SIST EN 61643-312:2013

Components for low-voltage surge protective devices - Part 312: Selection and applications principles for gas discharge tubes

IEC 61643-312:2013 is applicable to gas discharge tubes (GDT) used for overvoltage protection in telecommunications, signalling and low-voltage power distribution networks with nominal system voltages up to 1 000 V (r.m.s.) a.c. and 1 500 V d.c. They are defined as a gap, or several gaps with two or three metal electrodes hermetically sealed so that gas mixture and pressure are under control. They are designed to protect apparatus or personnel, or both, from high transient voltages. This standard provides information about the characteristics and circuit applications of GDTs having two or three electrodes. This standard does not specify requirements applicable to complete surge protective devices, nor does it specify total requirements for GDTs employed within electronic devices, where precise coordination between GDT performance and surge protective device withstand capability is highly critical.  Keywords: gas discharge tubes (GDT), overvoltage protection in telecommunications, signalling and low-voltage power distribution networks, nominal system voltages up to 1 000 V (r.m.s.) a.c. and 1 500 V d.c.

Bauelemente für Überspannungsschutzgeräte für Niederspannung - Teil 312: Auswahl- und Anwendungsprinzipien für Gasentladungsableiter

Composants pour parafoudres basse tension - Partie 312: Principes de choix et d'application pour les tubes à décharge

La CEI 61643-312:2013 est applicable aux tubes à décharge de gaz (TDG) utilisés pour la protection contre les surtensions des réseaux de télécommunications, de signaux et de distribution basse tension, dont les tensions nominales de réseau sont inférieures ou égales à 1 000 V (valeurs efficaces) c.a. et 1 500 V c.c. Ils sont définis comme un éclateur ou des éclateurs avec deux ou trois électrodes métalliques hermétiquement scellées de sorte que le mélange et la pression de gaz soient sous contrôle. Ils sont conçus pour protéger des matériels ou des personnes, ou les deux, contre des surtensions transitoires élevées. La présente norme fournit des informations relatives aux caractéristiques et aux applications des circuits des TDG comportant deux ou trois électrodes. La présente norme ne traite pas des exigences applicables aux parafoudres complets, ni de la totalité des exigences relatives aux TDG utilisés dans les dispositifs électroniques, où une coordination précise entre les performances des TDG et la résistance des parafoudres aux surtensions est primordiale.  Mots clés: tubes à décharge de gaz (TDG), protection contre les surtensions des réseaux de télécommunications, de signaux et de distribution basse tension, tensions nominales de réseau sont inférieures ou égales à 1 000 V (valeurs efficaces) c.a. et 1 500 V c.c.

Sestavni deli za nizkonapetostne naprave za zaščito pred prenapetostnimi udari - 312. del: Izbira in načini uporabe plinskih odvodnikov (IEC 61643-312:2013 + corrigendum Jul. 2013)

Ta del standarda IEC 61643 se uporablja za s plinom polnjene cevi, ki se uporabljajo za prenapetostno zaščito pri telekomunikacijah, signaliziranju in nizkonapetostnih razdelilnih omrežjih z nazivnimi sistemskimi napetostmi do 1000 V (efektivne izmenične napetosti) izmenične napetosti in 1500 V enosmerne napetosti. Določene so kot reža ali več rež z dvema ali tremi nepredušno zatesnjenimi kovinskimi elektrodami, tako sta zmes plinov in tlak pod nadzorom. Zasnovane so tako, da ščitijo aparat ali osebje ali oboje pred visokimi tranzientnimi napetostmi. Ta standard zagotavlja informacije o lastnostih in uporabah tokokroga s plinom polnjenih cevi z dvema ali tremi elektrodami. Ta standard ne določa zahtev, ki se uporabljajo za celotne prenapetostne zaščitne naprave, niti ne določa skupnih zahtev za s plinom polnjene cevi, ki se uporabljajo znotraj elektronskih naprav, kjer je natančna koordinacija med delovanjem s plinom polnjenih cevi in odpornostjo prenapetostne zaščitne naprave izjemno kritična. Ta del standarda IEC 61643 – ne obravnava elementov za pritrditev in njihovega vpliva na značilnosti s plinom polnjenih cevi. Navedene značilnosti se uporabljajo izključno za s plinom polnjene cevi, ki so pritrjene na načine, opisane za preskuse; – ne obravnava mehanskih dimenzij; – ne obravnava zahtev za zagotavljanje kakovosti; – morda ne zadostuje za s plinom polnjene cevi, ki se uporabljajo pri visoki frekvenci (>30 MHz); – ne obravnava elektrostatičnih napetosti; –ne obravnava komponent hibridne prenapetostne zaščite ali sestavljenih naprav s cevmi, polnjenimi s plinom.

