IEC TR 61000-1-5:2004

Electromagnetic compatibility (EMC) - Part 1-5: General - High power electromagnetic (HPEM) effects on civil systems

This part of IEC 61000 is a technical report that provides background material describing the motivation for developing IEC standards on the effects of high power electromagnetic (HPEM) fields, currents and voltages on civil systems. In the light of newly emerging transient antenna technology and the increasing use of digital electronics, the possibility of equipment being upset or damaged by these environments is of concern. This document begins with a general introduction to this subject and a listing of the pertinent definitions used. Following these clauses, the HPEM environments that are of concern are described and a discussion of the various effects that these environments can induce in civil systems is presented. Finally, techniques used to protect systems against these environments are summarised. More detailed information will be provided in separate documents in this 61000 series.

General Information

• Status: Published
• Publication Date: 14-Nov-2004
• ICS: 33.100.20 - Immunity
• Technical Committee: SC 77C - High power transient phenomena
• Current Stage: PPUB - Publication issued
• Start Date: 15-Nov-2004
• Completion Date: 15-May-2005

Standards Content (Sample)

TECHNICAL IEC
REPORT TR 61000-1-5
First edition
2004-11
Electromagnetic compatibility (EMC) –
Part 1-5:
General –
High power electromagnetic (HPEM)
effects on civil systems
Reference number
IEC/TR 61000-1-5:2004(E)
Publication numbering
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TECHNICAL IEC
REPORT TR 61000-1-5
First edition
2004-11
Electromagnetic compatibility (EMC) –
Part 1-5:
General –
High power electromagnetic (HPEM)
effects on civil systems
 IEC 2004  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
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International Electrotechnical Commission
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For price, see current catalogue

– 2 – TR 61000-1-5  IEC:2004(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 General introduction .12
4.1 Past experience with HPEM effects on systems.13
4.2 General EM protection techniques as applied to civil systems .14
5 Classification of HPEM environments .15
5.1 Radiated and conducted HPEM environments .17
5.2 Narrowband (CW) waveform.17
5.3 Ultrawideband/short pulse transient environment.19
5.4 Repetitive excitations .20
6 HPEM effects on systems.21
6.1 Topological representation of the system .21
6.2 Examples of HPEM effects on electronic systems and components .24
6.3 Component/subsystem burnout and permanent damage.26
6.4 Logic upset or service interruption.34
7 HPEM protection concepts .34
7.1 Strategy for selecting immunity levels.34
7.2 Overview of HPEM protection techniques.35
7.3 Realisation of HPEM protection .35

Bibliography.41

Figure 1 – Illustration of the spectral content of HPM and UWB signals, together with
other EM signals .16
Figure 2 – Plot of a normalised Gaussian modulated sine wave, serving as a simple
representation of a narrowband HPEM waveform.18
Figure 3 – Illustration of a wideband transient HPEM waveform together with its
spectral magnitude .19
Figure 4 – Illustration of a repetitive waveform of pulses similar to that of Figure 2 .20
Figure 5 – Simplified illustration of a hypothetical facility excited by an external
electromagnetic field.22
Figure 6 – The topological diagram for the simple system shown in Figure 5 .23
Figure 7 – General interaction sequence diagram for the facility of Figure 5 .23
Figure 8 – Example of measured susceptibility thresholds in a DM74LS00N [TTL] quad
2-input NAND gate as a function of frequency, illustrating increased susceptibility
thresholds at higher frequencies .27
Figure 9 – Example of damage caused by the telecom pulse generator due to a single
shot of 4,5 kV .29
Figure 10 – Description of conducted disturbance injection experiment.32
Figure 11 – Illustration of the deliberate and inadvertent penetrations into the
hypothetical system of Figure 5 .36

TR 61000-1-5  IEC:2004(E) – 3 –
Figure 12 – Example of a hypothetical deliberate coupling path into a system.37
Figure 13 – Insertion of a protective device in the deliberate coupling path to provide
EM protection against out-of-band disturbances.38
Figure 14 – Illustration of typical HPEM inadvertent penetration protection methods .39

