IEC TR 62271-208:2009

IEC/TR 62271-208 ®
Edition 1.0 2009-10
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
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
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

IEC/TR 62271-208:2009
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IEC/TR 62271-208 ®
Edition 1.0 2009-10
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
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
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

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 29.130.10 ISBN 978-2-88910-657-8
– 2 – TR 62271-208 © IEC:2009
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Evaluation requirements .9
4.1 General .9
4.2 Methods of evaluation .9
4.3 Evaluation of electric fields.10
4.3.1 HV switchgear assemblies.10
4.3.2 HV/LV prefabricated substations.10
4.4 Evaluation of magnetic fields.10
4.4.1 HV switchgear assemblies.10
4.4.2 HV/LV prefabricated substations.11
5 Measurements.12
5.1 General .12
5.2 Measuring instruments .12
5.3 Measurement procedures .12
5.3.1 General .12
5.3.2 Electric field .13
5.3.3 Magnetic field .16
5.3.4 Background fields .16
5.3.5 Environmental factors.16
5.4 Measurement set-up.17
5.4.1 General .17
5.4.2 Additional provisions for HV/LV prefabricated substations .20
6 Calculations .20
6.1 General .20
6.2 Software.21
6.3 Calculation procedures.21
6.4 Results.21
6.5 Validation .22
7 Documentation .22
7.1 Characteristics of the HV switchgear assembly or prefabricated substation .22
7.2 Evaluation method.22
7.3 Presentation of the measurement results.22
7.4 Presentation of the calculation results .23
Annex A (informative) Presentation of E or B field measurement data – Example for a
typical HV/LV pre-fabricated substation .24
Annex B (informative) Examples of analytical solutions to benchmark EMF

calculations.27
Bibliography.45

Figure 1 – Example of test circuits configuration to obtain the maximum external
magnetic field of a switchgear assembly and/or a prefabricated substation .11
Figure 2 – Reference surface (RS) for equipment of irregular shape .13

– 3 –
TR 62271-208 © IEC:2009
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 – Test set-up of main components, external cables, hot spot locations and
measurement volume.18
Figure 6 – Test circuit for electric and magnetic field measurement .19
Figure A.1 – Hot spot locations representing the field maxima .24
Figure A.2 – Graphical presentation of the field variation .25
Figure A.3 – Example diagram for the field variation at hot spots .26
Figure B.1 – Schematic for 3-phase magnetic field calculation.27
Figure B.2 – Variation of resultant magnetic field around 3-phase cable .30
Figure B.3 – Maximum resultant magnetic field around 3-phase cable .31
Figure B.4 – Schematic for 3-phase electric field calculation.35
Figure B.5 – Variation of resultant electric field around 3-phase cable .38
Figure B.6 – Maximum resultant electric field around 3-phase cable .40

Table A.1 – Listing of the hot spot coordinates.25
Table A.2 – Variation of field values for one hot spot .25
Table A.3 – Background fields .26
Table B.1 – Values of H for spatial angles θ and time angles ωt .30
res
Table B.2 – Values of maximum H for spatial angles θ.32
res
Table B.3 – Values of E for spatial angles θ and time angles ωt.39
res
Table B.4 – Values of maximum E for spatial angles θ .40

– 4 – TR 62271-208 © IEC:2009
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

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 62271-208, which is a technical report, has been prepared by subcommittee 17C: High-
voltage switchgear and controlgear assemblies, of IEC technical committee 17: Switchgear
and controlgear.
In this technical report the word “shall” is used as a conditional “shall”, in the event that this
technical report is applied.
– 5 –
TR 62271-208 © IEC:2009
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
17C/450/DTR 17C/462/RVC
Full information on the voting for the approval of this technical report 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.
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 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.
– 6 – TR 62271-208 © IEC:2009
INTRODUCTION
Manufacturers of electricity supply equipment may 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 technical report is to describe a methodology for the evaluation
(measurement or calculation) of generated electromagnetic fields.
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 technical report 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 may differ significantly from the single product
characteristics.
This technical report 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 is
within the content or intent of this technical report.

