Railway application - Fixed installations - D.C. surge arresters and voltage limiting devices - Part 3: Application Guide

This Application Guide supports the European Standards EN 50526 1 and EN 50526 2. Guidance is offered on the following subjects. – The selection and installation of surge arresters – The selection and installation of voltage limiting devices as VLD-O and VLD-F. – The arrangement of the surge arresters and VLDs Because of differences in the established, proven methods, electric traction systems of nominal voltage 600 V – 750 V are treated separately from the systems at higher nominal voltages. This application guide does not treat systems different from the d.c. electrified traction systems

Bahnanwendungen - Ortsfeste Anlagen - Überspannungsableiter und Spannungsbegrenzungseinrichtungen für Gleichspannungsnetze - Teil 3: Anwendungsleitfaden

Dieser Anwendungsleitfaden unterstützt die Europäischen Normen EN 50526 1 und EN 50526 2. Der Leitfaden ist auf folgende Themen ausgerichtet: – die Auswahl und Installation von Überspannungsableitern; – die Auswahl und Installation von Spannungsbegrenzungseinrichtungen als VLD-O und VLD-F; – die Anordnung von Überspannungsableitern und VLDs. Aufgrund der Unterschiede in den eingeführten und bewährten Methoden werden Bahnstromversorgungen mit einer Nennspannung von DC 600 V bis DC 750 V getrennt von Systemen mit höheren Nennspannungen behandelt. Dieser Anwendungsleitfaden gilt ausschließlich für Gleichstrom-Bahnenergieversorgungssysteme.

Applications ferroviaires - Installations fixes - Parafoudres et limiteurs de tension pour systèmes à courant continu - Partie 3: Guide d'application

Le présent guide d’application prend en charge les Normes européennes EN 50526-1 et EN 50526-2. Des lignes directrices sont données sur les points suivants: – Le choix et l’installation des parafoudres – Le choix et l’installation des limiteurs de tension tels que VLD-O et VLD-F. – Le montage des parafoudres et des limiteurs de tension Du fait des différences dans les méthodes établies et éprouvées, les réseaux de traction électrique de tension nominale de 600 V à 750 V sont traités séparément des réseaux à tensions nominales plus élevées. Le présent guide d’application ne traite pas des réseaux différents des réseaux de traction électrique à courant continu.

Železniške naprave - Stabilne naprave električne vleke - Enosmerni prenapetostni odvodniki in omejilniki napetosti - 3. del: Navodilo za uporabo

To navodilo za uporabo podpira evropska standarda EN 50526 1 in EN 50526 2.
Navodila so na voljo za naslednja področja:
– izbira in namestitev prenapetostnih odvodnikov,
– izbira in namestitev omejilnikov napetosti kot VLD-O in VLD-F,
– razvrstitev prenapetostnih odvodnikov in omejilnikov napetosti.
Zaradi razlik v uveljavljenih in dokazanih metodah se električni vlečni sistemi z nazivno napetostjo 600 V do 750 V obravnavajo ločeno od sistemov z višjo nazivno napetostjo.
To navodilo za uporabo ne obravnava sistemov drugače od enosmernih elektrificiranih vlečnih sistemov.

General Information

Status
Published
Publication Date
07-Jan-2016
Current Stage
6060 - Document made available
Due Date
07-Mar-2016

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SLOVENSKI STANDARD
SIST EN 50526-3:2016
01-junij-2016
äHOH]QLãNHQDSUDYH6WDELOQHQDSUDYHHOHNWULþQHYOHNH(QRVPHUQLSUHQDSHWRVWQL
RGYRGQLNLLQRPHMLOQLNLQDSHWRVWLGHO1DYRGLOR]DXSRUDER

