IEC 62848-2:2019

IEC 62848-2 ®
Edition 1.0 2019-06
INTERNATIONAL
STANDARD
Railway applications – DC surge arresters and voltage limiting devices –
Part 2: Voltage limiting devices

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org
The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,
variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English
committee,…). It also gives information on projects, replaced and French, with equivalent terms in 16 additional languages.
and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary
details all new publications released. Available online and 67 000 electrotechnical terminology entries in English and
once a month by email. French extracted from the Terms and Definitions clause of
IEC publications issued since 2002. Some entries have been
IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and
If you wish to give us your feedback on this publication or CISPR.

need further assistance, please contact the Customer Service

Centre: sales@iec.ch.
IEC 62848-2 ®
Edition 1.0 2019-06
INTERNATIONAL
STANDARD
Railway applications – DC surge arresters and voltage limiting devices –

Part 2: Voltage limiting devices

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 45.060.01 ISBN 978-2-8322-6884-1

– 2 – IEC 62848-2:2019 © IEC 2019
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Classes of VLD . 9
5 Characteristics and requirements of the VLDs . 10
5.1 Marking . 10
5.2 Service requirements . 11
5.2.1 Normal outdoor service conditions . 11
5.2.2 Normal indoor service conditions . 11
5.2.3 Abnormal service conditions . 11
5.3 General characteristics . 12
5.4 Minimum requirements . 12
5.4.1 Response time . 12
5.4.2 Additional requirements for VLDs of Class 1 . 12
5.4.3 Additional requirements for VLDs of Classes 3 and 4 . 12
5.5 Electrical characteristics and thermal rating . 12
5.6 Protection of VLDs against lightning. 13
5.7 Command and control (Classes 3 and 4 only) . 13
5.7.1 Local control . 13
5.7.2 Remote signalling . 13
5.7.3 Operation and alarm recordings . 14
6 Type tests . 14
6.1 General . 14
6.2 Nominal triggering voltage U and non-triggering voltage U . 15
Tn W
6.2.1 Procedure for welding shut spark gap VLDs (Class 1) . 15
6.2.2 Procedure for thyristor type VLDs (Class2) . 16
6.2.3 Procedure for mechanical switching VLDs and for combined thyristors
with mechanical switching devices VLDs (Class 3 and Class 4) . 17
6.3 Leakage current . 17
6.4 DC current withstand . 18
6.4.1 General . 18
6.4.2 DC rated current test . 18
6.4.3 Short time withstand current test . 19
6.5 AC current withstand characteristics (optional). 20
6.6 Response time characteristics . 20
6.6.1 Response time for DC voltage . 20
6.6.2 Response time for combined AC-DC voltage . 22
6.7 Lightning current impulse withstand characteristics for VLDs exposed to
direct lightning strikes . 24
6.8 Recovery voltage test (Classes 3, 4) . 25
6.9 Reverse voltage test (Class 2.1) . 26
6.10 Dielectric tests for panel type voltage limiting devices (Classes 3 and 4) . 27
6.10.1 Test conditions . 27
6.10.2 Power-frequency voltage withstand test . 27
6.11 Degree of protection of enclosures. 27
6.12 Environmental tests for outdoor equipment . 28

6.13 Determination of minimum current for safe short circuiting of Class 1 VLDs . 28
7 Routine tests . 29
7.1 General . 29
7.2 VLDs of Classes 3 and 4 . 29
7.3 Dielectric tests for panel type voltage limiting devices . 29
Annex A (informative) Preferred ranges of the principal properties of the VLDs. 30
Bibliography . 34

Figure 1 – Test circuit for testing of response time . 21
Figure 2 – T evaluation . 22
R
Figure 3 – Response time characteristic . 22
Figure 4 – Test circuit for testing of response time T for combined AC-DC voltage . 24
R
Figure 5 – Evaluation of response time T for combined AC-DC voltage . 24
R
Figure 6 – Circuit for the recovery voltage test . 26