– 7 –
TR 62271-208 © IEC:2009
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

1 Scope
This part of IEC 62271 gives practical guidance for the evaluation and documentation of the
external electromagnetic fields which are generated by HV switchgear assemblies and HV/LV
prefabricated substations. Basic requirements to measure or calculate the electric and
magnetic fields are summarised for switchgear 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 technical report refer to three-phase equipment. However, the
methodology may be used correspondingly for any single- or multi-phase equipment covered by this technical
report.
This technical report applies to equipment rated for voltages 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 technical report. 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.
This technical report 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 technical report may also be used for installations on
site.
It is not within the scope of this technical report to specify limit values of electromagnetic
fields or methods for the assessment of human exposure.
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 61000-6-2, Electromagnetic compatibility (EMC) – Part 6-2: Generic standards - Immunity
for industrial environments
IEC 61786, Measurement of low-frequency magnetic and electric fields with regard to
exposure of human beings – Special requirements for instruments and guidance 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

– 8 – TR 62271-208 © IEC:2009
IEC 62271-201, High-voltage switchgear and controlgear – Part 201: AC 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: High-voltage/low-voltage
prefabricated substation
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
EMF
abbreviation for the term “electromagnetic field(s)”
3.2
electric field characteristic
values (r.m.s.) and spatial distribution of the electric field strength at rated voltage and
frequency around all accessible surfaces of the equipment. The electric field characteristic is
the resultant of the r.m.s. values of the three orthogonal vector components
3.3
magnetic field characteristic
values (r.m.s.) and spatial distribution of the magnetic flux density at rated normal current and
frequency around all accessible surfaces of the equipment. The magnetic field characteristic
is the resultant of the r.m.s. values of the three orthogonal vector components
NOTE The terms “resultant electric field” and “resultant magnetic field” are defined in IEC 61786.
3.4
accessible surfaces
those parts of the walls and roof of prefabricated substations or HV switchgear 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
3.6
measurement surface
MS
defined outside the reference surface at 20 cm distance
NOTE This surface is used for measuring the hot spots and the variation of the EMF.
3.7
hot spot
centre of an area of a local maximum of the electric or the magnetic field
3.8
EMF characteristic
spatial distribution of the resultant (modulus) of the r.m.s. electric field strength (E) and the
magnetic flux density (B). The spatial distribution is derived from a measurement or
calculation grid
– 9 –
TR 62271-208 © IEC:2009
3.9
measurement volume
MV
virtual space in which the electromagnetic background field must not exceed an appropriate
level to permit the uninfluenced measurement of the electric and magnetic fields generated by
the equipment
4 Evaluation requirements
4.1 General
The EMF characteristic of HV switchgear 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 assemblies and, in a substation, of
the 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 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.
The highest current on the HV side is the rated normal current given on the nameplate of the
switchgear assembly, and on the LV side the rated normal current of the transformer with the
highest rating. In a calculation both currents have to be simulated. During a measurement it is
preferable to have both currents present.
Electric field strength and magnetic flux density shall be recorded as the resultant of the
r.m.s. values of the three orthogonal components.
The evaluation shall be carried out at the rated frequency of the equipment.
However, in the frequency range up to and including 60 Hz the actual value of frequency does
not significantly affect the levels of generated E 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 B fields by metallic enclosures at 50 Hz and 60 Hz
can be ignored for the purpose of this technical report. Therefore evaluation at 50 Hz is
considered applicable also for 60 Hz and vice versa.
In the power-frequency range covered by this technical report the electric and magnetic fields
may 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 shall be considered.
4.2 Methods of evaluation
The manufacturer may evaluate the EMF characteristic by measurement or by calculation.

– 10 – TR 62271-208 © IEC:2009
4.3 Evaluation of electric fields
4.3.1 HV switchgear assemblies
The equipment shall be evaluated at the rated voltage of the HV switchgear assembly.
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 may be extrapolated linearly.
4.3.2 HV/LV prefabricated substations
The equipment shall be evaluated at the rated high voltage of the HV/LV 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 may be extrapolated linearly.
4.4 Evaluation of magnetic fields
4.4.1 HV switchgear assemblies
The HV switchgear assembly is loaded with its highest permissible current determined by the
rated normal current given on the nameplate. The HV circuit must be selected to form the
widest possible current loop between the incoming and outgoing functional units (panels) of
the switchgear assembly to obtain the maximum magnetic field by using the smallest number
of circuits, taking into account their rated normal current. An example is shown in Figure 1.
If the evaluation cannot be carried out at the rated normal 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.