Railway applications - Fixed installations - D.C. surge arresters and voltage limiting

devices - Part 3 Application guide
Ta slovenski standard je istoveten z: EN 50526-3:2016
ICS:
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST EN 50526-3:2016 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50526-3:2016
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SIST EN 50526-3:2016
EUROPEAN STANDARD EN 50526-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2016
ICS 29.120.50; 29.280
English Version
Railway application - Fixed installations - D.C. surge arresters
and voltage limiting devices - Part 3: Application Guide

Applications ferroviaires - Installations fixes - Parafoudres et Bahnanwendungen - Ortsfeste Anlagen -

limiteurs de tension pour systèmes à courant continu - Überspannungsableiter und
Partie 3: Guide d'application Spannungsbegrenzungseinrichtung für
Gleichspannungsnetze - Teil 3: Anwendungsleitfaden

This European Standard was approved by CENELEC on 2015-12-07. 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.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 50526-3:2016 E
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SIST EN 50526-3:2016
EN 50526-3:2016 (E)
Content Page

European foreword .......................................................................................................................................... 4

Introduction ...................................................................................................................................................... 5

1 Scope ................................................................................................................................................. 6

2 Normative references ....................................................................................................................... 6

3 Terms and definitions....................................................................................................................... 7

4 General considerations .................................................................................................................. 13

4.1 General ............................................................................................................................................. 13

4.2 Application of surge arresters ....................................................................................................... 14

4.2.1 General ............................................................................................................................................. 14

4.2.2 Insulation level of equipment to be protected ............................................................................. 14

4.2.3 Internal overvoltages ...................................................................................................................... 14

4.2.4 Lightning Overvoltages .................................................................................................................. 15

4.3 Application of VLDs ........................................................................................................................ 16

4.3.1 General ............................................................................................................................................. 16

4.3.2 Short term protection ..................................................................................................................... 16

4.3.3 Long term protection ...................................................................................................................... 17

4.3.4 Selection of VLD-F or VLD-O ......................................................................................................... 17

5 Symbols for surge arresters and VLDs ........................................................................................ 17

6 Guideline for Surge Arresters ....................................................................................................... 18

6.1 General ............................................................................................................................................. 18

6.1.1 Electrical characteristics ............................................................................................................... 18

6.1.2 Housing ............................................................................................................................................ 19

6.1.3 Porcelain-housed surge arresters ................................................................................................ 19

6.1.4 Polymer-housed surge arresters .................................................................................................. 19

6.2 Systems and equipment to be protected by surge arresters ..................................................... 20

6.3 Nominal discharge current I ......................................................................................................... 23

6.4 Selection of Continuous Operating Voltage ................................................................................ 23

6.4.1 Continuous operating voltage U for arresters A1 ...................................................................... 23

6.4.2 Continuous operating voltage U for arresters A2 ...................................................................... 24

6.5 Protective level of A1 and A2 arresters. ....................................................................................... 24

6.6 Charge transfer capability ............................................................................................................. 27

6.6.1 General ............................................................................................................................................. 27

6.6.2 Typical overvoltages during clearing a line fault ........................................................................ 27

6.6.3 Arrester A1 ...................................................................................................................................... 33

6.6.4 Arrester A2 ...................................................................................................................................... 34

6.7 Procedure to select an A1 arrester ............................................................................................... 34

6.8 Procedure to select an A2 arrester ............................................................................................... 38

6.9 Connecting leads of arresters ....................................................................................................... 38

6.10 Earthing requirements.................................................................................................................... 38

7 Guideline for VLDs .......................................................................................................................... 39

7.1 Introduction ..................................................................................................................................... 39

7.2 General ............................................................................................................................................. 40

7.3 Mass transit railways and trams (U up to d.c. 750 V) ................................................................ 40

7.3.1 General ............................................................................................................................................. 40

7.3.2 Trams with OCL .............................................................................................................................. 40

7.3.3 Metros with a conductor rail .......................................................................................................... 42

7.3.4 Light-rail metros with OCLs ........................................................................................................... 43

7.4 Railways (d.c. 1 500V … d.c. 3 000 V) ........................................................................................... 43

