IEC TS 61000-5-9:2009

Electromagnetic compatibility (EMC) - Part 5-9: Installation and mitigation guidelines - System-level susceptibility assessments for HEMP and HPEM

IEC/TS 61000-5-9:2009(E) is to present a methodology to assess the impact of High-altitude Electromagnetic Pulse (HEMP) and High Power Electromagnetic (HPEM) environments on electronic systems. In this context a system refers to a collection of sub-systems, equipment and components brought together to perform a function. The techniques associated with this methodology and their advantages and disadvantages will be presented along with examples of how the techniques can be applied to evaluate the susceptibility of electronic systems such as those found in installations. This work is closely related to the evaluation of EMC system level susceptibility. The purpose of IEC/TS 61000-5-9:2009 is to provide information on available methods for the assessment of system-level susceptibility as a result of HEMP and HPEM environments. The advantages and disadvantages of the methods will be discussed along with examples of how the techniques should be employed. Typical systems have external connections, wired or wireless, and the assessment of these are included within this specification. IEC/TS 61000-5-9:2009 gives general guidance. It does not cover safety issues nor does it conflict with ITU-T efforts concerning the protection of telecommunications equipment. IEC/TS 61000-5-9:2009 has the status of a basic EMC publication in accordance with IEC Guide 107.

General Information

• Status: Published
• Publication Date: 07-Jul-2009
• ICS: 33.100.20 - Immunity
• Technical Committee: SC 77C - High power transient phenomena
• Current Stage: PPUB - Publication issued
• Start Date: 08-Jul-2009
• Completion Date: 31-Oct-2009

Standards Content (Sample)

IEC/TS 61000-5-9 ®
Edition 1.0 2009-07
TECHNICAL
SPECIFICATION
BASIC EMC PUBLICATION
Electromagnetic compatibility (EMC) –
Part 5-9: Installation and mitigation guidelines – System-level susceptibility
assessments for HEMP and HPEM
IEC/TS 61000-5-9:2009(E)
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IEC/TS 61000-5-9 ®
Edition 1.0 2009-07
TECHNICAL
SPECIFICATION
BASIC EMC PUBLICATION
Electromagnetic compatibility (EMC) –
Part 5-9: Installation and mitigation guidelines – System-level susceptibility
assessments for HEMP and HPEM
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XB
ICS 33.100.20 ISBN 978-2-88910-396-6
– 2 – TS 61000-5-9 © IEC:2009(E)
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.8
2 Normative references .8
3 Terms and definitions .9
4 General .11
4.1 Introduction .11
4.2 Systems and subsystems .12
5 Interaction mechanisms and protection methods .13
5.1 General .13
5.2 Front-door coupling .13
5.3 Back-door coupling.13
5.4 Protection methods .14
6 Description of overall assessment methodology .14
6.1 Methodology.14
6.2 Subsystems and equipment characterization phase.16
6.3 System analysis phase.17
6.4 System test phase.17
6.4.1 General .17
6.4.2 Low-level tests .18
6.4.3 High-level testing.18
6.5 Susceptibility assessment phase .20
6.6 The use of reverberation chambers to characterise immunity .20
Annex A (informative) Classification of effect .24
Annex B (informative) Good measurement practice.27
Annex C (informative) Computational electromagnetics .30
Annex D (informative) System level assessment – HEMP .33
Annex E (informative) System level assessment – HPEM .35
Annex F (informative) Limitations.39
Annex G (informative) Detailed description of low-level techniques.42
Annex H (informative) Detailed description of high-level test techniques .54
Annex I (informative) Data processing and analysis .61
Bibliography.66

Figure 1 – Example system architecture .
Figure 2 – Example of radiated HPEM at high frequencies [3].14
Figure 3 – Methodology flowchart .15
Figure 4 – Reverberation chamber results: all effects.21
Figure 5 – Reverberation chamber results: susceptibilities.22
Figure 6 – Frequency spectrum of several HPEM sources .23
Figure A.1 – Classification of effect.24
Figure B.1 – Effect of adding ferrites to connecting cable: swept frequency example .27

