IEC/TR 61000-5-6

SLOVENSKI SIST-TP IEC/TR 61000-5-6:2004

STANDARD
april 2004
Electromagnetic compatibility (EMC) - Part 5-6: Installation and mitigation
guidelines - Mitigation of external EM influences
ICS 33.100.01 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

TECHNICAL IEC
REPORT
TR 61000-5-6
First edition
2002-06
PUBLICATION FONDAMENTALE EN CEM
BASIC EMC PUBLICATION
Electromagnetic compatibility (EMC) –
Part 5-6:
Installation and mitigation guidelines –
Mitigation of external EM influences
Compatibilité électromagnétique (CEM) –
Partie 5-6:
Guides d'installation et d'atténuation –
Atténuation des influences électromagnétiques externes
 IEC 2002  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch  Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
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International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – TR 61000-5-6  IEC:2002(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope and general considerations.6
1.1 Scope.6
1.2 General considerations.6
2 Reference documents.8
3 Terms, definitions and acronyms .10
4 Mitigation of radiated and conducted disturbances .13
4.1 Topological concepts.13
4.2 Mitigation needs .14
4.3 The general concept of enclosure.15
4.4 Interactions at the enclosure boundary.16
5 Shielding .16
5.1 General .16
5.2 Classification of protection zones .18
5.3 Design principles for screening.19
5.4 Implementation of screening.21
6 Filters.26
6.1 General .26
6.2 Fundamental filter characteristics .27
6.3 Functional tasks .29
6.4 Additional filtering concerns .30
6.5 Selection criteria .30
6.6 Filter installation.33
6.7 Filter testing .36
7 Decoupling devices .37
7.1 Isolation transformers.37
7.2 Motor-generator sets .39
7.3 Engine generators .40
7.4 Uninterruptible power supplies (UPS) .40
7.5 Optical links .41
8 Surge-protective devices .41
8.1 General .41
8.2 Direct equipment protection.42
8.3 Installation of multiple SPDs.43
8.4 Side-effects of uncoordinated cascades .44
8.5 Typical protective devices .44
Bibliography.45

TR 61000-5-6  IEC:2002(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 5-6: Installation and mitigation guidelines –
Mitigation of external EM influences
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this technical report may be the subject of
patent rights. The 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”.
Technical reports do not necessarily have to be reviewed until the data they provide are
considered to be no longer valid or useful by the maintenance team.
IEC 61000-5-6, which is a technical report, has been prepared by subcommittee 77C: High
power transient phenomena, of IEC technical committee 77: Electromagnetic compatibility.
It has the status of a basic EMC publication in accordance with IEC Guide 107.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
77C/110/CDV 77C/122/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 document, which is purely informative, is not to be regarded as an International
Standard.
– 4 – TR 61000-5-6  IEC:2002(E)
The committee has decided that the contents of this publication will remain unchanged until
2007. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this technical report may be issued at a later date.

TR 61000-5-6  IEC:2002(E) – 5 –
INTRODUCTION
IEC 61000 is published in separate parts according to the following structure:
Part 1: General
General considerations (introduction, fundamental principles)
Definitions, terminology
Part 2: Environment
Description of the environment
Classification of the environment
Compatibility levels
Part 3: Limits
Emission limits
Immunity limits (in so far as they do not fall under the responsibility of product
committees)
Part 4: Testing and measurement techniques
Measurement techniques
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous
Each part is further subdivided into several parts published either as International Standards
or as technical specifications or technical reports, some of which have already been published
as sections. Others will be published with the part number followed by a dash and a second
number identifying the subdivision (example: IEC 61000-6-1).
This part of IEC 61000 gives guidelines for the mitigation of external electromagnetic
influences.
