IEC 61643-311:2013

Components for low-voltage surge protective devices - Part 311: Performance requirements and test circuits for gas discharge tubes (GDT)

IEC 61643-311:2013 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 contains a series of test criteria, test methods and test circuits for determining the electrical characteristics 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 second edition of IEC 61643-311 cancels and replaces the first edition published in 2001. It constitutes a technical revision. Specific changes with respect to the previous edition are: Addition of performance values. Key words: 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.

Composants pour parafoudres basse tension - Partie 311: Exigences de performance et circuits d'essai pour tubes à décharge de gaz (TDG)

La CEI 61643-311:2013 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 contient une série de critères d'essai, de méthodes d'essai et de circuits d'essai destinés à déterminer les caractéristiques électriques 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. Cette deuxième édition de la CEI 61643-311 annule et remplace la première édition publiée en 2001 dont elle constitue une révision technique. Les changements spécifiques par rapport à l'édition précédente sont: l'ajout des valeurs de performance. 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 sont inférieures ou égales à 1 000 V (valeurs efficaces) c.a. et 1 500 V c.c

General Information

• Status: Published
• Publication Date: 10-Apr-2013
• ICS: 31.100 - Electronic tubes
• ICS: 33.040.99 - Other equipment for telecommunication systems
• Technical Committee: SC 37B - Components for low-voltage surge protection
• Drafting Committee: MT 1 - TC 37/SC 37B/MT 1
• Current Stage: PPUB - Publication issued
• Start Date: 11-Apr-2013
• Completion Date: 31-Mar-2013

Relations

• Revises: IEC 61643-311:2001 - Components for low-voltage surge protective devices - Part 311: Specification for gas discharge tubes (GDT)
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 61643-311 ®
Edition 2.0 2013-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Components for low-voltage surge protective devices –
Part 311: Performance requirements and test circuits for gas discharge tubes
(GDT)
Composants pour parafoudres basse tension –
Partie 311: Exigences de performance et circuits d’essai pour tubes à décharge
de gaz (TDG)
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IEC 61643-311 ®
Edition 2.0 2013-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Components for low-voltage surge protective devices –

Part 311: Performance requirements and test circuits for gas discharge tubes

(GDT)
Composants pour parafoudres basse tension –

Partie 311: Exigences de performance et circuits d’essai pour tubes à décharge

de gaz (TDG)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX U
ICS 31.100; 33.040.99 ISBN 978-2-83220-678-2

– 2 – 61643-311 © IEC:2013
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and symbols . 7
3.1 Terms and definitions . 7
3.2 Symbols . 10
4 Service conditions . 10
4.1 Low temperature . 10
4.2 Air pressure and altitude . 10
4.3 Ambient temperature . 10
4.4 Relative humidity . 11
5 Mechanical requirements and materials . 11
5.1 Robustness of terminations . 11
5.2 Solderability . 11
5.3 Radiation . 11
5.4 Marking . 11
6 General . 11
6.1 Failure rates . 11
6.2 Standard atmospheric conditions . 11
7 Electrical requirements . 12
7.1 General . 12
7.2 Initial values . 12
7.2.1 Sparkover voltages . 12
7.2.2 Insulation resistance . 13
7.2.3 Capacitance . 13
7.2.4 Transverse voltage . 13
7.2.5 DC holdover . 13
7.3 Requirements after application of load. 13
7.3.1 General . 13
7.3.2 Sparkover voltages . 14
7.3.3 Insulation resistance . 14
7.3.4 AC follow current . 14
7.3.5 Fail-short (Failsafe) . 15
8 Test and measurement procedures and circuits . 15
8.1 DC sparkover voltage . 15
8.2 Impulse sparkover voltage . 16
8.3 Insulation resistance . 16
8.4 Capacitance . 16
8.5 Glow-to-arc transition current, glow voltage, arc voltage . 16
8.6 Transverse voltage . 18
8.7 DC holdover voltage . 19
8.7.1 General . 19
8.7.2 DC holdover voltage values . 21
8.8 Requirements for current-carrying capacity . 22
8.8.1 General . 22