Table 1 – Classes of voltage-limiting device. 10
Table 2 – Type tests . 15
Table 3 – Maximum response time as a function of DC voltages . 20
Table 4 – Response time for combined AC-DC voltages . 23
Table A.1 – Nominal triggering voltage U . 30
Tn
Table A.2 – Instantaneous triggering voltage U . 30
TI
Table A.3 – Rated current I . 30
r
Table A.4 – Short time withstand current I . 31
W
Table A.5 – Leakage current I . 31
L
Table A.6 – Making and breaking capacity . 31
Table A.7 – Lightning current impulse (8/20 µs) I . 31
imp-n
Table A.8 – High current impulse 8/20 μs and 4/10 μs I . 32
imp-high
Table A.9 – High charge impulse I . 32
imp-hc
Table A.10 – Current-time characteristic for safe short circuiting of Class 1 VLDs . 32
Table A.11 – Preferred parameters for high charge impulse I . 32
imp-hc
Table A.12 – Applicable tolerances according to IEC 61643-11:2011 . 33

– 4 – IEC 62848-2:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS –
DC SURGE ARRESTERS AND VOLTAGE LIMITING DEVICES –

Part 2: Voltage limiting devices

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 62848-2 has been prepared by IEC technical committee 9:
Electrical equipment and systems for railways.
This document is based on EN 50526-2:2014.
The text of this International Standard is based on the following documents:
FDIS Report on voting
9/2492/FDIS 9/2503/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.

A list of all parts in the IEC 62848 series, published under the general title Railway
applications – DC surge arresters and voltage limiting devices, can be found on the IEC
website.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
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.

– 6 – IEC 62848-2:2019 © IEC 2019
RAILWAY APPLICATIONS –
DC SURGE ARRESTERS AND VOLTAGE LIMITING DEVICES –

Part 2: Voltage limiting devices

1 Scope
This document applies to Voltage Limiting Devices (VLDs) to be applied in DC traction
systems in order to comply with protective provisions against electric shock from DC, and
combined AC – DC voltages, in accordance with the IEC 62128 series, taking into account
stray current provisions.
VLDs operate in such a way as to connect the track return circuit of DC railway systems to the
earthing system or to conductive parts within the overhead contact line zone or current
collector zone.
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, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60085, Electrical insulation – Thermal evaluation and designation
IEC 60529:1989, Degrees of protection provided by enclosures (IP Code)
IEC 60850:2014, Railway applications – Supply voltages of traction systems
IEC 61643-311, Components for low-voltage surge protective devices – Part 311:
Performance requirements and test circuits for gas discharge tubes (GDT)
IEC 61992-1:2006, Railway applications – Fixed installations – DC switchgear – Part 1:
General
IEC 61992-1:2006/AMD1:2014
IEC 61992-7:2006 (all parts), Railway applications – Fixed installations – DC switchgear –
Part 7-x: Measurement, control and protection devices for specific use in d.c. traction systems
IEC 62128-1:2013, Railway applications – Fixed installations – Electrical safety, earthing and
the return circuit – Part 1: Protective provisions against electric shock
IEC 62128-3:2013, Railway applications – Fixed installations – Electrical safety, earthing and
the return circuit – Part 3: Mutual Interaction of a.c. and d.c. traction systems
IEC 62497-1, Railway applications – Insulation coordination – Part 1: Basic requirements –
Clearances and creepage distances for all electrical and electronic equipment
IEC 62498-2, Railway applications – Environmental conditions for equipment – Part 2: Fixed
electrical installations
IEC 62848-1:2016, Railway applications – DC surge arresters and voltage limiting devices –
Part 1: Metal-oxide surge arresters without gaps
ISO 4287:1997, 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
lamps
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
voltage-limiting device
VLD
protective device whose function is to prevent existence of an impermissible high touch
voltage
[SOURCE: IEC 60050-811:2017, 811-29-41]
3.2
recoverable VLD
VLD that recovers after triggering
3.3
non-recoverable VLD
VLD remaining in its low resistance state permanently after triggering
3.4
welding shut spark gap
VLD which is triggered by electrical discharge across a gap causing a permanent short-circuit
by welding shut of metallic parts
Note 1 to entry: Sometimes the term voltage fuse is used for this type of VLD.
3.5
rated current
I
r
maximum value of the direct current that may flow for the
specified long term through the VLD in specified environmental conditions without exceeding
the temperature rise limits
– 8 – IEC 62848-2:2019 © IEC 2019
3.6
short time withstand current
I
W
current that a VLD can carry in closed status, during a specified short time under prescribed
conditions of use and behaviour
3.7
making capacity
I
NSS
value of prospective making current that a switching device
is capable of making at a stated voltage under prescribed conditions of use and behaviour
Note 1 to entry: The conditions to be prescribed are dealt with in the relevant specifications.
[SOURCE: IEC 60050-441:1984, 441-17-09, modified – The beginning of the Note has been
changed.]
3.8
breaking capacity
maximum current that a recoverable VLD can interrupt at a
stated voltage
3.9
leakage current
I
L
current which flows through the terminals when the VLD is in
open status
3.10
lightning current impulse
I
imp-n
8/20 µs current impulse with limits on the adjustment of equipment such that the measured
values are from 7 µs to 9 µs for the virtual front time and from 18 µs to 22 µs for the time to
half value on the tail
Note 1 to entry: The time to half-value on the tail is not critical and may have any tolerance during the residual
voltage type tests.
[SOURCE: IEC 60099-4:2014, 3.31]
3.11
high current impulse
I
imp-high
peak value of discharge current having a 4/10 µs or 8/20 µs impulse shape which is used to
test the ability of the VLD to withstand direct lightning strikes from the dielectric point of view
3.12
high charge impulse
I
imp-hc
crest value of a high charge impulse through the VLD with specified charge transfer Q and
specified energy W/R in the specified time
Note 1 to entry: A crest value of a high charge impulse having a 10/350 µs waveshape is also a commonly known
expression.
3.13
triggering voltage
U
T
voltage at which a VLD becomes conductive

