SIST EN 61000-4-18:2007
Electromagnetic compatibility (EMC) -- Part 4-18: Testing and measurement techniques - Damped oscillatory wave immunity test
Electromagnetic compatibility (EMC) -- Part 4-18: Testing and measurement techniques - Damped oscillatory wave immunity test
This part of IEC 61000-4 relates to the immunity requirements and test methods for electrical and electronic equipment, under operational conditions, with regard to: a) repetitive damped oscillatory waves occurring mainly in power, control and signal cables installed in high voltage and medium voltage (HV/MV) substations; b) repetitive damped oscillatory waves occurring mainly in power, control and signal cables installed in gas insulated substations (GIS) and in some cases also air insulated substations (AIS) or in any installation due to HEMP phenomena. The object of this basic standard is to establish the immunity requirements and a common reference for evaluating in a laboratory the performance of electrical and electronic equipment intended for residential, commercial and industrial applications, as well as of equipment intended for power stations and substations, as applicable.
Elektromagnetische Verträglichkeit (EMV) -- Teil 4-18: Prüf- und Messverfahren - Prüfung der Störfestigkeit gegen gedämpft schwingende Wellen
Compatibilité électromagnétique (CEM) -- Partie 4-18: Techniques d'essai et de mesure - Essai d'immunité à l'onde oscillatoire amortie
La présente partie de la CEI 61000-4 traite des exigences en matière d'immunité et des méthodes d'essai des matériels électriques et électroniques dans leurs conditions d'exploitation, vis-à-vis:
a) des oscillations transitoires amorties répétitives se manifestant principalement sur les câbles d'alimentation, de commande et de signal installés dans les postes à haute et à moyenne tension (HT/MT);
b) des ondes oscillatoires amorties répétitives se produisant principalement sur les câbles d'alimentation, de commande et de signal implantés dans les postes métalliques sous enveloppes à isolation gazeuse (GIS) et dans certains cas également dans des postes à isolation par air (AIS) ou toute installation du fait des phénomènes IEM-HA.
L'objet de cette norme fondamentale est d'établir les exigences d'immunité et de constituer une référence commune pour l'évaluation en laboratoire des performances d'équipements électriques et électroniques destinés aux applications résidentielles, commerciales et industrielles, ainsi que d'équipements destinés aux centrales électriques et aux postes, le cas échéant.
La présente norme a pour objet de définir les paramètres suivants:
- tension d'essai et formes d'ondes de courant;
- gammes de niveaux d'essais;
- matériel d'essai;
- installation d'essai;
- procédure d'essai.
Cette norme a pour objet d'établir une référence commune dans le but d'évaluer l'immunité des matériels électriques et électroniques, quand ils sont soumis aux ondes oscillatoires amorties. La méthode d'essai documentée dans cette partie de la CEI 61000 décrit une méthode logique en vue d'évaluer l'immunité d'un équipement ou d'un système vis-à-vis d'un phénomène donné.
Elle a le statut de publication fondamentale en CEM conformément au Guide 107 de la CEI.