61643-311 © IEC:2013 – 3 –
8.8.2 Nominal alternating discharge current . 22
8.8.3 Nominal impulse discharge current, waveshape 8/20 . 23
8.8.4 Life test with impulse currents, waveshape 10/1 000 . 24
8.8.5 AC follow current . 24
8.9 Fail-short (failsafe) . 25
Bibliography . 27

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 – Circuit for d.c. sparkover voltage test at 100 V/s . 15
Figure 5 – Circuit for impulse sparkover voltage at 1 000 V/µs . 16
Figure 6 – Test circuit for glow-to-arc transition current, glow voltage and arc voltage . 17
Figure 7 – Voltage-current characteristic of a typical GDT, suitable for measuring for

example the glow-to-arc transition current, glow voltage, and arc voltage . 18
Figure 8 – Test circuit for transverse voltage . 19
Figure 9 – Test circuit for dc holdover voltage, two-electrode GDTs . 20
Figure 10 – Test circuit for dc holdover voltage, three-electrode GDTs . 20
Figure 11 – Circuit for nominal alternating discharge current, two-electrode GDTs . 23
Figure 12 – Circuit for nominal alternating discharge current, three-electrode GDTs . 23
Figure 13 – Circuit for nominal impulse discharge current, two-electrode GDTs . 23
Figure 14 – Circuit for nominal impulse discharge current, three-electrode GDTs . 23
Figure 15 – Circuit for life test with impulse current, two-electrode GDTs . 24
Figure 16 – Circuit for life test with impulse current, three-electrode GDTs . 24
Figure 17 – Test circuit for alternating follow current . 25
Figure 18 – Test circuit for fail-short (failsafe), two-electrode GDTs . 26
Figure 19 – Test circuit for fail-short (failsafe), three-electrode GDTs . 26

Table 1 – DC and impulse sparkover voltage requirements, initial . 12
Table 2 – Values of sparkover voltages after the tests of Table 5 . 14
Table 3 – Values for different d.c. holdover voltage tests for two-electrode GDTs . 21
Table 4 – Values for different d.c. holdover voltage tests for three-electrode GDTs . 21
Table 5 – Different classes of current-carrying capacity . 22

– 4 – 61643-311 © IEC:2013
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE
SURGE PROTECTIVE DEVICES –
Part 311: Performance requirements and
test circuits for gas discharge tubes (GDT)

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
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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 61643-311 has been prepared by subcommittee 37B: Specific
components for surge arresters and surge protective devices, of IEC technical committee 37:
Surge arresters.
This second edition of IEC 61643-311 cancels and replaces the first edition published in 2001.
It constitutes a technical revision.
Specific changes with respect to the previous edition are:
– Addition of performance values.

61643-311 © IEC:2013 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
37B/113/FDIS 37B/118/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.
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.
– 6 – 61643-311 © IEC:2013
COMPONENTS FOR LOW-VOLTAGE
SURGE PROTECTIVE DEVICES –
Part 311: Performance requirements and
test circuits for gas discharge tubes (GDT)

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 contains a series of test criteria, test
methods and test circuits for determining the electrical characteristics 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 60068-2-1:2007, Environmental testing – Part 2: Tests. Tests A: Cold
IEC 60068-2-20:2008, Environmental testing – Part 2: Tests. Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-21:2006, Environmental testing – Part 2-21: Tests – Test U: Robustness of
terminations and integral mounting devices
IEC 61000-4-5:2005, Electromagnetic compatibility (EMC) – Part 4: Testing and measurement
techniques – Section 5: Surge immunity test
ITU-T Recommendation K.20:2011, Resistibility of telecommunication equipment installed in a
telecommunications centre to overvoltages and overcurrents

61643-311 © IEC:2013 – 7 –
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply
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 will be the peak value.

