Surge arresters - Part 5: Selection and application recommendations

This part of IEC 60099 is not a mandatory standard but provides information, guidance, and recommendations for the selection and application of surge arresters to be used in threephase systems with nominal voltages above 1 kV. It applies to gapless metal-oxide surge arresters as defined in IEC 60099-4, to surge arresters containing both series and parallel gapped structure - rated 52 kV and less as defined in IEC 60099-6 and metal-oxide surge arresters with external series gap for overhead transmission and distribution lines (EGLA) as defined in IEC 60099-8. In Annex H, some aspects regarding the old type of SiC gapped arresters are discussed. The principle of insulation coordination for an electricity system is given in IEC 60071 and IEC 60071-2 standards. Basically the insulation coordination process is a risk management aiming to ensure the safe, reliable and economic design and operation of high voltage electricity networks and substations. The use of surge arrester helps to achieve a system and equipment insulation level and still maintaining an acceptable risk and the best economic of scale. The introduction of analytical modelling and simulation of power system transients further optimise the equipment insulation level. The selection of surge arresters has become more and more important in the power system design and operation. It is worthwhile to note that the reliability of the power system and equipment is dependent on the safety margin adopted by the user in the design and selection of the equipments and surge arresters. Surge arrester residual voltage is a major parameter of which most users have paid a lot of attention to when selecting the type and rating. The typical maximum surge arresters residual voltage are given in Annex F. It is likely, however, that for some systems, or in some countries, the system reliability requirements and design are sufficiently uniform that the recommendations of the present standard may lead to the definition of narrow ranges of arresters. The user of surge arresters will, in that case, not be required to apply the whole process introduced here to any new installation and the selection of characteristics resulting from prior practice may be continued.

Überspannungsableiter - Teil 5: Anleitung für die Auswahl und die Anwendung

Parafoudres - Partie 5: Recommandations pour le choix et l'utilisation

IEC 60099-5:2013 n’est pas une norme obligatoire, mais comporte des informations, un guide et autres recommandations pour le choix et l'utilisation des parafoudres à utiliser sur des réseaux triphasés de tensions nominales supérieures à 1 kV. Elle concerne les parafoudres à oxyde métallique sans éclateur définis dans l’IEC 60099-4, les parafoudres contenant des structures avec éclateur en série et en parallèle – de tension assignée inférieure ou égale à 52 kV tels que définis dans l’IEC 60099-6 et les parafoudres à oxyde métallique à éclateur extérieur en série pour les lignes aériennes de transmission ou de distribution (EGLA) tels que définis dans l’IEC 60099-8. L’Annexe H traite de quelques aspects concernant les anciens parafoudres au carbure de silicium (SiC) avec éclateur. Cette deuxième édition annule et remplace la première édition parue en 1996, et son amendement 1 paru en 1999. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
-Présentation élargie des différents types de parafoudres et de leur utilisation, y compris des   éléments de présentation supplémentaires concernant: la transmission des parafoudres de ligne, les parafoudres pour manœuvre de condensateurs dérivés, les parafoudres pour la protection des condensateurs série, l’utilisation de parafoudres entre phases, la connexion de parafoudres en parallèle;
-Ajout d’une section relative à la gestion des biens, y compris: la gestion des parafoudres dans un réseau électrique, la maintenance des parafoudres, une présentation très élargie des outils de diagnostic des performances, les considérations relatives à la fin de vie;
- Nouvelles annexes portant sur: la modélisation des parafoudres pour les études de réseau, un exemple de données nécessaires pour la spécification des parafoudres.

Prenapetostni odvodniki - 5. del: Izbira in priporočila za uporabo (IEC 60099-5:2013)