Table 1 – Description of PCs tested, the environment and effects (after LoVetri ) .24
Table 2 – HPEM effects on an automobile as a function of range and source power
(Based on measured data from Bäckström).25
Table 3 – Summary of results of testing power and data ports with the telecom and
CWG pulse generators.28
Table 4 – Results of injecting EFT pulses on an AppleTalk cable with the number of
upsets/number of test sequences indicated .30
Table 5 – Results of injecting EFT pulses on a 10Base-T cable with the number of
upsets/number of test sequences indicated.30
Table 6 – Results of injecting EFT pulses on a 10Base-2 cable with the number of
upsets/number of test sequences indicated.31

– 4 – TR 61000-1-5  IEC:2004(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 1-5: General –
High power electromagnetic (HPEM) effects
on civil systems
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61000-1-5, which is a technical report, has been prepared by subcommittee 77C: High
power transient phenomena, of IEC technical committee 77: Electromagnetic compatibility.
This document has the status of a Basic EMC Publication in accordance with IEC Guide 107,
Electromagnetic compatibility – Guide to the drafting of electromagnetic compatibility
publications.
TR 61000-1-5  IEC:2004(E) – 5 –
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
77C/146/DTR 77C/152/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – TR 61000-1-5  IEC:2004(E)
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: 61000-6-1).

TR 61000-1-5  IEC:2004(E) – 7 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –

Part 1-5: General –
High power electromagnetic (HPEM) effects
on civil systems
1 Scope
This part of IEC 61000 is a technical report that provides background material describing the
motivation for developing IEC standards on the effects of high power electromagnetic (HPEM)
fields, currents and voltages on civil systems. In the light of newly emerging transient antenna
technology and the increasing use of digital electronics, the possibility of equipment being
upset or damaged by these environments is of concern. This document begins with a general
introduction to this subject and a listing of the pertinent definitions used. Following these
clauses, the HPEM environments that are of concern are described and a discussion of the
various effects that these environments can induce in civil systems is presented. Finally,
techniques used to protect systems against these environments are summarised. More
detailed information will be provided in separate documents in this 61000 series.
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. Members of IEC and ISO
maintain registers of currently valid International Standards.
IEC 60050-161, International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
IEC 61000-2-13, Electromagnetic compatibility (EMC) – Part 2-13: Environment – High-power
electromagnetic (HPEM) environments – Radiated and conducted
IEC 61000-4-4, Electromagnetic compatibility (EMC) – Part 4-4: Testing and measurement
techniques – Electrical fast transient/burst immunity test
IEC 61000-4-5, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement
techniques – Section 5: Surge immunity test
Amendment 1 (2000)
IEC 61000-5-3, Electromagnetic compatibility (EMC) – Part 5-3: Installation and mitigation
guidelines – HEMP protection concepts
IEC 61000-5-6, Electromagnetic compatibility (EMC) – Part 5-6: Installation and mitigation
guidelines – Mitigation of external EM influences
___________
To be published.
A consolidated edition 1.1 exists comprising IEC 61000-4-5:1995 and its Amendment 1 (2000).

– 8 – TR 61000-1-5  IEC:2004(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in IEC 60050-161,
some of which are repeated here, and the following terms and definitions apply.
3.1
aperture
an opening in an electromagnetic barrier (shield) through which EM fields may penetrate
3.2
bandratio
br
ratio of the high and low frequencies between which there is 90 % of the energy; if the
spectrum has a large d.c. content, the lower limit is nominally defined as 1 Hz
3.3
bandratio decades
brd
bandratio expressed in decades as: brd = log (br)
3.4
broadband
(1) (of an emission) – an emission which has a bandwidth greater than that of a particular
measuring apparatus or receiver
(IEV 161-06-11);
(2) (of a device) – a device whose bandwidth is such that it is able to accept and process all
the spectral components of a particular emission
(IEV 161-06-12)
3.5
conducted susceptibility
susceptibility of a system to conducted signals on cables connected to the system
3.6
coupling
interaction of electromagnetic fields with a system to produce currents and voltages on
system surfaces and cables
3.7
deliberate penetration
an intentional opening made in an electromagnetic (“EM”) shield that provides a path for the
transmission of intended signals into or out of the shielded region. It can also be a
consciously made opening for passing power, water, mechanical forces, or even personnel
from the outside to the interior, or vice versa
3.8
disturbance
see electromagnetic disturbance
3.9
electromagnetic barrier (shield)
topologically closed surface made to prevent or limit EM fields and conducted transients from
entering the enclosed space. The barrier consists of the shield surface and points-of-entry
treatments, and it encloses the protected volume

