IEC TR 63167:2018

IEC TR 63167 ®
Edition 1.0 2018-06
TECHNICAL
REPORT
colour
inside
Assessment of contact current related to human exposure to electric, magnetic
and electromagnetic fields
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IEC TR 63167 ®
Edition 1.0 2018-06
TECHNICAL
REPORT
colour
inside
Assessment of contact current related to human exposure to electric, magnetic

and electromagnetic fields
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20 ISBN 978-2-8322-5751-7

– 2 – IEC TR 63167:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Abbreviated terms . 8
5 Contact current in EMF exposure guidelines . 8
6 Consideration in evaluating contact currents . 9
6.1 General . 9
6.2 Assumed situations of human exposure to contact current . 9
6.2.1 General . 9
6.2.2 Capacitive coupling (power line) . 9
6.2.3 Inductive coupling (power line) . 9
6.2.4 Induction heating equipment . 9
6.2.5 Wireless power transfer (WPT) . 10
6.2.6 Broadcasting . 10
6.3 Methods of measurement of touch current used in electrical safety standards . 10
6.3.1 General . 10
6.3.2 IEC standards related to electrical safety . 10
6.3.3 Modelling human body impedance . 12
6.4 Proposed methods of measuring contact current . 15
6.4.1 General . 15
6.4.2 Contact current measurement using a human subject . 15
6.4.3 Contact current measurement using a human equivalent

impedance/circuit. 16
6.4.4 Contact current calculated from measurement of open-circuit voltage . 16
7 Consideration in standardization of evaluation method for contact current . 17
Annex A (informative) Contact current limits in international EMF guidelines. 18
Bibliography . 20

Figure 1 – Time/current zones of effects of alternating currents (15 Hz to 100 Hz) on
persons for a current path corresponding to left hand to feet (for explanation see
Table 2) . 12
Figure 2 – Measuring network for unweighted touch current [16] . 13
Figure 3 – Measuring network for touch current weighted for perception or startle-
reaction [16]. 14
Figure 4 – Simulated body impedance for contact current measurements shown in
IEEE C95.3 [27] . 14
Figure 5 – Impedances of various parts of the body proposed in IEC TS 62996 for 1
kHz to 6 MHz [11] . 15
Figure 6 – Realistic computational 3D human body model and results of calculation of
current density and pathway . 17

Table 1 – Selected IEC technical committees and standards related to electrical safety . 11
Table 2 – Time/current zones for alternating current 15 Hz to 100 Hz for hand to feet
pathway – Summary of zones in Figure 1 . 12

Table A.1 – Reference levels in ICNIRP guidelines for time varying contact current
from conductive object [1], [2] . 18
Table A.2 – Maximum permissible exposure (MPE) levels of contact current in IEEE
safety standards [3], [4] . 18

– 4 – IEC TR 63167:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ASSESSMENT OF CONTACT CURRENT RELATED TO HUMAN EXPOSURE
TO ELECTRIC, MAGNETIC AND ELECTROMAGNETIC FIELDS

FOREWORD
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example "state of the art".
IEC TR 63167, which is a Technical Report, 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 Technical Report is based on the following documents:
Enquiry draft Report on voting
106/422/DTR 106/436A/RVDTR
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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
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the specific document. At this date, the document will be
• reconfirmed,
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• replaced by a revised edition, or
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– 6 – IEC TR 63167:2018 © IEC 2018
INTRODUCTION
In the guidelines limiting human exposure to electric, magnetic and electromagnetic fields
(EMF guidelines), limits for the contact current are given to avoid adverse indirect effects, i.e.
electric shocks and burn hazards caused by contact with a conductive object located in an
electric and/or magnetic field, when the object has an electric potential owing to electric or
magnetic induction to the object.
At the moment, no standardized method for evaluating the contact current, in the context of
human exposures to the above fields has been well established. On the other hand, there is a
huge amount of knowledge, as well as many standards and regulations on the issue of
electrical safety (i.e. direct contact with live part of conductive object) to avoid severe electric
shock hazards. Therefore, the evaluation methods used in the field of electrical safety might
be useful references. This document summarizes general information on the assessment of
contact current related to human exposure to electric, magnetic and electromagnetic fields.