– 8 – 61643-311 © IEC:2013
3.1.9
discharge voltage
residual voltage of an arrester
peak value of voltage that appears across the terminals of a GDT during the passage of GDT
discharge current
3.1.10
discharge voltage current characteristic
V/I characteristic
variation of peak values of discharge voltage with respect to GDT discharge current
Figure 1c Figure 1a
v
v
V
s
G
V
g
V
e
A
V
a
i
t
A
G
Figure 1b
i
t
IEC  527/13
Legend
V spark-over voltage V arc voltage G glow mode range
s a
V glow voltage V extinction voltage A arc mode range
gl e
Figure 1a – Voltage at a GDT as a function of time when limiting a sinusoidal voltage
Figure 1b – Current at a GDT as a function of time when limiting a sinusoidal voltage
Figure 1c – V/I characteristic of a GDT obtained by combining the graphs of voltage and current
Figure 1 – Voltage and current characteristics of a GDT
3.1.11
extinction voltage
voltage at which discharge (current flow) ceases
3.1.12
fail-short
failsafe
thermally-activated external shorting mechanism

61643-311 © IEC:2013 – 9 –
3.1.13
follow on current
current that the GDT conducts from a connected power source after sparkover
Note 1 to entry: The GDT is expected to extinguish after sparkover to avoid overheating
3.1.14
gas discharge tube
GDT
gap, or several gaps with two or three metal electrodes hermetically sealed so that gas
mixture and pressure are under control, designed to protect apparatus or personnel, or both,
from high transient voltages
3.1.15
glow current
glow mode current
current that flows after breakdown when the circuit impedance limits the follow current to a
value less than the glow-to-arc transition current
Note 1 to entry: See Figure 1a region G.
3.1.16
glow-to-arc transition current
current required for the GDT to pass from the glow mode into the arc mode
Note 1 to entry: See Figure 1a region G.
3.1.17
glow voltage
glow mode voltage
peak value of voltage drop across the GDT when a glow current is flowing
Note 1 to entry: See Figure 1a region G.
3.1.18
impulse sparkover voltage
highest value of voltage attained by an impulse of a designated voltage rate-of-rise and
polarity applied across the terminals of a GDT prior to the flow of the discharge current
3.1.19
impulse waveshape
outline of an electrical surge designated as x/y having a rise time of x µs and a decay time to
half value of y µs
3.1.20
nominal alternating discharge current
current which the GDT is designed to conduct for a defined time
Note 1 to entry: For currents with a frequency of 15 Hz to 62 Hz.
3.1.21
nominal d.c. sparkover voltage
voltage specified by the manufacturer to indicate the target value of sparkover voltages of a
particular type of GDT products
Note 1 to entry: The nominal value is generally a rounded number such as: 75 V, 90 V, 150 V, 200 V, 230 V,
250 V, 300 V, 350 V, 420 V, 500 V, 600 V, 800 V, 1 000 V, 1 200 V, 1 400 V, 1 800 V, 2 100 V, 2 700 V, 3 000 V,
3 600 V, 4 000 V and 4 500 V.
Note 2 to entry: Values in between should be agreed jointly between the manufacturer and the user.

– 10 – 61643-311 © IEC:2013
3.1.22
nominal impulse discharge current
peak value of the impulse current with a defined waveshape with respect to time for which the
GDT is rated
3.1.23
sparkover
breakdown
abrupt transition of the gap resistance from practically infinite value to a relatively low value
3.1.24
transverse voltage
the difference in the discharge voltages between terminal A and B (see Figure 3) of the gaps
assigned to the two conductors of the circuit during the passage of discharge current
Note 1 to entry: Only for three electrode GDT conducting a longitudinal surge.
3.2 Symbols
A
A
C
C B
IEC  528/13 IEC  529/13
Figure 2 – Symbol for a Figure 3 – Symbol for a
two-electrode GDT
three-electrode GDT
4 Service conditions
4.1 Low temperature
The GDT shall be capable of withstanding IEC 60068-2-1, test Aa –40 °C, duration 2 h,
without damage. While at –40 °C, the GDT shall meet the d.c. and impulse sparkover
requirements of Table 1.
4.2 Air pressure and altitude
Air pressure is 80 kPa to 106 kPa.
These values represent an altitude of +2 000 m to –500 m respectively.
4.3 Ambient temperature
In this clause, the ambient temperature is the temperature of the air or other media, in the
immediate vicinity of the component.
operating range (GDTs without failsafe): –40 °C to +90 °C
operating range (GDTs with failsafe): –40 °C to +70 °C
NOTE This corresponds to class 3K7 in IEC 60721-3-3.
storage range (GDTs without failsafe): –40 °C to +90 °C
storage range (GDTs with failsafe): –40 °C to +40 °C