General Information

• Status: Published
• Public Enquiry End Date: 30-Mar-2010
• Publication Date: 23-Sep-2013
• ICS: 29.120.50 - Fuses and other overcurrent protection devices
• ICS: 29.240.10 - Substations. Surge arresters
• Technical Committee: POD - Surge aresters
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 27-Aug-2013
• Due Date: 01-Nov-2013
• Completion Date: 24-Sep-2013
• Directive: 2004/108/EC - Directive 2004/108/EC of the European Parliament and of the Council of 15 December 2004 on the approximation of the laws of the Member States relating to electromagnetic compatibility and repealing Directive 89/336/EEC
• Directive: 2004/108/EU - DIRECTIVE 2004/108/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 15 December 2004 on the approximation of the laws of the Member States relating to electromagnetic compatibility and repealing Directive 89/336/EEC
• Directive: 2014/30/EU - Directive 2014/30/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to electromagnetic compatibility (recast)
• Ref Project: EN 61643-312:2013 - Components for low-voltage surge protective devices - Part 312: Selection and application principles for gas discharge tubes

Relations

• Replaces: SIST EN 61643-311:2005 - Components for low-voltage surge protective devices -- Part 311: Specification for gas discharge tubes (GDT)
• Effective Date: 01-Oct-2013
• Revised: SIST EN 61643-311:2005 - Components for low-voltage surge protective devices -- Part 311: Specification for gas discharge tubes (GDT)
• Effective Date: 07-Jun-2022

Overview

EN 61643-312:2013 (CLC adoption of IEC 61643-312:2013) provides selection and application principles for gas discharge tubes (GDT) used for overvoltage protection in telecommunications, signalling and low-voltage power distribution networks. The standard applies to GDTs with two or three electrodes, hermetically sealed with a controlled gas mixture/pressure, intended to protect equipment and personnel from high transient voltages for systems with nominal voltages up to 1 000 V (r.m.s.) a.c. and 1 500 V d.c.. It addresses component-level characteristics and circuit applications but does not specify requirements for complete surge protective devices or detailed coordination inside electronic devices.

Key Topics

• Definitions, symbols and terminology relevant to GDTs and surge protection.
• Service conditions (ambient temperature, humidity, altitude/air pressure, low-temperature behaviour).
• Mechanical requirements and materials including robustness of terminations, solderability, radiation resistance and marking.
• Construction and design guidelines for two- and three-electrode GDTs, including hermetic sealing and internal gap arrangements.
• Functional behavior: protection principle, operating modes, static and dynamic response characteristics and typical voltage-current curves.
• Failsafe (fail-short) concepts and construction options to limit dangerous open-circuit failures.
• Application examples and protective circuits: 2-point (signal line), 3-point, 5-point, telephone/fax/modem, cable TV/coaxial and AC line protection.
• Normative references to related environmental and test standards (e.g., IEC 60068 series and IEC 61643-311).

Applications

EN 61643-312 is practical guidance for specifying and applying GDTs for overvoltage protection in:

• Telecommunications and signalling lines (voice, data, modem/fax protection)
• Cable TV and coaxial distribution systems
• Low-voltage power distribution up to 1 000 V AC / 1 500 V DC
• Equipment racks and junction panels where surge shunting via GDTs is required

The standard helps engineers select appropriate GDT types, design protective circuits (2-, 3-, 5-point topologies), and understand response and failsafe behavior for reliable surge protection.

Who should use this standard

• Surge protection component manufacturers and product designers
• System integrators and electrical/telecommunications engineers
• Specifiers writing procurement or installation requirements
• Test laboratories and certification bodies evaluating GDT components

Related standards

• IEC/EN 61643-311 - performance requirements and test methods for GDTs
• IEC 60068 series - environmental testing (solderability, temperature, robustness)
• Other IEC 61643 parts relevant to surge protective devices and components

EN 61643-312 is a component-level reference for safe, effective use of gas discharge tubes (GDT) in overvoltage protection systems across telecoms, signalling and low-voltage networks.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2013
1DGRPHãþD
SIST EN 61643-311:2005
6HVWDYQLGHOL]DQL]NRQDSHWRVWQHQDSUDYH]D]DãþLWRSUHGSUHQDSHWRVWQLPLXGDUL
GHO,]ELUDLQQDþLQLXSRUDEHSOLQVNLKRGYRGQLNRY,(&
FRUULJHQGXP-XO
Components for low-voltage surge protective devices - Part 312: Selection and
applications principles for gas discharge tubes
Composants pour parafoudres basse tension - Partie 312: Principes de choix et
d'application pour les tubes à décharge
Ta slovenski standard je istoveten z: EN 61643-312:2013
ICS:
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
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 61643-312
NORME EUROPÉENNE
August 2013
EUROPÄISCHE NORM
ICS 31.100; 33.040.99 Supersedes EN 61643-311:2001 (partially)

