SIST EN IEC 60099-8:2018

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

NEW!IEC 60099-8:2017 is available as IEC 60099-8:2017 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 60099-8:2017 covers metal-oxide surge arresters with external series gap (externally gapped line arresters (EGLA)) that are applied on overhead transmission and distribution lines, only to protect insulator assemblies from lightning-caused flashovers.  This document defines surge arresters to protect the insulator assembly from lightning-caused over-voltages only. Therefore, and since metal-oxide resistors are not permanently connected to the line, the following items are not considered for this document:
- switching impulse spark-over voltage;
- residual voltage at steep current and switching current impulse;
- thermal stability;
- long-duration current impulse withstand duty;
- power-frequency voltage versus time characteristics of an arrester;
- disconnector test;
- aging duties by power-frequency voltage.
Considering the particular design concept and the special application on overhead transmission and distribution lines, some unique requirements and tests are introduced, such as the verification test for coordination between insulator withstand and EGLA protective level, the follow current interrupting test, mechanical load tests, etc. Designs with the EGLA's external series gap installed in parallel to an insulator are not covered by this document. This second edition cancels and replaces the first edition published in 2011. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
The Lightning discharge capability test has been completely re-written and re-named to Test to verify the repetitive charge transfer rating, Qrs with lightning discharges to reflect changes introduced in IEC 60099-4 Ed.3 (2014) regarding new methods for rating the energy and charge handling capability of metal-oxide arresters. In addition to testing to evaluate the performance of the MO resistors, procedures for evaluating the performance of the EGLA series gaps have been introduced.
- Omissions from Ed. 1 of this standard have been included, notably an RIV test and a means for determining the thermal time constant of the SUV portion of the EGLA.
- Definitions for new terms have been added
- A number of NOTES in Ed. 1 have been converted to normative requirements
Keywords: externally gapped line arresters (EGLA), lightning-caused over-voltages

Überspannungsableiter - Teil 8: Metalloxid-Überspannungsableiter mit externer Serienfunkenstrecke (EGLA) für Übertragungs- und Verteilungsleitungen von Wechselstromsystemen über 1 kV

Parafoudres - Partie 8: Parafoudres à oxyde métallique avec éclateur extérieur en série (EGLA) pour lignes aériennes de transmission et de distribution de réseaux à courant alternatif de plus de 1 kV

NEW!IEC 60099-8:2017 est disponible sous forme de IEC 60099-8:2017 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.

Prenapetostni odvodniki - 8. del: Kovinskooksidni prenapetostni odvodniki z zunanjim zaporedno vezanim iskriščem (EGLA) za nadzemne prenosne in razdelilne vode v izmeničnih sistemih nad 1 kV

V tem delu standarda IEC 60099 so obravnavani prenapetostni odvodniki iz kovinskega oksida z zunanjim iskriščem skupinske strukture (linijski odvodniki z zunanjim iskriščem (EGLA)), ki se uporabljajo za nadzemni prenos in razdelilna omrežja, in sicer z izključnim namenom zaščite izolacijskih sklopov pred prebojnim vžigom zaradi delovanja strele.
V tem dokumentu so opredeljeni prenapetostni odvodniki samo zaradi zaščite izolacijskega sklopa pred prenapetostjo, ki jo povzroči udar strele. Zaradi tega in ker upori iz kovinskega oksida niso trajno priključeni na vod, naslednji elementi niso upoštevani za ta dokument:
• vžigna napetost pri stikalnem napetostnem udaru,
• preostala napetost pri strmem tokovnem impulzu in preklopnem tokovnem impulzu,
• toplotna stabilnost,
• odpornosti proti dolgotrajnemu tokovnemu impulzu,
• električne napetosti v odvisnosti od časa trajanja prenapetostnega odvodnika,
• preskusa prekinjal,
• vpliva električne napetosti na delovanje pri staranju.
Ob upoštevanju posebnega koncepta projektiranja in posebne uporabe pri omrežjih za nadzemni prenos in razdelilnih omrežjih so predstavljene nekatere edinstvene zahteve in preskusi, kot je preverjalni preskus za namen usklajevanja med odpornostjo izolatorjev in zaščitno ravnjo EGLA, prekinjevalni preskus sledilnega toka, preskusi z mehansko obremenitvijo itd.
Zasnove z nameščenim zunanjim iskriščem skupinske strukture EGLA vzporedno z izolatorjem niso obravnavane v tem dokumentu.