61643-311 © IEC:2013 – 11 –
4.4 Relative humidity
In this clause the relative humidity is expressed as a percentage, being the ratio of actual
partial vapour pressure to the saturation vapour pressure at any given temperature, 4.3, and
pressure, 4.2.
normal range: 5 % to 95 %
NOTE This corresponds to code AB4 in IEC 60364-5-51
5 Mechanical requirements and materials
5.1 Robustness of terminations
If applicable, the user shall specify a suitable test from IEC 60068-2-21.
5.2 Solderability
Solder terminations shall meet the requirements of IEC 60068-2-20, test Ta, method 1.
5.3 Radiation
Gas discharge tubes shall not contain radioactive material.
5.4 Marking
Legible and permanent marking shall be applied to the GDT as necessary to ensure that the
user can determine the following information by inspection:
Each GDT shall be marked with the following information:
– nominal d.c. sparkover voltage;
– date of manufacture or batch number;
– manufacturer name or trademark;
– part number;
– safety approval markings.
NOTE 1 The necessary information can also be coded.
NOTE 2 When the space is not sufficient for printing this data, it should be provided in the technical
documentation after agreement between the manufacturer and the purchaser.
6 General
6.1 Failure rates
Sampling size, electrical characteristics to be tested, etc. are covered by the quality
assurance requirements, which are not covered by this standard.
6.2 Standard atmospheric conditions
The following tests shall be performed on the GDTs as required by the application. Unless
otherwise specified, ambient test conditions shall be as follows:
• temperature: 15 °C to 35 °C;
• relative humidity 25 % to 75 %;

– 12 – 61643-311 © IEC:2013
7 Electrical requirements
7.1 General
All electrical requirements in this standard are minimum requirements. Users may specify
different values.
7.2 Initial values
7.2.1 Sparkover voltages
The sparkover voltages between electrodes A and C of a two-electrode GDT as shown in
Figure 2 or between either line electrode A or B and the earth electrode C of a three-electrode
GDT as shown in Figure 3 shall be within the limits shown in Table 1.
Table 1 – DC and impulse sparkover voltage requirements, initial
Values of sparkover voltage, initial
Preferred d.c. sparkover
100 V/s to 2 kV/s
1 kV/µs
voltage at 100 V/s
(99,7 % of measured values)
A – C or A/B – C Min. Max
V V V V
75 57 93
<650
a)
90/1 72 108
<600
a)
90/2 72 108
<500
150 120 180 <600
a)
200/1 160 240
<700
a)
200/2 160 240
<450
a)
230/1 184 280
<700
a)
230/2 184 280
<450
250 200 300 <700
300 240 360
<1 000
a)
350/1 280 420
<1 000
a)
350/2 265 455
<800
a)
420/1 360 520
<1 100
a)
420/2 360 520 <850
a)
500/1 400 600
<1200
a)
500/2 400 600
<900
a)
600/1 480 720
<1 400
a)
600/2 480 720
<1 000
800 640 960 <1 600
1 000 800 1 200
<2 000
1 200 960 1 440
<1 600
1 400 1 120 1 680
<2 800
1 800 1 440 2 160
<3 600
2 100 1 680 2 520 <4 000
2 700 2 160 3 240
<4 500
3 000 2 400 3 600
<4 500
3 600 2 900 4 300
<5 000
4 000 3 200 4 800
<5 500
4 500 3 600 5 400 <6 000
a)
Represents different technologies of GDTs.