TS 61000-5-9 © IEC:2009(E) – 3 –
Figure B.2 – Effect of adding ferrite to connecting cable: reverberation chamber
example.28
Figure B.3 – Effect of adding ferrite to connecting cable: transient example (time
domain) .28
Figure B.4 – Effect of adding ferrite to connecting cable: transient example (frequency
domain) .29
Figure E.1 – Steps taken in the system assessment .36
Figure E.2 – Maximum free-space separation distances.38
Figure E.3 – Critical regions for permanent damage.38
Figure G.1 – Electromagnetic interaction sequence diagram for a facility illuminated by
an external antenna .43
Figure G.2 – Illustration of the difference of a directed, narrow-beam antenna exciting
the facility with a spot beam, along with a plane wave providing illumination to the
entire facility .45
Figure G.3 – Measurement equipment and configuration for measuring transient
responses in a buried facility, as reported by [G-6] .47
Figure G.4 – Example of a measured transient cable current (a) and the resulting
spectral magnitude, as computed by a Fourier transform (b) .48
Figure G.5 – Plots of the analytical pulser output open circuit voltage waveform (a)
and spectral magnitude (b), which are used as reference for computing the transfer
function T .48
sc
Figure G.6 – The radiated E-field from the IRA at a distance of 6 meters for the
analytical pulser excitation (a) and the resulting spectral magnitude (b).49
Figure G.7 – The spectral magnitude of the computed transfer function T (a) and the
sc
corresponding transient transfer function (b).49
Figure G.8 – The spectral magnitude of the computed transfer function T (a) and the
ec
corresponding transient transfer function (b).50
Figure G.9 – LLCW reference field measurement.51
Figure G.10 – LLCW induced current measurement .51
Figure G.11 – Typical magnitude-only transfer function.52
Figure H.1 – Microwave injection testing of a low noise amplifier, LNA [H-2]. LNA at
the tip of the arrow.54
Figure H.2 – Aircraft testing at the Swedish Microwave Test Facility, MTF [H-3] .55
Figure H.3 – Measured shielding effectiveness of an equipment compared to the MTF
test frequencies (dashed bars) [3].56
Figure H.4 – Reverberation chamber .58
Figure I.1 – Prediction of induced current using magnitude-only transfer functions [I-1] .61
Figure I.2 – IEC 61000-2-9 HEMP Waveform .62
Figure I.3 – Convolution process.62
Figure I.4 – Predicted induced current .63
Figure I.5 – Comparison of transfer function predictions with simulator measurements .64
Figure I.6 – Extrapolation of measured transients .65

– 4 – TS 61000-5-9 © IEC:2009(E)
Table A.1 – Categorisation of effect by criticality.25
Table A.2 – Categorisation of effect duration .26
Table A.3 – Combination of criticality level and duration category.26
Table I.1 – Comparison of transfer function predictions and simulator measured
currents .63

TS 61000-5-9 © IEC:2009(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 5-9: Installation and mitigation guidelines –
System-level susceptibility assessments for HEMP and HPEM

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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The main task of IEC technical committees is to prepare International Standards. In
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specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC/TS 61000-5-9, which is a technical specification, has been prepared by subcommittee
77C: High power transient phenomena, of IEC technical committee 77: Electromagnetic
compatibility.
– 6 – TS 61000-5-9 © IEC:2009(E)
This Technical Specification forms Part 5-9 of IEC 61000. It has the status of a basic EMC
publication in accordance with IEC Guide 107 [1] .
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
77C/190/DTS 77C/194/RVC
Full information on the voting for the approval of this technical specification 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.
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
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

—————————
Figures in square brackets refer to the Bibliography.

TS 61000-5-9 © IEC:2009(E) – 7 –
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 the 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 and 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).