– 6 – TR 61000-5-6  IEC:2002(E)
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 5-6: Installation and mitigation guidelines –
Mitigation of external EM influences
1 Scope and general considerations
1.1 Scope
This part of IEC 61000 covers guidelines for the mitigation of external electromagnetic
influences impinging upon a facility, aimed at ensuring electromagnetic compatibility (EMC)
among electrical and electronic apparatus or systems. These influences include lightning,
RF transmitters, power-line and telecom transients, high-altitude electromagnetic pulse
(HEMP) and other high-power electromagnetic transients. More particularly, this technical
report is concerned with the arrangement of shielding and screening against radiated
disturbances, and with mitigation of conducted disturbances. These arrangements include
appropriate electromagnetic barriers for industrial, commercial, and residential installations.
The concept of barriers installed for mitigating potentially penetrating and unwanted
electromagnetic noise is applicable even when there is no designed-in electromagnetic shield.
The enclosure through which power and signal (communications, control, etc.) cables must
enter or exit may be considered as a potential electromagnetic barrier that will provide some
level of protection. The concept of enclosure can be understood as the perimeter walls of a
building, the walls of a single room, or the housing of an apparatus, with protection installed
at all points of electromagnetic penetration into the enclosure.
This technical report is intended for use by installers, manufacturers and users of sensitive
electrical or electronic installations or systems, and of equipment with emission levels that
could degrade the overall electromagnetic (EM) environment. It applies primarily to new
installations but, where economically feasible, it may be applied to extensions or
modifications to existing facilities. While the technical principles are applicable to individual
equipment or apparatus, such application is not included in the scope of this technical report.
1.2 General considerations
1.2.1 Elementary interference control
In its simplest form, the interference problem consists of a source of disturbance, a victim and
the medium between the two. Interference control consists of suppressing the disturbance
source, strengthening the victim, or impeding the source-victim interaction through the
medium. When the source is not controllable (for example, lightning, portable transmitters,
HEMP, etc.), and the inherent strength of the victim is dictated by other considerations (for
example, circuit density and operating power), interference control is relegated to the
intervening medium. Furthermore, for interference control oriented toward victim protection,
control measures tend to be applied fairly close to the susceptible circuits (at the system or
subsystem levels).
Increasing the separation between them, enclosing one or the other in a shield or ortho-
gonalizing them (for example, rejecting common-mode interference on differential-mode
signalling lines) can reduce the interaction between source and victim. All three techniques
can be combined to form a closed electromagnetic barrier between the source and the victim.
For sources outside the system, the barrier may be applied at the system level. For sources
inside the system, electromagnetic compatibility requires two barriers: one at the source to
control emissions, and one at the victim to control susceptibility. This concept is illustrated in
figure 1. In this technical report, we will concentrate on sources outside the system.

TR 61000-5-6  IEC:2002(E) – 7 –
System barrier
Outside
sources
System
sources
Subsystem 1
Subsystem 2
Source Source
Penetrating
Victim Victim
conductor
Barriers
IEC  1497/02
Figure 1 – System barrier topology
1.2.2 Shields and interfaces
Shields are used for attenuating the direct coupling of radiated electromagnetic disturbances
from the external environment onto the internal electronics circuits and, conversely, to limit
the radiation of disturbances from the internal circuits to the exterior, thus contributing to the
electromagnetic compatibility (EMC) of the installation. The shields considered in this
document are electromagnetically closed structures. Any form of electromagnetically open
structure is not recommended for achieving a fully compliant installation. Some examples of
structure shielding applications include
– telecom facilities, such as relay stations, multipurpose radio installations;
– TV and broadcasting studios;
– test rooms and laboratories (telecom, metrology, high-voltage engineering);
– metrology facilities in educational institutions;
– diagnostic and therapy rooms in medical facilities;
– computer rooms for business and industry.
Interface protection devices are used for mitigating the propagation of conducted
electromagnetic disturbances from the environment into the internal electronics and may,
conversely, limit the emission of disturbances from the internal electronics into the
environment. This assumes that bi-directional protection devices are applied. Thus, when
installed in conjunction with a shield, these devices contribute to achieving electromagnetic
compatibility for the installation. Protection devices that will be discussed in this technical
report include filters, decoupling devices and surge-protective devices (SPDs).