English version
Components for low-voltage surge protective devices -
Part 312: Selection and application principles for gas discharge tubes
(IEC 61643-312:2013 + corrigendum Jul. 2013)

Composants pour parafoudres basse Bauelemente für
tension - Überspannungsschutzgeräte für
Partie 312: Principes de choix et Niederspannung -
d'application pour les tubes à décharge de Teil 312: Auswahl- und
gaz Anwendungsprinzipien für
(CEI 61643-312:2013 Gasentladungsableiter
+ corrigendum Jul. 2013) (IEC 61643-312:2013
+ corrigendum Jul. 2013)
This European Standard was approved by CENELEC on 2013-05-27. 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 61643-312:2013 E
Foreword
The text of document 37B/114/FDIS, future edition 1 of IEC 61643-312, prepared by SC 37B, "Specific
components for surge arresters and surge protective devices", of IEC/TC 37, "Surge arresters" was
submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN 61643-312:2013.
The following dates are fixed:
• latest date by which the document has (dop) 2014-02-27
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2016-05-27
• latest date by which the national
standards conflicting with the

document have to be withdrawn
This document partially supersedes EN 61643-311:2001.
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 61643-312:2013 + corrigendum July 2013 was approved by
CENELEC as a European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
IEC 60364-5-51:2001 NOTE  Harmonised as HD 60364-5-51:2006 (modified).
IEC 60068-2-1 NOTE  Harmonised as EN 60068-2-1.
IEC 60068-2-20 NOTE  Harmonised as EN 60068-2-20.
IEC 60068-2-21 NOTE  Harmonised as EN 60068-2-21.
IEC 60721-3-3 NOTE  Harmonised as EN 60721-3-3.
IEC 61643-11 NOTE  Harmonised as EN 61643-11.
IEC 61643-21 NOTE  Harmonised as EN 61643-21.

- 3 - EN 61643-312:2013
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 60068-2-1 - Environmental testing - EN 60068-2-1 -
Part 2-1: Tests - Test A: Cold

IEC 60068-2-20 - Environmental testing - EN 60068-2-20 -
Part 2-20: Tests - Test T: Test methods for
solderability and resistance to soldering heat
of devices with leads
IEC 60068-2-21 - Environmental testing - EN 60068-2-21 -
Part 2-21: Tests - Test U: Robustness of
terminations and integral mounting devices

IEC 61643-311 - Components for low-voltage surge protective EN 61643-311 -
devices -
Part 311: Performance requirements and test
circuits and methods for gas discharge tubes
(GDT)
IEC 61643-312 ®
Edition 1.0 2013-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Components for low-voltage surge protective devices –

Part 312: Selection and application principles for gas discharge tubes

Composants pour parafoudres basse tension –

Partie 312: Principes de choix et d’application pour les tubes à décharge de gaz

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 31.100; 33.040.99 ISBN 978-2-83220-740-6

– 2 – 61643-312 © IEC:2013
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols . 6
3.1 Terms and definitions . 6
3.2 Symbols . 10
4 Service conditions . 10
4.1 General . 10
4.2 Low temperature . 10
4.3 Air pressure and altitude . 10
4.4 Ambient temperature . 10
4.5 Relative humidity . 11
5 Mechanical requirements and materials . 11
5.1 General . 11
5.2 Robustness of terminations . 11
5.3 Solderability . 11
5.4 Radiation . 11
5.5 Marking . 11
6 General . 11
7 Construction . 12
7.1 Design . 12
7.2 Description . 12
7.3 Fail-short (failsafe) . 13
8 Function . 14
8.1 Protection principle . 14
8.2 Operating mode . 14
8.3 Response behaviour . 14
8.3.1 Static response behavior . 14
8.3.2 Dynamic response behavior . 14
8.4 Fail-short (failsafe) . 15
9 Applications . 16
9.1 Protective circuits . 16
9.1.1 General . 16
9.1.2 2-point (signal line) protection . 16
9.1.3 3-point protection . 17
9.1.4 5-point protection . 18
9.2 Telephone/fax/modem protection . 19
9.3 Cable TV/coaxial cable protection . 19
9.4 AC line protection . 20
Bibliography . 21

Figure 1 – Voltage and current characteristics of a GDT . 8
Figure 2 – Symbol for a two-electrode GDT . 10
Figure 3 – Symbol for a three-electrode GDT . 10
Figure 4 – Example of a two-electrode GDT . 12