Ta del standarda IEC 60099 ni obvezen, vendar podaja informacije, smernice in priporočila za izbiro in uporabo prenapetostnih odvodnikov, ki se uporabljajo v trifaznih sistemih z nazivnimi napetostmi nad 1 kV. Uporablja se za prenapetostne odvodnike iz kovinskega oksida brez iskrišč, kot je določeno v standardu IEC 60099-4, na prenapetostne odvodnike s tako skupinsko kot vzporedno strukturo z iskrišči, ki so ocenjeni 52 kV in manj, kot je določeno v standardu IEC 60099-6, ter prenapetostne odvodnike iz kovinskega oksida z zunanjim iskriščem za nadzemni prenos in razdelilna omrežja (EGLA), kot je določeno v standardu IEC 60099-8. V dodatku H so obravnavani nekateri vidiki v zvezi s starejšo vrsto prenapetostnih odvodnikov SiC z iskriščem. Načelo koordinacije izolacije za električni sistem je podano v standardih IEC 60071 in IEC 60071-2. V osnovi je postopek koordinacije izolacije upravljanje tveganja, s katerim želimo zagotoviti varno, zanesljivo in ekonomično zasnovo ter brezhibno delovanje visokonapetostnih električnih omrežij in podpostaj. Uporaba prenapetostnega odvodnika pomaga doseči raven izolacije sistema in opreme ter še vedno ohranja sprejemljivo tveganje in najboljšo ekonomičnost obsega. Uvedba analitičnega modeliranja in simulacija prehodnih pojavov napajalnega sistema dodatno optimizirata raven izolacije opreme. Izbira prenapetostnih odvodnikov je vse pomembnejša pri zasnovi in delovanju napajalnega sistema. Treba je opozoriti, da je zanesljivost napajalnega sistema in opreme odvisna od varnostne meje, ki jo sprejme uporabnik pri zasnovi in izbiri opreme in prenapetostnih odvodnikov. Preostala napetost prenapetostnega odvodnika je glavni parameter, ki mu je večina uporabnikov posvetila veliko pozornosti pri izbiranju vrste in ocene. Običajne največje preostale napetosti prenapetostnih odvodnikov so podane v dodatku F. Vendar je verjetno, da so pri nekaterih sistemih ali v nekaterih državah zahteve za zanesljivost sistema in zasnova dovolj enotne, da lahko priporočila sedanjega standarda vodijo k določitvi ozkih območij odvodnikov. Uporabnikom prenapetostnih odvodnikov v tem primeru ne bo treba uporabiti celotnega tukaj predstavljenega postopka za vsako novo namestitev in lahko nadaljujejo z izbiro značilnosti, ki izhaja iz predhodne prakse.

General Information

Status
Withdrawn
Publication Date
23-Sep-2013
Withdrawal Date
20-Dec-2020
Technical Committee
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
21-Dec-2020
Due Date
13-Jan-2021
Completion Date
21-Dec-2020

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SLOVENSKI STANDARD
SIST EN 60099-5:2013
01-oktober-2013
1DGRPHãþD
SIST EN 60099-5:1998
SIST EN 60099-5:1998/A1:2002
3UHQDSHWRVWQLRGYRGQLNLGHO,]ELUDLQSULSRURþLOD]DXSRUDER ,(&

Surge arresters - Part 5: Selection and application recommendations
Parafoudres - Partie 5: Recommandations pour le choix et l'utilisation
Ta slovenski standard je istoveten z: EN 60099-5:2013
ICS:
29.240.10 Transformatorske postaje. Substations. Surge arresters
Prenapetostni odvodniki
SIST EN 60099-5:2013 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 60099-5:2013

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SIST EN 60099-5:2013

EUROPEAN STANDARD
EN 60099-5

NORME EUROPÉENNE
August 2013
EUROPÄISCHE NORM

ICS 29.120.50; 29.240.10 Supersedes EN 60099-5:1996 + A1:1999


English version


Surge arresters -
Part 5: Selection and application recommendations
(IEC 60099-5:2013)


Parafoudres -  Überspannungsableiter -
Partie 5: Recommandations pour le choix Teil 5: Anleitung für die Auswahl und die
et l'utilisation Anwendung
(CEI 60099-5:2013) (IEC 60099-5:2013)





This European Standard was approved by CENELEC on 2013-06-26. 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels


© 2013 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60099-5:2013 E

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SIST EN 60099-5:2013
EN 60099-5:2013 - 2 -

Foreword
The text of document 37/405/FDIS, future edition 2 of IEC 60099-5, prepared by IEC/TC 37 "Surge
arresters" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN 60099-5:2013.

The following dates are fixed:
• latest date by which the document has to be (dop) 2014-03-26
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2016-06-26
• latest date by which the national
standards conflicting with the
document have to be withdrawn

This document supersedes EN 60099-5:1996 + A1:1999.

EN 60099-5:2013 includes the following significant technical changes with respect to
EN 60099-5:1996 + A1:1999:
a) Expanded discussion of different types of arresters and their application, including additions of
discussion on
– transmission of line arresters,
– arresters for shunt capacitor switching,
– arresters for series capacitor protection,
– application of arresters between phases,
– connecting arresters in parallel.
b) Addition of section on asset management, including
– managing surge arresters in the power grid,
– arrester maintenance,
– significantly expanded discussion of performance diagnostic tools,
– end-of-life considerations.
c) New annexes dealing with
– arrester modelling for system studies,
– example of data needed for specifying arresters.