TR 61000-1-5  IEC:2004(E) – 9 –
3.10
electromagnetic disturbance
any electromagnetic phenomenon which may degrade the performance of a device,
equipment or system
[IEV 161-01-05, modified]
3.11
electromagnetic interference
EMI
degradation of the performance of a device, transmission channel or system caused by an
electromagnetic disturbance
NOTE Disturbance and interference are respectively cause and effect.
[IEV 161-01-06, modified].
3.12
electromagnetic stress
an electromagnetic stress is a voltage, current or electromagnetic field which acts on
equipment. If the electromagnetic stress exceeds the vulnerability threshold of the equipment,
mission-aborting damage or upset may occur. The stress may be described by characteristics
such as peak amplitude, rise time, duration or impulse
3.13
electromagnetic susceptibility
inability of a device, equipment or system to perform without degradation in the presence of
an electromagnetic disturbance
NOTE Susceptibility is a lack of immunity.
[IEV 161-01-21].
3.14
environment
electromagnetic field arising from an external source that excites a system, possibly causing
damage, upset or loss of function
3.15
failure level
specification of the amplitude (or other waveform attribute) of an electromagnetic field or
induced current (or voltage) that, when applied to an electrical component or system, causes
a failure in the device
3.16
high altitude electromagnetic pulse
HEMP
electromagnetic pulse produced by a nuclear explosion outside the earth’s atmosphere
NOTE Typically above an altitude of 30 km.
3.17
high power electromagnetics
HPEM
the general area or technology involved in producing intense electromagnetic radiated fields
or conducted voltages and currents which have the capability to damage or upset electronic
systems. Generally these disturbances exceed those produced under normal conditions (e.g.
100 V/m and 100 V)
– 10 – TR 61000-1-5  IEC:2004(E)
3.18
high power microwaves
HPM
subset of the HPEM environment, typically consisting of a narrowband signal having a pulsed
peak power at the source in excess of 100 MW
NOTE This is a historical definition that depended on the strength of the source. The interest in this document is
mainly on the EM field incident on an electronic system.
3.19
immunity (to a disturbance)
ability of a device, equipment or system to perform without degradation in the presence of an
electromagnetic disturbance
[IEV 161-01-20]
3.20
immunity level
maximum level of a given electromagnetic disturbance incident on a particular device,
equipment or system for which it remains capable of operating at a required degree of
performance
[IEV 161-03-14]
3.21
inadvertent [EM] penetration
an opening, not deliberately made, that may provide a path for electromagnetic (“EM”) energy
through the EM shield. Most often inadvertent penetration is undesired. Typically, leakage
through imperfectly conducting material is considered as an inadvertent penetration
3.22
intentional electromagnetic interference
IEMI
intentional malicious generation of electromagnetic energy introducing noise or signals into
electric and electronic systems, thus disrupting, confusing or damaging these systems for
terrorist or criminal purpose
3.23
interaction sequence diagram
ISD
graphical description of the paths that an external EM field is able to penetrate through one of
more shields surrounding a system or equipment
3.24
narrowband
signal or a waveform with a pbw (defined in 3.27) of <1 % or a bandratio (defined in 3.2)
<1.01
3.25
nuclear electromagnetic pulse
NEMP
all types of electromagnetic fields produced by a nuclear explosion
3.26
penetration
transfer of electromagnetic energy through an electromagnetic barrier from one volume to
another. This can occur by field diffusion through the barrier, by field leakage through
apertures, and by electrical current passing through conductors connecting the two volumes
(wires, cables, conduits, pipes, ducts, etc.)