General Information

• Status: Published
• Publication Date: 16-Apr-2018
• ICS: 29.240.10 - Substations. Surge arresters
• Technical Committee: POD - Surge aresters
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 16-Mar-2018
• Due Date: 21-May-2018
• Completion Date: 17-Apr-2018
• Ref Project: EN IEC 60099-8:2018 - 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

Relations

• Replaces: SIST EN 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
• Effective Date: 01-May-2018

Overview

EN IEC 60099-8:2018 (CLC adoption of IEC 60099-8:2017) specifies requirements and tests for metal‑oxide surge arresters with external series gap (externally gapped line arresters, EGLA) used on overhead transmission and distribution lines of a.c. systems above 1 kV. The standard is focused exclusively on protecting insulator assemblies from lightning‑caused flashovers. It is a technical revision of the 2011 edition and is published as an RLV (Redline version) showing changes from the previous edition.

Key topics and technical requirements

• Application scope: EGLAs applied on overhead lines only, for lightning‑caused over‑voltages. Designs with the EGLA’s external series gap installed in parallel to an insulator are excluded.
• What is not covered: Because EGLA MO resistors are not permanently connected to the line, the standard does not address switching‑impulse spark‑over voltage, residual voltage at steep and switching currents, thermal stability, long‑duration current duty, power‑frequency voltage/time behaviour, disconnector tests, or aging duties by power‑frequency voltage.
• New and revised test requirements:
  • Test to verify repetitive charge transfer rating (Qrs) with lightning discharges (aligned with IEC 60099‑4 Ed.3 methods).
  • Procedures for evaluating the EGLA series gap in addition to MO resistor performance.
  • Verification test for coordination between insulator withstand and EGLA protective level.
  • Follow current interrupting tests, mechanical load (bending, vibration) tests and weather‑aging tests.
  • Inclusion of a radio interference voltage (RIV) test and a method to determine the thermal time constant of the surge‑venting unit (SVU).
• Classification, ratings and service conditions: Standard rated voltages, frequencies and nominal discharge currents; definitions and identification for EGLAs and SVUs.
• Test categories: Type, routine, acceptance and specific performance tests (residual voltage, high‑current impulse, short‑circuit, partial discharge, etc.).

Applications and users

This standard is essential for:

• Utility design and protection engineers specifying over‑head line surge protection.
• Surge arrester manufacturers (design, type testing, quality control).
• Independent test laboratories performing type, routine and acceptance tests.
• Asset managers and procurement teams verifying EGLA compliance for deployment on a.c. systems above 1 kV. Practical uses include product qualification, insulator‑EGLA coordination studies, and lifecycle/field‑deployment acceptance criteria.

Related standards

• IEC/EN 60099‑4 (MO surge arresters without gaps)
• IEC 60060‑1 / IEC 60060‑2 (high‑voltage test techniques)
• IEC 60270 (partial discharge measurements)
• IEC 60507 (artificial pollution tests on insulators)
• IEC 62217 (polymeric HV insulators)
• IEC 60068 series (environmental tests)

Keywords: externally gapped line arresters (EGLA), lightning‑caused over‑voltages, metal‑oxide surge arresters, overhead transmission lines, surge protection standards.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2018
1DGRPHãþD
SIST EN 60099-8:2011
3UHQDSHWRVWQLRGYRGQLNLGHO.RYLQVNRRNVLGQLSUHQDSHWRVWQLRGYRGQLNL]
]XQDQMLP]DSRUHGQRYH]DQLPLVNULãþHP(*/$]DQDG]HPQHSUHQRVQHLQ
UD]GHOLOQHYRGHYL]PHQLþQLKVLVWHPLKQDGN9
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
Überspannungsableiter - Teil 8: Metalloxid-Überspannungsableiter mit externer
Serienfunkenstrecke (EGLA) für Übertragungs- und Verteilungsleitungen von
Wechselstromsystemen über 1 kV
Parafoudres - Partie 8: Parafoudres à oxyde métallique avec éclateur extérieur en série
(EGLA) pour lignes aériennes de transmission et de distribution de réseaux à courant
alternatif de plus de 1 kV
Ta slovenski standard je istoveten z: EN IEC 60099-8:2018
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 IEC 60099-8

NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2018
ICS 29.240.10 Supersedes EN 60099-8:2011
English Version
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 60099-8:2017)
Parafoudres - Partie 8: Parafoudres à oxyde métallique Überspannungsableiter - Teil 8: Metalloxid-
avec éclateur extérieur en série (EGLA) pour lignes Überspannungsableiter mit externer Serienfunkenstrecke
aériennes de transmission et de distribution de réseaux à (EGLA) für Übertragungs- und Verteilungsleitungen von
courant alternatif de plus de 1 kV Wechselstromsystemen über 1 kV
(IEC 60099-8:2017) (IEC 60099-8:2017)
This European Standard was approved by CENELEC on 2017-12-19. 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, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60099-8:2018 E

European foreword
The text of document 37/436/FDIS, future edition 2 of IEC 60099-8, 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) 2018-09-19
implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2020-12-19
• latest date by which the national
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60099-8:2011.

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

Endorsement notice
The text of the International Standard IEC 60099-8:2017 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated :

ISO 3274 NOTE Harmonized as EN ISO 3274.

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60060-1 2010 High-voltage test techniques -- Part 1: EN 60060-1 2010
General definitions and test requirements
IEC 60060-2 2010 High-voltage test techniques -- Part 2: EN 60060-2 2011
Measuring systems
IEC 60068-2-11 1981 Basic environmental testing procedures - EN 60068-2-11 1999
Part 2-11: Tests - Test Ka: Salt mist
IEC 60068-2-14 2009 Environmental testing -- Part 2-14: Tests - EN 60068-2-14 2009
Test N: Change of temperature
IEC 60099-4 2014 Surge arresters - Part 4: Metal-oxide surge EN 60099-4 2014
arresters without gaps for a.c. systems
IEC 60270 2000 High-voltage test techniques - Partial EN 60270 2001
discharge measurements
IEC 60507 2013 Artificial pollution tests on high-voltage EN 60507 2014
ceramic and glass insulators to be used on
a.c. systems
IEC 62217 2012 Polymeric HV insulators for indoor and EN 62217 2013
outdoor use - General definitions, test
methods and acceptance criteria
IEC/TS 60815-1 2008 Selection and dimensioning of high-voltage - -
insulators intended for use in polluted
conditions - Part 1: Definitions, information
and general principles
ISO 4287 -  Geometrical Product Specifications (GPS) EN ISO 4287 -
- Surface texture: Profile method - Terms,
definitions and surface texture parameters
ISO 4892-1 -  EN ISO 4892-1 -
ISO 4892-2 -  Plastics - Methods of exposure to EN ISO 4892-2 -
laboratory light sources - Part 2: Xenon-arc
lamps
ISO 4892-3 -  EN ISO 4892-3 -

IEC 60099-8 ®
Edition 2.0 2017-11
INTERNATIONAL
STANDARD
colour
inside
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

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.10 ISBN 978-2-8322-4987-1

– 2 – IEC 60099-8:2017 © IEC 2017
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Identification and classification . 13
4.1 EGLA identification . 13
4.2 EGLA classification . 13
5 Standard ratings and service conditions . 14
5.1 Standard rated voltages . 14
5.2 Standard rated frequencies . 14
5.3 Standard nominal discharge currents . 14
5.4 Service conditions . 14
5.4.1 Normal service conditions . 14
5.4.2 Special service conditions . 14
6 Requirements . 15
6.1 Insulation withstand of the SVU and the complete EGLA . 15
6.1.1 Insulation withstand of the housing of the SVU . 15
6.1.2 Insulation withstand of EGLA with shorted (failed) SVU . 15
6.2 Residual voltages . 15
6.3 High current duty . 15
6.4 Lightning discharge capability . 15
6.5 Short-circuit performance of the SVU . 15
6.6 Mechanical performance . 16
6.7 Weather aging of SVU . 16
6.8 Reference voltage of the SVU . 16
6.9 Internal partial discharges . 16
6.10 Coordination between insulator withstand and EGLA protective level . 16
6.11 Follow current interrupting . 17
6.12 Electromagnetic compatibility . 17
6.13 End of life . 17
7 General testing procedure . 17
7.1 Measuring equipment and uncertainty . 17
7.2 Test samples . 17
8 Type tests . 18
8.1 General . 18
8.2 Insulation withstand tests on the SVU housing and on the EGLA with failed
SVU . 18
8.2.1 General . 18
8.2.2 Insulation withstand test on the SVU housing . 19
8.2.3 Insulation withstand tests on EGLA with failed SVU . 19
8.3 Residual voltage tests . 20
8.3.1 General . 20
8.3.2 Procedure for correction and calculation of inductive voltages . 20
8.3.3 Lightning current impulse residual voltage test . 21