7.4.1 General ............................................................................................................................................. 43

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7.4.2 Application of VLDs along the lines or at the substations and in the sectioning posts ......... 43

7.4.3 Recommended characteristics of VLDs ....................................................................................... 45

7.5 Workshops ...................................................................................................................................... 46

7.5.1 Application of VLD-O ...................................................................................................................... 46

7.5.2 Application of VLD-F ...................................................................................................................... 46

8 Further considerations ................................................................................................................... 46

8.1 Installation recommendations ....................................................................................................... 46

8.1.1 Mounting aspect ............................................................................................................................. 46

8.1.2 Periodicity of inspection and management of alarms ................................................................ 48

8.1.3 Colours of the cables ..................................................................................................................... 49

8.2 Interaction between arresters and VLDs ...................................................................................... 49

8.3 Interaction with other systems ...................................................................................................... 49

8.3.1 Interaction with signalling systems .............................................................................................. 49

8.3.2 Interaction with earthing systems ................................................................................................. 50

8.3.3 Interaction with tunnel earthing systems ..................................................................................... 50

8.3.4 Separation of a.c. cable screens ................................................................................................... 50

Bibliography ................................................................................................................................................... 51

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SIST EN 50526-3:2016
EN 50526-3:2016 (E)
European foreword

This document (EN 50526-3:2016) has been prepared by CLC/SC 9XC, "Electric supply and earthing

systems for public transport equipment and ancillary apparatus (Fixed installations)", of CLC/TC 9X,

"Electrical and electronic applications for railways".
The following dates are fixed:
• latest date by which this document has to be (dop) 2016-12-07
implemented at national level by publication of
an identical national standard or by
endorsement
• latest date by which the national standards (dow) 2018-12-07
conflicting with this document have to
be withdrawn

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.
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SIST EN 50526-3:2016
EN 50526-3:2016 (E)
Introduction
This European Standard is divided into three parts.

Part 1 deals with metal oxide arresters without gaps for d.c. railway traction systems (fixed installations)

and is based on EN 60099-4.

Part 2 deals with voltage limiting devices for specific use in d.c. railway traction systems (fixed

installations).

Part 3 is a Guide of application of metal-oxide arresters and of voltage limiting devices.

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EN 50526-3:2016 (E)
1 Scope

This Application Guide supports the European Standards EN 50526-1 and EN 50526-2.

Guidance is offered on the following subjects:
– the selection and installation of surge arresters;
– the selection and installation of voltage limiting devices as VLD-O and VLD-F;
– the arrangement of the surge arresters and VLDs.

Because of differences in the established, proven methods, electric traction systems of nominal voltage

d.c. 600 V – d.c. 750 V are treated separately from the systems at higher nominal voltages.

This Application Guide only applies to d.c. electrified traction systems
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.

EN 50122-1:2011, Railway applications - Fixed installations - Electrical safety, earthing and the return

circuit - Part 1: Protective provisions against electric shock

EN 50122-2:2010, Railway applications - Fixed installations - Electrical safety, earthing and the return

circuit - Part 2: Provisions against the effects of stray currents caused by d.c. traction systems

EN 50123-2:2003, Railway applications - Fixed installations - D.C. switchgear - Part 2: D.C. circuit

breakers

EN 50123-7-1:2003, Railway applications - Fixed installations - D.C. switchgear - Part 7-1:

Measurement, control and protection devices for specific use in d.c. traction systems - Application guide

EN 50124-1:2001, Railway applications - Insulation coordination - Part 1: Basic requirements -

Clearances and creepage distances for all electrical and electronic equipment
EN 50163: 2004 , Railway applications - Supply voltages of traction systems

EN 50526-1:2012, Railway applications - Fixed installations - D.C. surge arresters and voltage limiting

devices - Part 1: Surge arresters

EN 50526-2:2014, Railway applications - Fixed installations - D.C. surge arresters and voltage limiting

devices - Part 2: Voltage limiting devices
EN 62305-2, Protection against lightning - Part 2: Risk management.