TR 61000-1-5  IEC:2004(E) – 11 –
3.27
percentage bandwidth
pbw
bandwidth of a waveform, expressed as a percentage of the centre frequency of that wave-
form
NOTE pbw has a maximum value of 200 % when the centre frequency is the mean of the high and low
frequencies; pbw does not apply to signals with a large d.c. content (ex: HEMP), for which the bandratio decades is
used.
3.28
point/port-of-entry
PoE
physical location (point/port) on the electromagnetic barrier, where EM energy may enter or
exit a topological volume, unless an adequate PoE protective device is provided
NOTE 1 A PoE is not limited to a geometrical point.
NOTE 2 PoEs are classified as aperture PoEs or conductor PoEs, according to the type of penetration. They are
also classified as architectural, mechanical, structural or electrical PoEs, according to the functions they serve.
3.29
radiated susceptibility
susceptibility of a system to radiated electromagnetic fields
3.30
rebar
shortening of the words “reinforcing bar”, which refers to the steel reinforcing rods located
within poured concrete to enhance structural integrity
3.31
shielding
act of reducing the magnitude of an electric or magnetic field provided by a good electrical
conductor such as sheet steel, reinforcing bars loops, conduit, etc. Also understood frequently
as the enclosure that provides this reduction
3.32
short pulse
SP
a transient signal with a rise time and pulse duration measured in ps or ns
3.33
surge protection device
SPD
device to suppress line conducted overvoltages and currents, such as surge suppressors
defined in IEC 61024-1
3.34
system
(1) collection of subsystems, assemblies and/or components that function together in a
coherent way to accomplish a basic mission;
(2) collection of equipment, subsystems, skilled personnel, and techniques capable of
performing or supporting a defined operational role. A complete system includes related
facilities, equipment, subsystems, materials, services, and personnel required for its operation
to the degree that it can be considered self sufficient within its operational or support
environment.
– 12 – TR 61000-1-5  IEC:2004(E)
3.35
topological control
maintaining of a closed electromagnetic shield around a system or equipment to reduce the
internal EM field environment, and hence, to provide protection to the equipment
3.36
ultrawideband
UWB
signal or a waveform with a pbw value between 163,4 % and 200 % or a bandratio > 10 (also
referred to as a hyperband signal)
4 General overview
Over the past 25 years, significant progress has been made in understanding and mitigating
the effects of the high altitude electromagnetic pulse (HEMP) fields on electrical systems and
equipment. Starting from early documents on the characteristics of HEMP [1], [2] and
continuing through recent IEC committee work on developing standards for HEMP protection
[3], there are clear-cut guidelines on protection methods and designs for protecting such
systems [4]. Recently, such HEMP protection guidelines have been incorporated into the
construction of military facilities [5, 6], and test facilities and procedures for the HEMP
environments have been developed.
Recently other EM environments have been developed or postulated, including the
ultrawideband (UWB) and short pulse (SP) environments [7] and the narrowband, high power
microwave (HPM) environments, all of which have operating frequency spectra extending well
beyond several GHz [8]. Such signals, together with conducted high-power currents and
voltages, are collectively denoted as “high power electromagnetic” (HPEM) environments.
Coupled with fact that modern electrical circuits and systems have used digital devices in
their designs, it is now evident that we need to extend our present thinking of system
protection concepts to include these new HPEM environments.
For analysing the effects of HEMP on systems, a well-developed analysis methodology has
evolved. This involves the following steps: 1) definition of the system’s electromagnetic
topology; 2) determination of the collectors of EM energy; 3) identification of the susceptible
equipment “interface” location; 4) computation of the EM stress at the interface element(s); 5)
determination of the failure levels at interface; and 6) a comparison of the stress/failure levels
to estimate the system vulnerability. For modern systems subjected to HPEM excitation, a
similar analysis methodology needs to be developed and tested. In particular, the following
issues need to be addressed:
• modification of topological decomposition concepts to include high-frequency effects and
distributed field excitations;
• extension of the EM interaction (e.g., coupling, penetration and propagation) models to
the higher frequencies (faster rise times) of HPEM stresses;
• development of a better understanding of the behaviour of components and systems
subjected to EM stresses, including failure mechanisms of individual components and
upset, latch-up or failure of systems.
Similarly, test methods for HEMP are well established. However, these are not directly
applicable for system-level testing of modern systems. Not only are there questions as to how
to produce a “standard” and representative HPEM test environment, but also test procedures
are lacking. A system can be in many different states, depending on its internal functioning,
and its response to an external EM stimulus may depend on the “initial conditions” of the
system. Moreover, in current HEMP testing, there is usually no control of the software
features or changes made to the tested equipment, since only the hardware is considered of
real importance. For such systems, its operating software is often changed and modified for
testing, so that the real properties of the system may not be present the tested system.