IEC 60099-8:2017 © IEC 2017 – 3 –
8.3.4 High current impulse residual voltage test . 22
8.4 Standard lightning impulse sparkover test . 22
8.5 High current impulse withstand test. 23
8.5.1 Selection of test samples . 23
8.5.2 Test procedure . 23
8.5.3 Test evaluation . 24
8.6 Test to verify the repetitive charge transfer rating, Q with lightning
rs
discharges . 24
8.6.1 MO resistors . 24
8.6.2 Series gap . 26
8.7 Short-circuit tests . 27
8.7.1 General . 27
8.7.2 Preparation of the test samples . 28
8.7.3 Mounting of the test sample . 29
8.7.4 High-current short-circuit tests . 30
8.7.5 Low-current short-circuit test . 32
8.7.6 Evaluation of test results . 32
8.8 Follow current interrupting test . 38
8.8.1 General . 38
8.8.2 "Test method A" . 38
8.8.3 "Test method B" . 40
8.9 Mechanical load tests on the SVU . 42
8.9.1 General . 42
8.9.2 Bending test . 42
8.9.3 Vibration test . 51
8.10 Weather aging tests . 52
8.10.1 General . 52
8.10.2 Sample preparation . 52
8.10.3 Test procedure . 52
8.10.4 Test evaluation . 52
8.10.5 Additional test procedure for polymer (composite and cast resin)
housed SVUs . 53
8.11 Radio interference voltage (RIV) test . 53
9 Routine tests . 53
9.1 General . 53
10 Acceptance tests . 54
10.1 General . 54
10.2 Reference voltage measurement of SVU . 54
10.3 Internal partial discharge test of SVU . 55
10.4 Radio interference voltage (RIV) test . 55
10.5 Test for coordination between insulator withstand and EGLA protective level . 55
10.5.1 General . 55
10.5.2 Steep front impulse test . 55
10.5.3 Standard lightning impulse sparkover test . 56
10.6 Follow current interrupting test . 56
10.6.1 General . 56
10.6.2 Test procedure . 57
10.6.3 Test sequence . 57
10.6.4 Test evaluation . 57

– 4 – IEC 60099-8:2017 © IEC 2017
10.7 Vibration test on the SVU with attached electrode . 57
10.7.1 General . 57
10.7.2 Sample preparation . 57
10.7.3 Test procedure and test condition . 57
10.7.4 Test evaluation . 58
Annex A (informative) Example of a test circuit for the follow current interrupting test . 59
Annex B (normative) Mechanical considerations . 60
B.1 Test of bending moment. 60
B.2 Definition of mechanical loads . 61
B.3 Definition of seal leak rate . 62
B.4 Calculation of wind-bending-moment. 63
B.5 Flow chart – Procedures of tests of bending moment for porcelain/cast resin
and polymer-housed SVUs . 64
Annex C (normative) Special service conditions . 65
C.1 General . 65
C.2 Temperature in excess of +40 °C or below –40 °C . 65
C.3 Application at altitudes higher than 1 000 m . 65
C.4 Fumes or vapours that may cause deterioration of insulating surface or
mounting hardware . 65
C.5 Excessive contamination by smoke, dirt, salt spray or other conducting
materials . 65
C.6 Excessive exposure to moisture, humidity, dripping water, or steam . 65
C.7 Live washing of arrester . 65
C.8 Unusual transportation or storage . 65
C.9 Non-vertical erection and suspended erection . 66
C.10 Wind speed > 34 m/s . 66
C.11 Earthquake . 66
C.12 Torsional loading of the arrester . 66
Bibliography . 67