– 8 – TS 61000-5-9 © IEC:2009(E)
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 5-9: Installation and mitigation guidelines –
System-level susceptibility assessments for HEMP and HPEM

1 Scope
The aim of this part of IEC 61000 is to present a methodology to assess the impact of High-
altitude Electromagnetic Pulse (HEMP) and High Power Electromagnetic (HPEM)
environments on electronic systems. In this context a system refers to a collection of sub-
systems, equipment and components brought together to perform a function. (A more
complete definition is given in 3.20.) The techniques associated with this methodology and
their advantages and disadvantages will be presented along with examples of how the
techniques can be applied to evaluate the susceptibility of electronic systems such as those
found in installations. This work is closely related to the evaluation of EMC system level
susceptibility.
The purpose of this Technical Specification is to provide information on available methods for
the assessment of system-level susceptibility as a result of HEMP and HPEM environments.
The advantages and disadvantages of the methods will be discussed along with examples of
how the techniques should be employed.
Typical systems have external connections, wired or wireless, and the assessment of these
are included within this specification.
This specification gives general guidance. It does not cover safety issues nor does it conflict
with ITU-T efforts concerning the protection of telecommunications equipment [2] .
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 60050(161), International electrotechnical vocabulary – Chapter 161: Electromagnetic
compatibility
IEC/TR 61000-1-5:2004, Electromagnetic compatibility (EMC) – Part 1-5: General – High
power electromagnetic (HPEM) effects on civil systems
IEC 61000-2-9:1996, Electromagnetic compatibility (EMC) – Part 2: Environment – Section 9:
Description of HEMP environment – Radiated disturbance. Basic EMC publication
IEC 61000-2-10:1998, Electromagnetic compatibility (EMC) – Part 2-10: Environment –
Description of HEMP environment – Conducted disturbance
IEC 61000-2-13:2005, Electromagnetic compatibility (EMC) – Part 2-13: Environment – High-
power electromagnetic (HPEM) environments – Radiated and conducted
—————————
Figures in square brackets refer to the Bibliography.

TS 61000-5-9 © IEC:2009(E) – 9 –
IEC/TR 61000-4-32:2002, Electromagnetic compatibility (EMC) – Part 4-32: Testing and
measurement techniques – High-altitude electromagnetic pulse (HEMP) simulator
compendium
IEC 61000-4-33:2005, Electromagnetic compatibility (EMC) – Part 4-33: Testing and
measurement techniques – Measurement methods for high-power transient parameters
IEC 61000-4-35:2009, Electromagnetic compatibility (EMC) – Part 4-35: Testing and
measurement techniques – HPEM simulator compendium
IEC/TR 61000-5-3:1999, Electromagnetic compatibility (EMC) – Part 5-3: Installation and
mitigation guidelines – HEMP protection concepts
IEC/TS 61000-5-4:1996, 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 61000-5-5:1996, Electromagnetic compatibility (EMC) – Part 5: Installation and mitigation
guidelines – Section 5: Specification of protective devices for HEMP conducted disturbance.
Basic EMC Publication
IEC/TR 61000-5-6:2002, Electromagnetic compatibility (EMC) – Part 5-6: Installation and
mitigation guidelines – Mitigation of external EM influences
IEC 61000-5-7:2001, Electromagnetic compatibility (EMC) – Part 5-7: Installation and
mitigation guidelines – Degrees of protection provided by enclosures against electromagnetic
disturbances (EM code)
3 Terms and definitions
For the purposes of this document the terms and definitions of IEC 60050-161 as well as the
following apply.
3.1
aperture coupling regime
frequency range where aperture coupling dominates; this is typically between 200 MHz to
18 GHz
3.2
back-door coupling
coupling of EM energy to equipment via connecting cables or apertures (not via antennas or
sensors
NOTE Detailed discussion of back-door coupling can be found in Clause 5.
3.3
cable coupling regime
frequency range where cable coupling dominates; this is typically between 500 kHz and
400 MHz
3.4
coupling
transfer of electromagnetic energy from source to victim
3.5
E/E/PE equipment
equipment that employs electrical, electronic or programmable electronic technologies