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.

Endorsement notice
The text of the International Standard IEC 60099-5:2013 was approved by CENELEC as a European
Standard without any modification.

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SIST EN 60099-5:2013
- 3 - EN 60099-5:2013
Annex ZA
(normative)

Normative references to international publications
with their corresponding European publications

The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. 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

IEC 60071-1 2006 Insulation co-ordination - EN 60071-1 2006
Part 1: Definitions, principles and rules


IEC 60071-2 1996 Insulation co-ordination - EN 60071-2 1997
Part 2: Application guide


IEC/TR 60071-4 - Insulation co-ordination - - -
Part 4: Computational guide to insulation co-
ordination and modelling of electrical
networks


IEC 60099-4 (mod) 2004 Surge arresters - EN 60099-4 2004
+ A1 2006 Part 4: Metal-oxide surge arresters without + A1 2006
+ A2 2009 gaps for a.c. systems + A2 2009


IEC 60099-6 2002 Surge arresters - - -
Part 6: Surge arresters containing both
series and parallel gapped structures - Rated
52 kV and less


IEC 60099-8 2011 Surge arresters - EN 60099-8 2011
Part 8: Metal-oxide surge arresters with
external series gap (EGLA) for overhead
transmission and distribution lines of a.c.
systems above 1 kV


IEC 60507 - Artificial pollution tests on high-voltage EN 60507 -
insulators to be used on a.c. systems


IEC/TS 60815-1 - Selection and dimensioning of high-voltage - -
insulators intended for use in polluted
conditions -
Part 1: Definitions, information and general
principles


IEC/TS 60815-2 - Selection and dimensioning of high-voltage - -
insulators intended for use in polluted
conditions -
Part 2: Ceramic and glass insulators for a.c.
systems


IEC/TS 60815-3 - Selection and dimensioning of high-voltage - -
insulators intended for use in polluted
conditions -
Part 3: Polymer insulators for a.c. systems


IEC 62271-1 - High-voltage switchgear and controlgear - EN 62271-1 -
Part 1: Common specifications

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SIST EN 60099-5:2013
EN 60099-5:2013 - 4 -
Publication Year Title EN/HD Year
IEC 62271-200 - High-voltage switchgear and controlgear - EN 62271-200 -
Part 200: AC metal-enclosed switchgear and
controlgear for rated voltages above 1 kV
and up to and including 52 kV


IEC 62271-203 - High-voltage switchgear and controlgear - EN 62271-203 -
Part 203: Gas-insulated metal-enclosed
switchgear for rated voltages above 52 kV

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SIST EN 60099-5:2013




IEC 60099-5

®


Edition 2.0 2013-05




INTERNATIONAL



STANDARD








colour

inside










Surge arresters –

Part 5: Selection and application recommendations



























INTERNATIONAL

ELECTROTECHNICAL

COMMISSION

PRICE CODE
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ICS 29.120.50; 29.240.10 ISBN 978-2-83220-804-5



  Warning! Make sure that you obtained this publication from an authorized distributor.


® Registered trademark of the International Electrotechnical Commission

---------------------- Page: 7 ----------------------

SIST EN 60099-5:2013
– 2 – 60099-5 © IEC:2013(E)
CONTENTS
FOREWORD . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 General principles for the application of surge arresters . 18
5 Surge arrester fundamentals and applications issues . 19
5.1 Evolution of surge protection equipment . 19
5.2 Different types and designs and their electrical and mechanical
characteristics . 20
5.2.1 General . 20
5.2.2 Metal-oxide arresters without gaps according to IEC 60099-4 . 20
5.2.3 Metal-oxide surge arresters with internal series gaps according to
IEC 60099-6 . 30
5.2.4 Externally gapped line arresters (EGLA) according to IEC 60099-
8:2011 . 32
5.3 Installation considerations for arresters . 35
5.3.1 High-voltage station arresters . 35
5.3.2 Distribution arresters . 43
5.3.3 Line surge arresters (LSA) . 46
6 Insulation coordination and surge arrester applications . 47
6.1 General . 47
6.2 Insulation coordination overview . 48
6.2.1 General . 48
6.2.2 IEC insulation coordination procedure . 48
6.2.3 Overvoltages . 48
6.2.4 Line insulation coordination: Arrester Application Practices . 53
6.2.5 Substation insulation coordination: Arrester application practices . 58
6.2.6 Insulation coordination studies . 62
6.3 Selection of arresters . 63
6.3.1 General . 63
6.3.2 General procedure for the selection of surge arresters . 65
6.3.3 Selection of line surge arresters, LSA . 75
6.3.4 Selection of arresters for cable protection . 84
6.3.5 Selection of arresters for distribution systems – special attention . 86
6.3.6 Selection of UHV arresters . 88
6.4 Normal and abnormal service conditions . 89
6.4.1 Normal service condition . 89
6.4.2 Abnormal service conditions . 89
7 Surge arresters for special applications . 92
7.1 Surge arresters for transformer neutrals . 92
7.1.1 General . 92
7.1.2 Surge arresters for fully insulated transformer neutrals . 92
7.1.3 Surge arresters for neutrals of transformers with non-uniform
insulation . 93
7.2 Surge arresters between phases . 93
7.3 Surge arresters for rotating machines . 94
7.4 Surge arresters in parallel . 95