Figure 1 – Configuration of an EGLA with insulator and arcing horn . 8
Figure 2 – Test procedure to verify the repetitive charge transfer rating, Q . 25
rs
Figure 3 – Test procedure to verify the repetitive charge withstand of the series gap . 27
Figure 4 – Examples of SVU units . 36
Figure 5 – Short-circuit test setup . 37
Figure 6 – Example of a test circuit for re-applying pre-failing circuit immediately
before applying the short-circuit test current . 38
Figure 7 – Thermo-mechanical test . 46
Figure 8 – Example of the test arrangement for the thermo-mechanical test and
direction of the cantilever load . 47
Figure 9 – Test sequence of the water immersion test . 48
Figure A.1 – Example of a test circuit for the follow current interrupting test . 59
Figure B.1 – Bending moment – Multi-unit SVU. 60
Figure B.2 – Definition of mechanical loads . 61
Figure B.3 – SVU unit . 62
Figure B.4 – SVU dimensions . 63

IEC 60099-8:2017 © IEC 2017 – 5 –
Figure B.5 – Procedures of tests of bending moment for porcelain/cast resin and
polymer-housed SVUs . 64

Table 1 – EGLA classification – “Series X” and “Series Y“ . 13
Table 2 – Steps of rated voltages (r.m.s. values) . 14
Table 3 – Type tests (all tests to be performed with or without insulator assembly; by
manufacturer's decision) . 18
Table 4 – Test requirements . 34
Table 5 – Required currents for short-circuit tests . 35
Table 6 – Acceptance tests . 54
Table 7 – Virtual steepness of wave front of steep front impulses . 55

– 6 – IEC 60099-8:2017 © IEC 2017
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
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
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
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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 60099-8 has been prepared by IEC technical committee 37: Surge
arresters.
This second edition cancels and replaces the first edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The Lightning discharge capability test has been completely re-written and re-named to
Test to verify the repetitive charge transfer rating, Qrs with lightning discharges to reflect
changes introduced in IEC 60099-4 Ed. 3 (2014) regarding new methods for rating the
energy and charge handling capability of metal-oxide arresters. In addition to testing to

IEC 60099-8:2017 © IEC 2017 – 7 –
evaluate the performance of the MO resistors, procedures for evaluating the performance
of the EGLA series gaps have been introduced.
b) Omissions from Ed. 1 of this standard have been included, notably an RIV test and a
means for determining the thermal time constant of the SUV portion of the EGLA.
c) Definitions for new terms have been added
d) A number of NOTES in Ed. 1 have been converted to normative requirements
A number of editorial changes have been made throughout the document to improve grammar
and general flow of information.
The text of this International Standard is based on the following documents:
FDIS Report on voting
37/436/FDIS 37/438/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of IEC 60098 series, under the general title Surge arresters, can be found on
the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document 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 – IEC 60099-8:2017 © IEC 2017
INTRODUCTION
This part of IEC 60099 applies to the externally gapped line arrester (EGLA)
This type of surge arrester is connected directly in parallel with an insulator assembly. It
comprises a series varistor unit (SVU), made up from non-linear metal-oxide resistors
encapsulated in a polymer or porcelain housing, and an external series gap (see Figure 1).
The purpose of an EGLA is to protect the parallel-connected insulator assembly from
lightning-caused over-voltages. The external series gap, therefore, should spark over only
due to fast-front over-voltages. The gap should withstand all power-frequency and slow-front
over-voltages occurring on the system.
In the event of SVU failure, the external series gap should be able to isolate the SVU from the
system.
EGLA
Tower arm
Insulator assembly
S
(insulator assembly,
V
Series varistor unit with/without arcing horns
U
or grading elements)
External series gap
(without an insulator
Conductor
in parallel)
IEC
Figure 1 – Configuration of an EGLA with insulator and arcing horn

