SIST IEC 61786-2:2017

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 61786-2:2014 provides requirements for the measurement of quasi-static magnetic and electric fields that have a frequency content in the range 1 Hz to 100 kHz, and DC magnetic fields, to evaluate the exposure levels of the human body to these fields. Specifically, this standard gives requirements for establishing measurement procedures that achieve defined goals pertaining to human exposure. Because of differences in the characteristics of the fields from sources in the various environments, e.g. frequency content, temporal and spatial variations, polarization, and magnitude, and differences in the goals of the measurements, the specific measurement procedures will be different in the various environments. Sources of fields include devices that operate at power frequencies and produce power frequency and power-frequency harmonic fields, as well as devices that produce fields independent of the power frequency, and DC power transmission, and the geomagnetic field. The magnitude ranges covered by this standard are 0,1 micro-Tesla to 200 mili-Tesla for AC (1 micro-Tesla to 10 Tesla for DC) for magnetic fields, and 1 V/m to 50 kV/m for electric fields. When measurements outside this range are performed, most of the provisions of this standard will still apply, but special attention should be paid to the specified uncertainty and calibration procedures. Examples of sources of fields that can be measured with this standard include:
- devices that operate at power frequencies (50/60 Hz) and produce power frequency and power-frequency harmonic fields (examples: power lines, electric appliances...);
- devices that produce fields that are independent of the power frequency.(Examples: electric railway (DC to 20 kHz);
- commercial aeroplanes (400 Hz), induction heaters (up to 100 kHz), and electric vehicles);
- and devices that produces static magnetic fields: MRI, DC power lines, DC welding, electrolysis, magnets, electric furnaces, etc. DC currents are often generated by converters, which also create AC components (power frequency harmonics), which should be assessed. When EMF products standards are available, these products standards should be used. With regard to electric field measurements, this standard considers only the measurement of the unperturbed electric field strength at a point in space (i.e. the electric field prior to the introduction of the field meter and operator) or on conducting surfaces. Sources of uncertainty during measurements are also identified and guidance is provided on how they should be combined to determine total measurement uncertainty.

Mesure de champs magnétiques continus et de champs magnétiques et électriques alternatifs dans la plage de fréquences de 1 Hz à 100 kHz dans leur rapport à l'exposition humaine - Partie 2: Norme de base pour les mesures

L'IEC 61786-2:2014 fournit des exigences pour la mesure des valeurs des champs magnétiques et électriques quasi-statiques avec un contenu fréquentiel compris entre 1 Hz et 100 kHz ainsi que des champs magnétiques continus, permettant d'évaluer les niveaux d'exposition du corps humain à ces champs. De manière spécifique, la présente norme donne les exigences relatives à la mise en place de procédures de mesure permettant d'atteindre les objectifs définis quant à l'exposition humaine. Compte tenu des différences de caractéristiques des champs par rapport aux sources dans les divers environnements (contenu fréquentiel, variations temporelles et spatiales, polarisation et amplitude, par exemple) et des différences d'objectifs des mesures, les procédures de mesure spécifiques sont différentes selon les environnements. Parmi les sources de champs figurent des dispositifs qui fonctionnent aux fréquences industrielles et qui produisent des champs à ces fréquences et aux fréquences harmoniques, ainsi que des dispositifs produisant des champs indépendants de la fréquence industrielle, la transmission d'énergie en courant continu, et le champ magnétique statique terrestre. Les plages d'amplitudes couvertes par la présente norme vont respectivement de 0,1 micro-Tesla à 200 mili-Tesla en alternatif (1 micro-Tesla à 10 Tesla en continu) pour les champs magnétiques et de 1 V/m à 50 kV/m pour les champs électriques. Si des mesures hors de cette plage sont réalisées, la plupart des dispositions de la présente norme s'appliquent toujours, mais il convient de veiller particulièrement à l'incertitude spécifiée et aux procédures d'étalonnage. Par exemple, les sources de champs qui peuvent être mesurées avec la présente norme sont:
- les dispositifs fonctionnant aux fréquences industrielles (50/60 Hz) et générant des champs de fréquence industrielle et des harmoniques de ces fréquences (exemples: lignes d'énergie, appareils électriques...);
- les dispositifs générant des champs indépendants de la fréquence industrielle. (Exemples: voie de chemin de fer électrifiée (du continu à 20 kHz), avions de ligne (400 Hz), les appareils de chauffage par induction (jusqu'à 100 kHz) et les véhicules électriques);
- et les dispositifs générant des champs magnétiques statiques: imagerie par résonance magnétique (IRM), lignes d'énergie à courant continu, soudage par courant continu, électrolyse, aimants, fours électriques, etc. Les courants continus sont souvent générés par des convertisseurs, qui créent également des composantes alternatives (harmoniques à fréquence industrielle), qu'il convient d'évaluer. Si des normes de produit concernant les champs électromagnétiques sont disponibles, il convient de les utiliser. Eu égard aux mesures de champs électriques, la présente norme considère uniquement la mesure du champ électrique non perturbé en un point de l'espace (c'est-à-dire le champ électrique avant l'introduction du mesureur du champ et de l'opérateur) ou sur des surfaces conductrices. Les sources d'incertitude pendant les mesures sont également identifiées, et des lignes directrices sont fournies quant à la manière dont il convient de les combiner afin de déterminer l'incertitude de mesure totale.