Elektromagnetna združljivost (EMC) - 4-18. del: Preskusne in merilne tehnike - Preskus odpornosti proti nihajnemu valu (IEC 61000-4-18:2006)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 61000-4-18:2007
01-september-2007
1DGRPHãþD
SIST EN 61000-4-12:1997
SIST EN 61000-4-12:1997/A1:2002
Elektromagnetna združljivost (EMC) - 4-18. del: Preskusne in merilne tehnike -
Preskus odpornosti proti nihanjemu valu (IEC 61000-4-18:2006)
Electromagnetic compatibility (EMC) -- Part 4-18: Testing and measurement techniques -
Oscillatory wave immunity test
Elektromagnetische Verträglichkeit (EMV) -- Teil 4-18: Prüf- und Messverfahren -
Prüfung der Störfestigkeit gegen schwingende Wellen
Compatibilité électromagnétique (CEM) -- Partie 4-18: Techniques d'essai et de mesure -
Essai d'immunité a l'onde oscillatoire amortie
Ta slovenski standard je istoveten z: EN 61000-4-18:2007
ICS:
33.100.20 Imunost Immunity
SIST EN 61000-4-18:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN 61000-4-18
NORME EUROPÉENNE
April 2006
EUROPÄISCHE NORM
ICS 33.100.20 Partially supersedes EN 61000-4-12:1995 + A1:2001
English version
Electromagnetic compatibility (EMC) -
Part 4-18: Testing and measurement techniques -
Damped oscillatory wave immunity test
(IEC 61000-4-18:2006)
Compatibilité électromagnétique (CEM) - Elektromagnetische Verträglichkeit (EMV) -
Partie 4-18: Techniques d'essai Teil 4-18: Prüf- und Messverfahren -
et de mesure - Prüfung der Störfestigkeit
Essai d'immunité gegen schwingende Wellen
à l'onde oscillatoire amortie (IEC 61000-4-18:2006)
(CEI 61000-4-18:2006)
This European Standard was approved by CENELEC on 2007-03-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61000-4-18:2007 E
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- 2 - EN 61000-4-18:2007
Foreword
The text of document 77B/517/FDIS, future edition 1 of IEC 61000-4-18, prepared by SC 77B, High
frequency phenomena, of IEC TC 77, Electromagnetic compatibility, was submitted to the IEC-CENELEC
parallel vote and was approved by CENELEC as EN 61000-4-18 on 2007-03-01.
This European Standard deals with the immunity test against oscillatory waves which was formerly
covered by EN 61000-4-12:1995 + A1:2001, now superseded by EN 61000-4-12:2006. It constitutes a
technical revision by extending the frequency range.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2007-12-01
national standard or by endorsement
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2010-03-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 61000-4-18:2006 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60694 NOTE Harmonized as EN 60694:1996 (not modified).
IEC 61000-2-9 NOTE Harmonized as EN 61000-2-9:1996 (not modified).
IEC 61000-2-10 NOTE Harmonized as EN 61000-2-10:1999 (not modified).
IEC 60068-1 NOTE Harmonized as EN 60068-1:1994 (not modified).
IEC 61000-4-25 NOTE Harmonized as EN 61000-4-25:2002 (not modified).
IEC 61010-1 NOTE Harmonized as EN 61010-1:2001 (not modified).
__________
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EN 61000-4-18:2007 - 3 -
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year
1)
IEC 60050-161 - International Electrotechnical Vocabulary - -
(IEV) -
Chapter 161: Electromagnetic compatibility
1) 2)
IEC 61000-4-4 - Electromagnetic compatibility (EMC) - EN 61000-4-4 2004
Part 4-4: Testing and measurement
techniques - Electrical fast transient/burst
immunity test
1)
IEC 61000-6-6 - Electromagnetic compatibility (EMC) - -
-
Part 6-6: Generic standards - HEMP immunity
for indoor equipment
1)
Undated reference.
2)
Valid edition at date of issue.