TR 61000-1-5  IEC:2004(E) – 13 –
Thus, we must develop a suitable test protocol for systems with rules for acceptable software
flexibility.
4.1 Past experience with HPEM effects on systems
There have been several well-documented cases in the past where there have been unwanted
effects on a system due to EM environments – sometimes with disastrous consequences.
A report by NASA [9] examined many of these EMI events, and a few of these will be
summarised here.
As has been noted in the past, damage to systems is not limited only to modern-day
equipment, in 1967, the USS Forrestal was involved in perhaps the worst case of EMI ever
recorded. According to [9],
“In 1967 off the coast of Vietnam, a Navy jet landing on the aircraft carrier
USS Forrestal experienced the uncommanded release of munitions that
struck a fully armed and fuelled fighter on deck. The results were
explosions, the deaths of 134 sailors, and severe damage to the carrier and
aircraft. This accident was caused by the landing aircraft being illuminated
by carrier-based radar, and the resulting EMI sent an unwanted signal to the
weapons system. Investigations showed that degraded shield termination on
the aircraft allowed the radar frequency to interfere with routine operations.
As a result of this case, system level EMC requirements were revised to
include special considerations for electro explosive devices.”
Problems with the flight control system on the F-16 fighter were reported:
“An F-16 fighter jet crashed in the vicinity of a Voice of America (VOA) radio
transmitter because its fly-by-wire flight control system was susceptible to
the HIRF transmitted. Since the F-16 is inherently unstable, the pilot must
rely on the flight computer to fly the aircraft. Subsequently, many of the
F-16’s were modified to prevent this type EMI, caused by inadequate
military specifications on that particular electronics system. This F-16 case
history was one of the drivers for institution by the Federal Aviation
Administration (FAA) of the HIRF certification program.”
A more recent occurrence involved a UH-60 Blackhawk helicopter being affected by nearby
radio transmitters:
“An Army Sikorsky UH-6O Blackhawk helicopter, while flying past a radio
broadcast tower in West Germany in 1987, experienced an uncommanded
stabiliser movement. Spurious warning light indications and false cockpit
warnings were also reported. Subsequent investigation and testing showed
that the stabiliser system was affected by EMI from high intensity radiated
fields (HIRF). The Blackhawk has a conventional mechanically linked flight
control system with hydraulic assist. The stabiliser system, however, uses
transmitted digital signals (fly-by-wire) to automatically adjust its position
relative to control and flight parameters. These digital signals are highly
susceptible to HIRF. When the Blackhawk was initially designed, the Army
did not routinely fly near large RF emitters. The Navy version of the
Blackhawk, the SB-60 Seahawk, however, has not experienced similar EMI
problems because it is hardened against the severe EME aboard modern
ships. Despite the Army identifying several hundred worldwide emitters that
could cause problems and instructing its pilots to observe proper clearance
distances, between 1981 and 1987 five Blackhawk helicopters crashed and
killed or injured all on board. In each crash, the helicopter flew too near
radio transmitters. The long-term solution was to increase shielding of
sensitive electronics and provide as a backup some automatic control
resets.”
– 14 – TR 61000-1-5  IEC:2004(E)
Such occurrences of EMI are not limited to the military, as evidenced in the following case
involving an automobile:
“During the early years of the antilock braking system (ABS), automobiles
equipped with ABS had severe braking problems along a certain stretch of
the German autobahn. The brakes where affected by a near-by radio
transmitter as drivers applied them on the curved section of highway. The
near-term solution was to erect a mesh screen along the roadway to
attenuate the EMI. This enabled the brakes to function properly when
drivers applied them.”
The medical care sector also has been affected by EMI, as noted in the following account:
“Susceptibility of medical equipment to conducted or radiated emission is
a concern (in an ambulance heart monitor/defibrillator unit.) In this case, a
93-year-old heart attack victim was being taken to the hospital and the
medical technician had attached a monitor/defibrillator to the patient.
Because the machine shut down every time the technicians turned on the
radio transmitter to request medical advice, the patient died. An
investigation showed that the monitor/defibrillator was exposed to
exceptionally high radiated emissions because the ambulance roof had been
changed from metal to fibreglass and fitted with a long-range radio antenna.
Reduced shielding combined with the strong radiated radio signal resulted in
EMI to the vital machine.”
These instances of HPEM fields affecting electrical systems were inadvertent consequences
of a poor system design, abnormally large EM fields, or both. It is possible, however, to
envision the use of HPEM sources to deliberately cause upset or damage in a system. Such
an occurrence could occur in a military setting, where the HPEM environment could be
directed towards an enemy missile, aircraft, or other system containing susceptible
electronics. Similarly, this attack concept could be used by hackers, terrorists or similar
organizations against civil systems in what has been referred to as “EM terrorism” [10], [11] or
more recently Intentional Electromagnetic Interference (IEMI).