– 11 –
TR 62271-208 © IEC:2009
HV/LV prefabricated substation
LV switchgear assembly
HV switchgear assembly
I
Transformer/s
I I I
1 2 4
IEC  2039/09
Key
I = HV switchgear 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 switchgear assembly and/or a prefabricated substation
4.4.2 HV/LV prefabricated substations
For the HV switchgear assembly, 4 . 4. 1 appli e s .
The LV switchgear assembly and the transformer shall be loaded with the highest normal
current derived from the maximum rated power of the prefabricated substation 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 normal current. An example is shown in Figure 1.
If the design of the HV/LV prefabricated substation admits transformers of different rated
power, the manufacturer shall at least provide an evaluation for the transformer with the
highest rated power for a given LV level.
NOTE The rated power of the transformer should correspond to the cooling by natural ventilation. EMF evaluation
with other means of cooling (for example forced cooling) should be subject to agreement between manufacturer
and user.
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.

– 12 – TR 62271-208 © IEC:2009
5 Measurements
5.1 General
At power-frequency the electric and magnetic field are independent from each other. Hence,
magnetic flux density and electric field strength characteristic need not be recorded
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 and IEC 61786.
5.2 Measuring instruments
Instruments for measuring electric and magnetic fields shall meet the requirements of
specification and calibration given by IEC 61786. 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 r.m.s. values of resultant field F . A single-axis instrument
r
may be used to obtain F by measuring F , F , and F , using Equation (1), where F , F and F
r x y z x y z
are r.m.s. values of the orthogonal three-axis components of electric or magnetic field.
2 2 2
F = F + F + F (1)
r x y z
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 switchgear 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
sc
field source and sensor radius (a). For measurements with a three-axis instrument, a
minimum ratio of 4 is considered suitable.
NOTE When using a probe with radius 5 cm the minimum distance to the field source should be at least 20 cm
considering a ratio of 4. More information about this topic can be found in IEC 61786.
5.3 Measurement procedures
5.3.1 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

– 13 –
TR 62271-208 © IEC:2009
irregularities and to eliminate abrupt changes in the measurement surface (MS). The MS is
defined outside the RS at 20 cm distance.
Protruding elements (for example handles) shall be disregarded.

d
d
IEC  2040/09
Key
1 Equipment surface
2 Measurement surface
3 Reference surface
d Distance between equipment
and measurement surface (20 cm)
Figure 2 – Reference surface (RS) for equipment of irregular shape
5.3.2 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.

– 14 – TR 62271-208 © IEC:2009

Only if roof is accessible
d
sc
d d
sc sc
Standing
surface
Lateral view
d
sc
d d
sc sc
Only if roof
is accessible
d
sc
Top view
Reference surface (RS) of equipment
Scanning area
Measurement surface (MS)
d
sc  Measurement distance from the RS (d = 20 cm)
sc
IEC  2041/09
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 may 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 technical report. However,
it is the intention of this technical report to give guidance for the measurement of these fields where manufacturers
and users require them.
– 15 –
TR 62271-208 © IEC:2009
d
1/10
E
Only if roof is accessible
d
B
1/10
C
D
d
1/10
A
Standing
surface
Lateral view
Only if roof
is accessible
d
1/10
A
D
d
1/10
B
E
d
1/10
C
d
1/10
Top view
A
Hot spot location at distance d from the RS
sc
d
1/10
Series of measurements until the measured value
is lower than 1/10 (–20 dB) of the hot spot value
IEC  2042/09
Figure 4 – Determination of the field variation as a function of the distance
from the hot spot locations (perpendicular to the reference surface)