IEC 60099-8:2017 © IEC 2017 – 9 –
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
1 Scope
This part of IEC 60099 covers metal-oxide surge arresters with external series gap (externally
gapped line arresters (EGLA)) that are applied on overhead transmission and distribution
lines, only to protect insulator assemblies from lightning-caused flashovers.
This document defines surge arresters to protect the insulator assembly from lightning-caused
over-voltages only. Therefore, and since metal-oxide resistors are not permanently connected
to the line, the following items are not considered for this document:
• switching impulse spark-over voltage;
• residual voltage at steep current and switching current impulse;
• thermal stability;
• long-duration current impulse withstand duty;
• power-frequency voltage versus time characteristics of an arrester;
• disconnector test;
• aging duties by power-frequency voltage.
Considering the particular design concept and the special application on overhead
transmission and distribution lines, some unique requirements and tests are introduced, such
as the verification test for coordination between insulator withstand and EGLA protective
level, the follow current interrupting test, mechanical load tests, etc.
Designs with the EGLA's external series gap installed in parallel to an insulator are not
covered by this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements 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.
IEC 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60060-2:2010, High-voltage test techniques – Part 2: Measuring systems
IEC 60068-2-11:1981, Basic environmental testing procedures – Part 2-11: Tests – Test Ka:
Salt mist
IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of
temperature
– 10 – IEC 60099-8:2017 © IEC 2017
IEC 60099-4:2014, Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.
systems
IEC 60270:2000, High-voltage test techniques – Partial discharge measurements
IEC 60507:2013, Artificial pollution tests on high-voltage ceramic and glass insulators to be
used on a.c. systems
IEC TS 60815-1:2008, Selection and dimensioning of high-voltage insulators intended for use
in polluted conditions – Part 1: Definitions, information and general principles
IEC 62217:2012, Polymeric HV insulators for indoor and outdoor use – General definitions,
test methods and acceptance criteria
ISO 4287, Geometrical Product Specifications (GPS) – Surface texture: Profile method –
Terms, definitions and surface texture parameters
ISO 4892-1, Plastics – Methods of exposure to laboratory light sources – Part 1: General
Guidance
ISO 4892-2, Plastics – Methods of exposure to laboratory light sources – Part 2: Xenon-arc
sources
ISO 4892-3, Plastics – Methods of exposure to laboratory light sources – Part 3: Fluorescent
UV lamps
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
externally gapped line arrester
EGLA
arrester designed for installation on overhead lines to protect an insulator assembly from
lightning-caused fast-front over-voltages only
Note 1 to entry: This is accomplished by raising the spark-over level of the external series gap to a level that
isolates the arrester from power-frequency over-voltages and from the worst case slow-front over-voltages due to
switching and fault events expected on the line to which it is applied.
3.2
series varistor unit
SVU
non-linear metal-oxide resistor part, contained in a housing, which must be connected with an
external series gap to construct the complete arrester
Note 1 to entry: The series varistor unit may include several units.
3.3
section of an EGLA
complete, suitably assembled part of a complete EGLA necessary to represent the behaviour
of a complete EGLA with respect to a particular test

