SIST EN 61000-2-10:2001
(Main)Electromagnetic compatibility (EMC) -- Part 2-10: Environment - Description of HEMP environment - Conducted disturbance
Electromagnetic compatibility (EMC) -- Part 2-10: Environment - Description of HEMP environment - Conducted disturbance
Defines the high-altitude electromagnetic pulse (HEMP) conducted environment that is one of the consequences of a high-altitude nuclear explosion. Establishes a common reference for this environment in order to select realistic stresses to apply to victim equipment for evaluating their performance. Presents the conducted HEMP environment induced on metallic lines, such as cables or power lines, external and internal to installations, and external antennas.
Elektromagnetische Verträglichkeit (EMV) -- Teil 2-10: Umgebungsbedingungen - Beschreibung der HEMP-Umgebung - Leitungsgeführte Störgrößen
Compatibilité électromagnétique (CEM) -- Partie 2-10: Environnement - Description de l'environnement IEMN-HA - Perturbations conduites
Définit l'environnement IEMN-HA conduit (l'impulsion électromagnétique à haute altitude) consécutif à une explosion nucléaire à haute altitude. Etablit une référence commune sur cet environnement permettant de définir des contraintes réalistes à appliquer aux équipements victimes afin d'évaluer leurs performances. Décrit l'environnement conduit induit par l'IEMN-HA sur les câbles ou lignes d'énergie externes et internes aux installations et sur des antennes externes.
Electromagnetic compatibility (EMC) - Part 2-10: Environment - Description of HEMP environment - Conducted disturbance
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61000-2-10:2001
01-marec-2001
Electromagnetic compatibility (EMC) - Part 2-10: Environment - Description of
HEMP environment - Conducted disturbance
Electromagnetic compatibility (EMC) -- Part 2-10: Environment - Description of HEMP
environment - Conducted disturbance
Elektromagnetische Verträglichkeit (EMV) -- Teil 2-10: Umgebungsbedingungen -
Beschreibung der HEMP-Umgebung - Leitungsgeführte Störgrößen
Compatibilité électromagnétique (CEM) -- Partie 2-10: Environnement - Description de
l'environnement IEMN-HA - Perturbations conduites
Ta slovenski standard je istoveten z: EN 61000-2-10:1999
ICS:
33.100.01 Elektromagnetna združljivost Electromagnetic compatibility
na splošno in general
SIST EN 61000-2-10:2001 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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NORME
CEI
INTERNATIONALE
IEC
61000-2-10
INTERNATIONAL
Première édition
STANDARD
First edition
1998-11
Compatibilité électromagnétique (CEM) –
Partie 2-10:
Environnement – Description de l’environnement
IEMN-HA – Perturbations conduites
Electromagnetic compatibility (EMC) –
Part 2-10:
Environment – Description of
HEMP environment – Conducted disturbance
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CODE PRIX
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Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61000-2-10 © IEC:1998 – 3 –
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 7
Clause
1 Scope. 9
2 Normative references . 9
3 General . 11
4 Definitions . 13
5 Description of HEMP environment, conducted parameters. 19
5.1 Introductory remarks. 19
5.2 Early-time HEMP external conducted environment. 21
5.3 Intermediate-time HEMP external conducted environment . 25
5.4 Late-time HEMP external conducted environment. 27
5.5 Antenna currents. 29
5.6 HEMP internal conducted environments . 39
Annex A (informative) Discussion of early-time HEMP coupling for long lines . 43
Annex B (informative) Discussion of intermediate-time HEMP coupling for long lines. 49
Annex C (informative) Responses of simple linear antennas to the IEC early-time
HEMP environment. 53
Annex D (informative) Measured cable currents inside telephone buildings. 85
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61000-2-10 © IEC:1998 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-10: Environment – Description of HEMP environment –
Conducted disturbance
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 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 International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61000-2-10 has been prepared by subcommittee 77C: Immunity to
high altitude nuclear electromagnetic pulse (HEMP), of IEC technical committee 77:
Electromagnetic compatibility.
The text of this standard is based on the following documents:
FDIS Report on voting
77C/61/FDIS 77C/65/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
Annexes A, B, C and D are for information only.
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61000-2-10 © IEC:1998 – 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 (insofar as these limits do not fall under the responsibilty 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, published either as International Standards
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.
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61000-2-10 © IEC:1998 – 9 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 2-10: Environment – Description of HEMP environment –
Conducted disturbance
1 Scope
This International Standard defines the high-altitude electromagnetic pulse (HEMP) conducted
environment that is one of the consequences of a high-altitude nuclear explosion.
Those dealing with this subject consider two cases:
– high-altitude nuclear explosions;
– low-altitude nuclear explosions.