IEC 60050-195:1998, International Electrotechnical Vocabulary - Chapter 195: Earthing and protection

against electric shock

IEC 60050-441:1984, International Electrotechnical Vocabulary - Chapter 441: Switchgear, controlgear

and fuses

IEC 60050-604:1987, International Electrotechnical Vocabulary. Chapter 604: Generation, transmission

and distribution of electricity - Operation
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IEC 60050-811:1991, International Electrotechnical Vocabulary - Chapter 811: Electric traction

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nominal voltage
designated value for a system
[SOURCE: EN 50163:2004, 3.3]
3.2
highest permanent voltage
max1
maximum value of the voltage likely to be present indefinitely
[SOURCE: EN 50163:2004, 3.4]
3.3
highest non-permanent voltage
max2
maximum value of the voltage likely to be present for a limited period of time
[SOURCE: Adapted from EN 50163:2004, 3.5]
3.4
rated insulation voltage

d.c withstand voltage value assigned by the manufacturer to the equipment or a part of it, characterising

the specified permanent (over five minutes) withstand capability of its insulation

[SOURCE: EN 50526-1:2012, 3.4]
3.5
rated impulse withstand voltage

impulse voltage value assigned by the manufacturer to the equipment or a part of it, characterising the

specified withstand capability of its insulation against transient overvoltages
[SOURCE: EN 50526-1:2012, 3.5]
3.6
overvoltage

voltage having a peak value exceeding the corresponding peak value of the highest non-permanent

voltage U
max2
[SOURCE: EN 50526-1:2012, 3.6]
3.7
transient overvoltage

short duration overvoltage of a few (up to 20 ms) milliseconds or less associated with a transient regime

Note 1 to entry: Two particular transient overvoltages are defined: switching overvoltage and lightning overvoltage.

[SOURCE: EN 50526-1:2012, 3.7]
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3.8
switching overvoltage

transient overvoltage at any point of the system due to specific switching operation or fault

[SOURCE: EN 50526-1:2012, 3.8]
3.9
lightning overvoltage
transient overvoltage at any point of the system due to a lightning discharge
[SOURCE: EN 50124-1:2001,1.3.3.2.2]
3.10
surge arrester
device intended to limit the transient overvoltages to a specified level
[SOURCE: EN 50526-1:2012, 3.10]
3.11
metal-oxide surge arrester

arrester having non-linear metal-oxide resistors connected in series and/or in parallel without any

integrated series or parallel spark gaps
[SOURCE: EN 50526-1:2012, 3.11]
3.12
continuous operating voltage of an arrester

designated permissible d.c. voltage value that may be applied continuously between the arrester

terminals
[SOURCE: EN 50526-1:2012, 3.12]
3.13
rated voltage of an arrester
voltage by which the arrester is designated

Note 1 to entry: Because of the particular nature of the d.c. electrical installation dealt with, the rated voltage of a

d.c. arrester coincides with the continuous operating voltage.
[SOURCE: EN 50526-1:2012, 3.13]
3.14
lightning impulse protection level
the maximum residual voltage for the nominal discharge current
[SOURCE: EN 50526-1:2012, 3.15]
3.15
switching impulse protection level
maximum residual voltage at the specified switching impulse current
[SOURCE: EN 50526-1:2012, 3.16]
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3.16
charge transfer capability

maximum charge per impulse that can be transferred during the charge transfer test and during the

operating duty test
[SOURCE: EN 50526-1:2012, 3.17]
3.17
discharge current of an arrester
impulse current which flows through the arrester
[SOURCE: EN 50526-1:2012, 3.18]
3.18
nominal discharge current of an arrester
peak value of lightning current impulse which is used to classify an arrester
[SOURCE: EN 50526-1:2012, 3.19]
3.19
high current impulse of an arrester

peak value of discharge current having a 4/10 µs impulse shape which is used to test the stability of the

arrester on direct lightning strikes
[SOURCE: EN 50526-1:2012, 3.20]
3.20
steep current impulse

current impulse with a virtual front time of 1 µs with limits in the adjustment of equipment such that the

measured values are from 0,9 µs to 1,1 µs and the virtual time to half-value on the tail is not longer than