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SIST EN 60099-5:2013
60099-5 © IEC:2013(E) – 3 –
7.4.1 General . 95
7.4.2 Combining different designs of arresters . 96
7.5 Surge arresters for capacitor switching . 96
7.6 Surge arresters for series capacitor banks . 98
8 Asset management of surge arresters . 98
8.1 General . 98
8.2 Managing surge arresters in a power grid . 98
8.2.1 Asset database . 98
8.2.2 Technical specifications . 98
8.2.3 Strategic spares . 99
8.2.4 Transportation and storage . 99
8.2.5 Commissioning . 99
8.3 Maintenance . 99
8.3.1 General . 99
8.3.2 Polluted arrester housing . 100
8.3.3 Coating of arrester housings . 100
8.3.4 Inspection of disconnectors on surge arresters . 101
8.3.5 Line surge arresters . 101
8.4 Performance and diagnostic tools . 101
8.5 End of life . 101
8.5.1 General . 101
8.5.2 GIS arresters . 101
8.6 Disposal and recycling . 102
Annex A (informative) Determination of temporary overvoltages due to earth faults . 103
Annex B (informative) Current practice . 107
Annex C (informative)  Arrester modelling techniques for studies involving insulation
coordination and energy requirements . 108
Annex D (informative) Diagnostic indicators of metal-oxide surge arresters in service . 111
Annex E (informative) Typical data needed from arrester manufacturers for proper
selection of surge arresters . 125
Annex F (informative) Typical maximum residual voltages for metal-oxide arresters
without gaps according to IEC 60099-4 . 126
Annex G (informative) Steepness reduction of incoming surge with additional line
terminal surge capacitance . 127
Annex H (informative) End of life and replacement of old gapped SiC-arresters . 136
Bibliography . 141

Figure 1 – GIS arresters of three mechanical/one electrical column (middle) and one
column (left) design and current path of the three mechanical/one electrical column
design (right) . 25
Figure 2 – Typical deadfront arrester . 26
Figure 3 – Internally gapped metal-oxide surge arrester designs . 30
Figure 4 – Components of an EGLA acc. to IEC 60099-8 . 32
Figure 5 – Examples of UHV and HV arresters with grading and corona rings . 36
Figure 6 – Same type of arrester mounted on a pedestal (left), suspended from an
earthed steel structure (middle) or suspended from a line conductor (right . 37
Figure 7 – Typical arrangement of a 420-kV arrester. 39
Figure 8 – Installations without earth-mat (distribution systems) . 40