For civil systems the most important case is the high-altitude nuclear explosion. In this case,
the other effects of the nuclear explosion: blast, ground shock, thermal and nuclear ionizing
radiation are not present at the ground level.
However, the electromagnetic pulse associated with the explosion may cause disruption of, and
damage to, communication, electronic and electric power systems thereby upsetting the
stability of modern society.
The object of this standard is to establish a common reference for the conducted HEMP
environment in order to select realistic stresses to apply to victim equipment for evaluating
their performance.
2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this part of IEC 61000. At the time of publication, the editions indicated
were valid. All standards are subject to revision, and parties to agreements based on this part
of IEC 61000 are encouraged to investigate the possibility of applying the most recent editions
of the normative documents indicated below. Members of IEC and ISO maintain registers of
currently valid International Standards.
IEC 60050(161):1990, International Electrotechnical Vocabulary (IEV) – Chapter 161:
Electromagnetic Compatibility
IEC 61000-2-9:1996, Electromagnetic compatibility (EMC) – Part 2: Environment – Section 1:
Description of HEMP environment – Radiated disturbance – Basic EMC publication
IEC 61000-4-24:1997, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement
techniques – Section 24: Test methods for protective devices for HEMP conducted disturbance –
Basic EMC publication
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61000-2-10 © IEC:1998 – 11 –
3 General
A high-altitude (above 30 km) nuclear burst produces three types of electromagnetic pulses
which are observed on the earth's surface:
– early-time HEMP (fast);
– intermediate-time HEMP (medium);
– late-time HEMP (slow).
Historically most interest has been focused on the early-time HEMP which was previously
referred to as simply HEMP. Here we will use the term high-altitude EMP or HEMP to include
1)
all three types. The term NEMP covers many categories of nuclear EMPs including those
2) 3)
produced by surface bursts (SREMP) or created on space systems (SGEMP) .
Because the HEMP is produced by a high-altitude detonation, we do not observe other nuclear
weapon environments such as gamma rays, heat and shock waves at the earth's surface.
HEMP was reported from high-altitude nuclear tests in the South Pacific by the US and over
the USSR during the early 1960s, producing effects on electronic equipment far from the burst
location.
This standard presents the conducted HEMP environment induced on metallic lines, such as
cables or power lines, external and internal to installations, and external antennas.
________
1)
NEMP: Nuclear electromagnetic pulse.
2)
SREMP: Source region EMP.
3)
SGEMP: System generated EMP.
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61000-2-10 © IEC:1998 – 13 –
4 Definitions
For the purpose of this International Standard, the definitions given in IEC 60050(161) apply,
as well as the following definitions:
Horizontal
polarisation
inc
Vertical
E
x
k
polarisation
inc
inc
H k
E
z
inc
H
y
ψ
φ
Ground plane
IEC 1 528/98
Figure 1 – Geometry for the definition of polarization and
of the angles of elevation and azimuth
ψψ φφ
4.1
angle of elevation in the vertical plane, ψψ
angle ψ measured in the vertical plane between a flat horizontal surface such as the ground
and the propagation vector (see figure 1)
4.2
azimuth angle, φφ
angle between the projection of the propagation vector on the ground plane and the principal
axis of the victim object (z axis for the transmission line of figure 1)
4.3
composite waveform
waveform which maximizes the important features of a waveform
4.4
coupling
interaction of the HEMP field with a system to produce currents and voltages on system
surfaces and cables. Voltages result from the induced charges and are only defined at low
frequencies with wavelengths larger than the surface or gap dimensions
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61000-2-10 © IEC:1998 – 15 –
4.5
direction of propagation of the electromagnetic wave
→
direction of the propagation vector k , perpendicular to the plane containing the vectors of the
electric and the magnetic fields (see figure 2)
E
k
H
IEC 1 529/98
Figure 2 – Geometry for the definition of the plane wave
4.6
E1, E2, E3
terminology for the early, intermediate and late-time HEMP electric fields
4.7
EMP
any electromagnetic pulse, general description
4.8
geomagnetic dip angle, θθ
dip
→
dip angle of the geomagnetic flux density vector B , measured from the local horizontal in the
e
magnetic north-south plane. θ = 90° at the magnetic north pole, –90° at the magnetic south
dip
pole, (see figure 3)
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61000-2-10 © IEC:1998 – 17 –
Magnetic north/south plane
B
e
θ
dip
Earth
North
South
IEC 1 530/98
Figure 3 – Geomagnetic dip angle
4.9
HEMP
high-altitude nuclear EMP
4.10
high-altitude (nuclear explosion)
height of burst above 30 km altitude
4.11
horizontal polarization
an electromagnetic wave is horizontally polarized if the magnetic field vector is in the incidence
plane and the electric field vector is perpendicular to the incidence plane and thus parallel to
the ground plane (see figure 1). (This type of polarization is also called perpendicular or
transverse electric (TE).)
