SIST EN 50123-2:2003

Railway applications - Fixed installations - D.C. switchgear -- Part 2: D.C. circuit breakers

This part of EN 50123 specifies requirements for d.c. circuit breakers for use in fixed installations of traction systems.
NOTE   Switchgear assemblies, electromagnetic compatibility (EMC) and dependability are not covered in this part of EN 50123, but by other parts of this standard or by other standards, as indicated in EN 50123-1.

Bahnanwendungen - Ortsfeste Anlagen - Gleichstrom-Schalteinrichtungen -- Teil 2: Gleichstrom-Leistungsschalter

Dieser Teil von EN 50123 behandelt Gleichstrom-Leistungsschalter, die in stationären Anlagen von Bahnnetzen eingesetzt werden.
ANMERKUNG   Schaltanlagen, Elektromagnetische Verträglichkeit und Abhängigkeiten sind nicht Bestandteil dieses Teils der EN 50123, werden aber durch andere Teile dieser Norm oder weitere Normen festgelegt, wie in EN 50123 1 angegeben.

Applications ferroviaires - Installations fixes - Appareillages à courant continu -- Partie 2: Disjoncteurs pour courant continu

La présente partie de la EN 50123 spécifie les exigences relatives aux disjoncteurs pour courant continu, destinés à être utilisés dans les installations fixes des systèmes de traction.
NOTE   Les ensembles d'appareillage, la compatibilité électromagnétique (CEM) et la disponibilité ne sont pas couvertes dans la présente partie des EN 50123, mais par d'autres parties de cette norme ou par d'autres normes indiquées dans la EN 50123 1.

Železniške naprave – Stabilne naprave električne vleke – Stikalne naprave za enosmerni tok – 2. del: Močnostna stikala za enosmerni tok

General Information

• Status: Published
• Publication Date: 30-Apr-2003
• ICS: 29.130.99 - Other switchgear and controlgear
• ICS: 29.280 - Electric traction equipment
• Technical Committee: ŽEN - Electrical applications for railways
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-May-2003
• Due Date: 01-May-2003
• Completion Date: 01-May-2003
• Directive: TP055 - Pravilnik o projektiranju, gradnji in vzdrževanju stabilnih naprav električne vleke enosmernega sistema 3 kV
• Ref Project: EN 50123-2:2003 - Railway applications - Fixed installations - D.C. switchgear - Part 2: D.C. circuit breakers

Relations

• Replaces: SIST EN 50123-2:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 2: D.C. circuit breakers
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 50123-2:1998/A1:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 2: D.C. circuit breakers
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 50123-2:1998/A1:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 2: D.C. circuit breakers
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 50123-2:2003
01-maj-2003
1DGRPHãþD
SIST EN 50123-2:1998
SIST EN 50123-2:1998/A1:1998
äHOH]QLãNHQDSUDYH±6WDELOQHQDSUDYHHOHNWULþQHYOHNH±6WLNDOQHQDSUDYH]D
HQRVPHUQLWRN±GHO0RþQRVWQDVWLNDOD]DHQRVPHUQLWRN
Railway applications - Fixed installations - D.C. switchgear -- Part 2: D.C. circuit breakers
Bahnanwendungen - Ortsfeste Anlagen - Gleichstrom-Schalteinrichtungen -- Teil 2:
Gleichstrom-Leistungsschalter
Applications ferroviaires - Installations fixes - Appareillages à courant continu -- Partie 2:
Disjoncteurs pour courant continu
Ta slovenski standard je istoveten z: EN 50123-2:2003
ICS:
29.130.99 Druge stikalne in krmilne Other switchgear and
naprave controlgear
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST EN 50123-2:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50123-2:2003

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SIST EN 50123-2:2003
EUROPEAN STANDARD EN 50123-2
NORME EUROPÉENNE
EUROPÄISCHE NORM February 2003

ICS 29.120.60; 45.020 Supersedes EN 50123-2:1995 + A1:1996


English version


Railway applications –
Fixed installations – D.C. switchgear
Part 2: D.C. circuit breakers


Applications ferroviaires – Bahnanwendungen –
Installations fixes – Ortsfeste Anlagen –
Appareillages à courant continu Gleichstrom-Schalteinrichtungen
Partie 2: Disjoncteurs Teil 2: Gleichstrom-Leistungsschalter
pour courant continu






This European Standard was approved by CENELEC on 2002-09-01. 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 Central Secretariat 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 Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.