61643-311 © IEC:2013 – 13 –
For three-electrode GDTs the sparkover voltage between the line electrodes A – B shall not
be higher than twice of A or B – C or not be less than the minimum d.c. sparkover voltage in
Table 1, column 2.
7.2.2 Insulation resistance
The values shall not be less than 1 GΩ.
7.2.3 Capacitance
The values shall not be greater than 20 pF.
7.2.4 Transverse voltage
The transverse voltage for a three-electrode gas discharge tube is the difference in the
discharge voltages between terminals a and b of the gaps assigned to the two conductors of
the circuit during the passage of discharge current. For a three-electrode GDT the difference
in time between the sparkover of the first and second gap shall not exceed 200 ns.
7.2.5 DC holdover
The current turn-off time shall be less than 150 ms, depending upon the d.c. sparkover
voltage and the test circuit parameters.
7.3 Requirements after application of load
7.3.1 General
After the tests shown in Table 5, the GDTs shall be within the following limits of sparkover
voltage (Table 2) and insulation resistance (see 7.3.3.).

– 14 – 61643-311 © IEC:2013
7.3.2 Sparkover voltages
Table 2 – Values of sparkover voltages after the tests of Table 5
Values of sparkover voltage after testing
Preferred d.c. sparkover
100 V/s to 2 kV/s
voltage at 100 V/s 1 kV/µs
A – C or A/B – C
Min. Max. (99,7 % of measured values)
V V V V
75 57 100
<750
a)
90/1 65 120
<700
a)
90/2 65 120
<600
150 110 195
<700
a)
200/1 150 250 <800
a)
200/2 150 250
<550
a)
230/1 170 300
<800
a)
230/2 170 300
<550
250 180 325
<800
300 225 375 <1 300
a)
350/1 260 455
<1 100
a)
350/2 265 600
<900
a)
420/1 360 550
<1 200
a)
420/2 360 650
<1 000
a)
500/1 400 650 <1 300
a)
500/2 400 700
<1 050
a)
600/1 450 780
<1 500
a)
600/2 450 800
<1 200
800 600 1 000
<2 000
1 000 750 1 250
<2 500
1 200 900 1 680
<2 500
1 400 1 050 1 750
<3 500
1 800 1 350 2 250 <4 500
2 100 1 550 2 650
<5 000
2 700 2 150 3 350
<5 500
3 000 2 450 3 700
<5 500
3 600 2 550 4 700
<6 000
4 000 2 800 5 200 <6 500
4 500 3 150 5 850
<7 000
a)
Represents different technologies of GDTs.

7.3.3 Insulation resistance
The values shall not be less than 10 MΩ.
NOTE In some countries the insulation resistance shall not be less than 100 MΩ.
7.3.4 AC follow current
In the absence of special requirements, it is recommended that the device be required to
extinguish not later than thirty electrical degrees after the first alternating current zero
crossing without failure and that subsequent breakdown does not occur.

61643-311 © IEC:2013 – 15 –
7.3.5 Fail-short (Failsafe)
For GDTs with an integrated fail-safe feature only.
Alternating currents shall be applied at the specified current of the GDT in accordance with
the circuits in Figure 18 and Figure 19.
After the tests, the resistance of the GDTs shall be less than 1 Ω between electrodes A and C
of a two-electrode GDT or between either line electrode (A or B) and the earth electrode (C)
of a three-electrode GDT.
8 Test and measurement procedures and circuits
8.1 DC sparkover voltage
The GDT shall be placed in darkness for at least 15 min with no application of energizing
voltage supply and tested in this condition using a test circuit as shown in Figure 4 with a
voltage rate of rise between 100 V/s to 2 000 V/s. Values of V and R1 are adjusted to give
du/dt = 100 V/s to 2 000 V/s, e.g for d.c. sparkover voltage of 230 V, V= 500 V and
R1 = 2 MΩ. Two measurement values shall be recorded for each GDT between A and C for
each polarity. Time between measurements should be equal to 1 s or more.
NOTE Placing the GDT in darkness for 24 h assures that it is not pre-ionized before the measurement. GDTs that
are not pre-ionized may have a slight ignition delay depending on their technology. This is called First-Time-Effect
(dark effect) as it only appears at the first out of several ignitions (after the first ignition the GDT is pre-ionized).
Depending on the design of a GDT it may stay pre-ionized for a span of time after firing or being exposed to light.
In most cases the decay time is less than 15 min.
Each pair of terminals of a three-electrode GDT shall be tested separately with the other
terminal unterminated.
All measured values shall meet the limits given in Table 1.