61643-312 © IEC:2013 – 3 –
Figure 5 – Example of a three-electrode GDT . 12
Figure 6 – Failsafe construction of a three-electrode GDT using a solder pill as
sensitive spacer . 13
Figure 7 – Failsafe construction of a three-electrode GDT, using a plastic foil as
sensitive spacer . 13
Figure 8 – Typical response behaviour of a 230 V GDT . 15
Figure 9 – Spark-over voltages versus response time . 15
Figure 10 – Current through the GDT versus response time of fail-short (failsafe) . 16
Figure 11 – 2-point (Signal line) protection . 17
Figure 12 – 3-point protection using two-electrode GDTs . 17
Figure 13 – 3-point protection using three-electrode GDTs . 17
Figure 14 – 3-point protection using two-electrode GDTs with fail-short . 18
Figure 15 – 3-point protection using three-electrode GDTs with fail-short . 18
Figure 16 – 5-point protection using two-electrode GDTs . 18
Figure 17 – 5-point protection using three-electrode GDTs . 18
Figure 18 – 5-point protection using two-electrode GDTs with fail-short . 19
Figure 19 – 5-point protection using three-electrode GDTs with fail-short . 19
Figure 20 – Telephone/fax/modem protection using two-electrode GDTs . 19
Figure 21 – Telephone/fax/modem protection using three-electrode GDTs . 19
Figure 22 – Cable TV/ coaxial cable protection . 20
Figure 23 – AC line protection . 20

– 4 – 61643-312 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

Part 312: Selection and application principles for gas discharge tubes

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 61643-312 has been prepared by subcommittee 37B: Specific
components for surge arresters and surge protective devices, of IEC technical committee 37:
Surge arresters.
The text of this standard is based on the following documents:
FDIS Report on voting
37B/114/FDIS 37B/120/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.
A list of all parts of IEC 61643 series, under the general title Components for low-voltage
surge protective devices can be found on the IEC website.

61643-312 © IEC:2013 – 5 –
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.
The contents of the corrigendum of July 2013 have been included in this copy.

– 6 – 61643-312 © IEC:2013
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

Part 312: Selection and application principles for gas discharge tubes

1 Scope
This part of IEC 61643 is applicable to gas discharge tubes (GDT) used for overvoltage
protection in telecommunications, signalling and low-voltage power distribution networks with
nominal system voltages up to 1 000 V (r.m.s.) a.c. and 1 500 V d.c. They are defined as a
gap, or several gaps with two or three metal electrodes hermetically sealed so that gas
mixture and pressure are under control. They are designed to protect apparatus or personnel,
or both, from high transient voltages. This standard provides information about the
characteristics and circuit applications of GDTs having two or three electrodes. This standard
does not specify requirements applicable to complete surge protective devices, nor does it
specify total requirements for GDTs employed within electronic devices, where precise
coordination between GDT performance and surge protective device withstand capability is
highly critical.
This part of IEC 61643
– does not deal with mountings and their effect on GDT characteristics. Characteristics
given apply solely to GDTs mounted in the ways described for the tests;
– does not deal with mechanical dimensions;
– does not deal with quality assurance requirements;
– may not be sufficient for GDTs used on high-frequency (>30 MHz);
– does not deal with electrostatic voltages;
– does not deal with hybrid overvoltage protection components or composite GDT devices.
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 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-20, Environmental testing – Part 2-20: Tests – Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices
IEC 61643-311, Components for low-voltage surge protective devices – Part 311:
Specification for gas discharge tubes (GDT)
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply:

61643-312 © IEC:2013 – 7 –
3.1.1
arc current
current that flows after sparkover when the circuit impedance allows a current to flow that
exceeds the glow-to-arc transition current
3.1.2
arc voltage
arc mode voltage
voltage drop across the GDT during arc current flow
Note 1 to entry: See Figure 1a, region A.
3.1.3
arc-to-glow transition current
current required for the GDT to pass from the arc mode into the glow mode
3.1.4
current turn-off time
time required for the GDT to restore itself to a non-conducting state following a period of
conduction.
Note 1 to entry: This applies only to a condition where the GDT is exposed to a continuous d.c. potential (see d.c.
holdover).
3.1.5
d.c. sparkover voltage
d.c. breakdown voltage
voltage at which the GDT transitions from a high-impedance off to a conduction state when a
slowly rising d.c. voltage up to 2 kV/s is applied
Note 1 to entry: The rate of rise for d.c. sparkover voltage measurements is usually equal or less 2 000 V/s.
3.1.6
d.c. holdover
state in which a GDT continues to conduct after it is subjected to an impulse sufficient to
cause breakdown
Note 1 to entry: In applications where a d.c. voltage exists on a line. Factors that affect the time required to
recover from the conducting state (current turn-off time) include the d.c. voltage and the d.c. current
3.1.7
d.c. holdover voltage
maximum d.c. voltage across the terminals of a gas discharge tube under which it may be
expected to clear and to return to the high-impedance state after the passage of a surge,
under specified circuit conditions
3.1.8
discharge current
current that flows through a GDT after sparkover occurs
Note 1 to entry: In the event that the current passing through the GDT is alternating current, it will be r.m.s. value.
In instances where the current passing through the GDT is an impulse current, the value wi
...