ASSESSMENT OF CONTACT CURRENT RELATED TO HUMAN EXPOSURE
TO ELECTRIC, MAGNETIC AND ELECTROMAGNETIC FIELDS

1 Scope
This document, which is a Technical Report, provides general information on the assessment
of contact current related to human exposure to electric, magnetic and electromagnetic fields.
The contact currents in this context occur when a human body comes into contact with a not
electrified conductive object exposed to an electric and/or magnetic field at a different electric
potential owing to electric and/or magnetic induction to the object. This is distinguished from
the issue of electrical safety where contact with live parts of a conductive object is dealt with.
In reference to the international EMF guidelines [1]-[4] , the frequency range of contact
current covered in this document is direct current to 110 MHz, and only steady-state
(continuous) contact currents are covered. Transient contact currents (spark discharges)
which may occur immediately before the contact with the object are not covered.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
contact current
current flowing into the body resulting from contact with a conductive object in an electric,
magnetic or electromagnetic field
3.2
electric field strength
magnitude of a field vector at a point that represents the force (F) on an infinitely small charge
(q) divided by the charge
3.3
exposure
state that occurs when a person is subjected to an electric, magnetic or electromagnetic field,
or to a contact current other than those originating from physiological processes in the body
and other natural phenomena
___________
Numbers in square brackets refer to the Bibliography.

– 8 – IEC TR 63167:2018 © IEC 2018
3.4
indirect effect
effect resulting from physical contact between a person and a not electrified object, such as a
metallic structure in an electric, magnetic or electromagnetic field, at an electric potential that
is at least at a point of the object different from the potential of the person
3.5
touch current
electric current flowing through a human body when it touches one or more accessible parts
of an installation or of equipment
Note 1 to entry: The term “leakage current” had also been used as a synonym for touch current in the field of
electrical safety.
3.6
spark discharge
transfer of current through an air gap prior to making contact with another conductive object at
a different potential
4 Abbreviated terms
AM amplitude modulation
EMF electric, magnetic or electromagnetic field
EV electric vehicle
FM frequency modulation
ICNIRP International Commission on Non-Ionizing Radiation Protection
IEEE Institute of Electrical and Electronics Engineers
IH induction heating
MPE maximum permissible exposure
MRI magnetic resonance imaging
PC personal computer
RF radio frequency
WPT wireless power transfer
5 Contact current in EMF exposure guidelines
Clause 5 overviews contact currents described in the EMF guidelines [1]-[4].
In the frequency range up to approximately 10 MHz (dominantly up to 100 kHz), the flow of
electric current from an object in a field to the body of an individual may result in the
stimulation of muscles and/or peripheral nerves. With increasing current, this may be
manifested as perception, pain from an electric shock and/or burn, the inability to release the
object, difficulty in breathing and, at higher currents, cardiac ventricular fibrillation.
In the frequency range of about 100 kHz to 110 MHz, shocks and burns can result either from
an individual touching an ungrounded metal object that has acquired a charge in a field or
from contact between a charged individual and a grounded metal object.
In the EMF guidelines, reference levels for steady state (continuous) contact current are given
for frequencies up to 110 MHz to avoid shock and burn hazards (see Annex A). The reference
levels are not intended to avoid ventricular fibrillation, which is the basis of standards for
electrical safety. The upper frequency of 110 MHz is the upper frequency limit of the FM
broadcast band. Here, the transient currents resulting from spark discharges [5], which can