3.14
nominal triggering voltage
U
Tn
voltage at which the VLD becomes conductive when a DC voltage is applied for long term
Note 1 to entry: This voltage is used to identify the VLD.
3.15
instantaneous triggering voltage
U
Ti
minimum triggering voltage at which the VLD becomes conductive shortly after its application
Note 1 to entry: A maximum delay of 5 ms is taken in this document.
3.16
non-triggering voltage
U
W
maximum voltage below which the VLD will not trigger for any duration of the applied voltage
3.17
residual voltage of a VLD
U
res
value of voltage that appears between the terminals of the VLD
during the passage of a specified current
3.18
combined voltage
voltage having significant AC and DC components
3.19
response time
T
R
time between the application of a voltage until VLD becomes
conductive
3.20
degree of protection
extent of protection provided by an enclosure against access to hazardous parts, against
ingress of solid foreign objects and/or against ingress of water and verified by standardized
test methods
[SOURCE: IEC 60529:1989, 3.3]
3.21
IP Code
coding system to indicate the degree of protection provided by an enclosure against access to
hazardous parts, ingress of solid foreign objects, ingress of water and to give an additional
information in connection with such protection
[SOURCE: IEC 60529:1989, 3.4]
4 Classes of VLD
This document identifies the properties and the technology of a VLD using the classes of VLD
which are defined in Table 1.
– 10 – IEC 62848-2:2019 © IEC 2019
Table 1 – Classes of voltage-limiting device
Able to
Auxiliary
Method for interrupt
power supply
switching between Maximum response time Recoverable the
Class necessary Polarity
the high and low T or not current
R
for normal
resistance status in the
operation
VLD
Can be
Welding shut of recoverable in
1 No Bidirectional 5 ms No
metallic parts some
a
conditions
Passive
5 ms
at natural
Triggering of
2.1 No Unidirectional Yes zero
(for voltages equal to or
thyristors
crossing
higher than U )
TI
of current
Passive
5 ms
at natural
Triggering of
2.2 No Bidirectional Yes zero
(for voltages equal to or
thyristors
crossing
higher than U )
TI
of current
Voltage dependent and
not exceeding the limits
given in IEC 62128-
3.1 Contactor only Yes Bidirectional Yes Yes
1:2013, 9.3.2.2 or
IEC 62128-3:2013, 7.2
through 7.5
Voltage dependent and
not exceeding the limits
3.2 Contactor only Yes Bidirectional given in IEC 62128- Yes Yes
1:2013, 9.3.2.3,
IEC 62128-3:2013, 7.6
Specified by the
3.3 Contactor only Yes Bidirectional manufacturer or the Yes Yes
purchaser
For voltages up to U ,
TI
voltage dependent and
not exceeding the limits
given in IEC 62128-
Combination of
1:2013, 9.3.2.2 or
4.1 thyristors and Yes Bidirectional Yes Yes
IEC 62128-3:2013, 7.2
contactor
through 7.5.
For voltages equal to or
higher than U 5 ms.
Ti
For voltages up to U ,
TI
voltage dependent and
not exceeding the limits
Combination of given in IEC 62128-
4.2 thyristors and Yes Bidirectional Yes Yes
1:2013, 9.3.2.3,
contactor
IEC 62128-3:2013, 7.6.
For voltages equal to or
higher than U 5 ms
Ti
Combination of Specified by the
4.3 thyristors and Yes Bidirectional manufacturer or the Yes Yes
contactor purchaser
NOTE IEC 62128-1 defines two functionalities for VLDs, VLD-O and VLD-F. In this document a discrimination
is not necessary.
a
For transient low currents associated with low energy dissipation no welding shut may occur.