4.12
incidence plane
plane formed by the propagation vector and the normal to the ground plane
4.13
low-altitude (nuclear explosion)
height of burst below 1 km altitude
4.14
NEMP
nuclear EMP; all types of EMP produced by a nuclear explosion
4.15
point-of-entry (PoE)
the physical location (point) on an electromagnetic barrier, where EM energy may enter or exit
a topological volume, unless an adequate PoE protective device is provided. A PoE is not
limited to a geometrical point. PoEs are classified as aperture PoEs or conductive PoEs
according to the type of penetration. They are also classified as architectural, mechanical,
structural or electrical PoEs, according to the functions they serve
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61000-2-10 © IEC:1998 – 19 –
4.16
pulse width
the time interval between the points on the leading and trailing edges of a pulse at which the
instantaneous value is 50 % of the peak pulse amplitude, unless otherwise stated
4.17
rectified impulse (RI)
the integral of the absolute value of a time waveform’s amplitude over a specified time interval
4.18
rise time (pulse)
the time interval between the instants in which the instantaneous amplitude of a pulse first
reaches specified lower and upper limits, namely 10 % and 90 % of the peak pulse amplitude,
unless otherwise stated
4.19
short-circuit current
the value of current that flows when the output terminals of a circuit are shorted. This current is
normally of interest when checking the performance of surge protection devices
4.20
source impedance
the impedance presented by a source of energy to the input terminals of a device or network
4.21
vertical polarization
an electromagnetic wave is vertically polarized if the electric field vector is in the incidence
plane, and the magnetic field vector is perpendicular to the incidence plane and thus parallel to
the ground plane (see figure 1). (This type of polarization is also called parallel or transverse
magnetic (TM).)
5 Description of HEMP environment, conducted parameters
5.1 Introductory remarks
The electromagnetic field generated by a high-altitude nuclear explosion described in
IEC 61000-2-9 can induce currents and voltages in all metallic structures. These currents and
voltages propagating in conductors represent the conducted environment. This means that the
conducted environment is a secondary phenomenon, a consequence of the radiated field
alone.
All metallic structures (i.e. wires, conductors, pipes, ducts, etc.) will be affected by the HEMP.
The conducted environment is important because it can direct the HEMP energy to sensitive
electronics through signal, power, and grounding connections. It should be noted that there are
two distinct categories of conductors: external and internal conductors (with regard to a
building or any other enclosure). While this may seem simplistic, this separation is critical in
terms of the information to be provided in this standard.
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61000-2-10 © IEC:1998 – 21 –
The difference between these two types of conductors is explained by electromagnetic
topology. In general, external conductors are those which are located outside of a building and
are completely exposed to the full HEMP environment. This category includes power, metallic
communication lines, antenna cables, and water and gas pipes (if metallic). For the purposes
of this standard the conductors can be elevated above the ground or buried in the earth.
Internal conductors are those which are located in a partially or completely shielded building
where the HEMP fields have been reduced by the building. This is a much more complex
situation, because the HEMP field waveforms will be significantly altered by the building shield,
and the coupling to internal wires and cables is consequently very difficult to calculate,
although some measured data are available from simulated HEMP tests.
In this standard the external conducted common mode environments are calculated using
simplified conductor geometries and the specified HEMP environments for the early,
intermediate, and late-time waveforms. These conducted external environments are intended
to be used to evaluate the performance of protection devices outside of a building, and
because of variations in telecom and power systems, the effects of transformers and telephone
splice boxes are not considered here. This process results in approximate, but well-defined
waveforms that are needed to test protective elements on external conductors in a
standardized manner. For the internal conductors, a procedure is defined to estimate the
conducted environments appropriate for equipment testing. For unshielded multiconductor
wires, it is assumed that the line-to-ground currents are equal to the common-mode current.
5.2 Early-time HEMP external conducted environment
For the early-time HEMP, the high-amplitude electric field couples efficiently to antennas and to
any exposed lines such as power and telephone lines. The antenna coupling mechanism is
extremely variable and dependent on the details of the antenna design. In many cases, it is
advisable to perform continuous wave (CW) testing of an antenna and to ”combine” the
response function of the antenna with the incident HEMP environment using a convolution
technique. We have, however, provided simple equations to compute the response of thin
antennas (see 5.5). For long lines, it is possible to perform a comprehensive set of common
mode calculations that are reliable and depend only upon a few parameters. These parameters
include conductor length, exposure situation (above ground or buried), and the surface ground
conductivity (for depths between 0 m and 5 m). In addition, because the HEMP coupling is
dependent on angle of elevation and polarization (see figure 1), it is possible to statistically
examine the probability of producing particular levels of current.
