SIST-TS CLC/TS 50544:2014

SLOVENSKI STANDARD
SIST-TS CLC/TS 50544:2014
01-julij-2014
1L]NRQDSHWRVWQLHQRVPHUQLSUHQDSHWRVWQLRGYRGQLNL]DVLVWHPHHOHNWULþQHYOHNH
,]ELUDLQSUDYLODXSRUDEH]DSUHQDSHWRVWQHRGYRGQLNH
Low voltage d.c. surge protective device for traction systems - Selection and application
rules for surge arresters
Parafoudres basse tension courant continu pour traction - Principes de choix et
d’application pour les parafoudres
Ta slovenski standard je istoveten z: CLC/TS 50544:2010
ICS:
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST-TS CLC/TS 50544:2014 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS CLC/TS 50544:2014

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SIST-TS CLC/TS 50544:2014

TECHNICAL SPECIFICATION
CLC/TS 50544

SPÉCIFICATION TECHNIQUE
February 2010
TECHNISCHE SPEZIFIKATION

ICS 29.120.50; 29.280


English version


Low voltage d.c. surge protective device for traction systems -
Selection and application rules for surge arresters



Parafoudres basse tension courant Überspannungsschutzgeräte
continu pour traction - für Niederspannungs-Gleichstrom-
Principes de choix et d’application Bahnsysteme -
pour les parafoudres Auswahl und Anwendungsregeln
für Überspannungsableiter






This Technical Specification was approved by CENELEC on 2009-12-25.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to
make the TS available promptly at national level in an appropriate form. It is permissible to keep conflicting
national standards in force.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.



CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: Avenue Marnix 17, B - 1000 Brussels


© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TS 50544:2010 E

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Foreword
This Technical Specification was prepared by the Technical Committee CENELEC TC 37A,
Low voltage surge protective devices.
It also concerns the expertise of SC 9XC, Electric supply and earthing systems for public transport
equipment and ancillary apparatus (Fixed installations), of Technical Committee CENELEC TC 9X,
Electrical and electronic applications for railways.
The broad subject of overvoltage protection in d.c. traction systems need to address the approaches,
requirements and definitions of several disciplines and TC’s. Concerned European Standards are
referenced for generic definitions.
This Technical Specification reflects the common practise of overvoltage protection in the d.c. traction
community, as far as protection of equipment in the primary power supply is concerned (e.g. feeders,
overhead contact lines, return circuits, power side of rolling stock).
Therefore, definitions and approaches in this Technical Specification, covering a specific application in
line with EN 50526-1, are different for some aspects from the definitions and approaches in the
EN 61643 series.
The text of the draft was circulated for voting in accordance with the Internal Regulations, Part 2,
Subclause 11.3.3.3. and was approved by CENELEC as CLC/TS 50544 on 2009-12-25.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following date is proposed:
– latest date by which the existence of the CLC/TS

has to be announced at national level
(doa) 2010-06-25
1)
This Technical Specification will be withdrawn once the SC 9XC document on the same subject is
published.
__________
———————
1)
Under development at the time of issue.

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Contents
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
3.1 System voltages . 5
3.2 Arrester . 7
4 Systems and equipment to be protected . 9
4.1 General . 9
4.2 Substations . 9
4.3 Overhead contact line system .10
4.4 Return circuit .11
4.5 Rolling stock .12
5 Supply voltages .13
6 Overvoltages .13
6.1 Lightning overvoltages .13
6.2 Switching overvoltages .14
7 Function and characteristics of MO surge arresters .14
7.1 Basic function .14
7.2 Characteristics .15
7.3 Classification .16
8 Insulation co-ordination and application of MO surge arresters .17
8.1 General .17
8.2 Principles of insulation co-ordination .17
8.3 Protective distance .19
8.4 Protection level .22
8.5 Surge arresters connected in parallel .22
9 Selection of MO surge arresters .23
9.1 Continuous operating voltage U .23
c
9.2 Arrester class .23
9.3 Mechanical considerations .23
Annex A (informative) Supply voltages .24
Bibliography .25