Such possibilities have been the subject of technical sessions in recent scientific symposia
[12], [13], [14], and [15], and continue to be discussed in the popular press [16], [17]. Although
there are several unconfirmed accounts of instances where such (EM) weapons have been
used against civil and military systems [18], [19], obtaining clear, convincing and documented
evidence as to this HPEM environment remains elusive.
Notwithstanding the lack of indisputable proof linking the use of such HPEM sources to attack
civil facilities, several governments continue with research programs into the assessment of
the possible effects of HPEM environments on their systems and infrastructure. For example,
there has been one effort in Sweden [20]. Also, the possibility of using radio frequency (RF)
weapons was recently described [21] to the U.S. Congress.
For further information concerning the intentional use of HPEM environments, the reader is
invited to consult the special issue of the IEEE Transactions on Electromagnetic Compatibility
covering Intentional EMI (IEMI) [50].
4.2 General EM protection techniques as applied to civil systems
Significant work has been conducted in developing protection concepts for both military and
civil systems against the nuclear high-altitude electromagnetic pulse (HEMP) environment
[22]. Protection measures include global shielding (e.g., system topological control [23]),
installation of filters and surge protection on incoming power or signal lines [24], and the
protection of individual pieces of equipment that may be especially sensitive to the HEMP
environments [25], [26].
TR 61000-1-5  IEC:2004(E) – 15 –
Much of this past HEMP work is directly applicable to the protection of electrical systems and
facilities against the higher frequency HPEM environments. As in the HEMP case, the most
significant coupling paths for an external HPEM stress are the long lines entering into the
facility. However, because of the higher frequency content in the HPEM environment,
the induced signals in these lines typically exhibit a larger attenuation with distance than does
the HEMP-induced signal. Thus, in some cases, the requirements placed on protection
elements for the HPEM signals on “deliberate” EM penetrations into the facility may not be as
strict as for HEMP.
For the HPEM environment, there are other penetrations that are of concern, however. These
3)
are the so-called “inadvertent” penetrations , which occur through EM field penetration
through imperfections in the system shield. Typically, as the frequency of the external EM
environment increases, the penetration efficiency of the fields also increases through these
inadvertent (and undesired) paths, and the system interior can be excited more strongly.
Improving the global (topological) shielding of the system under consideration will help to
mitigate this problem.
Because many of the electronic systems of interest are digital, there is an additional
dimension to the HPEM field interaction phenomenon. Because the HPEM environment can
be repetitive, such a periodic pulsing of the electrical stress on the system can interfere with
the clock cycles in digital circuitry. Thus, there may be system upset at certain critical pulse
rates – even though the EM field intensity is below the threshold for permanent component
damage. This suggests that an additional EM protection concept is the careful design of the
digital electronics to be impervious to such periodic disruptions. Such an approach is
commonly called “circumvention” in the HEMP community.
Further details and specifications of recommended HPEM protection concepts and their
realisations will be forthcoming in future standards in this 61000 series.
5 Classification of HPEM environments
HPEM is a term used to refer to a man-made electromagnetic environment that can adversely
affect the operation of electrical systems. It can occur in the form of a pulsed waveform of
microwave energy, and in this form, it is often referred to as high power microwave (HPM)
signal. Alternatively, this excitation can also occur in the form of a broadband pulse of EM
energy, commonly referred to as an ultrawideband (UWB) pulse. Typically, this HPEM energy
arrives at the system in the form of an incident electromagnetic field.
One way to illustrate the difference between the HPM and UWB environments is to examine
their frequency domain spectra, as shown qualitatively in Figure 1. This figure illustrates the
magnitude of the spectral density for typical lightning and the high altitude electromagnetic
pulse (HEMP), together with HPM and UWB short pulse (SP) signals. Note that the both the
UWB and HPM environments are significant for frequencies greater than about 300 MHz. The
broadband nature of the UWB environment is evident, and the HPM spectra are seen to
resemble nearly single frequency signals. It should be noted that the UWB frequency content
will often decrease above 3 - 5 GHz and the narrowband “arrows” in Figure 1 are intended to
indicate large values.
Also shown in this figure is a low-level continuum of signals denoted as “EMI environments”,
which represents the ambient level of electromagnetic noise environment due to the operation
of nearby electrical equipment or distant EM emitters, and which may cause EMI in
equipment.
___________
3)
The terms “front-door” and “back-door” penetrations are often used to describe how HPEM energy is able to penetrate into a
system. These are non-technical descriptive terms, and for this IEC document we chose to define the HPEM penetration
mechanisms as “deliberate” and “inadvertent”, respectively, since these latter terms more adequately characterize the
reason for the external HPEM energy being able to penetrate into the system.