– 10 – TS 61000-5-9 © IEC:2009(E)
3.6
equipment
general designation which includes modules, devices, apparatuses, subsystems, complete
systems and installations
3.7
equipment under test
EUT
refers to the equipment being tested
3.8
front-door coupling
coupling of EM energy to equipment via antennas and/or sensors
NOTE Detailed discussion of front-door coupling can be found in Clause 5.
3.9
HEMP
High-altitude Electromagnetic Pulse
3.10
high-level illumination
HLI
use of high-level (>100 V/m) signals to assess the immunity or susceptibility
3.11
HPEM
High Power Electromagnetic
3.12
immunity
ability of a device equipment or system to perform without degradation in the presence of an
electromagnetic disturbance
[IEV 161-01-20]
3.13
installation
combination of apparatuses, components and systems assembled and/or erected
(individually) in a given area
NOTE For physical reasons (e.g. long distances between individual items) it is in many cases not possible to test
an installation as a unit.
3.14
low-level continuous wave
LLCW
use of low-level signals (typically <1 V/m) to characterise the coupling of an external
electromagnetic environment to an internally induced current, voltage or field (magnetic or
electric)
3.15
margin
usually expressed in dB, this in the amount added to a result to improve confidence or to
allow for uncertainties
TS 61000-5-9 © IEC:2009(E) – 11 –
3.16
norm
mathematical function used to describe a parameter of a waveform; several norms can be
used to describe the ‘uniqueness’ of a waveform
3.17
pulsed current injection
PCI
use of current injection methods to assess the immunity or susceptibility with a pulsed
waveform as opposed to more traditional continuous wave (CW) signals
3.18
surface current injection
SCI
injection of current directly on to the surface of an equipment box of system skin
3.19
susceptibility
inability of a device, equipment or system to perform without degradation in the presence of
an electromagnetic disturbance
[IEV 161-01-21]
3.20
system
combination of apparatuses and/or active components constituting a single functional unit and
intended to be installed and operated to perform (a) specific task(s)
4 General
4.1 Introduction
HEMP occurs as a result of a high-altitude nuclear explosion and can cover several millions of
square kilometres with electric field strengths of up to tens of kV/m. Further discussion of
HEMP can be found in IEC 61000-2-9 and IEC 61000-2-10.
HPEM is the collective name given to a set of high power radio frequency (RF) sources that
are capable of generating high levels of RF at ranges <1 km. The waveforms generated by
these types of sources vary and include Ultra Wideband (UWB), Damped Sine (DS) also
known as Non-Nuclear EMP (N2EMP) and High power Microwave (HPM). Further discussion
of these sources can be found in IEC 61000-2-13.
This specification discusses methods available for the assessment of systems as defined in
4.2 (not distributed civil infrastructure ) to the effects of HEMP and HPEM. Typical system
examples are vehicles, aircraft and small ships. The techniques can be applied to larger
systems such as buildings, however, with careful consideration.
The assessment methodology discussed in this specification is not appropriate for
geographically large connected or distributed systems. However, the techniques may be
applicable to individual components, equipments, subsystems or systems contained within a
large connected or distributed system.
The assessment methodology may be used to determine the status of a particular system with
respect to its hardening to HEMP and/or HPEM environments.
—————————
Distributed civil infrastructure is discussed in IEC 61000-5-8.