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NORME CEI
INTERNATIONALE
IEC
61000-4-18
INTERNATIONAL
Première édition
STANDARD
First edition
2006-11
PUBLICATION FONDAMENTALE EN CEM
BASIC EMC PUBLICATION
Compatibilité électromagnétique (CEM) –
Partie 4-18:
Techniques d’essai et de mesure –
Essai d’immunité à l’onde oscillatoire amortie
Electromagnetic compatibility (EMC) –
Part 4-18:
Testing and measurement techniques –
Damped oscillatory wave immunity test
© IEC 2006 Droits de reproduction réservés ⎯ Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in any
utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
CODE PRIX
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PRICE CODE
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
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61000-4-18 © IEC:2006 – 3 –
CONTENTS
FOREWORD.7
INTRODUCTION.11
1 Scope and object.13
2 Normative references .13
3 Terms and definitions .15
4 General .17
4.1 Information on the slow damped oscillatory wave phenomenon .17
4.2 Information on the fast damped oscillatory wave phenomenon .19
5 Test levels.23
6 Test equipment.27
6.1 Generator.27
6.2 Specifications of the coupling/decoupling network .31
7 Test setup .35
7.1 Earthing connections.35
7.2 Ground reference plane.37
7.3 Equipment under test .37
7.4 Coupling/decoupling networks .39
7.5 Generators .39
8 Test procedure .39
8.1 Laboratory reference conditions .41
8.2 Execution of the test.41
9 Evaluation of test results .43
10 Test report.45
Annex A (informative) Information on test levels for the damped oscillatory wave .69
Bibliography.71
Figure 1 – Waveform of the damped oscillatory wave (open circuit voltage) .47
Figure 2 – Example of schematic circuit of the test generator for the damped oscillatory
wave.47
Figure 3 – Example of test setup for table-top equipment using the ground reference plane .49
Figure 4 – Example of test setup for floor-standing equipment using the ground
reference plane.49
Figure 5 – AC/DC power supply port, single phase, line-to-ground tests .51
Figure 6 – AC power supply port, three phases, line-to-ground test .53
Figure 7 – Input/output port, single circuit, line-to-ground test.55
Figure 8 – Input/output port, group of circuits with common return, line-to-ground test .57
Figure 9 – AC/DC power supply port, single phase, line-to-line test .59
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61000-4-18 © IEC:2006 – 5 –
Figure 10 – AC power supply port, three phases, line-to-line test.61
Figure 11 – Input/output port, single circuit, line-to-line test .63
Figure 12 – Input/output port, group of circuits with common return, line-to-line test .65
Figure 13 – Test of a system with communication ports with fast operating signals
(generator output earthed) .67
Table 1 – Test levels for the slow damped oscillatory wave (100 kHz or 1 MHz) .25
Table 2 – Test levels for the fast damped oscillatory wave (3 MHz, 10 MHz or 30 MHz).25
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61000-4-18 © IEC:2006 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 4-18: Testing and measurement techniques –
Damped oscillatory wave immunity test
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
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
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.
International Standard IEC 61000-4-18 has been prepared by subcommittee 77B: High
frequency phenomena, of IEC technical Committee 77: Electromagnetic compatibility.
It forms Part 4-18 of IEC 61000. It has the status of a basic EMC publication in accordance
with IEC Guide 107, Electromagnetic compatibility – Guide to the drafting of electromagnetic
compatibility publications.
This first edition of the standard cancels and replaces the content regarding damped
oscillatory waves in the first edition of IEC 61000-4-12, published in 1995, and its Amendment
1 (2000), and constitutes a technical revision by extending the frequency range.
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61000-4-18 © IEC:2006 – 9 –
The text of this standard is based on the following documents:
FDIS Report on voting
77B/517/FDIS 77B/522/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.
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.
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61000-4-18 © IEC:2006 – 11 –
INTRODUCTION
This standard is part of the IEC 61000 series, 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
Testing techniques
Part 5: Installation and mitigation guidelines
Installation guidelines
Mitigation methods and devices
Part 6: Generic standards
Part 9: Miscellaneous
Each part is further subdivided into several parts, published either as international standards
or as technical specifications or technical reports, some of which have already been published
as sections. Others will be published with the part number followed by a dash and a second
number identifying the subdivision (example: 61000-6-1).
This part is an international standard which gives immunity requirements and test procedures
related to damped oscillatory waves.
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61000-4-18 © IEC:2006 – 13 –
ELECTROMAGNETIC COMPATIBILITY (EMC) –
Part 4-18: Testing and measurement techniques –
Damped oscillatory wave immunity test
1 Scope and object
This part of IEC 61000-4 relates to the immunity requirements and test methods for electrical
and electronic equipment, under operational conditions, with regard to:
a) repetitive damped oscillatory waves occurring mainly in power, control and signal cables
installed in high voltage and medium voltage (HV/MV) substations;
b) repetitive damped oscillatory waves occurring mainly in power, control and signal cables
installed in gas insulated substations (GIS) and in some cases also air insulated
substations (AIS) or in any installation due to HEMP phenomena.