The filters considered in this document are limited to low-voltage passive circuits for high-
frequency disturbances that are part of an installation. Filters and other interface devices
incorporated in individual apparatus are not included within the scope of this document. Low-
frequency filters, such as those used to mitigate power-line harmonics, are also not included
in the scope of this document.
A complete installation can include the interconnection of several properly shielded cabinets
with screened cables. However, the selection of such cables and proper bonding of the cable
screens is not within the scope of this publication, but is addressed in IEC 61000-5-2.
The installation of filters and other mitigation means, including shields, is predicated on the
existence of a properly designed earthing system, as described in IEC 61000-5-2.

– 8 – TR 61000-5-6  IEC:2002(E)
The recommendations presented in this technical report address the EMC concerns of the
installation. The safety aspects of any installation are of prime importance but while not
ignored, are not within the scope of this technical report. Reference to safety issues may be
found in IEC 60364-1, IEC 60364-5-54, and IEC 60364-5-548. The efficient transportation of
power within the installation is a prime function of any facility, but is also excluded from the
scope of this technical report. Nevertheless, these two issues are taken into consideration in
the recommendations concerning EMC. These two issues can be implemented concurrently
for enhanced EMC of the installed sensitive apparatus or systems without conflict by applying
the recommended practices presented in this technical report and the relevant safety
requirements such as those of IEC 60364. As each installation is unique, it is the
responsibility of the designer and the installer to select and abide by the relevant
recommendations most appropriate to a particular installation. It is important to note that
the recommendations presented in this technical report do not seek to preclude existing
installation practices, when they have been shown to perform satisfactorily. Special mitigation
methods might not be necessary when the installed equipment satisfy applicable emission
and immunity standards.
1.2.3 Summary
Clauses 1-3 provide general information concerning the scope, references and definitions
applicable to this publication.
Clause 4 provides an overview and introduction of the general approach to applying EMC
concepts in the design of installations through the use of appropriate interface protection
devices.
Clause 5 provides information on the application of shields to mitigate the coupling of radiated
disturbances and to create a boundary between different zones of disturbance levels.
Clause 6 provides information on the application of filters as interface protection devices that
can be inserted in power and signal cables entering the shield or enclosure.
Clause 7 provides information on the application of decoupling devices as interface protection
devices that can be inserted in power cables or applied to signal cables entering the shield or
enclosure.
Clause 8 provides information on the application of SPDs as interface protection devices that
can be inserted in power or signal cables entering the shield or enclosure.
It is emphasized that this technical report does not discuss in detail the internal design of
these mitigation means. However, some knowledge of their fundamental characteristics,
as well as some information on the EM disturbance environment, is necessary to make an
appropriate selection of measures and to install them in a way that will not make them
ineffective.