Figures
Figure 1 – Protective circuit in a substation (principle arrangement) .10
Figure 2 – Principle of a protective circuit of a line (outdoor system) .11
Figure 3 – Installation of surge arresters on the overhead contact line and the running rails .12
Figure 4 – Surge arrester arrangement on a vehicle .13
Figure 5 – Current-voltage characteristic of an MO surge arrester .15
Figure 6 – Requirements and design of surge arresters .17
Figure 7 – Assumption for the calculation of the voltage at the open end of a line and for the
determination of the protective distance L .20
Figure 8 – Voltage funnel and illustration of protective distance .21

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Tables
Table 1 – Arrester classification and related parameters. .16
Table 2 – Insulation levels .18
Table A.1 – Supply voltages .24

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1 Scope
This Technical Specification applies to non linear metal-oxide resistor type surge arresters (MO surge
arresters) without spark gaps designed to limit voltage surges on d.c. traction systems with nominal
voltage up to 1 500 V.
This Technical Specification applies to protection of equipment.
Same principles for selection and application apply for MO surge arresters on d.c. traction systems
with nominal voltage 3 000 V.
2 Normative references
The following referenced documents are indispensable for the application 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.
EN 50122-2 Railway applications – Fixed installations – Part 2: Protective provisions against
the effects of stray currents caused by d.c. traction systems
EN 50124-1 Railway applications – Insulation coordination – Part 1: Basic requirements –
Clearances and creepage distances for all electrical and electronic equipment
EN 50163 Railway applications – Supply voltages of traction systems
1)
EN 50526-1 Railway applications – Fixed installations – D.C. surge arresters and voltage
limiting devices – Part 1: Surge arresters
EN 60071-1 Insulation co-ordination – Part 1: Definitions, principles and rules (IEC 60071-1)
EN 62305-3 Protection against lightning – Part 3: Physical damage to structures and life
hazard (IEC 62305-3, mod.)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 System voltages
3.1.1
nominal voltage
U
n
designated value for a system
[EN 50163]
3.1.2
highest permanent voltage
U
max1
maximum value of the voltage likely to be present indefinitely
[EN 50163]
———————
1)
 At draft stage.

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3.1.3
highest non permanent voltage
U
max2
maximum value of the voltage likely to be present as highest non permanent voltage for a limited
period of time
[EN 50163]
3.1.4
highest long term overvoltage
U
max3
voltage defined as the highest value of the long-term overvoltage for t = 20 ms. This value is
independent from frequency
[EN 50163]
3.1.5
rated insulation voltage
U
Nm
d.c. withstand voltage value assigned by the manufacturer to the equipment or part of it, characterizing
the specified permanent (over five minutes) withstand capability of its insulation
[EN 50124-1, mod.]
3.1.6
rated impulse voltage
U
Ni
impulse voltage value assigned by the manufacturer to the equipment or a part of it, characterizing the
specified withstand capability of its insulation against transient overvoltages
[EN 50124-1]
3.1.7
overvoltage
any voltage having a peak value exceeding the corresponding peak value (including recurrent
overvoltages) of maximum steady-state voltage at normal operating conditions
[EN 50124-1]
3.1.8
long-term overvoltage
overvoltage higher than U lasting typically more than 20 ms, due to low impedance phenomena
max2
e.g. a rise in substation primary voltage
[EN 50163]
3.1.9
transient overvoltage
short duration overvoltage of a few milliseconds or less due to current transfers
[EN 50124-1]
3.1.10
switching overvoltage
transient overvoltage at any point of the system due to specific switching operation or fault
[EN 50124-1]
3.1.11
lightning overvoltage
transient overvoltage at any point of the system due to a specific lightning discharge
[EN 50124-1]