– 16 – TR 62271-208 © IEC:2009
5.3.3 Magnetic field
The maximum value(s) of the magnetic field over the MS 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.
The variation of the magnetic 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 may be carried out to fulfil specific requirements (e.g. for a client
or country).
5.3.4 Background fields
Immediately after the measurements, the equipment shall be switched off and the background
field level shall be measured and recorded.
By coarsely scanning the electric or magnetic field within the MV when voltage or current is
switched off, it shall be verified that the background field level is below 1/10 (–20 dB) of the
lowest value measured at any of the hot spots found during the live measurement.
Guidance on reducing the interfering background fields, caused by the external cables
connected to the test specimen, to a minimum, is given in 5.4.1.
5.3.5 Environmental factors
5.3.5.1 Electric field measurement
Environmental factors (e.g. humidity, temperature etc.) have no significant influence on the
electric field. However, the electric field measuring instrument can be influenced significantly
when the humidity is sufficient to cause condensation on the sensor and the supporting
structure. Thus the environmental factors shall be measured to ensure that the measuring
instruments are used within their specified environmental limits. Special attention should be
paid to humidity.
Acceptable humidity limits for proper measurements are deemed to be
• 60 % relative humidity when using a normal tripod,
• 70 % relative humidity when using an offset tripod
(measuring instrument shifted by 0,50 m form the vertical axis of the tripod).
If those limits are exceeded, the measurements shall be considered as conservative, due to
the fact that the values measured in high humidity are higher than those in lower humidity for
the same equipment excited with the same voltages.
Likewise, electric field measurements in rain conditions are inappropriate.
5.3.5.2 Magnetic field measurement
Environmental factors (e.g. humidity, temperature etc.) have no significant influence on the
magnetic field. However, the environmental factors shall be measured to ensure that the
measuring instruments are being used within their specified environmental limits.
5.3.5.3 Other conditions
During electric field measurements, objects or persons shall be kept outside the influence
zone of the measuring device.
– 17 –
TR 62271-208 © IEC:2009
Only objects containing or consisting of high permeability materials can cause significant
distortions of the magnetic field. Persons do not influence the magnetic field, thus measuring
instruments may be directly held by persons when making measurements.
The presence of high permeability materials, which are not part of the equipment, in the
vicinity of the field source and/or the measuring instruments, shall be stated in the
measurement report.
All parts of the equipment intended to be earthed shall be earthed according to the
manufacturer’s instructions.
5.4 Measurement set-up
5.4.1 General
All measurements shall be carried out with a three-phase voltage or current supply. The test
set-up shall meet the following requirements; see also Figure 6.
The equipment under test shall be surrounded by a virtual measurement volume (MV) large
enough to allow the decay of the field perpendicular to the reference surface at each hot spot
to 1/10 (–20 dB) of its value; see Figure 5.

– 18 – TR 62271-208 © IEC:2009

d
1/10
E
Only if roof is accessible
d
1/10
B
C
d
D
1/10
Standing
surface
Lateral view
Only if roof d
1/10
is accessible
A
d
1/10 D
d
1/10
B
E
C
d
1/10
Top view
A
Hot spot location at distance d from the RS
sc
HV and LV cables (external connections)
MV: background field level is below 1/10 (–20 dB)
the lowest value measured at any of the hot spots
IEC  2043/09
Figure 5 – Test set-up of main components,
external cables, hot spot locations and measurement volume
HV HV
switchgear switchgear
HV/LV
HV/LV
transformer
transformer
LV LV
switchgear
switchgear
– 19 –
TR 62271-208 © IEC:2009
LV supply for
Alternative
energizing the
HV
HV supply
complete circuit
Transformer
LV
U U
rHV rLV
Alternative voltage
measurement
HV/LV prefabricated substation
Measurement reference volume
IEC  2044/09
Figure 6a – Test circuit for electric field measurement

Special connection for measurement and/or
modified HV switchgear (where required)
HV cable loop supply
I
HV
Transformer Short-circuit of
LV
outgoing LV cables
Short-circuit I I
2 3
of HV cable loop
Transformer and
LV side supply
HV/LV prefabricated substation
Measurement reference volume
IEC  2045/09
Key
I Rated normal current of HV cable loop
I Rated HV normal current of transformer
I Rated LV normal current of transformer
Figure 6b – Test circuit for magnetic field measurement
Figure 6 – Test circuit for electric and magnetic field measurement

– 20 – TR 62271-208 © IEC:2009
The objective during the test is to reduce external influence, in order to characterize the
equipment rather than the test circuit. To minimize the interfering background fields inside the
MV, some provisions are made for the external connections to the test specimen. Preferably
three-phase shielded cables on the HV side and 4-core cables on the LV side shall be used. If
other cables are used they shall be arranged so that their near field is minimized. This cable
arrangement shall be maintained to a sufficient distance outside the MV boundaries so that
the background field level inside the MV is not affected.
Where the contribution of the field generated by the external connections is deemed to have
significant influence on the measurement results (for example in a single phase system), it is
allowed to subtract the field values due to the external connections from the actual
measurement results. The method used shall be stated in the test report.
NOTE When no correction is made for the field generated by the external connections, the measured results will
be an overestimate.
The type of cables and connections should represent those used in normal service conditions.
The HV cables shall leave the equipment perpendicular to the sides until they reach the
boundary of the measurement reference volume.
The field generated by the short-circuit connection of the HV cable loop and the LV (outgoing)
cable circuits shall not alter the field level at the boundary of the measurement reference
vo
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