2 Reference documents
IEC 60050(161), International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
IEC 60050(195), International Electrotechnical Vocabulary (IEV) – Chapter 195: Earthing and
protection against electric shock
IEC 60050(300), Part 312, International Electrotechnical Vocabulary (IEV) – Electrical and
electronic measurements and measuring instruments – Part 312: General terms relating to
electrical measurements
TR 61000-5-6  IEC:2002(E) – 9 –
IEC 60335-1, Household and similar electrical appliances – Safety – Part 1: General
requirements
IEC 60364-1, Electrical installations of buildings – Part 1: Fundamental principles,
assessment of general characteristics, definitions
IEC 60364-5-54, Electrical installations of buildings – Part 5: Selection and erection of
electrical equipment – Chapter 54: Earthing arrangements and protective conductors
IEC 60364-5-548, Electrical installations of buildings – Part 5: Selection and erection of
electrical equipment – Section 548: Earthing arrangements and equipotential bonding for
information technology installations
IEC 60939-1, Complete filter units for radio frequency suppression – Part 1: Generic
specification
IEC 60939-2, Complete filter units for radio frequency suppression – Part 2: Sectional
specification. Selection of methods for test and general requirements
IEC/TR2 61000-2-5, Electromagnetic compatibility – Part 2: Environment – Section 5:
Classification of electromagnetic environments. Basic EMC publication
IEC 61000-2-11, Electromagnetic compatibility – Part 2-11: Environment – Classification of
HEMP environments
IEC 61000-4-4, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement
techniques – Section 4: Electrical fast transient/burst immunity test. Basic EMC publication
IEC 61000-4-5, Electromagnetic compatibility (EMC) – Part 4-5: Testing and measurement
techniques – Surge immunity test
IEC 61000-4-12, Electromagnetic compatibility (EMC) – Part 4-12: Testing and measurement
techniques – Oscillatory waves immunity test
IEC/TR 61000-5-1, Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation
guidelines – Section 1: General considerations. Basic EMC publication
IEC/TR 61000-5-2, Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation
guidelines – Section 2: Earthing and cabling
IEC/TR 61000-5-3, Electromagnetic compatibility (EMC) – Part 5-3: Installation and mitigation
guidelines – HEMP protection concepts
IEC/TR2 61000-5-4, Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation
guidelines – Section 4: Immunity to HEMP – Specifications for protective devices against
HEMP radiated disturbance. Basic EMC publication
IEC 61000-5-5, Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation
guidelines – Section 5: Specification of protective devices for HEMP conducted disturbance.
Basic EMC publication
IEC 61000-5-7, Electromagnetic compatibility (EMC) – Part 5-7: Installation and mitigation
guidelines – Degrees of protection provided by enclosures against electromagnetic
disturbances (EM code)
IEC 61024-1, Protection of structures against lightning – Part 1: General principles

– 10 – TR 61000-5-6  IEC:2002(E)
IEC 61312-1, Protection against lightning electromagnetic impulse (LEMP) – Part 1 – General
principles
IEC/TS 61312-2, Protection against lightning electromagnetic impulse (LEMP) – Part 2:
Shielding of structures, bonding inside structures and earthing
IEC/TS 61312-3, Protection against lightning electromagnetic impulse (LEMP) – Part 3:
Requirements of surge protective devices (SPDs)
IEC 61312-4, Protection against lightning electromagnetic impulse (LEMP) – Part 4:
Protection of equipment in existing structures
IEC/TR 62066, General basic information regarding surge overvoltages and surge protection
in low-voltage a.c. power systems
CISPR 17, Methods of measurement of the suppression characteristics of passive radio
interference filters and suppression components
3 Terms, definitions and acronyms
For the purposes of this technical report, the definitions of IEC 60050(161) together with the
following definitions apply.
3.1
apparatus
finished combination of devices (or equipment) with an intrinsic function intended for the final
user and intended to be placed on the market as a single commercial unit
3.2
attenuation
ratio of the input to the output values of quantities of the same kind in a device or system
NOTE When this ratio is less than unity it is usually replaced by its reciprocal, the gain.
[IEV 312-06-06]
3.3
device
combination of components having a given function, forming part of a piece of equipment,
apparatus, or system
NOTE For example, thermostat, relay, push buttons, switch or contactor.
3.4
(local) earth
(local) ground (US)
part of the earth which is in electric contact with an earth electrode and the electric potential
of which is not necessarily equal to zero
3.5
earth (verb)
ground (verb) (US)
make an electric connection between a given point in a system or in an installation or in
equipment and a local earth
NOTE The connection to local earth may be
– intentional, or
___________
To be published
TR 61000-5-6  IEC:2002(E) – 11 –
– unintentional or accidental
and may be permanent or temporary.