– 16 – TR 61000-1-5  IEC:2004(E)
Electrical systems are generally protected against some level of interference to achieve EMC
according to the applicable standard. However in most cases HPEM environment levels are
considerably higher than typical civil protection levels.

Spectral
density
(V/m)/Hz
Frequency  Hz
Narrow band extending from ~0,2 to ~5 GHz
Not necessarily HPEM
Significant spectral components up to ~10 MHz depending on range and application
IEC  1531/04
Note that both scales are logarithmic.
Figure 1 – Illustration of the spectral content of HPM and UWB signals,
together with other EM signals [8]
The production, radiation, coupling and damage/upset possibilities of each of these EM
environments can be very different; however, their effects on electrical systems can be the
same – upset or physical damage of the system.
Depending on its design, a high power microwave source typically produces a waveform that
appears like a gated sinusoidal signal [27] as in Figure 2. Frequencies between 0,2 GHz –
5 GHz are typical, with pulse durations lasting up to several microseconds. Other important
features of this type of signal, and its effects on systems, are as follows.
• Waveform pulses can be repetitive; pulse frequency can vary with time and be modulated.
– Maximum coupling occurs if tuned to significant resonance in the system’s transfer
function.
– A hundred cycles or so are necessary to ring up resonance.
– Likely to cause interference through the inadvertent coupling and penetration paths,
and even permanent damage through the deliberate penetration paths.
• Many illuminated systems have significant resonance susceptibilities at particular
frequencies.
– This suggests the possibility of ”tuning” a source for causing a particular effect on a
system.
TR 61000-1-5  IEC:2004(E) – 17 –
• Sources for this EM environment are typically radar or microwave oven tubes, relativistic
magnetrons, vircators or super-reltrons.
The fast transient UWB pulse excitation is different, in that it produces frequency and energy
content over a wide range of frequencies, and in this regard it is similar to that of HEMP.
Salient features are as follows.
• Rise time typically on the order of 100 ps and the pulse width on the order of 1 ns.
– The major frequency content and power is spread over a very broad spectrum,
approximately within the 0,2 GHz – 5 GHz frequency range.
• Pulses can be repetitive.
– Resonances of different systems can be stimulated simultaneously.
– However, energy produced in a single pulse is spread over many frequencies.
– Thus power density is lower than for than the high power microwave sources
• More likely to cause interference from the inadvertent coupling paths than permanent
damage.
To better understand the effe
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