5 Characteristics and requirements of the VLDs
5.1 Marking
VLDs shall be identified by the following minimum information which shall appear on the rating
plate (nameplate):
– manufacturer's name or trademark and manufacture type designation;

– class of VLD according to IEC 62848-2 (optional);
– rated current I in A;
r
– short time withstand current I in kA;
w
– nominal triggering voltage U ;
Tn
– year of manufacture;
– serial number.
The terminals of unidirectional devices shall be marked with the symbols + and -.
In case of small VLDs not having space for a rating plate with all information, the devices
shall be marked with the manufacturer’s name or trademark, the type designation and the
nominal triggering voltage. The remaining information shall be given in a data-sheet.
5.2 Service requirements
5.2.1 Normal outdoor service conditions
VLDs which conform to this document shall be suitable for operation under the following
normal service conditions:
– ambient temperature within the range of -40 °C to +40 °C;
– solar radiation lower than 1 120 W/m as given in IEC 62498-2;
– altitude not exceeding 1 400 m (from Annex B in IEC 61992-1:2006);
– any pollution not exceeding PD 4 as given in IEC 62497-1.
The equipment shall be suitable for installation in the vicinity of a rail track on foundations
designed so as to damp the main effects of the passage of the trains. Nevertheless, a limited
vibration or limited shocks may affect the equipment, which shall be capable of operating
satisfactorily when subjected to the following conventional accelerations separately applied:
– g : vertical acceleration:5 m/s ;
v
– g : horizontal acceleration:5 m/s .
h
5.2.2 Normal indoor service conditions
VLDs which conform to this document shall be suitable for operation under the following
normal service conditions:
– ambient temperature within the range of -5 °C to +40 °C (from Annex B in IEC 61992-
1:2006);
– altitude not exceeding 1 400 m (from Annex B in IEC 61992-1:2006);
– any pollution not exceeding PD3 as given in IEC 62497-1.
5.2.3 Abnormal service conditions
The following are examples of abnormal service conditions which require special
consideration in the manufacture or application of VLD and should be brought to the attention
of the supplier:
– temperature in excess of +40 °C or below -5 °C for indoor installations or below -40 °C for
outdoor installations;
– application at altitudes higher than 1 400 m; in this case the temperature-rise tests and
dielectric tests (for VLDs inside a cabinet), carried out at laboratories at lower levels, shall
take into account a correction in the temperature-rises and dielectric test values to be
agreed between the involved parties;