[IEV 195-01-08]
3.6
earth electrode
ground electrode (US)
conductive part, which may be embedded in a specific conductive medium, e.g. concrete or
coke, in electric contact with the Earth
[IEV 195-02-01]
3.7
earthing arrangement
grounding arrangement (US)
earthing system (deprecated)
all the electric connections and devices involved in the earthing of a system, an installation
and equipment; the electrical circuit, or a part of it, including the earth electrode, which
performs the earthing of a system, an installation and equipment
[IEV 195-02-20, modified]
3.8
electromagnetic compatibility
EMC (abbreviation)
ability of an equipment or system to function satisfactorily in its electromagnetic environment
without introducing electromagnetic disturbances to anything in that environment
[IEV 161-01-07]
3.9
electromagnetic disturbance
any electromagnetic phenomenon which may degrade the performance of a device,
equipment or system, or adversely affect living or inert matter
NOTE An electromagnetic disturbance may be an electromagnetic noise, an unwanted signal, or a change in the
propagation medium itself.
[IEV 161-01-05]
3.10
electromagnetic interference
EMI (abbreviation)
degradation of the performance of an equipment, transmission channel, or system caused by
an electromagnetic disturbance
[IEV 161-01-06]
3.11
equipment
general term for apparatus, appliance, system, etc.
NOTE For the purposes of the present document, to make a distinction between the collective (plural) nature of
the term “equipment” and an individual “piece of equipment”, the term “apparatus” will be used when the meaning
is a single piece.
3.12
equipotential bonding
provision of electric connections between conductive parts, intended to achieve equipotentiality

– 12 – TR 61000-5-6  IEC:2002(E)
[IEV 195-01-10]
3.13
facility
entity (such as a hospital, a factory, machinery, etc.) that is built, constructed, installed or
established to perform some particular function or to serve or facilitate some particular end
3.14
filter
two-port network that transmits signals with low attenuation at all frequencies within one or
more frequency bands and with high attenuation at all other frequencies
3.15
HEMP
high altitude electromagnetic pulse
3.16
installation
several combined items of apparatus or systems put together at a given place to fulfil
a specific objective but not intended to be placed into service as a single functional unit
3.17
maximum continuous operating voltage
maximum voltage which may be continuously applied to the SPDs mode of protection (equal
to the rated voltage)
3.18
residual voltage (current)
peak value of voltage (current) that appears at the output terminals of an SPD or filter during
application of a standard stress at the input terminals
3.19
screen
shield
device intended to reduce the penetration of an electric, magnetic or electromagnetic field into
a given region, or to separate electric circuits. A shield is used when a mechanical barrier is
intended
3.20
screening
shielding
act of reducing the magnitude of an electric or magnetic field provided by a good electrical
conductor
3.21
shielded enclosure, screened room
mesh or sheet metallic housing designed expressly for the purpose of separating electro-
magnetically the internal and the external environment
[IEV 161-04-37]
3.22
shielding effectiveness, EMC
for a given external source, the ratio of electric or magnetic field strength at a point before
and after the placement of the shield in question

TR 61000-5-6  IEC:2002(E) – 13 –
3.23
surge-protective device
SPD
device that is intended to limit transient overvoltages and divert surge currents. It contains at
least one non-linear component that is intended to limit surge voltages and divert surge
currents
3.24
system
several items of apparatus combined to fulfil a specific objective
Acronyms
EM electromagnetic
EMC electromagnetic compatibility
EMI electromagnetic interference
HEMP high-altitude electromagnetic pulse
RF radio frequency
SE shielding effectiveness
SPD surge-protective device
UPS uninterruptible power supply
4 Mitigation of radiated and conducted disturbances
4.1 Topological concepts
As a practical matter, the system to be protected is required to communicate with the outside
world via conductive and non-conductive (radiating) paths that penetrate the enclosure
electromagnetic shield and thus introduce imperfections (openings) in the shield. In addition,
other penetrations may be introduced for entry and egress as well as for providing internally a
controlled environment for system operators as well as for the internal equipment, such as
electronics, water, air, sewers, etc. Therefore, a conceptually simple problem may become
quite complex electromagnetically. The concept of topological control has been introduced to
account for a system's inherent electromagnetic complexity. Such a concept may be applied
to simplify both the system electromagnetic coupling problem and to develop and implement
electromagnetic interference control.
