EN 60099-5:2013

SLOVENSKI STANDARD
01-oktober-2013
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SIST EN 60099-5:1998
SIST EN 60099-5:1998/A1:2002
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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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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
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
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 60099-5:1996 + 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.

- 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
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

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
XG
ICS 29.120.50; 29.240.10 ISBN 978-2-83220-804-5

– 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

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

– 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
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

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
– 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-
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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 60099-5 has been prepared by committee 37: Surge arresters.
This second edition cancels and replaces the first edition published in 1996 and its
amendment 1 published in 1999. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
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:

60099-5 © IEC:2013(E) – 7 –
– 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
The text of this standard is based on the following documents:
FDIS Report on voting
37/405/FDIS 37/408/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 stability 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 8 – 60099-5 © IEC:2013(E)
SURGE ARRESTERS –
Part 5: Selection and application recommendations

1 Scope
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 three-
phase 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.
2 Normative references
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.
IEC 60071-1:2006, Insulation coordination – Part 1: Definitions, principles and rules
IEC 60071-2:1996, Insulation coordination – Part 2: Application guide
IEC/TR 60071-4, Insulation coordination – Part 4: Computational guide to insulation
coordination and modelling of electrical networks
IEC 60099-4:2009, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.
systems
60099-5 © IEC:2013(E) – 9 –
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 – 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 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 – Part 1: Common specifications
IEC 62271-200, High-voltage switchgear and controlgear – 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 – Part 203: Gas-insulated metal-
enclosed switchgear for rated voltages above 52 kV
3 Terms and definitions
For the purposes of this document, the following terms and abbreviations are used.
NOTE These terms follow standard definitions as close as possible, but are not in all cases exact citations of
definitions in other IEC standards.
3.1
arrester – dead-front type, dead-front arrester
arrester assembled in a shielded housing providing system insulation and conductive earth
shield, intended to be installed in an enclosure for the protection of underground and
padmounted distribution equipment and circuits
Note 1 to entry: Most dead-front arresters are load-break arresters.
Note 2 to entry: The use of dead-front arresters is common in the USA.
3.2
arrester disconnector
device for disconnecting an arrester from the system in the event of arrester failure, to
prevent a persistent fault on the system and to give visible indication of the failed arrester
Note 1 to entry: Clearing of the fault current through the arrester during disconnection generally is not a function
of the device.
3.3
arrester – liquid-immersed type
arrester designed to be immersed in an insulating liquid
3.4
arrester – separable type, separable arrester
arrester assembled in an insulated or screened housing providing system insulation, intended
to be installed in an enclosure for the protection of distribution equipment and systems.

– 10 – 60099-5 © IEC:2013(E)
Electrical connection may be made by sliding contact or by bolted devices; however, all
separable arresters are dead-break arresters
Note 1 to entry: The use of separable arresters is common in Europe.
3.5
back flashover rate
BFOR
characteristics of an overhead line or system with respect to the number of back flashovers
typically given per 100 km and year
3.6
bending moment
horizontal force acting on the arrester housing multiplied by the vertical distance between the
mounting base (lower level of the flange) of the arrester housing and the point of application
of the force
3.7
continuous current of an arrester
current flowing through the arrester when energized at the continuous operating voltage
Note 1 to entry: The continuous current, which consists of a resistive and a capacitive component, may vary with
temperature, stray capacitance and external pollution effects. The continuous current of a test sample may,
therefore, not be the same as the continuous current of a complete arrester.
Note 2 to entry: The continuous current is, for comparison purposes, expressed either by its r.m.s. or peak value.
3.8
continuous operating voltage of an arrester
U
c
designated permissible r.m.s. value of power-frequency voltage that may be applied
continuously between the arrester terminals in accordance with IEC 60099-4 and 60099-6
3.9
dead-break arrester
arrester which can be connected and disconnected from the circuit only when the circuit is de-
energized
3.10
discharge current of an arrester
impulse current which flows through the arrester
3.11
disruptive discharge
phenomenon associated with the failure of insulation under electric stress, which include a
collapse of voltage and the passage of current
Note 1 to entry: The term applies to electrical breakdowns in solid, liquid and gaseous dielectric, and
combinations of these.
Note 2 to entry: A disruptive discharge in a solid dielectric produces permanent loss of electric strength. In a
liquid or gaseous dielectric the loss may be only temporary.
3.12
externally gapped line arresters
EGLA
a line surge arrester designed with an external spark gap in series with a SVU part to protect
the insulator assembly from lightning caused fast-front overvoltages only
Note 1 to entry: This is accomplished by raising the sparkover level of the external series gap to a level that
isolates the arrester from power frequency overvoltages and from the worst case slow-front overvoltages due to
switching and fault events expected on the line to which it is applied.

60099-5 © IEC:2013(E) – 11 –
3.13
fast-front overvoltage
FFO
transient overvoltage usually unidirectional, with time to peak between 0,1 µs to 20 µs, and
tail duration < 300 µs
3.14
fault indicator
device intended to provide an indication that the arrester is faulty and which does not
disconnect the arrester from the system
3.15
flashover
disruptive discharge over a solid surface
3.16
flashover rate
FOR
characteristics of an overhead line or system with respect to total number of flashovers
typically given per 100 km and year
3.17
follow current
the current immediately following an impulse through an EGLA with the power frequency
voltage as the source
Note 1 to entry: The external series gap shall be able to interrupt follow current due to external leakage current
on a polluted SVU as well as due to internal resistive current through the non-linear metal oxide resistors; that is,
the performance of the EGLA under polluted conditions is introduced by the gap resealing performance under wet
and polluted condition, and it is verified by the follow current interruption test.
3.18
follow current of an arrester
the current from the connected power source which flows through an arrester following the
passage of discharge current
3.19
gas-insulated metal enclosed surge arrester
GIS-arrester
gas-insulated metal-enclosed metal-oxide surge arrester without any integrated series or
parallel spark gaps, filled with gas other than air and used in gas-insulated switchgears
Note 1 to entry: The gas pressure is normally higher than 1 bar = 10 Pa.
3.20
grading current
current flowing through the arrester while a power frequency voltage is applied
3.21
grading ring of an arrester
metal part, usually circular in shape, mounted to modify electro-statically the voltage
distribution along the arrester
3.22
high current impulse
peak value of discharge current having a 4/10 or 2/20 impulse shape, which is used to test the
withstand capability of the SVU on extreme lightning occasions

– 12 – 60099-5 © IEC:2013(E)
3.23
highest voltage for equipment
U
m
highest value of the phase-to-phase voltage (r.m.s. value) for which the equipment is
designed in respect of its insulation as well as other characteristics which relate to this
voltage in the relevant equipment Standards. Under normal service conditions specified by the
relevant apparatus committee this voltage can be
...