Table 1 below describes the calculated, coupled, common-mode short-circuit currents and the
Thévenin equivalent source impedances (used to determine the open-circuit voltages) as
functions of severity level, length of conductor, and ground conductivity. These results are
appropriate for the common-mode currents flowing on bare wires, overhead insulated wires,
and the shields of shielded cables or coaxial transmission lines. For shielded cables one
should use measured or specified cable transfer impedances to determine internal wire
currents and voltages. Although some waveform variation occurs for different exposure
geometries, a single time waveform is specified for elevated lines. The waveform is defined in
terms of the rise time (10 % to 90 %) and the pulse width (at half maximum); when the pulse
characteristics of rise time and pulse width are described together, the usual description is
Δt /Δt .
r pw
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61000-2-10 © IEC:1998 – 23 –
In table 1 a severity level of 99 % indicates that 99 % of the currents produced will be less than
this value. The buried line currents calculated vary much less with angle of incidence and
indicate a very broad probability distribution (small differences between 10 % and 90 %
severity) and therefore are not described in terms of severity levels; variations are shown for
ground conductivity. In terms of applicability for table 1, the elevated conductor currents are
accurate for heights above 5 m while the buried currents can be used for conductors slightly
(h < 30 cm) above the surface and below the surface. For conductor heights below 5 m, the
values in table 1 may be linearly interpolated (between 0,3 m and 5 m). For cases where the
lines from an elevated geometry enter the ground in an insulated manner, the currents will
initially resemble waveform 1, decreasing as a function of burial distance until waveform 2 is
reached (requires approximately 20 m). Consult annex A for further information regarding the
derivation of these waveforms.
Table 1 – Early-time HEMP conducted common-mode short-circuit currents including
the time history and peak value I as a function of severity level,
pk
length L in metres and ground conductivity σ
g
Table 1a – Elevated conductor
I
pk
A
Severity L > 200 m 100 < L < 200 m L < 100 m
1)
(%)
50 500 500
5,0 × L
90 1 500 7,5 × L
7,5 × L
99 4 000
20 × L L
20 ×
1)
Percentage of currents smaller than the indicated value.
Waveform 1: 10/100 ns.
Source impedance: Z = 400 Ω.
s
Table 1b – Buried conductor
I
pk
A
σσ All lengths > 10 m
g
S/m
–2
10 200
–3
10 300
–4
10 400
Waveform 2: 25/500 ns.
Source impedance: Z = 50 Ω.
s
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61000-2-10 © IEC:1998 – 25 –
5.3 Intermediate-time HEMP external conducted environment
The intermediate-time HEMP environment only couples efficiently to long conductors in excess
of 1 km. It is therefore of interest primarily for external conductors such as power and commu-
nication lines. Because the pulse width of this environment is much wider than that of the early-
time environment, the coupling varies less as a function of angle of elevation. This means that
the statistical variation is less important than in the case of the early-time coupling. On the
other hand, the ground conductivity is more important here affecting the coupling to elevated
lines in addition to buried lines. See annex B for a more detailed discussion.
Table 2 describes the conducted external environment as a function of line length and ground
conductivity (to depths of 1 km).
Table 2 – Intermediate-time HEMP conducted common-mode short-circuit currents
including the time history and peak value I as a function of
pk
length L in metres and ground conductivity σ
g
Table 2a – Elevated conductor
I
pk
A
L > 10 000 m 1 000 < L < 10 000 m 100 < L < 1 000 m L < 100 m
σσ
g
S/m
–2
10 150 75 0
0,05 × L
–3
10 350 200 0
0,15 × L
–4
10 800 600 0
0,45 × L
Waveform 3: 25/1 500 μs.
Source impedance: Z = 400 Ω.
s
Table 2b – Buried conductor
I
pk
A
σσ L > 1 000 m 100 < L < 1 000 m L < 100 m
g
S/m
–2
10 50 0
0,05 × L
–3
10 150 0
0,15 L
×
–4
10 450 0
0,45 × L
Waveform 3: 25/1 500 μs.