– 12 – IEC 62848-2:2019 © IEC 2019
– all excessive environmental conditions that may degrade insulating surface or mounting
hardware: fumes, vapours dirt, salt spray or other conducting materials; moisture,
humidity, dropping water or steam;
– explosive mixtures of dust, gases or fumes;
– special mechanical requirements (earthquakes, vibrations, high ice loads, high cantilever
stresses);
– unusual transportation or storage;
– heat sources near the VLD.
5.3 General characteristics
The following characteristics shall be defined to identify each VLD:
– the class of VLD;
– if relevant, the auxiliary power supply voltage, with its tolerances.
The manufacturer shall specify whether the device is recoverable or non-recoverable at
defined currents and durations.
5.4 Minimum requirements
5.4.1 Response time
A VLD shall become conductive in a time not greater than the specified response time
depending on the applied voltage. The response time of the VLD shall be stated as function of
the applied voltage.
For VLDs of Classes 2, 3 and 4 the triggering may be delayed intentionally in order that
unwanted triggering will not take place due to switching transients and similar phenomena.
5.4.2 Additional requirements for VLDs of Class 1
If gas discharge tubes are used in VLDs, they shall comply with IEC 61643-311.
5.4.3 Additional requirements for VLDs of Classes 3 and 4
The VLD shall not open if the current through it exceeds its breaking capacity.
The VLD shall open at an adjustable time after it has closed unless the breaking capacity is
exceeded. The range of variation of this time setting shall be specified.
If the VLD re-opens automatically and then re-triggers, after a set number of operations in a
given time interval either:
– it shall be prevented from re-opening and a warning or an alarm shall be signalled; or
– only a warning or an alarm shall be signalled.
The VLD shall provide the possibility to be manually operated at site.
If the VLD requires a power supply for operation, the VLD shall be provided with a failsafe
function such that it turns into the conductive state in case of failure of the power supply.
5.5 Electrical characteristics and thermal rating
In addition to the general characteristics indicated in 5.3, the manufacturer shall state the
following electrical characteristics of each type of VLD if applicable. In case of adjustable
parameters, the setting ranges shall be stated:

– for VLDs of Classes 3 and 4, the nominal voltages of the electric traction systems in which
the VLDs are to be installed;
– the nominal triggering voltage U ;
Tn
– the non-triggering voltage U ;
W
– the maximum response time as function of the voltage;
– the instantaneous triggering voltage U ;
Ti
– the maximum leakage current I at U , when the VLD is in its non-conducting state;
L W
– the short-time withstand current I and the duration of the current flow;
W
– the rated current I ;
r
– the maximum residual voltage at the short-time withstand current;
– the maximum residual voltage at the rated current;
– the conditions in which the VLD is recoverable;
– the lightning current impulse, or sequence of lightning impulses, which the VLD can
withstand in the specified test conditions;
– for VLDs of Classes 3 and 4, the breaking capacity, determined in accordance with 6.8;
– for VLDs of Classes 3 and 4, the making capacity, in accordance with 6.4.3.
5.6 Protection of VLDs against lightning
If requested by the purchaser the VLD shall withstand the effects of the specified lightning
surges. The requirements can be different according to the class of VLD. If necessary a surge
arrester, according to IEC 62848-1, may be integrated into the VLD.
5.7 Command and control (Classes 3 and 4 only)
5.7.1 Local control
On the cabinet, the following characteristics and measuring indications should be foreseen to
provide a monitoring and control locally:
a) the instantaneous DC voltage across the terminals of the VLD;
b) the instantaneous DC current flowing through the device;
c) the operating state of the VLD (open or closed);
d) a push or touch button to manually command the closing and the opening of the device;
e) a push or touch button to start a manual self-test (if possible);
f) access to recorded data as given in 5.7.3, the activations, warnings, alarms, etc., in the
past and stored in a register file (if applicable).
NOTE 1 Conventionally the voltage in item a) is the voltage on the rails relative to earth. This means that if the
rail potential is positive the figure displayed is positive.
NOTE 2 The manual self-test procedure in item e) will trigger the thyristor and will also close the contactor for a
limited time (typically 1 s).
5.7.2 Remote signalling
If remote signalling is requested at least the following signals shall be offered:
a) contactor open;
b) contactor closed;
c) warnings, alarms.
Further information may be agreed between purchaser and manufacturer such as current or
voltage.
– 14 – IEC 62848-2:2019 © IEC 2019
5.7.3 Operation and alarm recordings
Recordings are optional. A list of the recordings that can be stored is indicated as an example
in the following:
a) operation recordings:
1) the status of the VLD;
2) the total number of operations (1 operation = 1 x close + 1 x open);
b) alarm recordings with time stamp:
1) interruption of the auxiliary power supply of the device;
2) device in closed position state during a long period of time, eventually parameterised
in 2 or more levels;
3) internal operation faults: an internal self-diagnostic function controls the correct
functioning of closing and opening the device; in case of an internal fault, an alarm is
created;
4) the exceeding of a given frequency of operations, eventually parameterised in 2 or
more levels.
6 Type tests
6.1 General
The characteristics of the VLD shall be verified by type tests.
Type tests shall be carried out as indicated in Table 2. All tests are mandatory unless stated
otherwise.
Once made, these type tests need not be repeated unless the design is changed so as to
modify the VLD performance. In such a case only the relevant tests need be repeated.
For all the tests the ambient temperature shall be recorded.
An alternating current test is foreseen, if requested, because even if the VLD is not specified
to conduct AC, the wave-form of the current in the VLD can flow in both directions due to
ripple currents from the substations, tripping of the feeders during short-circuits or earth faults
in the DC power system, transient effects due to switching of the current by the trains,
regenerative braking currents of the trains or AC currents injected by AC power systems.