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3.2 Arrester
3.2.1
surge protective device
SPD
device that is intended to limit transient overvoltages and divert surge currents. It contains at least one
nonlinear component
[EN 61643-11]
3.2.2
voltage limiting type SPD
SPD that has a high impedance when no surge is present, but will reduce it continuously with
increased surge current and voltage. Common examples of components used as nonlinear devices
are varistors and suppressor diodes. These SPDs are sometimes called “clamping type”
[EN 61643-11]
3.2.3
surge arrester
device intended to limit transient overvoltages to a specified level
NOTE Surge arrester, or shorter “arrester”, is a more general term for metal-oxide surge arrester (see 3.2.4). Surge arresters
contain one or more nonlinear metal-oxide resistors (MO resistor). A nonlinear metal-oxide resistor (MO resistor) is the same as
a variable metal-oxide resistor (MO varistor).
[EN 50526-1]
3.2.4
metal-oxide surge arrester without gaps
arrester having non-linear metal-oxide resistors connected in series and/or in parallel without any
integrated series or parallel spark gaps
[EN 60099-4]
3.2.5
maximum continuous operating voltage of an arrester

U
c
designated permissible value of d.c. voltage that may be applied continuously between the arrester
terminals
[EN 60099-4, mod.]
3.2.6
rated voltage of an arrester
U
r
voltage by which the arrester is designated. For d.c. traction systems the rated voltage is the
maximum continuous operating voltage
[EN 60099-4, mod.]
3.2.7
charge transfer capability
maximum charge per impulse that can be transferred during the charge transfer test and during the
operating duty test
[EN 50526-1, mod.]
3.2.8
discharge current of an arrester
impulse current which flows through the arrester
[EN 50526-1]

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3.2.9
nominal discharge current of an arrester
I
n
peak value of lightning current impulse which is used to classify an arrester
[EN 60099-4]
3.2.10
high current impulse of an arrester
peak value of discharge current having a 4/10 µs impulse shape
[EN 60099-4]
3.2.11
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 shall be not
longer than 20 µs
[EN 60099-4]
3.2.12
lightning current impulse
8/20 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
[EN 60099-4]
3.2.13
direct lightning current impulse
impulse defined by the charge Q and the peak value of the current impulse I
imp
[EN 50526-1]
3.2.14
long duration current impulse
rectangular impulse which rises rapidly to maximum value, remains substantially constant for a
specified period and then falls rapidly to zero
[EN 60099-4]
3.2.15
switching current impulse of an arrester
the 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
[EN 60099-4]
3.2.16
continuous current of an arrester
I
c
current flowing through the arrester when energized at the continuous operating voltage
[EN 60099-4]
3.2.17
reference current of an arrester
I
ref
d.c. current defined by the manufacturer used to determine the reference voltage of the arrester
[EN 60099-4, mod.]

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3.2.18
reference voltage of an arrester
U
ref
d.c. voltage applied to the arrester to obtain the reference current
[EN 60099-4, mod.]
3.2.19
residual voltage of an arrester
U
res
peak value of voltage that appears between the terminals of an arrester during the passage of
discharge current
[EN 60099-4]
4 Systems and equipment to be protected
4.1 General
Electrical traction d.c. systems should be protected against overvoltages by surge arresters. Main field
of application are in substations, at sectioning posts and at singular points along the contact lines.
The terminations of the insulated cables connected to the contact line system and the electronic
apparatuses connected to the return pole of the rectifier in the substations should be protected by
surge arresters.
4.2 Substations
An important element of a lightning protection concept is the protection of the line feeders and return
conductors in the substations with arresters (see Figure 1). The arresters have the following functions.
• The arresters A1, which are connected in the substation between the feeder circuit-breakers
(cable connection) and the return circuit, reduce the overvoltages at the feeder circuit-breakers
and the rectifiers, inclusive of their measuring and monitoring devices, in case of positive lightning
strokes. In case of negative lightning strokes the diodes of the rectifier are conductive, but this
does not endanger the elements.
• The arrester A2 between the return circuit and the structure earth is to limit overvoltages of the
running rails. The arrester A2 is also important in case of direct lightning strokes into the running
rails, e.g. if lines above earth have a conductor rail. The arrester A2 is not intended for protection
against electric shock coming from impermissible rail potential.
NOTE Protection against electric shock is considered in EN 50526-2. When arresters A2 and protective devices as per
EN 50526-2 are used at the same place, a coordination of both low voltage protective devices is needed (under consideration).