The object of this basic standard is to establish the immunity requirements and a common
reference for evaluating in a laboratory the performance of electrical and electronic equipment
intended for residential, commercial and industrial applications, as well as of equipment
intended for power stations and substations, as applicable.
NOTE As described in IEC guide 107, this is a basic EMC publication for use by product committees of the IEC.
As also stated in Guide 107, the IEC product committees are responsible for determining whether this immunity
test standard should be applied or not, and if applied, they are responsible for determining the appropriate test
levels and performance criteria. TC 77 and its sub-committees are prepared to co-operate with product committees
in the evaluation of the value of particular immunity tests for their products.
The purpose of this standard is to define:
– test voltage and current waveforms;
– ranges of test levels;
– test equipment;
– test setup;
– test procedure.
The object of this standard is to establish a common reference for evaluating the immunity of
electrical and electronic equipment when subjected to damped oscillatory waves. The test
method documented in this part of IEC 61000 describes a consistent method to assess the
immunity of an equipment or system against a defined phenomenon.
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.
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61000-4-18 © IEC:2006 – 15 –
lEC 60050(161): International Electrotechnical Vocabulary (IEV) – Chapter 161: Electro-
magnetic compatibility
IEC 61000-4-4: Electromagnetic compatibility (EMC) – Part 4-4: Testing and measurement
techniques – Electrical fast transient/burst immunity test
IEC 61000-6-6: Electromagnetic compatibility (EMC) – Part 6-6: Generic standards – HEMP
immunity for indoor equipment
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in lEC 60050-161,
some of which are repeated here for convenience, and the following terms and definitions
apply.
NOTE These terms are applicable to the restricted field of oscillatory transients.
3.1
air insulated substation
AIS
substation which is made up with only air insulated switchgear
3.2
burst
sequence of a limited number of distinct pulses or an oscillation of limited duration
[IEV 161-02-07]
3.3
calibration
set of operations which establishes, by reference to standards, the relationship which exists
under specified conditions, between an indication and a result of a measurement
NOTE 1 This term is based on the "uncertainty" approach.
NOTE 2 The relationship between the indications and the results of measurement can be expressed, in principle,
by a calibration diagram.
[IEV 311-01-09]
3.4
coupling
interaction between circuits, transferring energy from one circuit to another
3.5
coupling network
electrical circuit for the purpose of transferring energy from one circuit to another
3.6
decoupling network
electrical circuit for the purpose of preventing test voltages applied to the EUT (equipment
under test) from affecting other devices, equipment, or systems which are not under test
3.7
gas insulated (metal-enclosed) substation
GIS
substation which is made up with only gas insulated metal enclosed switchgear
[IEV 605-02-14]
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61000-4-18 © IEC:2006 – 17 –
3.8
high-altitude electromagnetic pulse
electromagnetic pulse produced by a nuclear explosion outside the earth’s atmosphere
NOTE Typically above an altitude of 30 km
3.9
immunity (to a disturbance)
the ability of a device, equipment, or system to perform without degradation in the presence of
an electromagnetic disturbance
[IEV 161-01-20]
3.10
port
particular interface of the EUT with the external electromagnetic environment
3.11
rise time
interval of time between the instants at which the instantaneous value of a pulse first reaches
10 % value and then the 90 % value
[IEV 161-02-05, modified]
3.12
transient (adjective and noun)
pertaining to or designating a phenomenon or a quantity which varies between two
consecutive steady states during a time interval short compared with the time-scale of interest
[IEV 161-02-01]
3.13
verification
set of operations which is used to check the test equipment system (e.g. the test generator
and the interconnecting cables) and to demonstrate that the test system is functioning within
the specifications given in Clause 6
NOTE 1 The methods used for verification may be different from those used for calibration.
NOTE 2 The procedure of 6.1.3 and 6.2 is meant as a guide to insure the correct operation of the test generator,
and other items making up the test setup so that the intended waveform is delivered to the EUT.