Merjenje enosmernih in izmeničnih magnetnih polj ter izmeničnih električnih polj od 1 Hz do 100 kHz glede na izpostavljenost ljudi - 2. del: Osnovni standard za meritve

Standard IEC 61786-2:2014 podaja zahteve za meritve navidezno statičnih magnetnih in električnih polj, katerih frekvenčni delež je v razponu od 1 Hz do 100 kHz, in enosmernih magnetnih polj, s čimer se ovrednoti ravni izpostavljenosti človeškega telesa tem poljem. Natančneje, ta standard določa zahteve za vzpostavitev merilnih postopkov, ki dosegajo določene cilje, ki se nanašajo na izpostavljenost ljudi. Zaradi razlik v lastnostih polj iz virov v različnih okoljih, npr. frekvenčne vsebine, časovnih in prostorskih sprememb, polarizacije in velikosti ter razlik v ciljih meritev, bodo posebni merilni postopki različni v različnih okoljih. Viri polj zajemajo tako naprave, ki delujejo na omrežnih frekvencah ter proizvajajo omrežne frekvence in harmonična polja omrežnih frekvenc, kot tudi naprave, ki proizvajajo polja neodvisno od omrežne frekvence in prenos moči enosmernega toka ter geomagnetno polje. Obsegi magnitude, ki jih zajema ta standard, so 0,1 mikrotesla do 200 militesla za izmenični tok (1 mikrotesla do 10 tesla za enosmerni tok) za magnetna polja in 1 V/m do 50 kV/m za električna polja. Če je meritev zunaj tega razpona, se večina določil iz tega standarda še vedno uporablja, vendar naj bi posebno pozornost posvetili določenim postopkom negotovosti in kalibriranja. Primeri virov polj, ki jih je mogoče meriti s tem standardom, so:
- naprave, ki delujejo pri omrežnih frekvencah (50/60 Hz) in proizvajajo omrežno frekvenco in harmonična polja omrežnih frekvenc (primeri: napajalni vodi, električni aparati ...);
- naprave, ki proizvajajo polja, ki so neodvisna od omrežne frekvence.(Primeri: električna železnica (enosmerni tok do 20 kHz);
- komercialna letala (400 Hz), indukcijski grelci (do 100 kHz) in električna vozila);
- in naprave, ki proizvajajo statična magnetna polja: slikanje z magnetno resonanco (MRI), napajalne vodi enosmernega toka, varjenje enosmernega toka, elektroliza, magneti, električne pečice itd. Enosmerne tokove pogosto proizvajajo pretvorniki, ki prav tako ustvarjajo komponente izmeničnega toka (obratovalna frekvenca harmonike), ki naj bi jih ocenili. Kadar so na voljo standardi izdelkov elektromagnetnega sevanja (EMF), naj bi uporabili te standarde izdelkov. Ta standard z vidika merjenja električnega polja upošteva le merjenje nespremenjene jakosti električnega polja v točki v prostoru (tj. električno polje pred uvedbo merilnika in meritelja) ali na prevodnih površinah. Opredeljeni so tudi viri negotovosti med meritvami in zagotovljena so navodila o tem, kako jih je treba združiti, da bi določili skupno merilno negotovost.