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Key
1 feeder
2 return conductor
3 arrester A1
4 arrester A2
5 MEB
6 earth resistance
Figure 1 – Protective circuit in a substation (principle arrangement)
4.3 Overhead contact line system
Surge arresters should be installed between the overhead contact line system or return circuit and
earth where discontinuities in the line are present and reflections of the overvoltage waves can occur,
in particular (see Figure 2):
• at each feeding switch-disconnector or disconnector;
• along the line, at both sides of a normally open switch-disconnector or disconnector (bridging a
section-insulator);
• in the line, at a normally closed switch-disconnector or disconnector (bridging a section-insulator);
• at the ends of a section;
• at power demand points (e.g. for switch heating).
Additional arresters can be necessary for track sections where frequent lightning strokes are likely, for
instance on bridges or on elevated lines, and cross country lines.

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The arresters A1 are preferably fitted at the height of the overhead contact line so that the electrical
connection to the overhead contact line can be led in a short, straight way. Moreover, the arresters A1
are connected to the earth electrodes as directly as possible (see Figure 3). The arresters A1 and the
cable between the arresters and the earth electrodes are insulated against the mast of the overhead
contact line or the structure earth.

Key
1 arrester A1
2 current tap, e.g. switch heater
3 feeder from the substation
Figure 2 – Principle of a protective circuit of a line (outdoor system)
4.4 Return circuit
For stray current reasons the return circuit is not connected to earthing installations or earth according
to EN 50122-2.
Running rails
To reduce the stray current corrosion, the resistance to earth of the running rails has to be high for d.c.
traction systems. Consequently, the running rails are not suited as earth electrodes for lightning
protection. Therefore, either low-resistance pole foundations, driven pipes as well as the reinforcement
of tracks of reinforced concrete or separate buried earth electrodes are to be used as earth electrodes
for lightning protection along the line dependent on the local conditions. Earthing resistance ≤ 10 Ω is
regarded as sufficient (see for instance EN 62305-3).
It has to be born in mind that the discharged lightning energy may also appear on the tracks and that
this can endanger the electrical or electronic equipment (e.g. switch controllers, signalling equipment,
switch heaters) that is fitted near the tracks or in the tracks. This hazard can only be minimised if the
equipment is provided with additional surge arresters against overvoltages.

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a) Protection of the overhead contact line b) Protection of the overhead contact line and the
running rail (return conductor)
Key
1 arrester A1
2 arrester A2
In both cases the running rails are insulated against earth.
Figure 3 – Installation of surge arresters on the overhead contact line and the running rails
4.5 Rolling stock
Surge arresters are installed on the vehicle roof close to the current collector, as shown in Figure 4.

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Key
1 overhead contact line
2 current collector
3 arrester A1
4 main circuit breaker
5 electrical equipment of traction vehicle
6 vehicle body
Figure 4 – Surge arrester arrangement on a vehicle
5 Supply voltages
The relevant values for the supply voltages of the traction systems with the relevant admissible
voltage ranges are given in EN 50163. See Table A.1.
6 Overvoltages
6.1 Lightning overvoltages
Traction systems can be treated the same as medium voltage distribution systems with respect to
overvoltages and insulation co-ordination.
Lightning parameters are derived from statistical analysis of worldwide lightning measurements. The
mostly occurring negative cloud-to-ground flashes have current peak values between 14 kA (95 %
probability) and 80 kA (5 % probability). With a probability of 50 % the following values are reached or
exceeded (see for instance Cigré TB 287):
Current peak value: 30 kA
Rise time: 5,5 µs
Time to half value: 75 µs