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

Central Secretariat: rue de Stassart 35, B - 1050 Brussels


© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 50123-2:2003 E

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SIST EN 50123-2:2003
EN 50123-2:2003 - 2 -
Foreword
This European Standard was prepared by SC 9XC, Electric supply and earthing systems for
public transport equipment and ancillary apparatus (fixed installations), of the Technical
Committee CENELEC TC 9X, Electrical and electronic applications for railways.
The text of the draft was submitted to the Unique Acceptance Procedure and was approved by
CENELEC as EN 50123-2 on 2002-09-01.
This European Standard supersedes EN 50123-2:1995 + A1:1996. It has been prepared taking
into account IEC 61992-2 in order to align technically as much as possible this EN 50123-2
and IEC 61992-2. These documents are to be considered as technically equivalent except for
those references and peculiarities which are due to the European standardization in the
railway application field.
The following dates were fixed:
- latest date by which the EN has to be implemented
 at national level by publication of an identical
 national standard or by endorsement (dop) 2003-09-01
- latest date by which the national standards conflicting
 with the EN have to be withdrawn (dow) 2005-09-01
This Part 2 is to be used in conjunction with EN 50123-1:2003.
Annexes designated “informative” are given for information only.
In this standard, annex A is informative.
_____________

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Contents
Page
1 Scope . 4
2 Normative references. 4
3 Definitions . 4
4 Service requirements. 4
5 Characteristics of the circuit breaker. 4
5.1 Enumeration of the characteristics. 4
5.2 Type of circuit breaker . 5
5.3 Rated values and limit values for the main circuit . 7
5.4 Control circuits . 10
5.5 Auxiliary contacts and circuits . 11
5.6 Releases . 11
5.7 Arc voltage . 12
6 Construction . 12
6.1 General. 12
6.2 Circuit breaker enclosures . 13
6.3 Temperature-rises . 14
6.4 Dielectric strength. 14
6.5 Electrical and mechanical endurance . 14
6.6 Operation . 15
6.7 Corrosion protection. 15
6.8 Noise emission. 16
6.9 Cooling . 16
6.10 Servo-control (where applicable) . 16
6.11 Other facilities . 16
7 Information and marking. 16
7.1 Information. 16
7.2 Marking . 17
8 Tests . 17
8.1 General. 17
8.2 Applicable tests and test sequence. 18
8.3 Performance of tests . 18

Annex A (informative) Information required. 25
A.1 General . 25
A.2 Procurement specification . 25
A.3 Manufacturer's specification. 25

Table 1 – Shortened type-designation. 6
Table 2 – Circuit breaker duties . 9
Table 3 – Test duty cycles. 10
Table 4 – List of applicable tests and sequence . 18
Table 5 – Verification of the behaviour of the circuit breaker when performing
test duties f, ff and fr . 23

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EN 50123-2:2003 - 4 -
1 Scope
This part of EN 50123 specifies requirements for d.c. circuit breakers for use in fixed
installations of traction systems.
NOTE  Switchgear assemblies, electromagnetic compatibility (EMC) and dependability are not covered in this
part of EN 50123, but by other parts of this standard or by other standards, as indicated in EN 50123-1.
2 Normative references
This European Standard incorporates by dated or undated references, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions
of any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
See EN 50123-1:2003.
3 Definitions
For the purposes of this European Standard, the terms and definitions given in EN 50123-1
apply.
4 Service requirements
Environmental conditions applicable to the equipment discussed in this standard are covered
in 4.1 of EN 50123-1.
5 Characteristics of the circuit breaker
5.1 Enumeration of the characteristics
The characteristics of a circuit breaker and its assigned designations and values (where
applicable) are covered below as follows:
• type of circuit breaker (5.2);
• rated values and limit values of the main circuit and short-circuit characteristics (5.3);
• control circuits (5.4);
• auxiliary circuits (5.5);
• releases (5.6);
• arc voltages (5.7).

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5.2 Type of circuit breaker
A circuit breaker is defined by the following details, as applicable.
NOTE 1  As far as applicable, the following requirements also apply to single-pole circuit breakers electrically
or mechanically interlocked in multiple systems.
a) Interruption:
• in air;
• via a semiconductor.
NOTE 2  In this standard only interruption in air or via a semiconductor is addressed. This standard may
be used for other specified interrupting media, as far as applicable, where clearly specified by mutual
agreement between purchaser and supplier.
b) Breaking characteristics (class designation):
• high speed current limiting circuit breakers H;
• very-high speed current limiting circuit breakers V;
• semi-high speed circuit breakers S.
c) Use (installation point) in the system:
• interconnector circuit breaker I (also called bus-section or section circuit breaker);
• line circuit breaker L;
• rectifier circuit breaker R.
d) Current interruption direction:
• unidirectional U:
- fitted with a series unidirectional release U ;
1
- fitted with a series bidirectional release U .
2
NOTE 3  U circuit breakers are used for application where the reverse fault current is low (distant fault
2
current) and cannot operate the overload protection for normal discrimination purposes (i.e. substations
where adjacent substations are a far distance away).
• bidirectional B.
e) Duty of the main circuit
NOTE 4  To be specified when different from 5.3.4.2 and Table 2.
f) Actuating of the closing and opening operations:
• stored energy operation;
• independent manual operation;
• independent power operation;
• use of magnet;
• type of automatic tripping due to a release or relay;
• interlocks for opening and/or closing operations;
• trip-free provision;
• anti-pumping device.