– 12 – TS 61000-5-9 © IEC:2009(E)
It is important to note that the assessment methodology presented within this specification
should help to assist in reducing the risk of detrimental system performance due to exposure
to HEMP and HPEM environments. This methodology can be applied during the design and
development phases of a system. A full system-level test using the HEMP or HPEM
environment of interest is an important part of this methodology. Information on worldwide
HEMP and HPEM simulators can be found in IEC 61000-4-32 and IEC 61000-4-35
respectively.
4.2 Systems and subsystems
In the context of this specification, a system may consist of several subsystems which are
each comprised of several equipments which, in turn, consist of several components. Figure 1
shows a typical system architecture.
A system can also be considered to be a set of supplied equipments located within a
defined physical boundary that are interconnected in order to perform a defined function.
The defined physical boundary may be
the outer hull (for systems located on military platforms – vehicles, aircraft and ships),
the outer building wall (for systems located within buildings).
The interconnection may be either
wireline (using either metallic or optical cables),
or wireless,
and the interconnection is made for the purpose of either
exchanging information,
or receiving or supplying electrical power.
Any physical connection (i.e. wireline or wireless) with supplied equipment that does not
originate from within the system's defined physical boundary is an interface. Interfaces may
be permanent (in the case of buildings, where a permanent connection with wireline power
and telecommunications infrastructure can be expected) or temporary (in the case of military
platforms, where the inherent mobility of the platform prevents permanent wireline
interfacing).
Individual supplied pieces of equipment may themselves be individual systems (i.e.
subsystems, or sub-subsystems, and so forth) that should themselves have been subject to
the methods contained within this specification.

Figure 1 – Example system architecture

TS 61000-5-9 © IEC:2009(E) – 13 –
For example, a vehicle (system) may consist of an engine management unit (subsystem)
which consists of circuit boards (equipment) and integrated circuits (component).
5 Interaction mechanisms and protection methods
5.1 General
Within IEC 61000-1-5, the terms deliberate penetration and inadvertent penetration are used
to describe the penetration of EM energy into a system. This specification uses the terms
back-door coupling and front-door coupling (see Figure 2) since they better relate to the
fundamental difference that exists regarding the possibility to protect a system without
degrading its function. While careful back-door shielding should not degrade the function of a
system at all, protection against in-band front-door coupling may degrade the function of the
system.
5.2 Front-door coupling
The radiation couples to equipment ports intended for wireless communication or other
interaction with the external environment. Hence, they cannot easily be fully shielded against
electromagnetic radiation without loosing or severely degrading their function. Examples are
antennas and sensors.
Front-door coupling can be subdivided into first and second order, as follows.
a) Front-door coupling, first order (in-band)
The frequency of the radiation coincides, at least partly, with the working frequency of the
equipment. An example is a telecom base-station irradiated in its pass band.
b) Front-door coupling, second order (out-of-band)
The frequency of the radiation does not coincide with the working frequency of the
equipment. An example is a HF radio antenna exposed to high power microwaves.
5.3 Back-door coupling
The radiation couples to electronic circuits through imperfections (apertures) in the
electromagnetic shield enclosing the electronics, or directly to the electronic circuit boards. In
the case of a shielded structure this leakage gives rise to a diffuse and complex field pattern
within the structure. The apertures can be unintentional or intentional. An example of the
former is a paint, or an oxide, layer in a shielding joint between conductive surfaces.
Examples of the latter are holes for drainage or ventilation. The radiation may also couple
directly to an external wire connected to a component or a subsystem [3]. The reason to
define such a wire as back-door coupling and not as a second-order front-door coupling is
motivated by the fact that the wire could be shielded without degrading the function of the
equipment.
It is important to note that HEMP or HPEM disturbances can be radiated or conducted in
nature. It follows therefore, that the source of the front-door or back-door coupling can be
radiated or conducted in nature. It should be noted that conducted disturbances cannot only
be out-of-band but also occur under normal operating conditions (in-band and out-of-band).
Examples of this include transient overvoltages much higher than the voltage under normal
operation or surge currents flowing in a system.
This specification deals mainly with back-door coupling although some attention is given to
A n nex H .
front-door coupling in
– 14 – TS 61000-5-9 © IEC:2009(E)