General Information

• Status: Published
• Publication Date: 19-Sep-2017
• ICS: 17.220.20 - Measurement of electrical and magnetic quantities
• Technical Committee: INIR - Electromagnetic fields in human enviornment
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 19-Sep-2017
• Due Date: 24-Nov-2017
• Completion Date: 20-Sep-2017
• Ref Project: 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

Standards Content (Sample)

SLOVENSKI STANDARD
SIST IEC 61786-2:2017
01-oktober-2017
0HUMHQMHHQRVPHUQLKLQL]PHQLþQLKPDJQHWQLKSROMWHUL]PHQLþQLKHOHNWULþQLKSROM
RG+]GRN+]JOHGHQDL]SRVWDYOMHQRVWOMXGLGHO2VQRYQLVWDQGDUG]D
PHULWYH
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
Mesure de champs magnétiques continus et de champs magnétiques et électriques
alternatifs dans la plage de fréquences de 1 Hz à 100 kHz dans leur rapport à
l'exposition humaine - Partie 2: Norme de base pour les mesures
Ta slovenski standard je istoveten z: IEC 61786-2
ICS:
17.220.20 0HUMHQMHHOHNWULþQLKLQ Measurement of electrical
PDJQHWQLKYHOLþLQ and magnetic quantities
SIST IEC 61786-2:2017 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST IEC 61786-2:2017

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SIST IEC 61786-2:2017




IEC 61786-2

®


Edition 1.0 2014-12




INTERNATIONAL



STANDARD




NORME



INTERNATIONALE
colour

inside










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




Mesure de champs magnétiques continus et de champs magnétiques et

électriques alternatifs dans la plage de fréquences de 1 Hz a 100 kHz dans leur


rapport à l'exposition humaine –

Partie 2: Norme de base pour les mesures












INTERNATIONAL

ELECTROTECHNICAL

COMMISSION


COMMISSION

ELECTROTECHNIQUE

PRICE CODE
INTERNATIONALE

CODE PRIX W


ICS 17.220.20 ISBN 978-2-8322-1970-6



Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST IEC 61786-2:2017
– 2 – IEC 61786-2:2014 © IEC 2014
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 General considerations . 8
4.1 Different goals of measurement . 8
4.1.1 General . 8
4.1.2 Characterisation of field levels for compliance with safety standards . 9
4.1.3 Characterisation of spatial variations . 9
4.1.4 Characterisation of temporal variation . 11
4.1.5 Characterisation of frequency content in magnetic field or electric field . 12
4.1.6 Characterisation of population exposure to magnetic field and definition
of metric . 13
4.2 Sources with multiple frequencies . 14
4.2.1 General . 14
4.2.2 Sum of weighted magnitudes . 14
4.2.3 Weighted peak value . 15
4.2.4 Impulse separation . 15
4.2.5 Weighted RMS value . 15
4.2.6 Highest weighted spectral line . 16
4.2.7 Conclusion and recommendation. 16
4.3 Considerations before measurements . 16
5 Measurement procedures and precaution . 17
5.1 AC magnetic field . 17
5.2 DC magnetic field . 18
5.3 AC electric field . 19
6 Measurement uncertainty . 21
7 Measurement report . 22
Annex A (informative) Examples of fields characteristics in typical environments . 24
Annex B (informative) Examples of measurement distances . 27
B.1 IEC 62110:2009 [9] . 27
B.2 IEC 62233: 2005 [10] . 27
B.3 IEC 62311:2007 [11] . 27
B.4 IEC 62369-1:2008 [12] . 27
B.5 IEC/TS 62597:2011 [14] . 27
B.6 IEC 62493:2009 [13] . 28
Annex C (normative) Measurement uncertainty . 29
C.1 Overview. 29
C.2 Assessment of type A uncertainty . 29
C.3 Assessment of type B uncertainty . 29
C.3.1 Non-uniform field . 29
C.3.2 Pass-band limitations . 30
C.3.3 Temperature . 30
C.3.4 Humidity . 30
C.3.5 Location of measurement. 30

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IEC 61786-2:2014 © IEC 2014 – 3 –
C.3.6 Long-term drift . 31
C.3.7 Instrument time constant . 31
C.3.8 Proximity effect of observer (for electric field) . 31
C.3.9 Correction factor . 31
C.3.10 Hysteresis between scales . 31
Annex D (informative) Example of measurement uncertainty . 32
Bibliography . 33