occur when an individual comes into very close proximity with an object at a different electric
potential, are not considered in the reference levels of contact current. Instead, the effect of
spark discharge is considered in the reference levels of electric field exposure for the general
public by including a sufficient margin to prevent surface electric-charge effects such as
perception by most people.
It is noteworthy that different methods for evaluation of conformity to the guidelines are
provided for multiple-frequency exposure for low-frequency (below 100 kHz) and
high-frequency (above 10 kHz) ranges. In the frequencies between 10 kHz and 100 kHz, both
evaluation methods are applied (see Annex A).
6 Consideration in evaluating contact currents
6.1 General
Clause 6 describes items to be considered in evaluating contact currents:
a) assumed situations of human exposure to a contact current (6.2);
b) methods for evaluating a touch current used in electrical safety standards for
references (6.3);
c) some proposed methods for evaluating contact currents (6.4).
6.2 Assumed situations of human exposure to contact current
6.2.1 General
There are several situations to be considered for human exposure to a contact current.
Different cases have to be considered depending on the type of coupling between fields
(electric or magnetic) and human bodies/objects.
6.2.2 Capacitive coupling (power line)
An electric field induces, by capacitive coupling (electrostatic induction), a voltage in a person
or a conductive object that is isolated from the ground. When a person touches an object
having a different potential, a contact current flows so as to cancel the potential difference.
This can be categorized into two cases: (a) an isolated person touches a grounded object and
(b) a grounded person touches an isolated object (especially a large object such as a bus or a
truck) [6]. Comprehensive studies have been carried out for typical cases encountered under
overhead transmission lines [7].
6.2.3 Inductive coupling (power line)
By inductive coupling (electromagnetic induction), a magnetic field induces a voltage,
especially in long conductive objects such as telecommunication lines, fences and gas
pipelines, having at least one reasonable grounding, when they are installed close to and
parallel to magnetic field sources such as overhead power lines [8]. When a person touches
the object, a contact current flows. In particular, in the case of fault condition in overhead
power lines, the limit values for the open-circuit voltage in telecommunication lines are set by
an international regulation-setting body [9]. In contrast to the capacitive coupling, grounding a
conductive object at a large distance from the point of contact will actually increase the
amplitude of the open-circuit voltage, thereby increasing the contact current.
6.2.4 Induction heating equipment
Induction heating (IH) equipment is heating equipment using the Joule effect produced by
magnetically induced currents. For a domestic IH cooker, a metal pan or pot is heated by a
magnetic field, and when a person touches a conductive part of the pan or pot, a contact
current can occur typically in the frequency ranges of around 20 kHz to 100 kHz. The method
used to evaluate human exposure to magnetic fields produced by IH cookers is standardized

– 10 – IEC TR 63167:2018 © IEC 2018
in IEC 62233 [10]; however, the contact current is not mentioned in IEC 62233. Note that it
may be appropriate to categorize this exposure situation as an issue of electrical safety.
For industrial IH equipment, a method of evaluating touch current in terms of electrical safety
is being standardized in IEC TC 27 (industrial electroheating and electromagnetic processing)
for the frequency ranges between 1 kHz and 6 MHz [11].
6.2.5 Wireless power transfer (WPT)
A wireless power transfer (WPT) system is a system capable of transferring power between a
transmitter and receiver using wireless technologies including electromagnetic induction. They
are used for wirelessly charging mobile phones, tablet PCs, electric vehicles (EV) and, so
forth. There are several types of WPT, and the frequency range used is from tens of kilohertz
to tens of megahertz. When a conductive object is placed in the immediate vicinity of a
system and a person touches it, a contact current can occur. As touching the metal body of an
EV when charging using a WPT charging system may be the case [12], it may be appropriate
to categorize the exposure situation as an issue of electrical safety. Details regarding
exposure assessment methods for WPT systems are reported in IEC TR 62905 [13].
In IEC TR 62905, contact currents are considered for the conditions where ungrounded or
grounded metal object is placed in the vicinity of WPT systems.
6.2.6 Broadcasting
Burns can occur at a point of contact between a human body and a metallic structure that is
exposed to
...