Table 2 – Type tests
Tests Classes of Subclause
VLD
Nominal triggering voltage and non-triggering voltage: 6.2
Procedure for welding shut spark gap VLDs 1 6.2.1
Procedure for thyristor type VLDs 2 6.2.2
Procedure for mechanical switching VLDs and for combined thyristor with 3, 4 6.2.3
mechanical switching devices
Leakage current 1, 2, 4 6.3
DC current withstand All 6.4
Procedure to determine long-term current All 6.4.2
Procedure to determine short time withstand All 6.4.3
AC current withstand characteristics All 6.5
(Optional)
Response time characteristics All 6.6
Lightning current withstand characteristics for VLDs exposed to direct lightning All 6.7
strikes
Recovery test 3, 4 6.8
Reverse voltage test 2.1 6.9
Dielectric test 3, 4 6.10
Degree of protection All 6.11
Environmental tests for outdoor equipment All 6.12
Determination of minimum current for safe short circuiting of Class 1 VLDs 1 6.13

The required number of samples and their conditions are specified in the individual
subclauses.
VLDs are considered to be of the same design if the following conditions are fulfilled:
– they are based on the same components resulting in the same performance
characteristics;
– they are characterised by similar construction resulting in equivalent heat dissipation
conditions whereas mounting or arrangement on the supporting structure may differ.
If not specified otherwise in the individual clauses, tests shall be carried out on the complete
VLD as used in service, i.e. with surge arrester in parallel, if applicable.
6.2 Nominal triggering voltage U and non-triggering voltage U
Tn W
6.2.1 Procedure for welding shut spark gap VLDs (Class 1)
6.2.1.1 General
This test shall be carried out on 3 samples of VLD in dry condition at 20 °C ± 15 °C.
6.2.1.2 Non-triggering voltage test
The non-triggering voltage U of the VLD shall be applied for a duration greater than 300 s.
W
This test shall be carried out at both polarities. The non-triggering voltage U should typically
W
be 80 % of U as given in Table A.1 (see Annex A).
Tn
– 16 – IEC 62848-2:2019 © IEC 2019
a) Pass criteria
No trigger shall occur.
6.2.1.3 Triggering voltage test
The test samples are connected to a DC voltage generator with a current ≥ 1 mA after
triggering but such that the device recovers after the trigger.
NOTE For VLD class 1 the nominal triggering voltage and the instantaneous triggering voltage are equal.
The test samples shall be further tested by applying a DC voltage increasing from 0 V with a
rise du/dt within 100 V/s up to 2 000 V/s according to IEC 61643-311 until the test sample
VLD triggers.
The procedure shall be repeated 5 times per sample for positive and negative polarity within a
period of 15 min.
The value of the trigger voltage shall be recorded.
a) Pass criteria
All measured triggering voltages are below or equal to the nominal triggering voltage U , no
Tn
mechanical destructions occurred and the VLD will not trigger for any duration when
non-triggering voltage U is applied. The nominal triggering voltage U should be in
W Tn
accordance with Table A.1.
6.2.2 Procedure for thyristor type VLDs (Class2)
6.2.2.1 General
This test shall be carried out on 3 samples of VLD in dry condition at 20 °C ± 15 °C. The test
shall be carried out at both polarities for bidirectional VLDs.
6.2.2.2 Non-triggering voltage test
The non-triggering voltage of the VLD shall be applied for a duration greater than 300 s. The
non-triggering voltage U should be 80 % of U as given in Table A.1.
W Tn
a) Pass criteria
No trigger shall occur.
6.2.2.3 Triggering and instantaneous triggering voltage test
The test samples shall be further tested by applying a DC voltage increasing from 0 V with a
rise to the:
– instantaneous triggering voltage within 5 ms;
– triggering voltage(s) according to a duration which is specified for the triggering voltage,
until the test sample VLD triggers.
The test of the triggering voltage(s) may be omitted, if the nominal triggering voltage
coincides with the instantaneous triggering voltage.