In figure 2 we show a generalized, but simple, system topology enclosed in a volume
surrounded by the outer surface. The outer surface may be fabricated from common materials
(concrete, brick, steel reinforcing bars, metal, etc.) and is penetrated by conductive and non-
conductive penetrations such as doors, windows, seams, electrical lines, plumbing, etc. The
electronic equipment may be located in different compartments or rooms. This equipment is
usually interconnected by wiring harnesses or cables. Environmental control equipment and
ducts may also interconnect the equipment rooms. These conductors provide paths for
electromagnetic energy to either exit or enter the enclosure.

– 14 – TR 61000-5-6  IEC:2002(E)
Communication
lines
Exterior region
V
Antenna
V
2,4
V
1,3
V
3,5
V
2,3
System
power
V V
1,4 3,1
V
3,4
Power line
V
2,5
V
2,2
V
V 3,3
3,2
V
2,1
Door
V
1,1
V
1,2
Aperture (doors, windows,
Outer surface
etc.)
S
1 IEC  1498/02
.
Figure 2 – Generalized system topology
All electrical devices, systems and installations produce or utilize at various frequencies
energy which propagates through conductors connected to the apparatus. This energy can
interfere with other equipment. Screening may be necessary either to protect a facility from an
external electromagnetic environment, or to prevent the radiation of electromagnetic
disturbances created by the internal equipment operation.
A formal topological approach may be used 1) to describe the system, and 2) to design a
consistent approach to protect the equipment. A formal approach for decomposing a system
into its smaller, more tractable, parts is possible. Following the notation provided in figure 2
the generalized system is subdivided into the volumes and surfaces. The exterior region or
volume is identified as V ; interior volumes or layers are identified as V , where the first
o j,k
subscript indicates the surface traversed (outside to inside) and the second subscript
indicates the volume within that (jth) surface. The topological approach aids in identifying the
various surfaces and volumes in a particular system and is very useful in describing and
accounting for system electromagnetic shields. The notation may be used for further analysis
as may be warranted. For example, in figure 2, the surface of volume 2 could have different
characteristics in the boundaries to volume 1 and volume 3. This approach also aids in
accounting for the assessment of every penetration in all surfaces.
4.2 Mitigation needs
Mitigation is required if EMC between an apparatus and its environment is not achieved.
However, if EMC has been achieved then no further mitigation is required. Mitigation can be
achieved by using a barrier between the source and the victim. For conducted disturbances
this barrier is typically a combination of SPDs and filters or other decoupling devices, and for
radiated disturbances it can be a screen and perhaps a filter as needed, the attenuation of
which is compatible with that of the screen in the frequency range considered.

TR 61000-5-6  IEC:2002(E) – 15 –
The attenuation provided by a barrier has to be compatible with the need, that is, be at least
equal to the difference between the disturbance level and the immunity level of the apparatus
to that disturbance. For verification purposes, in most of the cases, disturbances are
simulated and the immunity of an apparatus is compared against a standard. Thus, the
attenuation provided corresponds to the difference between the disturbance level (expected
or measured) and the immunity level determined in a laboratory test or by reference to an
established immunity level.
According to uncertainties on disturbance level(s) and immunity level(s), a margin should be
considered as well, and added to the basic attenuation needed. This margin generally
depends on the criticality of the equipment. For most low-risk domestic or industrial
applications of equipment satisfying applicable EMC requirements, there is no need for
additional mitigation.
4.3 The general concept of enclosure
As discussed in IEC 61000-5-1, it is useful to extend the concept of enclosure as being the
boundary of a facility. An enclosure may be envisaged as a complete building, a room, a rack,
a single cabinet and even, by extension of the concept, as an individual apparatus or a circuit
board within an apparatus. This facility interfaces with its environment by “ports” as shown in
figure 3. IEC 61000-5-1 provides further discussion of the concept of ports.