[IEV 311-01-13, modified]
4 General
The damped oscillatory wave phenomena are divided into two parts. The first part is referred
to as the slow damped oscillatory wave and includes oscillation frequencies between 100 kHz
and 1 MHz. The second part is referred to as the fast damped oscillatory wave, and it includes
oscillation frequencies above 1 MHz. The causes of these two types of damped oscillatory
waves are described below.
4.1 Information on the slow damped oscillatory wave phenomenon
This phenomenon is representative of the switching of disconnectors in HV/MV open-air
substations, and is particularly related to the switching of HV busbars, as well as to the
background disturbance in industrial plants.
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61000-4-18 © IEC:2006 – 19 –
In electrical stations, the opening and closing operations of HV disconnectors give rise to
sharp front-wave transients, with rise times of the order of some tens of nanoseconds.
The voltage front-wave has an evolution that includes reflections, due to the mismatching of
the characteristic impedance of HV circuits involved. In this respect, the resulting transient
voltage and current in HV busbars are characterized by a fundamental oscillation frequency
that depends on the length of the circuit and on the propagation time.
The oscillation frequency ranges from about 100 kHz to a few megahertz for open-air sub-
stations, depending on the influence of the parameters mentioned above and the length of the
busbars, which may vary from some tens of metres to hundreds of metres (400 m may occur).
In this respect, the oscillation frequency of 1 MHz may be considered representative of most
situations, but 100 kHz has been considered appropriate for large HV substations.
The repetition frequency is variable between a few hertz and a few kilohertz depending on the
distance between the switching contacts: that is, for close contacts, there is a maximum
repetition frequency, while for distances between the contacts near to the extinction of the
arc, the minimum repetition frequency, in respect of each phase, is twice the power frequency
(100/s per phase for 50 Hz and 120/s per phase for 60 Hz HV systems).
The repetition rates selected, 40/s and 400/s, represent therefore a compromise, taking into
account the different durations of the phenomena, the suitability of the different frequencies
considered and the problem related to the energy to which the circuits under test are
subjected.
In industrial plants, repetitive oscillatory transients may be generated by switching transients
and the injection of impulsive currents in power systems (networks and electrical equipment).
The systems have a local response in a frequency band well covered by the rise time and the
fundamental frequency of oscillation of the damped oscillatory wave selected for testing
purposes.
4.2 Information on the fast damped oscillatory wave phenomenon
The fast damped oscillatory wave immunity test should cover phenomena present in two
specific environments:
– substations of the power network (produced by switchgear and controlgear);
– all installations exposed to the high-altitude electromagnetic pulse (HEMP).
4.2.1 Disturbances produced by switchgear and controlgear
During opening or closing disconnector operations, between both contacts of the operated
device, a large number of restrikes take place due to the slow speed of the contacts.
Therefore, disconnector switch operations generate very fast transients, which propagate as
travelling waves in the busbars of the substation. The electrical length of the shielded
conductors and the length of the open circuit busbars determine the oscillation frequencies of
the transient overvoltages.
For air insulated substations (AIS) these transients will radiate an electromagnetic field in the
substation environment. Recent measurements have been performed in air insulated
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61000-4-18 © IEC:2006 – 21 –
1
substations using instruments with a large frequency bandwidth [1]) . These measurements
have shown that transient phenomena with frequencies higher than 1 MHz can also take place
in these substations.
For gas insulated substations (GIS), these transients propagate inside the metallic enclosure,
which contains the SF gas. Due to the skin effect, high frequency transients are confined
6
inside the enclosure and cause no problems. At the enclosure discontinuities however, a part
of transients is transferred to the external surface of the enclosure tube. As a consequence,
the enclosure potential rises and the current flowing on the enclosure surface radiates an
electromagnetic field in the substation environment. The transient ground potential rise is a
direct source of transient common mode currents in the secondary circuits. The radiated
electromagnetic field also induces common mode currents in the secondary circuits.
Measurements have shown that the maximum frequency of significant components in the
spectral density of these currents can be as high as 30 MHz to 50 MHz (see Figures 1 and 2)
[2].
In Figures 1 and 2, it can be seen that several peaks occur in the current spectral density
characteristic and important spectral components are observed at frequencies of some tens of
M
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