Figure 1 – Magnetic field levels under a 77 kV overhead transmission line (from [9] ) . 10
Figure 2 – Electric field levels under an overhead transmission line (from [9] ). 10
Figure 3 – Example of load variation of 735kV line due to the human activities (daily)
and outdoor temperature (seasonal) . 11
Figure 4 – 50 Hz magnetic field in a high speed train in France . 12
Figure 5 – Waveform (a) and frequency spectrum (b) of magnetic field generated by a
66,04 cm (26 inches) flat-screen LCD television . 13
Figure 6 – Example of DC magnetic field profile above DC underground cable
(calculated at a height of 1 m) . 19
Figure 7 – Observer proximity effects during electric field measurements in vertical
electric field . 20
Figure A.1 – Magnetic field exposure of typical worker (electrician) in North American
power plant (based on 3 days recording) . 25
Figure B.1 – Lighting equipment and measurement distances (from [13]) . 28

Table A.1 – Example of field characteristics inside (workers environment) and outside
(public environment) electric substations in a North American utility . 24
Table A.2 – Field characteristics (mT) in different mass transportation system in US:
average and (maximum) . 26
Table D.1 – Example of measurement uncertainty . 32

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

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

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
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61786-2 has been prepared by IEC technical committee 106:
Methods for the assessment of electric, magnetic and electromagnetic fields associated with
human exposure.
The text of this standard is based on the following documents:
FDIS Report on voting
106/322/FDIS 106/326/RVD

Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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IEC 61786-2:2014 © IEC 2014 – 5 –
The committee has decided that the contents of this publication will remain unchanged until
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IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
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understanding of its contents. Users should therefore print this document using a
colour printer.

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SIST IEC 61786-2:2017
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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



1 Scope
This part of IEC 61786 provides requirements for the measurement of quasi-static magnetic
and electric fields that have a frequency content in the range 1 Hz to 100 kHz, and DC
magnetic fields, to evaluate the exposure levels of the human body to these fields.
Specifically, this standard gives requirements for establishing measurement procedures that
achieve defined goals pertaining to human exposure.
NOTE Requirements on field meters and calibration are described in IEC 61786-1
Because of differences in the characteristics of the fields from sources in the various
environments, e.g. frequency content, temporal and spatial variations, polarization, and
magnitude, and differences in the goals of the measurements, the specific measurement
procedures will be different in the various environments.
Sources of fields include devices that operate at power frequencies and produce power
frequency and power-frequency harmonic fields, as well as devices that produce fields
independent of the power frequency, and DC power transmission, and the geomagnetic field.
The magnitude ranges covered by this standard are 0,1 mT to 200 mT for AC (1 mT to 10 T for
DC) for magnetic fields, and 1 V/m to 50 kV/m for electric fields.
When measurements outside this range are performed, most of the provisions of this standard
will still apply, but special attention should be paid to the specified uncertainty and calibration
procedures.
Examples of sources of fields that can be measured with this standard include:
− devices that operate at power frequencies (50/60 Hz) and produce power frequency and
power-frequency harmonic fields (examples: power lines, electric appliances…)
− devices that produce fields that are independent of the power frequency. (Examples:
electric railway (DC to 20 kHz), commercial aeroplanes (400 Hz), induction heaters (up to
100 kHz), and electric vehicles.)
− devices that produces static magnetic fields: MRI, DC power lines, DC welding,
electrolysis, magnets, electric furnaces, etc. DC currents are often generated by
converters, which also create AC components (power frequency harmonics), which should
be assessed.
When EMF products standards are available, these products standards should be used.
With regard to electric field measurements, this standard considers only the measurement of
the unperturbed electric field strength at a point in space (i.e. the electric field prior to the
introduction of the field meter and operator) or on conducting surfaces.
Sources of uncertainty during measurements are also identified and guidance is provided on
how they should be combined to determine total measurement uncertainty.