Enclosure port
AC power Control
port port
Apparatus
or
facility
DC power
Signal
port
port
Earth
port
IEC  1499/02
Figure 3 – Ports of an apparatus or facility
The scope of this technical report is restricted to the practices involved in the implementation
of the electrical installation in a facility. These activities involve the selection of functional
elements of the system and the relevant interconnections. This should also include the inter-
connection to external sensors, actuators, telecommunication networks and the power supply.

– 16 – TR 61000-5-6  IEC:2002(E)
4.4 Interactions at the enclosure boundary
Interactions at the enclosure boundary involve two directions of propagation:
– disturbances originating in the environment that can enter the enclosure;
– disturbances generated within the enclosure that can exit the enclosure;
– a shield provided mainly to protect a circuit against radiated disturbances that will also
restrict the emission of radiated disturbances from the circuit;
– likewise, a filter installed to mitigate the entry of a certain type of conducted
disturbances will also restrict the emission of the same type of disturbances, although
the effect might not be bi-directional.
This technical report presents the fundamental concepts for installation practices that limit
radiated disturbances by screening and limiting the propagation of conducted disturbances
across the enclosure boundaries through the use of filters, decoupling devices, and
overvoltage protective devices.
5 Shielding
5.1 General
Electromagnetic shielding of buildings, rooms, compartments, cabinets, rack chassis and
equipment makes it possible to ensure compliance with the EMC for equipment exposed to
radiated disturbances. IEC 61000-2-5 may be used as a guide for EMC limits within each
zone, and IEC 61000-2-11 and IEC 61000-5-3 together may be used as a guide to develop
HEMP limits within each zone. Conversely, radiated disturbances emitted by equipment can
be prevented from “polluting” the environment by enclosing it in an appropriate shielded
enclosure (figure 4). Low-frequency electric fields are relatively easy to mitigate. Low-
frequency magnetic fields are more difficult to screen and will involve a shield with a large
wall thickness and/or a high permeability. IEC 61000-5-7 may be used to qualify the
protection levels for equipment enclosures once the level of desired protection is identified.

TR 61000-5-6  IEC:2002(E) – 17 –
Radiated
disturbances
impinging upon
enclosure
Shielding of
Control-centre building
building armour
Computer room
Shielding of
the room
Sensitive
Radiated
equipment
disturbances
coupling
into external
Shielding of
cabling
the equipment
Conducted
disturbances
Flters and surge-protective
devices
IEC  1500/02
Figure 4 – Topological concept of shields with
interfaces at penetration points
Screening of rooms and cabinets with appropriate penetration protection is only one of
several actions that may be used to limit the effect of radiated electromagnetic disturbances.
For instance, maintaining appropriate distances between emitters and victims is a relatively
effective means of mitigation for radiated disturbances. Obtaining a satisfactory result may
involve other actions such as
a) selecting correct cabling and wiring (adding a screen jacket over cables or wires);
b) applying good cable layout and management;
c) implementing good earthing and bonding practices;
d) using devices limiting the emissions or increasing the immunity.
Refer to IEC 61000-5-1 and IEC 61000-5-2) and to other clauses of this technical reportfor
guidelines concerning these actions:
– clause 6 ;
– clause 7 ;
– clause 8 .
The objective of this clause is to present the main arrangements used in mitigation methods
involving screening of installations, that is:
– introduction of the concept of mitigation zones and review of the corresponding types of
shielded enclosures;
– guidance on preservation of shielding effectiveness for housings with apertures based on
a set of generic EMC rules;
– 18 – TR 61000-5-6  IEC:2002(E)
– generic information on the implementation of screening, progressing from the sensitive
apparatus to the complete building, as well as on the means of dealing with the
unavoidable apertures/penetrations.