IEC 60099-8:2017 © IEC 2017 – 11 –
3.4
section of an SVU
complete, suitably assembled part of an SVU unit necessary to represent the behaviour of an
SVU with respect to a particular test
3.5
unit of an SVU
completely housed part of an SVU which may be connected in series and/or in parallel with
other units of an SVU to construct, in combination with the external series gap, an EGLA of
higher voltage and/or current rating
3.6
rated voltage of an EGLA
U
r
maximum permissible r.m.s. value of power-frequency voltage that can be applied
continuously between the EGLA terminals, and at which it is designed to operate correctly
Note 1 to entry: The rated voltage is used as a reference parameter for the specification of operating and current
interrupting characteristics.
Note 2 to entry: The rated voltage of an EGLA is comparable to Uc of all other types of MO-arresters.
3.7
reference voltage of an SVU
U
ref
peak value of power-frequency voltage divided by √2, which should be applied to the SVU to
obtain the reference current
Note 1 to entry: The reference voltage of a multi-unit SVU is the sum of the reference voltages of the individual
units.
3.8
reference current of an SVU
I
ref
peak value (the higher peak value of the two polarities if the current is asymmetrical) of the
resistive component of a power-frequency current used to determine the reference voltage of
the SVU
Note 1 to entry: The reference current should be high enough to make the effects of stray capacitances at the
measured reference voltage of the SVU units negligible. It is to be specified by the manufacturer.
Note 2 to entry: Depending on the nominal discharge current of the EGLA, the reference current will be typically
in the range of 0,05 mA to 1,0 mA per square centimetre of metal-oxide resistor area for a single column SVU.
3.9
rated short-circuit current of an SVU
I
s
r.m.s. value of the highest short-circuit current under which the SUV will not fail in a manner
that causes violent shattering of the housing and under which self-extinguishing of open
flames (if any) will occur within a defined period of time
3.10
residual voltage of an EGLA
peak value of voltage that appears across the terminal-to-terminal length of the EGLA
including series gap and connection leads during the passage of discharge current
3.11
residual voltage of an SVU
peak value of voltage that appears between the terminals of the SVU during the passage of
discharge current
– 12 – IEC 60099-8:2017 © IEC 2017
3.12
surface leakage current of an SVU
current that flows on the surface of the SVU
3.13
follow current
I
follow
the current immediately following an impulse through an EGLA with the power-frequency
voltage as the source
3.14
specified long-term load of an SVU
SLL
mechanical force perpendicular to the longitudinal axis of an SVU, allowed to be continuously
applied during service without causing any mechanical damage to the SVU
3.15
specified short-term load of an SVU
SSL
greatest mechanical force perpendicular to the longitudinal axis of an SVU, allowed to be
applied during service for short periods and for relatively rare events (for example, short-
circuit current loads and extreme wind gusts) without causing any mechanical damage to the
SVU
3.16
mean breaking load of an SVU
MBL
average breaking load for porcelain or cast resin-housed SVUs determined from tests
3.17
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
3.18
salt deposit density
SDD
amount of salt in the deposit on a given surface of the SVU housing, divided by the area of
this surface; generally expressed in mg/cm
3.19
verification test for coordination between insulator withstand and EGLA protective level
test used to verify that the EGLA will exhibit correct sparkover operation and clamp the
overvoltage caused by lightning considerably lower than the flashover voltage of the parallel-
connected insulator assembly
3.20
vibration withstand test
test to verify that the SVU and its connectors can withstand the specified mechanical vibration
levels
3.21
lightning impulse discharge
approximately sine half-wave current impulse having a time duration within 200 μs to 230 μs
during which the instantaneous value of the impulse current is between 5 % and 100 % of its
peak value
IEC 60099-8:2017 © IEC 2017 – 13 –
3.22
repetitive charge transfer rating
Q
rs
maximum specified charge transfer capability of an EGLA, in the form of a single event or
group of surges that may be transferred through an EGLA without causing mechanical failure
or unacceptable electrical degradation to the MO resistors
Note 1 to entry: The charge is calculated as the absolute value of current integrated over time. For the purpose of
this standard this is the charge that is accumulated in a single event or group of surges lasting for not more than 2
s and which may be followed by a subsequent event at a time interval not shorter than 60 s.
4 Identification and classification
4.1 EGLA identification
An EGLA shall be identified by the following minimum information, which shall appear on a
nameplate permanently attached to the arrester:
• rated voltage U in kV;
r
• rated frequency in Hz, only if it is less than 48 Hz or larger than 62 Hz;
• classification series information (examples: "X1", "Y2");
• rated short-circuit current I in kA;
s
• manufacturer’s name or trade mark;
• year of manufacture;
• serial number (at least for arresters for U > 52 kV);
s
• lightning discharge capability (only charge value) in C; example: "0.4 C".
Information on required gap spacing including tolerances shall be given in an appropriate
way, for example in the manual.
4.2 EGLA classification
EGLAs are classified by their nominal discharge currents and their high current impulse
withstand capabilities as per Table 1, and they shall meet at least the test requirements and
performance characteristics specified in Table 3. These arresters have no operating duties for
slow-front surges and power-frequency over-voltages.
Table 1 – EGLA classification – “Series X” and “Series Y“
Series X Series Y
Class name X1 X2 X3 X4 Class name Y1 Y2 Y3 Y4
Nominal discharge 5 5 10 20 Nominal discharge 5 10 15 20
current (kA), 8/20 current (kA), 2/20
High current impulse 40 65 100 100 High current impulse 10 25 40 65
(kA), 4/10 (kA), 2/20
"Series X" corresponds to the classification used in IEC 60099-4. A nominal discharge current of 8/20 wave
shape and a high current impulse of 4/10 wave shape are used in IEC and in IEEE standards. "Series Y"
corresponds to the clas
...