S
R1 51 kΩ
+
A
V
2 µF GDT CV
C
–
IEC 530/13
Components
CV crest voltmeter, oscilloscope with impedance higher than 10 MΩ
S switch
V d.c. voltage source
NOTE 1 Avoid oscillating operation.
NOTE 2 With other circuit parameters the rate of rise can be changed up to 2 kV/s. This can be jointly agreed
between the manufacturer and the user.
Figure 4 – Circuit for d.c. sparkover voltage test at 100 V/s

– 16 – 61643-311 © IEC:2013
8.2 Impulse sparkover voltage
The GDT shall be placed in darkness for at least 15 min with no application of energizing
voltage supply and tested in this condition using a test-circuit as shown in Figure 5. Figure 5
circuit values of d.c. supply voltage, resistor and capacitor shall be adjusted to
du/dt = 1 000 V/µs. The values shown in Figure 5 are suitable for GDTs up to 1 000 V d.c.
sparkover voltage. The test is performed with a voltage rate of rise of 1 000 V/µs ± 20 %. Two
measurement values shall be recorded for each GDT between A and C for each polarity.
The duration of breaks between the measurement shall be at least 1 s.
Each pair of terminals of a three-electrode GDT shall be tested separately with the other
terminal unterminated.
All measured values shall meet the limits given in Table 1.

1 kΩ
50 Ω
+
A
10 MΩ S
5 kV 0,1 µF 5 nF
GDT
C
–
IEC 531/13
Components
S crest voltmeter, oscilloscope with impedance higher than 10 MΩ
Figure 5 – Circuit for impulse sparkover voltage at 1 000 V/µs
8.3 Insulation resistance
Insulation resistance shall be measured from each terminal to every other terminal of the
GDT. For GDTs with a nominal d.c. sparkover voltage of up to and including 150 V, the test is
performed using 50 V d.c. For higher nominal d.c. sparkover voltage, the test is performed
with 100 V d.c.
All measured values shall meet the requirement of 7.2.2. Terminals of three-electrode GDTs
not involved in the measurement shall be left unterminated.
8.4 Capacitance
The capacitance shall be measured once at 1 MHz between all terminals unless otherwise
specified.
All measured values shall meet the requirement in 7.2.3. Terminals of three-electrode GDTs
not involved in the measurement shall be left unterminated.
8.5 Glow-to-arc transition current, glow voltage, arc voltage
The GDT shall be placed in a test circuit as shown in Figure 6.
The r.m.s. voltage of the secondary side of transformer Tr should be a minimum of twice the
nominal d.c. sparkover voltage. The peak value of discharge current is approximately twice

61643-311 © IEC:2013 – 17 –
that of the expected glow-to-arc transition current, however not more than 2 A. The test
duration shall be a maximum of 1 s.
The voltage current characteristic of a typical GDT is shown in Figure 7, generated by the test
circuit of Figure 6 for the positive half cycle.

A
GDT
Tr
C
G
~ OSC
R2
R1
IEC 532/13
Components
G generator 50 Hz or 60 Hz
OSC oscilloscope
R1 regulating resistor
R2 current sensing resistor
Tr transformer
Figure 6 – Test circuit for glow-to-arc transition
current, glow voltage and arc voltage
Voltage-current characteristic u = f(i) (schematic)

– 18 – 61643-311 © IEC:2013
v
v1
v2
Glow-to-arc
transition
v3
i3 i1 i2
i
IEC 533/13
Legend
v1 d.c. sparkover voltage
v2 glow voltage
v3 arc voltage
i1 glow-to-arc transition current
i3 arc-to-glow transition current
i2 peak current
Figure 7 – Voltage-current characteristic of a typical GDT, suitable for measuring
for example the glow-to-arc transition current, glow voltage, and arc voltage
8.6 Transverse voltage
The magnitude and the duration of transverse voltage shall be measured for GDTs with three
electrodes, while an impulse voltage having a virtual steepness of impulse wave front of
1 000 V/µs is applied simultaneously to both discharge gaps. Measurement may be made with
an arrangement as indicated in Figure 8. The difference in time between the sparkover of the
first gap and that of the second shall be determined for each test for both polarities. The
maximum time shall be less than specified in 7.2.4.