5.2 Classification of protection zones
For the purpose of designing and applying appropriate mitigation measures, it is useful to
consider a hierarchy of zones of protection, from the unprotected environment to the strong
protection of especially sensitive equipment. For the purposes of this technical report, the
particular zones are defined as follows:
zone 0 – no protection
zone 1 – buildings protected by reinforced concrete outdoor walls
zone 2 – rooms shielded by special materials
zone 3 – internal equipment shielded by metallic materials or metallized enclosures
zone 4 – sensitive apparatus enclosed within a special shielded rack
Figure 5 shows a schematic representation of the hierarchy of the classification for protection
of zones 0 through 4. Note that not all barriers may be present in a given installation. Zones
may be selected in a more arbitrary manner.
5.2.1 Zone 1 – Building shield
Zone 1 applies to buildings containing welded iron reinforcing bars for concrete outdoor walls.
The reinforcement bars should be interconnected preferentially by as many welds as feasible.
Thus the reinforcement forms a good earthing structure. Note that steel reinforcing bars may
not always be interconnected so that a good electrical bond is made. In such situations the
steel reinforcing bars may not represent an adequate shield. An important first measure is a
well-designed and implemented lightning conductor with conductive connections to the earth.
Conductive penetrations should be protected with appropriate limiting (surge-protective
device) and filtering.
5.2.2 Zone 2 – Room shield
Zone 2 applies to indoor facilities with protection measures. In this case the shield is effective
when it consists of continuously connected (welded) sheet-metal walls or walls with a metal
surface. Bolted or otherwise interconnected walls will result in some degradation of the
shielding effectiveness. All the screens of leads entering this zone must have a short
connection to the metal walls. The penetrating leads should also be protected against
overvoltages with appropriate limiting (surge-protective device) and filtering.
5.2.3 Zone 3 – Equipment shield
Zone 3 applies where individual apparatus is protected by metal cabinets or metallized
enclosures. The earth connection should be a short lead to the earthing arrangement.
Conductive penetrations should be protected with appropriate limiting (surge-protective
device) and filtering.
TR 61000-5-6  IEC:2002(E) – 19 –
5.2.4 Zone 4 – Apparatus shield
External lightning
protection system
Zone 0
Bonding according
Zone 1 to building height
Shielding of
Zone 2
building armour
Zone 3
Shielding of
the room
Zone 4
Sensitive
equipment Shielding of
the equipment
Earth electrode
system
IEC  1501/02
Figure 5 – Zones of protection of shielding and earthing systems
Zone 4 applies at the individual apparatus level; it is not within the scope of this technical
report, but is the responsibility of the apparatus manufacturer. This zone may also include
highly sensitive equipment that may require additional protection.
5.3 Design principles for screening
5.3.1 General
The design principles presented in this clause are not intended to serve as a comprehensive
guide for the detailed design of a specific installation; rather, they are offered as an overview
of design considerations that can serve as useful checks for a proposed installation. Providing
effective screening techniques require a design by specialists, taking into consideration the
specifics of the installation. By application of different materials it is possible to obtain a good
shielding effectiveness over the whole disturbance spectrum of electromagnetic fields.
Screening can be provided by the following materials and constructions:
– metallic enclosure or cabinets;
– rooms with continuous metallic walls;
– clamped or welded iron mats, grids and sheets inside of walls;
– metallic meshed wire or meshed screen;
– metallic or metalled fabric;
– metallic foil;
– metal sheets (copper or aluminium or other good conductive metals);
– metallized plastics with undamaged surfaces and a good contact across all seams;
– window glass with wire mesh fused in the glass or metallized glass, both continuously
bonded to the wall shield.
– 20 – TR 61000-5-6  IEC:2002(E)
Note that for screening against low-frequency electric fields, metallized plastic might be
adequate. However, screening against low-frequency magnetic fields requires metal walls of
sufficient thickness, conductivity and permeability. The electrical conti
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