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Extreme lightning’s can reach peak values up to 200 kA, with half-time values of 2 000 µs. A peak
value of 20 kA with a probability of 80 % is often used in the standardisation work, and for test and
co-ordination purposes for surge arresters. This standardized nominal lightning current has a rise time
of 8 µs and a half time of 20 µs (wave shape 8/20).
Other standardized currents are the high current impulse with the wave shape 4/10 and peak values
up to 100 kA, and the switching current impulse with 30/60 wave shape and up to peak values of 2 kA.
A specific wave shape 10/350 for direct lightning is also defined (see EN 50526-1). Normally, there is
flash over at each pole (see below) leading after a few spans to an 8/20 wave shape, so that this wave
shape is finally used for classifying surge arresters.
In case of a direct lightning to the conductor line, the charge is flowing in the form of two equal current
waves in both directions, starting from the point of strike. A voltage wave is conjoined with the current
wave due to the surge impedance of the line.
Typical values for the surge impedances of overhead lines in d.c. traction systems are 460 Ω (single
line), and 380 Ω for inclined overhead lines. For bus bars a value of 160 Ω can be used.
Considering the peak value of 30 kA, as mentioned above, and a surge impedance of 460 Ω, an
overvoltage of 6 900 kV occurs, with a steepness of about 1 250 kV/µs. This overvoltage leads
immediately to a flash over of one or more insulators, limiting the overvoltage to the value of the flash
over voltage. This voltage is, depending on the type of insulator, in the range of 500 kV to 2 000 kV.
None of the equipment in d.c. railway systems up to 3 000 V is insulated for such voltage stresses.
Measures have to be taken to limit the overvoltages according to the rules of the insulation co-
ordination.
6.2 Switching overvoltages
The circuit breakers used in direct current systems produce switching overvoltage. These depend on
the type of breaker and on the magnitude of the applied d.c voltage in the traction system. The peak
value of the switching overvoltage can be up to 3 times the nominal voltage of a traction system.
7 Function and characteristics of MO surge arresters
7.1 Basic function
Metal-oxide surge arresters have an extreme non-linear current voltage characteristic, which is
described as
α
I = k ×U ,
α being variable between α ≤ 5 and α ≈ 50. An exact value for α can only be provided for a very
restricted range of the current in the characteristic curve.
The U-I characteristic of such an MO varistor is shown in Figure 5. I is the nominal discharge current,
n
U is the lightning impulse protection level of the surge arrester. It is defined as the maximum voltage
pl
between the terminals of the surge arrester during the flow of I . U is the maximum permissible
n c
continuous operating voltage.

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d
b
c U
pl
U
U
c
a
log I

Key
a lower linear part
b knee point
c strongly non-linear part
d upper linear part (“turn up” area)
U continuous operating voltage
c
U lightning protective level
pl
Figure 5 – Current-voltage characteristic of an MO surge arrester
7.2 Characteristics
The protection characteristic of an arrester is given by the maximum voltage U at the terminals of an
res
arrester during the flow of a current surge. Generally, a lightning impulse protective level of U ≤ 4 p.u.
pl
is considered. This is a value that is generally accepted for the insulation coordination. The real
residual voltage with nominal discharge current I (thus U ) can lie above or below that, depending on
n pl
the type of arrester. If U is set in a relationship with U of an arrester, it is possible to get very good
pl c
information about the quality of the arrester performance with regard to the protective level. The
smaller the ratio U /U , the better is the protection taking also into account the switching overvoltages.
pl c
In addition to the residual voltage at I , the residual voltages at steep current impulse and at switching
n
current impulse are also important. The residual voltage increases slightly with the current, but also
with the steepness of the current impulse. Depending on the usage, the residual voltage at the steep
current impulse and at switching current impulse must be taken into account besides the residual
voltage at I .
n

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7.3 Classification
Table 1 – Arrester classification and related parameters.
Arrester class Nominal High current Switching Charge Equivalent current
discharge impulse current transfer value of a long
current impulse capability duration current
with
I I I Q T = 2 ms
n hc sw
kA kA A As A
I 10 100 500 1,0 500
II 10 100 1 000 2,5 1 250
III 20 200 2 000 7,5 3 750

T
...