20 µs
[SOURCE: EN 50526-1:2012, 3.21]
3.21
lightning current impulse

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

[SOURCE: EN 50526-1:2012, 3.22]
3.22
direct lightning current impulse
impulse defined by the charge Q and the peak value of the current impulse I
imp
[SOURCE: EN 50526-1:2012, 3.23]
3.23
switching current impulse of an arrester

peak value of discharge current having a virtual front time greater than 30 µs but less than 100 µs and a

virtual time to half value on the tail of roughly twice the virtual front time
[SOURCE: EN 50526-1:2012, 3.24]
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3.24
porcelain-housed arrester
arrester using porcelain as housing material, with fittings and sealing systems
[SOURCE: EN 50526-1:2012, 3.30]
3.25
polymer-housed arrester
arrester using polymeric and/or composite materials for housing
[SOURCE: EN 50526-1:2012, 3.31]
3.26
flashover
disruptive discharge over a solid surface
[SOURCE: EN 50526-1:2012, 3.44]
3.27
impulse

unidirectional wave of voltage or current which without appreciable oscillations rises rapidly to a

maximum value and falls – usually less rapidly – to zero with small, if any, excursions of opposite

polarity

Note 1 to entry: The parameters which define a voltage or current impulse are polarity, peak value, front time and

time to half value on the tail.
[SOURCE: EN 50526-1:2012, 3.45]
3.28
voltage-limiting device
VLD

protective device whose function is to prevent existence of an impermissible high touch voltage

[SOURCE: EN 50122-1:2011, 3.1.20]
3.29
recoverable VLD
VLD that recovers after triggering
[SOURCE: EN 50526-2:2014, 3.2]
3.30
non-recoverable VLD
VLD remaining in its low resistance state permanently after triggering
[SOURCE: EN 50526-2:2014, 3.3]
3.31
welding-shut spark gap
voltage fuse

VLD which triggers by electrical discharge across a gap causing a permanent short-circuit by melting of

metallic parts
[SOURCE: EN 50526-2:2014, 3.4]
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3.32
rated current

maximum value of the direct current that may flow permanently through the VLD in specified

environmental conditions
[SOURCE:EN 50526-2:2014, 3.5]
3.33
short time withstand current

current that a VLD can carry in closed status, during a specified short time under prescribed conditions

of use and behaviour
[SOURCE: EN 50526-2:2014, 3.6]
3.34
breaking capacity
maximum current that a recoverable VLD can interrupt at a stated voltage
[SOURCE: IEC 60050-441:1984, 17-08]
3.35
residual voltage
res

a) peak value of voltage that appears between the terminals of an arrester during the passage of

discharge current

b) value of voltage that appears between the terminals of the VLD during the passage of a specified

current
[SOURCE: EN 50526-1:2012, 3.27] and [SOURCE: EN 50526-2:2014, 3.17]
3.36
structure earth

construction made of metallic parts or construction including interconnected metallic structural parts,

which can be used as an earth electrode
[SOURCE: EN 50122-1:2011, 3.2.4]
3.37
open connection

connection of conductive parts to the return circuit by a voltage-limiting device which makes a

conductive connection either temporarily or permanently if the limited value of the voltage is exceeded

[SOURCE: EN 50122-1:2011, 3.2.12]
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3.38
return circuit
all conductors which form the intended path for the traction return current
EXAMPLE Conductors may be:
– running rails,
– return conductor rails,
– return conductors,
– return cables.
[SOURCE: EN 50122-1:2011, 3.3.1]
3.39
rail potential
voltage occurring between running rails and earth
[SOURCE: EN 50122-1:2011, 3.3.7]
3.40
(traction) substation

installation to supply a contact line system and at which the voltage of a primary supply system, and in

certain cases the frequency, is transformed to the voltage and the frequency of the contact line