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SIST IEC 61786-2:2017
IEC 61786-2:2014 © IEC 2014 – 7 –
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 61786-1:2013, 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
ISO/IEC Guide 99:2007, International vocabulary of metrology – Basic and general concepts
and associated terms (VIM)
ISO/IEC Guide 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE Throughout this standard, the words "magnetic flux density" and "magnetic field" will be considered
synonymous.
3.1
average exposure level
spatial average over the entire human body of fields to which the individual is exposed
3.2
correction factor
numerical factor by which the uncorrected result of a measurement is multiplied to
compensate for a known error
Note 1 to entry: Since the known error cannot be determined perfectly, the compensation cannot be complete.
3.3
coverage factor
numerical factor used as a multiplier of the combined standard uncertainty in order to obtain
an expanded uncertainty
Note 1 to entry: For a quantity z described by a normal distribution with expectation m and standard deviation σ,
z
the interval m ± kσ encompasses 68,27 %, 95,45 %, and 99,73 % of the distribution for a coverage factor k = 1, 2,
z
and 3, respectively.
3.4
repeatability (of results of measurements)
closeness of agreement between the results of successive measurements of the same
measurand, carried out under the same conditions of measurement, i.e.:
− by the same measurement procedure,
− by the same observer,
− with the same measuring instruments, used under the same conditions,
− in the same laboratory,
− at relatively short intervals of time.
[SOURCE: IEC 60050-311:2001, 311-06-06, modified –The note to entry has been deleted.]

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3.5
reproducibility (of measurements)
closeness of agreement between the results of measurements of the same value of a quantity,
when the individual measurements are made under different conditions of measurement:
− principle of measurement,
− method of measurement,
− observer,
− measuring instruments,
− reference standards,
− laboratory,
− under conditions of use of the instruments, different from those customarily used,
− after intervals of time relatively long compared with the duration of a single measurement
[SOURCE: IEC 60050-311:2001, 311-06-07, modified –The notes to entry have been deleted.]
3.6
standard uncertainty
uncertainty of the result of a measurement expressed as a standard deviation
3.7
uncertainty of measurement
parameter, associated with the result of a measurement, that characterises the dispersion of
the values that could reasonably be attributed to the measurand
Note 1 to entry: Uncertainty of measurement generally comprises many components. Some of these components
may be estimated on the basis of the statistical distribution of the results of series of measurements, and can be
characterised by experimental standard deviations. Estimates of other components can be based on experience or
other information.
4 General considerations
4.1 Different goals of measurement
4.1.1 General
Magnetic and electric fields can be characterised according to a number of parameters, i.e.
magnitude, frequency, polarization, etc. (see IEC 61786-1:2013, Annex C). Characterisation
of one or more of these parameters and how they might relate to human exposure may serve
as possible goals of a measurement programme. As an aid for readers interested in
developing a field measurement protocol, this subclause provides a list of such possible
measurement goals and possible methods for their accomplishment.
Except in the vicinity of high voltage sources, there is no need to measure the power
frequency electric field, because the electric field will be, at most, a few tens of volts per
1
metre [3; 22] .
Annex A gives examples of typical field characteristics in different environments.
The goals of a measurement programme, such as those considered below, shall be clearly
defined. A clear definition of goals is required for the determination of instrumentation and
calibration requirements, e.g. instrumentation pass-band, magnitude range, frequency
calibration points, etc. Once the goals have been identified and appropriate instrumentation
has been acquired, a pilot study in the measurement environment of interest may be desirable
___________
1
 Numbers in square brackets refer to the Bibliography.

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IEC 61786-2:2014 © IEC 2014 – 9 –
before decisions are made as to the final measurement methods and associated protocol. The
protocol will describe the step-by-step procedure to follow, using the possible methods
indicated, to accomplish the measurement goals. The protocol may explicitly indicate such
things as instrument requirements (e.g. pass-band, probe size, magnitude range), location of
measurements and duration of measurements. It should then be possible, using the same
protocol, to compare with confidence measurement results obtained in similar electrical
environments.
Possible measurement goals and possible methods for their accomplishment are given in
4.1.2 to 4.1.6.
4.1.2 Characterisation of field levels for compliance with safety standards
Limits on permissible electric or magnetic field levels expressed as resultant values and as a
function of frequency have been indicated in a number of documents, such as [17-19; 21]
necessitating the determination of field levels with the maximum value or spatial value in
specified areas. The choice of measurement location shall be done in consideration of the
possible location of people.
Method: Three-axis meters shall be used to make such measurements of the resultant
magnetic and electric fields. Standards and guidance exist for such measurements near
power lines [4; 9; 15] and electric appliances [10] .
Measurements of magnetic fields near power lines should be correlated with load currents.
Load currents for appliances are either constant or, typically, periodic through a fixed range in
a relatively short time, enabling the determination of the largest resultant magnetic field with
relatively few measurements.
4.1.3 Characterisation of spatial variations
Magnetic and electric fields are not constant around sources. For example, variations of
magnetic or electric fields below power lines are typical (Figures 1 and 2) and can be
calculated.
In Figure 1, non-uniformity is defined by [4; 9] as the maximum value of
( B − B ) / B ×100 (%)
h avg avg
Where
B is the magnetic field level at heights of 0,5 m, 1,0 m and 1,5 m above ground;

h
B is the arithmetic mean of the three levels.