Source impedance: Z = 50 Ω.
s
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61000-2-10 © IEC:1998 – 27 –
5.4 Late-time HEMP external conducted environment
The late-time HEMP environment is only important for coupling to long external conductors
such as power and communication lines. In this case, however, the computation of short circuit
currents for typical cases of interest is not easily accomplished. This is because the late-time
HEMP environment is described as a voltage source that is produced in the earth which
induces currents to flow only in conductors that are connected to the earth at two or more
points. Since the current that flows is strongly dependent on the resistance present in the
circuit, an analytical method is provided here to develop a standard conducted environment.
In order to describe the method to be used, an example case is provided. In figure 4a, a three-
phase Y-delta power configuration is shown along with an equivalent circuit in figure 4b (where
E is the peak value of the late-time HEMP). Note that the problem can be described as a
o
quasi-d.c. problem with the voltage source calculated directly from the late-time HEMP
environment. Since the highest frequencies contained in the late-time HEMP environment are
of the order of 1 Hz, this is clearly appropriate. It can therefore be assumed that the voltage
source V has the same time dependence as E . Given that the resistances in figure 4b (the
s o
parallel Y winding resistances R and the "footing" or grounding resistances R) are not
y f
frequency dependent for f < 1 Hz, then the induced current I will have the same time
pk
dependence as E .
o
IEC 1 531/98
Figure 4a – Three-phase line and transformer configuration
R r L
=
y L I
pk
R R
y y
R R
f f
+ −
IEC 1 532/98
V E L
=
s o
Figure 4b – Simple equivalent circuit where E is the induced
o
late-time HEMP electric field
Figure 4 – Three-phase line and equivalent circuit for computing
late-time HEMP conducted current
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61000-2-10 © IEC:1998 – 29 –
Using the example provided, the peak current can be calculated as:
EL
O
I= (1)
pk
2(RR++)rL
fy L
where
r is the parallel wire resistance per unit length (Ω/m);
L
R is the ground resistance ( );
Ω
f
R is the parallel winding resistance in one transformer (Ω);
y
L is the line length (m).
For a long transmission line in North America, a 500 kV line would have a resistance per unit
–6
length of 8,3 × 10 Ω/m, a transformer winding resistance of 0,06 Ω and a grounding
5
resistance of 0,75 Ω. For a 10 m length line, this provides a peak current of approximately
40 000 × E (where E is given as 0,04 V/m in IEC 61000-2-9 for a deep (d >> 10 km) ground
o o
–4
conductivity of 10 S/m) or approximately 1 600 A. Given this peak value, the current time
waveform can be approximated by a unipolar pulse with a rise time and pulse width of 1/50 s.
To simulate the waveform for this example, one should use a voltage source of 4 kV with a
source impedance of 2,45 Ω. It is important to recognize the necessity to ground transformers
in order to use the circuit in figure 4. Some transformers are delta-delta and do not possess a
direct path to ground.
Equation 1 above can easily be translated to cover cases other than power lines by computing
the total resistance in the circuit, and dividing it into the total voltage induced over the length of
the conductor. Equation 1 is provided for the case of long cables over land, and for deep
undersea cables, the currents calculated may be reduced by up to a factor of 100. This
reduction is due to the behaviour of the electric field E which is inversely proportional to the
o
square root of the deep ground conductivity (to depths of 10 km to 100 km). For freshwater
lakes or shallow seas, the currents may not be reduced as much.
5.5 Antenna currents
Antennas come in many different sizes and shapes. At frequencies in the VLF and LF range
(3 kHz to 300 kHz), such antennas are often in the form of very long wires which are
sometimes buried in the earth. Antennas in the MF band (300 kHz to 3 000 kHz) are often in
the form of a vertical tower which is fed against a buried counterpoise grid buried in the earth.
In the HF and VHF bands (3 MHz to 30 MHz and 30 MHz to 300 MHz, respectively), the
antennas typically appear as centre-fed dipoles, and at the higher frequencies (UHF, SHF, etc.)
they become more like a distributed system, involving reflecting dishes and radiating apertures.
Usually, antennas are operated in a narrow band of frequencies located around a fundamental
design frequency. In order to enhance their narrow-band performance, such antennas are often
“tuned” by adding lumped impedance elements, by adding additional passive elements near the
active antenna, or by locating the antenna in an array.
Given such a large variation in antenna configurations, it is difficult to provide an accurate
response specification (current and voltage waveforms) for every type of antenna. As an
approximate model, however, it is possible to consider the simple thin-wire vertical dipole
antenna shown in figure 5, and to use its response as an indication of what would be the
responses for other more complex antennas. Of course, this model is applicable only to
antennas of the electric dipole class: loop (i.e. magnetic) antennas and aperture antennas are
not adequately modelled by this simple structure. For more complex antennas, it is recommended
that CW illumination or high level pulse testing be performed to evaluate antenna responses.
-------
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