The procedure shall be repeated 5 times per sample for positive and negative polarity within a
period of 15 min. The value of the instantaneous triggering voltage and the triggering
voltage(s) shall be recorded.
a) Pass criteria
All measured triggering voltages are below or equal to the specified nominal triggering voltage
U . The nominal triggering voltage U should be in accordance with Table A.1.
Tn Tn
6.2.3 Procedure for mechanical switching VLDs and for combined thyristors with
mechanical switching devices VLDs (Class 3 and Class 4)
6.2.3.1 General
This test shall be carried out on 1 sample of VLD in dry condition at 20 °C ± 15 °C. The test
shall be carried out at both polarities for bidirectional VLDs.
6.2.3.2 Non-triggering voltage test
The non-triggering voltage of the VLD shall be applied for a duration greater than 300 s. The
non-triggering voltage U should be 80 % of U as given in Table A.1.
W Tn
a) Pass criteria
No trigger shall occur.
6.2.3.3 Triggering and instantaneous triggering voltage test
The test samples shall be further tested by applying a DC voltage increasing from 0 V with a
rise to the:
– instantaneous triggering voltage within 5 ms;
– triggering voltage(s) according to a duration which is specified for the triggering voltage
until the test sample VLD triggers.
The procedure shall be repeated 5 times per sample for positive and negative polarity within a
period of 15 min. The value of the instantaneous triggering voltage and the triggering
voltage(s) shall be recorded.
a) Pass criteria
All measured triggering voltages are below or equal to the specified instantaneous triggering
voltage U and the nominal triggering voltage(s) U . The instantaneous triggering voltage
TI Tn
U should be in accordance with Table A.2. The nominal triggering voltage U shall be in
TI Tn
accordance with Table A.1.
6.3 Leakage current
This test shall be carried out on one sample of VLD in dry condition at a temperature of
20 °C ± 15 °C for minimum duration of 1 min.
A DC voltage equal to the non-triggering voltage U of the VLD shall be applied and the
W
leakage current through the VLD shall be recorded. This test shall be carried out at both
polarities.
a) Pass criteria
The leakage current for each polarity should be within the specified limits of Table A.5.

– 18 – IEC 62848-2:2019 © IEC 2019
6.4 DC current withstand
6.4.1 General
The test is intended to check that the device withstands the rated current.
6.4.2 DC rated current test
This test shall be carried out on one VLD in dry condition at an ambient temperature of
20 °C ± 15 °C.
The DC rated current shall be applied to the VLD for a time duration of 60 min. Values of DC
rated current should be in the range of Table A.3.
The test sample shall be mounted and connected with connecting cables of equivalent cross-
section such that the current density of 1,5 A/mm² of copper or equivalent is not exceeded
based on the rated current.
The temperature of the device and its terminal temperatures shall be measured by at least 3
thermo elements or equivalent temperature sensors, one at each terminal and at least one on
the surface of the device. Good thermal conductivity shall be ensured between the sensor and
the surface of the VLD. The position of the temperature sensors shall be noted in the test
report.
The current, residual voltage and temperatures shall be monitored during the test and plotted
versus time in a diagram.
For VLDs of Classes 1, 3 and 4 the test current may also be an AC current with an RMS equal
to the specified DC test current.
The test comprises:
– select polarity;
...