avg

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100
untransposeduntransposed
5,0
1,1,5 m5 m
4,5 90
A A
1,1,0 m0 m
AA AA
80
4,0 0,0,5 m5 m
B B
BB BB
-
Non-uniformity 70
3,5 C C
CC CC
60
3,2 m 3,2 m
3,0
50
2,5
40 3,0 m
2,0
3,5 m 3,5 m
30
1,5
20
1,0
10
3,0 m
0,5
0 3,8 m 3,8 m
–10
0,0
–30 –20 –10 0 10 20 30
Distance  (m)
Conductor
transposedtransposed
7,0
100
1,1,5 m5 m
phase sequencephase sequence
90
6,0 1,1,00m m
C
AAA  CC
6,0 m
0,0,5 m5 m
80
B B
BB BB
non -
Non-uniformity
5,0 70
C A
CC AA
60
4,0
50
1,0 m
3,0
40
G.L.
30
2,0
Distance  (m)
0
20
1,0
10
0
0,0
–30 –20 –10 0 10 20 30
77 kV, double-circuit, vertical configuration
Distance  (m)
IEC

Figure 1 – Magnetic field levels under a 77 kV overhead transmission line (from [9])
3,2 m 3,2 m

Phase sequence
phase sequencphase sequencee
3,0 m
AAA  AAA  A C
AA CC
900
3,5 m 3,5 m
Electric Field (V/m)
900
BBB  BBB  B B
BB BB
800 C C C A
CC CC CC AA
800
3,0 m
UntranspoUntransposedsed transposetransposedd
700
700 3,8 m 3,8 m
600
600
500
500
Conductor
400
400
11,0 m
300
300
200
200
100
100
1,0 m
0
0
G.L.
–30 –20 –10 0 10 20 30
- 30 - 20 - 10 0 10 20 30
Distance x  (m)
0
Distance (m)
distance x (m)
77 kV, double-circuit, vertical configuration
IEC

Figure 2 – Electric field levels under an overhead transmission line (from [9])
The spatial distribution of magnetic fields away from power lines or single identifiable sources
is typically unknown.
Alternating magnetic fields in most environments will be non-uniform because of the spatial
dependence of the fields from the source currents. It is noteworthy that static magnetic fields
also show considerable spatial variability in residences [29].
Method: The magnetic field components shall be recorded as a function of coordinate position
when characterising spatial variation. Standards exist for carrying out such measurements
Electric field  (V/m)
Magnetic field  (mT) Magnetic field  (mT)
Non-uniformity  (%) Non-uniformity  (%)

---------------------- Page: 12 ----------------------

SIST IEC 61786-2:2017
IEC 61786-2:2014 © IEC 2014 – 11 –
near power lines [4; 9; 15] and electric appliances [[9]]. While such measurements can be
made with survey meters, instrumentation incorporating "measurement wheels" is available
for characterising spatial distributions of magnetic fields in environments where physical
obstructions do not hinder the movement of the wheel. As the wheel rotates, it periodically
triggers a three-axis magnetic field meter to record the resultant magnetic field. Software
provided with such instrumentation permits the generation of plots of magnetic field profiles,
equifield contours, statistical analyses of the field levels, etc [2; 26]. As for characterisation of
field levels for compliance with safety limits, such data will not take the temporal variations of
the field profiles into account without repeated measurements.
4.1.4 Characterisation of temporal variation
Because magnetic fields are produced by load currents and ground return currents that can
vary greatly with time, the temporal variations of magnetic fields can easily exceed a factor of
2.
Under a power line, the magnetic field depends on the load of the line. For single circuit lines
or double circuit lines operated in parallel, the magnetic field is directly proportional to the
load of the line. Figure 3 gives an example of the load of a 735 kV line and the outdoor
temperature. In this case, the load is influenced by human activities (daily cycle) and by
outdoor temperature (season cycle) and by the place of the line in the network. Moreover, the
magnetic field level can vary with the sagging of the conductors because of heating due to
large current loads and environmental conditions [16] .
IEC

Figure 3 – Example of load variation of 735kV line due to
the human activities (daily) and outdoor
...