry: The terms “resultant electric field” and “resultant magnetic field” are defined in IEC 61786-1 and
IEC 61786-2.
3.4
accessible surfaces, pl.
those parts of the walls and roof of prefabricated substations or HV switchgear and controlgear
assemblies that can be touched with all covers and doors in closed position in normal service
conditions
3.5
reference surface
RS
virtual envelope containing the equipment for evaluation purposes
IEC 62271-208:2025 © IEC 2025
3.6
measurement surface
MS
virtual envelope defined outside the reference surface at 20 cm distance for measuring hot
spots
3.7
hot spot
centre of an area of a local maximum of the electric or the magnetic field at the measurement
surface
3.8
EMF characteristic
spatial distribution of the electric field characteristic and of the magnetic field characteristic
Note 1 to entry: The spatial distribution is derived from a measurement or calculation grid.
3.9
measurement volume
MV
virtual space in which the electromagnetic background field does not exceed an appropriate
level to permit the uninfluenced measurement of the electric and magnetic fields generated by
the high-voltage switchgear and controlgear assembly or the prefabricated substation
3.10
measurement plane
MP
horizontal virtual plane on a specific height above floor level on which the measurement points
are taken
3.11
isoline
line of constant electric or magnetic field characteristic on a measurement plane
4 Evaluation requirements
4.1 General
The EMF characteristic of HV switchgear and controlgear assemblies or HV/LV prefabricated
substations is the measured or calculated electric field strength and magnetic flux density
around all accessible surfaces under the conditions for evaluation described below. These
conditions represent the service, where the loading of the switchgear and controlgear
assemblies and, in a substation, of the power transformer is at defined values.
As the electric and magnetic fields are dependent on the physical arrangement of incoming and
outgoing cables and their loadings, these parameters have to be recorded. The presence of
other field sources and shielding or other metallic structures shall be recorded.
The recordings shall be carried out in such a way that the loadings, material characteristics,
and geometrical configuration (including metric distances) are clearly indicated.
The EMF characteristic shall be evaluated for the conditions that would result in the highest
levels of electric and magnetic fields in normal, undisturbed service. These conditions include
the highest currents and largest loops realistically possible through the assembly working at
maximum capacity. EMF caused by switching operations, including interruption of fault currents,
or other transient phenomena is deemed to be incidental and shall not be considered.
IEC 62271-208:2025 © IEC 2025
Electric field strength and magnetic flux density shall be recorded as the resultant of the RMS
values of the three orthogonal vector components.
The evaluation shall be carried out at the rated frequency of the equipment.
However, in the frequency range from 15 Hz up to and including 60 Hz the actual value of
frequency does not significantly affect the levels of generated electric fields for any given values
of voltage. Therefore, evaluation at any frequency up to and including 60 Hz is considered valid.
Similarly, the difference in attenuation of magnetic fields by metallic enclosures at 50 Hz and
60 Hz can be ignored for the purpose of this document. Therefore, evaluation at 50 Hz is
considered applicable also for 60 Hz and vice versa.
In the power-frequency range covered by this document the electric and magnetic fields can be
treated separately. When selecting the conditions to obtain the highest level of electric and
magnetic fields as realistically as possible in undisturbed service, the following subclauses
should be considered.
4.2 Methods of evaluation
The EMF characteristic can be evaluated by measurement or by calculation.
4.3 Evaluation of electric fields
4.3.1 HV assemblies
The equipment shall be evaluated at the rated voltage of the HV switchgear and controlgear
assemblies.
Only if the evaluation cannot be carried out at rated voltage, the results shall be extrapolated
to the rated value. Since the electric field strength is a linear function of the voltage, the field
strengths for different high voltages can be extrapolated linearly.
4.3.2 HV/LV prefabricated substations
The equipment shall be evaluated at the rated high voltage of the HV/LV power transformer(s).
Only if the evaluation cannot be carried out at rated voltage, the results shall be extrapolated
to the rated value. Since the electric field strength is a linear function of the voltage, the field
strengths for different high voltages can be extrapolated linearly.
4.4 Evaluation of magnetic fields
4.4.1 HV assemblies
To evaluate the HV assembly magnetic field, use the rated continuous current given on the
switchgear nameplate. The HV circuit shall be selected to form the widest possible current loop
between the incoming and outgoing functional units (panels) of the switchgear and controlgear
assemblies to obtain the maximum magnetic field by using the smallest number of circuits,
taking into account their rated continuous current. An example is shown in Figure 1.
If the evaluation cannot be carried out at the rated continuous current the results shall be
extrapolated to the rated value. Any saturation effect will be less pronounced at lower currents,
therefore extrapolation from lower to higher values of current is allowed since it can only result
in an overestimate of the B-field.
IEC 62271-208:2025 © IEC 2025
Key
I = HV assembly highest loop current
I = HV/LV loop (HV side) current
I = HV/LV loop (LV side) highest current
I = HV/LV (LV outgoing) highest current
Figure 1 – Example of test circuits configuration to obtain the maximum external
magnetic field of a HV assembly or a prefabricated substation
4.4.2 HV/LV prefabricated substations
For the HV assembly, 4.4.1 applies.