The van in the centre of the picture contains the HPEM source.
Figure 2 – Example of radiated HPEM at high frequencies [3]
5.4 Protection methods
Front-door coupling: While in-band disturbances are difficult to neutralize, permanent damage
effects can be mitigated by use of transient protectors. Out-of-band disturbances, that is,
second-order front-door coupling, can be handled by use of filtering, for example for radio
equipment, or by use of metallic meshes or thin films for optical equipment. Often, protective
measures will lead to some degradation of the intended function of the system.
Back-door coupling: Use of conventional EMC protection techniques, such as shielding and

filtering, should suffice to achieve a 30 dB protection level [4], which should be sufficient for
the HPEM threat (although not for the military HPM threat). Transient protection devices may
be required to protect filters from high-voltage transients and should be carefully combined
with filters to increase the level of protection.
An alternative way of considering protection is based on the type of HEMP or HPEM
disturbance to be protected against. Radiated disturbances can be mitigated by the use of
shielding and conducted disturbances can be mitigated by the use of transient protection
devices and filters.
Detailed information on protection methods can be found in IEC/TR 61000-5-3,
IEC/TS 61000-5-4, IEC 61000-5-5, IEC/TR 61000-5-6 and IEC 61000-5-7.
6 Description of overall assessment methodology
6.1 Methodology
This clause discusses the overall assessment methodology.

TS 61000-5-9 © IEC:2009(E) – 15 –

Figure 3 – Methodology flowchart

– 16 – TS 61000-5-9 © IEC:2009(E)
6.2 Subsystems and equipment characterization phase
Characterization of the subsystems and equipment shall be completed prior to any detailed
evaluation or assessment. At this stage, it is essential that functional and topological
descriptions of the system are generated to allow for critical aspects of the system to be
identified.
A functional description deals with the intentional flow of information within the system that is
the information flow for decision-making and responses from the intentional external interface
throughout the system.
A topological description deals with;
a) the physical units that correspond to each function within the functional description (i.e.
the individual boxes, cards or units),
b) the intended physical interconnections between the physical electronics (i.e. cabling),
c) the relative location of each physical unit and intended physical interconnection. This
allows an assessment to be made of the relative importance of the three fundamental
interactions: box-to-box, cable-to-box and box-to-cable radiation.
Together, functional and topological descriptions allow the propagation of front-door and
back-door coupling within the system to be understood and hence hardening strategies to be
developed. In addition, these descriptions will enable the impact of any HEMP or HPEM
induced effect to be correctly assigned as either immunity or susceptibility during the
susceptibility assessment phases. Also, areas of potential weakness should be identified
based upon information about similar systems or technology types.
During this phase it is necessary to gather immunity and/or susceptibility information that may
be relevant. This should be obtained from electromagnetic compatibility (EMC) test data. If
waveforms associated with susceptibilities are available, waveform norms that allow
parameters of waveforms to be mathematically quantified should be computed for later use.
Further details on the use of waveform norms can be found in IEC 61000-4-33, Annex A [5].
A typical subsystem and equipment characterization will breakdown the system into its
component subsystems and equipments. Each of these subsystems and pieces of equipment
will then be assessed for coupling paths relevant to the frequency density of the illuminating
HEMP or HPEM environment of interest. This is performed by translation of the frequency
content of the illuminating environment into wavelengths by using the simple expression given
in Equation (1).
c = fλ (1)
where
c is the speed of light in a vacuum (3 × 10 m/s),
f is the frequency (Hz),
λ is the wavelength (m).
Depending on the type of coupling path, frequencies corresponding to a wavelength of L/2 or
L/4 (where L is the length of the conductor of interest, for example, a cable) tend to dominate
and this provides an indication of the ability of the illuminating HEMP or HPEM environment to
couple to the subsystem and equipment being characterised.
Any protection added should be noted during this phase of the assessment and may negate
the need for more extensive testing during the later stages. An effective shield at the
frequencies of interest may reduce the illuminating HEMP or HPEM environment to a level
that is below the immunity requirements for commercial electronics, thus demonstrating that
further radiated testing of the commercial electronics is not required. In this case, a conducted