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EN 50123-2:2003 - 6 -
g) Relay or release type:
• type of the relay(s) or release(s) involved.
h) Provision of an enclosure:
• without provision of an enclosure O (see 3.3.16 of EN 50123-1);
• with provision of an integral enclosure E (see 3.3.17 of EN 50123-1);
• with provision of a separate protection enclosure P.
The purchaser shall indicate which characteristics are to be present in the required circuit
breaker(s) and only those tests which relate to the chosen type are applicable to the selected
type of circuit breaker.
The above designations are used in this standard and may be used elsewhere adopting the
conventional grouping as given in Table 1:
Table 1 - Shortened type-designation
a a
Items above b c d h
H /I /U /O
1
Options V /L /U /E
2
S /R /B /P
Examples H/L/B/E
S/R/O
V/I/P
b
H /R and L/U
2
NOTE When a circuit breaker is not suitable to perform all duties as given
in 5.3.4.2, this fact will be indicated by means of the lower case letter(s)
designating actual capability according to Table 2, first column (for
example, H/Iff, fr/ P).
a
 Optional designations.
b
 When a circuit breaker is or shall be suitable for multiple alternate
functions, the indication of these functions shall be preceded by an «and».
Where semiconductor circuit breakers are only designed for use in rectifier equipped
substations, they shall be clearly so marked. If they may also be used as track paralleling
circuit breakers, when the substation rectifier circuit breakers are out of service, they shall
also be clearly so marked.

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5.3 Rated values and limit values for the main circuit
5.3.1 General
The rated characteristic values shall be specified by the purchaser. Nominal voltage values are
to be selected from the values indicated in Table 1 of EN 50123-1; current values and track
time constant (based on the track configuration which gives the largest track time constant)
should have one of the preferred values listed in 5.1.2 of EN 50123-1.
These values should be confirmed by the supplier, who should indicate the rated values for
the type of circuit breaker proposed and supply any other relevant data.
All these values are to be stipulated in accordance with 5.3.2 to 5.3.4. Definitions are given in
EN 50123-1. Some data may be omitted by agreement.
5.3.2 Voltages
A circuit breaker is identified by the following voltages:
• system voltages and limits (see 3.2.1 and 5.1.3 of EN 50123-1);
• nominal voltage U (see EN 50163);
n
• rated voltage U (see 3.2.3 of EN 50123-1);
Ne
• rated insulation voltage U (see 3.2.2 of EN 50123-1). It shall be equal to or higher than
Nm
U ;
max
• rated impulse withstand voltage U (see 3.2.4 of EN 50123-1);
Ni
• power-frequency voltage withstand level (dry) U (see 3.2.5 and Table 1 of EN 50123-1);
a
• maximum arc voltage (see 3.2.6.1 of EN 50123-1);
• rated auxiliary and control supply voltages (see 3.2.3.1 of EN 50123-1).
5.3.3 Currents
A circuit breaker is defined by the following currents:
• conventional thermal current I , I (see 3.2.8 and 3.2.9 of EN 50123-1);
th the
• rated service current I (see 3.2.10 of EN 50123-1);
Ne
• rated short circuit current I (see 3.2.12.1 of EN 50123-1);
Nss
• rated short-time withstand current I (see 3.2.11 of EN 50123-1).
Ncw
NOTE 1  Short-time ratings only apply to circuit breakers not fitted with series trip devices, or in a
unidirectional device where a series trip is inoperative. In practice this would apply to a rectifier circuit
breaker in the forward direction where a series trip only acts in the reverse direction.
NOTE 2  Rated short-time currents donot need to have the same value as the rated short-circuit current
I .
Nss
• overload capability: the purchaser shall inform the supplier of the load cycle requirements
(see 3.2.10, note 2 of EN 50123-1).