61643-311 © IEC:2013 – 19 –
S
1 kΩ
50 Ω
5 kV
0,2 µF 5 nF
10 MΩ
A
C
OSC
GDT
B
10 MΩ
5 nF
50 Ω
1 kΩ
IEC 534/13
Component
OSC dual channel oscilloscope
S switch
Figure 8 – Test circuit for transverse voltage
8.7 DC holdover voltage
8.7.1 General
The d.c. holdover voltage of GDTs is dependent upon the test circuits and is therefore
application specific. The user and the manufacturer should agree on the special test circuits,
the number of tests, test parameters, etc.
The major application of GDTs is the protection of telecommunication equipment. The test
circuits shown in Figure 9 and Figure 10 provide examples suitable for breakdown voltages
equal or higher than 230 V.
The test shall be conducted using the circuit of Figure 9 or Figure 10. Values of circuit
components shall be selected from Table 3 or Table 4. The simultaneous currents that are
applied to the gaps of the three-electrode GDT shall have an impulse waveform of 100 A,
10/1 000 µs or 5/320 µs measured through a short-circuit replacing the GDT under test. The
polarity of the impulse current through the GDT shall be the same as the current from PS1
and PS2.
For each test condition, measurement of the time of current turn-off shall be made for both
polarities of the impulse current. Three impulses in each direction shall be applied at intervals
not greater than 1 min, and the time to current turn-off measured for each impulse.
All measured values shall meet the requirements of 7.2.5.

– 20 – 61643-311 © IEC:2013
D1
R3
E1 R1
+
+
A
R2
GDT
SG OSC PS1
C
–
C1
–
IEC 535/13
Components
C1 see Table 3
D1 isolation diode or other isolation device
E1 isolation gap or equivalent device
OSC oscilloscope
PS1 constant voltage d.c. supply or battery
R1 impulse current-limiting resistor or waveshaping network
R2, R3 see Table 3
SG surge generator, 100 A, 10/1 000 µs
Figure 9 – Test circuit for dc holdover voltage, two-electrode GDTs

E1
R1 R1
C1
+ R2
D1 D2
A B
SG
C2
C2 GDT
D3 D4
C
+ +
R4 R4
PS1 PS2
–
R3 R3
– –
OSC
IEC 536/13
Components
C1, C2 see Table 4
E1 isolation gap or equivalent device
OSC dual channel oscilloscope
PS1, PS2 batteries or d.c. power supplies
R1 impulse current-limiting resistors or wave-shaping networks
R2, R3, R4 see Table 4
SG surge generator, 100 A per path, 10/1 000 µs
NOTE The polarity of diodes D1 to D4 must be reversed when the polarity of the d.c. power supplies and surge
generators is reversed.
Figure 10 – Test circuit for dc holdover voltage, three-electrode GDTs

61643-311 © IEC:2013 – 21 –
8.7.2 DC holdover voltage values
Examples for telecommunication applications are given in Table 3 for two-electrode GDTs and
in Table 4 for three-electrode GDTs (test circuits as shown in Figure 9 and Figure 10).
Table 3 – Values for different d.c. holdover voltage tests for two-electrode GDTs
b)
Component Test 1 Test 2 Test 3 Test 4
PS1 52 V 80 V 135 V 135 V
R3 200 Ω 330 Ω 1 300 Ω 450 Ω
a)
R2
150 Ω 150 Ω 150 Ω
a)
C1 100 nF 100 nF 100 nF
a
...