The LV switchgear and controlgear assembly and the power transformer shall be loaded with
the highest continuous current derived from the rated power of the prefabricated substation and
the highest LV rated current of the corresponding power transformer for a given LV level. The
circuit shall be configured to form the highest concentration of currents to obtain the maximum
magnetic field. This can be achieved by using the smallest number of circuits, choosing those
located closest to the enclosure of the prefabricated substation and taking into account their
rated continuous currents. An example is shown in Figure 1.
NOTE Regarding different rated continuous currents, see relevant clause(s) in IEC 62271-202.
If the evaluation cannot be carried out at the rated power for a given LV level, the results shall
be extrapolated to the rated value. Any saturation effect will be less pronounced at lower
currents, therefore extrapolation from lower to higher values of current is allowed since it can
only result in an overestimate of the B-field.
The extrapolation of magnetic field values is not permitted if the currents on the HV and LV
sides of the prefabricated substation vary independently.
IEC 62271-208:2025 © IEC 2025
5 Measurements
5.1 General
At power-frequency the electric and magnetic field are independent from each other. Hence, it
is not necessary to record magnetic flux density and electric field strength characteristic
simultaneously.
The electric field characteristic of the equipment is independent of the load current.
The magnetic field characteristic of the equipment is independent of the voltage.
NOTE General guidance on measurement procedures for electric and magnetic fields can also be found in
IEC 62110 [2] , and IEC 61786-1 and IEC 61786-2.
5.2 Measuring instruments
Instruments for measuring electric and magnetic fields shall meet the requirements of
specification and calibration given by IEC 61786-1 and IEC 61786-2. The calibration report shall
be traceable to national or international standards. These instruments should be used in
appropriate conditions, in particular with regard to
• electromagnetic immunity according to IEC 61000-6-2,
• immunity of power-frequency electric field on magnetic field measurement,
• temperature and humidity ranges as recommended by the instrument manufacturer.
A three-axis instrument measures RMS values of resultant field F . A single-axis instrument can
r
be used to obtain F by measuring F , F , and F , using Formula (1), where F , F and F are
r x y z x y z
RMS values of the orthogonal three-axis components of electric or magnetic field.
2 22
F FFF++ (1)
r x yz
The use of a three-axis instrument with three concentric sensors is preferred. However, if a
single-axis instrument is used, special attention should be paid to the orientation of the sensor
along three orthogonal directions. The orientation of the sensor shall be changed without
moving the position of its centre.
In the case of non-concentric sensors, the locations and orientations of the sensors that are
contained within the housings of field meters shall be clearly indicated on the instrument or in
the instruction manual.
During the evaluation of the magnetic field generated by HV assemblies and HV/LV
prefabricated substations, the distance between the field source and the measuring instrument
is relatively short (in comparison to other AC power equipment like overhead lines). In general,
the measurements will be carried out in non-uniform fields. In case of the magnetic field
measurement, it is necessary to consider the ratio of distance (d ) from the field source and
sc
sensor radius (a). For measurements with a three-axis instrument, a minimum ratio of 4 is
considered suitable.
___________
Numbers in square brackets refer to the Bibliography.
=
IEC 62271-208:2025 © IEC 2025
For example, when using a probe with radius 5 cm the minimum distance to the field source
would be 20 cm considering a ratio of 4. More information about this topic can be found in
IEC 61786-1 and IEC 61786-2.
5.3 Measurement procedures
5.3.1 General
If measurement procedures are used, one of the following methods shall be used:
a) hot spot measurement procedure, or
b) isoline measurement procedure.
5.3.2 General
To consider equipment of all kinds of shape, a virtual envelope containing the equipment is
defined as the reference surface (RS); see Figure 2. The purpose of the RS is to integrate
irregularities and to eliminate abrupt changes in the measurement surface (MS). The MS is
defined outside the RS at 20 cm distance.
NOTE A measurement distance between 10 cm and 20 cm corresponds to the distance from the centre of a person’s
body to an accessible surface when a person is leaning against it. Taking into account the practical sizes of field
probes and the necessary clearance to avoid direct contact of the probe with the accessible surface, 20 cm is
considered the minimum measurement distance. Some national regulations as well as IEC 62110 [2] take this
distance as their basis.
Protruding elements (for example handles) shall be disregarded.
IEC 62271-208:2025 © IEC 2025
Key
1 Equipment surface
2 Measurement surface (MS)
3 Reference surface (RS)
d Distance between equipment and measurement surface (20 cm)
Figure 2 – Reference surface (RS) and measurement surface (MS)
for equipment of irregular shape
5.3.3 Hot spot measurement procedure
5.3.3.1 Electric field
The maximum value(s) of the electric field over the accessible measurement surface shall be
found by first scanning on a coarse grid to find the regions of maximum field and then refining
the grid for the hot spot locations. See also Figure 3.
IEC 62271-208:2025 © IEC 2025
Figure 3 – Scanning areas to find the hot spots
The variation of the electric field shall be determined as a function of the distance from the MS.
Starting at each hot spot, the field values shall be measured along a line perpendicular to the
MS until the measured value is lower than 1/10 (–20 dB) of the hot spot value; see Figure 4.
Additional measurements can be carried out to fulfil specific requirements (e.g. for a client or
country).
NOTE Significant electric fields are not expected for the equipment in the scope of this document. However, it is
the intention of this document to give guidance for the measurement of these fields where manufacturers and users
require them.
IEC 62271-208:2025 © IEC 2025
Figure 4 – Determination of the field va
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