[SOURCE: EN 50122-1:2011, 3.4.2]
3.41
(traction) switching station

installation from which electrical energy can be distributed to different feeding sections or from which

different feeding sections can be switched on and off or can be interconnected
[SOURCE: EN 50122-1:2011, 3.4.3]
3.42
normal operation
operation without fault condition on the line

Note 1 to entry: In this standard normal operation includes also degraded mode (loss of one or several substations)

3.43
fault (or fault condition)

non intended condition caused by short-circuit. The time duration is terminated by the correct function of

the protection devices and circuit breakers

Note 1 to entry: For the relevant fault duration the correct operation of protection devices and circuit breakers is

taken into account.
[SOURCE: Adapted from EN 50122-1:2011, 3.4.5]
3.44
internal overvoltage

an overvoltage in the system resulting from switching or from a fault in the system itself

[SOURCE: IEC 60050-604:1987, 03-31]
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3.45
short-circuit

accidental or intentional conductive path between two or more conductive parts forcing the electric

potential differences between these conductive parts to be equal to or close to zero

[SOURCE: IEC 60050-195:1998, 04-11]
3.46
stray current

part of the current caused by a d.c.-traction system which follows paths other than the return circuit

[SOURCE: Adapted from EN 50122-1:2011, 3.6.3]
3.47
overhead contact line
OCL

contact line placed above (or beside) the upper limit of the vehicle gauge and supplying vehicles with

electric energy through roof-mounted current collection equipment
[SOURCE: IEC 60050-811:1991, 33-02]
3.48
conductor rail

contact line made of a rigid metallic section or rail, mounted on insulators located near the running rails

[SOURCE: EN 50119:2009, 3.1.7]
3.49
overhead contact line zone
OCLZ
zone whose limits are in general not exceeded by a broken overhead contact line
[SOURCE: EN 50122-1:2011, 3.5.9]
3.50
current collector zone
CCZ

zone whose limits are in general not exceeded by an energised collector no longer in contact with the

contact line or broken collector and its fragments
[SOURCE: EN 50122-1:2011, 3.5.10]
4 General considerations
4.1 General

Surge arresters are intended to protect power equipment from the lightning overvoltages. A surge

arrester can be used also in order to protect electronic equipment against high transient voltages in the

circuits to which the equipment is connected. See EN 50526-1 for the product specification.

VLDs are intended to protect persons from impermissible touch voltages between conductive parts

caused by train operating currents or faults. When selecting a VLD, it should be considered whether the

required function is VLD-F, or VLD-O or both as described in EN 50122-1. This is a question for the

system design. See EN 50526-2 for the product specification.
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4.2 Application of surge arresters
4.2.1 General

The contact lines of electric railways are exposed to direct and to indirect lightning overvoltages. These

overvoltages may cause flashover of the line insulation and, travelling along the lines, may enter the

supply substations and stress or even damage the insulation of the equipment inside. Overvoltages may

also appear on the track and, travelling along it, stress the insulation of the electronic equipment

connected to it.

The insulation of the substation equipment is critical, as flashover of such insulation in most cases

causes a permanent outage of the substation. Also the insulation of the equipment connected to the

track is critical as it is not self-restoring. Such equipment should be protected by surge arresters of such

characteristics as to reduce the overvoltages below its insulation level.

Flashover of the line insulation is in general non critical. The flash over initiates a short circuit of the

power supply system which is then cleared by the protective circuit breaker. In most cases the insulation

is self-restoring and the line can be re-energized after a short time (a few seconds) following the tripping

Therefore, line insulation does not require to be protected by surge arresters except in special cases:

...

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