TS 61000-5-9 © IEC:2009(E) – 17 –
test would still be required, unless adequate filtering can be demonstrated to show that
anticipated conducted currents and voltages would be attenuated to a level for which the
electronics has been demonstrated to be immune. However, testing at the later stages is
recommended to assure that the added protection is adequate.
For example, a shield affording 80 dB (a factor of 10 000 in terms of electric field strength) of
attenuation would reduce an external illuminating HEMP field of 50 kV/m to 5 V/m. Immunity
test data (driven by EMC requirements) are typically amplitude modulated (AM) continuous
wave (CW) but the induced current expected from HEMP illumination will be damped
sinusoidal in nature. Evaluation of the energy content of a CW and a damped sinusoidal
waveform of the same (centre) frequency shows that the CW waveform has much greater
energy. Thus, if an equipment or system is immune to 5 V/m CW, it is possible that it will be
immune to larger peak amplitudes of transient (damped sinusoidal) signals. For interference
the peak amplitude is likely to be the susceptibility driver, but for permanent damage, energy
is a key susceptibility driver.
A further consideration here is that EMC tests are driven by the need to demonstrate
continued operation in a particular EM environment that is they are required to demonstrate
immunity in that environment. Without the appropriate test information, it is generally not
possible to make conclusions about susceptibility based on immunity data only. However, in
the context of system level assessments, the immunity data plays an important role as it can
be used as a lower bound on equipment strength and provide an indication of the range from
HPEM environments where continued functionality (immunity) can be expected. Without
susceptibility information, this type of calculation will provide the system user with a range at
which the system will continue to operate, but does not provide information on the range at
which effects can be expected. Detailed susceptibility data is required in order to generate
this information.
Knowledge of the shielding effectiveness of equipment, subsystem and system interfaces also
provides important information as subsystem immunity of 5 V/m (CW) with system shielding of
26 dB means that the subsystem will continue to operate in an externally illuminating field of
100 V/m (CW).
Information obtained during this phase will be used in the next phase. Waveform norms can
be computed to enable a rigorously mathematical method of comparing data. Norms are
discussed in more detail in C.2.2.
6.3 System analysis phase
The purpose of the system analysis phase is to identify critical subsystems and equipment,
system configurations and operational modes that will be assessed through a combination of
low-level and high-level tests to estimate a system’s susceptibility to the HEMP and HPEM
environments. A key element in this process is selection of a set of measurement or test
points at critical interface locations within the system that will be used later in the
susceptibility assessment phase to compare coupled stress waveform data (obtained in the
system test phase) to EUT immunity or susceptibility waveform data at corresponding
interfaces (obtained in the subsystems and equipment characterization phase). During the
test point selection process, emphasis should be placed on choosing test points at EUT
interfaces that both;
a) are predicted to have the highest level stresses and
b) are functionally critical to proper operation of the system.
6.4 System test phase
6.4.1 General
This phase describes EUT and/or system level testing that can be used to provide information
on the system’s overall protection against a HEMP or HPEM environment. In some cases, test
facilities cannot manage large systems therefore breaking down the system level test into a

– 18 – TS 61000-5-9 © IEC:2009(E)
test for subsystems and/or equipments and combining the results may be an acceptable
alternative. If this approach is to be adopted, extreme care shall be taken to ensure that the
integration of equipments and subsystems does not impact on the effect of the HEMP or
HPEM environment at the system level.
To conduct a complete system level test, all subsystems and equipment should be installed in
the system, interconnected and functioning in its normal intended operational state.
6.4.2 Low-level tests
Low-level (LL) tests can be conducted with either continuous wave (CW) or pulsed
illuminating fields.
Transfer function and attenuation data should be collected for those cable bundles and areas
of interest identified by the system analysis. For HEMP and/or HPEM environments that
dominate in the cable coupling regime (500 kHz to 400 MHz, depending on the length of
cabling) convolution with cable bundle transfer functions will result in predicted currents as a
result of the incident field of the environment of interest. For HEMP and/or HPEM
environments that dominate in the aperture coupling regime (400 MHz to 18 GHz) convolution
with attenuation data will result in predicted fields within the system enclosure. This data can
then be compared with any available electromagnetic c
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