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SIST EN 60099-5:2013
– 4 – 60099-5 © IEC:2013(E)
Figure 9 – Installations with earth-mat (high-voltage substations) . 40
Figure 10 – Definition of mechanical loads according to IEC 60099-4 . 42
Figure 11 – Distribution arrester with disconnector and insulating bracket. 44
Figure 12 – Examples of good and poor earthing principles for distribution arresters . 45
Figure 13 – Typical voltages and duration example for an efficiently earthed system . 49
Figure 14 – Typical phase-to-earth overvoltages encountered in power systems . 50
Figure 15 – Arrester Voltage-Current Characteristics . 51
Figure 16 – Direct strike to a phase conductor with LSA . 55
Figure 17 – Strike to a shield wire or tower with LSA . 56
Figure 18 – Typical procedure for a surge arrester insulation coordination study . 64
Figure 19 – Flow diagrams for standard selection of surge arrester . 67
Figure 20 – Examples of arrester TOV capability . 68
Figure 21 – Flow diagram for the selection of NGLA . 77
Figure 22 – Flow diagram for the selection of EGLA . 81
Figure 23 – Common neutral configurations . 87
Figure 24 – Typical configurations for arresters connected phase-to-phase and phase-
to-ground . 94
Figure A.1 – Earth fault factor k on a base of X /X , for R /X = R = 0 . 104
0 1 1 1 1
Figure A.2 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 0 . 104
1
Figure A.3 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 0,5 X . 105
1 1
Figure A.4 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = X . 105
1 1
Figure A.5 – Relationship between R /X and X /X for constant values of earth fault
0 1 0 1
factor k where R = 2X . 106
1 1
Figure C.1 – Schematic sketch of a typical arrester installation . 108
Figure C.2 – Increase in residual voltage as function of virtual current front time . 109
Figure C.3 – Arrester model for insulation coordination studies – fast- front
overvoltages and preliminary calculation (Option 1) . 110
Figure C.4 – Arrester model for insulation coordination studies – fast- front
overvoltages and preliminary calculation (Option 2) . 110
Figure C.5 – Arrester model for insulation coordination studies – slow-front
overvoltages. . 110
Figure D.1 – Typical leakage current of a non-linear metal-oxide resistor in laboratory
conditions . 113
Figure D.2 – Typical leakage currents of arresters in service conditions . 114
Figure D.3 – Typical voltage-current characteristics for non-linear metal-oxide
resistors . 115
Figure D.4 – Typical normalized voltage dependence at +20 °C . 115
Figure D.5 – Typical normalized temperature dependence at U . 116
c
Figure D.6 – Influence on total leakage current by increase in resistive leakage current . 117
Figure D.7 – Measured voltage and leakage current and calculated resistive and
capacitive currents (V = 6,3 kV r.m.s) . 119
Figure D.8 – Remaining current after compensation by capacitive current at Uc . 120

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SIST EN 60099-5:2013
60099-5 © IEC:2013(E) – 5 –
Figure D.9 − Error in the evaluation of the leakage current third harmonic for different
phase angles of system voltage third harmonic, considering various capacitances and
voltage-current characteristics of non-linear metal-oxide resistors . 121
Figure D.10 − Typical information for conversion to "standard" operating voltage
conditions . 123
Figure D.11 − Typical information for conversion to "standard" ambient temperature
conditions . 123
Figure G.1 − Surge voltage waveforms at various distances from strike location
(0,0 km) due to corona . 128
Figure G.2 – Case 1: EMTP Model: Thevenin equivalent source, line (Z,c) & station
bus (Z,c) & Cap(C ) . 131
s
Figure G.3 – Case 2: Capacitor Voltage charge via line Z: u(t) = 2×U × (1 − exp[-
s
t/(Z×C]) . 132
Figure G.4 – EMTP model . 133
Figure G.5 − Simulated surge voltages at the line-station bus interface. 133
Figure G.6 − Simulated Surge Voltages at the Transformer . 134
Figure G.7 – EMTP Model . 134
Figure G.8 – Simulated surge voltages at the line-station bus interface . 135
Figure G.9 − Simulated surge voltages at the transformer . 135
Figure H.1 – Internal SiC-arrester stack . 137

Table 1 – Minimum mechanical requirements (for porcelain-housed arresters) . 42
Table 2 – Arrester classification for surge arresters . 69
Table 3 – Definition of factor A in formulas (15) to (17) for various overhead lines . 74
Table 4 – Examples for protective zones calculated by formula (10) for open-air
substations . 74
Table 5 – Example of the condition for calculating lightning current duty of EGLA in
77 kV transmission lines . 83
Table 6 – Probability of insulator flashover in Formula (19) . 84
Table D.1 – Summary of diagnostic methods . 124
Table D.2 – Properties of on-site leakage current measurement methods . 124
Table E.1 – Arrester data needed for the selection of surge arresters . 125
Table F.1 – Residual voltages for 20 000 A and 10 000 A arresters in per unit of rated
voltage . 126
Table F.2 – Residual voltages for 5 000 A, 2 500 A and 1 500 A arresters in per unit of
rated voltage . 126
Table G.1 − C impact on steepness ratio f and steepness S . 130
s s n
Table G.2 − Change in coordination withstand voltage, U , . 130
cw

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SIST EN 60099-5:2013
– 6 – 60099-5 © IEC:2013(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

SURGE ARRESTERS –

Part 5: Selection and application recommendations

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-
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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)
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