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EN 50123-2:2003 - 8 -
5.3.4 Short-circuit characteristics
5.3.4.1 Rated short-circuit breaking and making capacities
These values are defined in 3.2.19 and 3.2.23 of EN 50123-1 and are associated with the rated
voltage U , the rated service current I , the rated short-circuit current I , the rated track
Ne Ne Nss
time-constant T and the class designation H or V or S.
Nc
The rated short-circuit making capacity is the prospective peak value of the rated short-circuit
current I (see 3.2.12.1 of EN 50123-1).
Nss
A rated short-circuit breaking capacity requires the circuit breaker to be able to interrupt any
short-circuit current of a value lower than or equal to this rated breaking capacity at the circuit
time constant stipulated.
A circuit breaker having a breaking capacity at a rated track time constant T is capable of
Nc
the same breaking capacity at all lower values of track time constant T .
c
The prospective maximum short-circuit current is the sum of the prospective short-circuit
currents from all sources connected to the system, including rectifier converters and
regenerative trains.
When fixing the maximum short-circuit current and the above track time constant, clause 5 of
EN 50123-1 shall be considered.
5.3.4.2 Duties and test duty cycles
The duties required of a circuit breaker for each of the three uses are listed in Table 2. The test
duty cycles applying to the duties are shown in Table 3.
NOTE  Where the circuit breaker chosen by the manufacturer or offered by the supplier has been designed with
short circuit breaking characteristics in excess of those actually required in the installation, it may be agreed
between purchaser and supplier to perform additional tests in accordance with 8.3.8 for duties f) and/or e) and/or
d) using the test current actually required. These tests may be performed either at a standard test duty cycle (duty
1 or duty 2) or at an agreed duty cycle and may be repeated a number of times upon agreement between
purchaser and supplier.

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Table 2 - Circuit breaker duties
Duty Use Conditions Test current Prospective peak Time constant
f L Maximum fault I By consequence of
≥ 1,42 I
Nss
Nss
other circuit
parameters
a
e Maximum energy 0,5 I By consequence of 0,5 T
L Nss Nc
other circuit
parameters
d L Distant fault 2 I By consequence of T
Ne Nc
other circuit
parameters
l L Low current I Not applicable
≅ 0,01 s
c
ff I Maximum fault forward I By consequence of
≥ 1,42 I
Nss Nss
other circuit
parameters
fr I Maximum fault reverse I By consequence of
≥ 1,42 I
Nss
Nss
other circuit
parameters
b
lr Forward low current after I Not applicable ≅ 0,01 s
I, R c

reverse short circuit

r R Max fault reverse with I
≥ 1,42 I
Nss
Nss
paralleled converters
s R Short time current I
≥ 1,42 I
Ncw Ncw
forward
NOTE 1  For substations equipped with smoothing reactors of high value, the maximum energy condition may
correspond to the maximum fault condition.
NOTE 2  I is to be determined for each type of actual circuit situation. Therefore I may be different for Line
Nss Nss
L, Interconnector I and Rectifier R circuit breakers.
a
The factor affecting both I and T for maximum fault position is taken for practical reasons as 0,5. For
Nss Nc

low values of T , see Table 2 in 5.1.1.3 of EN 50123-1.
Nc
b

R only when explicitly required by the purchaser.

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EN 50123-2:2003 - 10 -
Table 3 - Test duty cycles
Duties Test cycle
a


f, e, d
O - 15 s - CO - 15 s - CO - 60 s - CO
Duty 1
O - 7 s - CO - 10 s - CO - 60 s - CO
Duty 2
ff, fr, r O - 15 s - CO
l, lr 10 times (O - 120 s - CO)
s Carrying for 0,25 s
NOTE 1  O = opening operation; C = closing operation.
NOTE 2  First opening is made on a short circuit being established.
a

The choice of duty 1 or 2 is left to the purchaser. If no choice is made, then the duty cycle required is duty 1.
Circuit breakers designed to comply with more than one duty shall be fully tested for each
duty; unless otherwise agreed between purchaser and supplier, these tests are to be carried out
on a single circuit breaker which may be maintained between duty cycles. Any further duty
cycles on the same circuit breaker shall not be performed unless a sufficient time to cool
down the circuit breaker components is allowed.
The tests shall be performed with the series overcurrent release set at the maximum setting,
e.g. four times I , I or I for test duties f, e, ff, fr, and 0,5 times for test duties r and s.
Ne
th the
For test duties d) and l), the circuit breaker shall be set to trip when the sustained value is
reached. For test duty d), when the track time constants are long, the trip shall be initiated at
0,15 s.
5.4 Control circuits
The control circuits are identified by the following characteristics as a minimum:
• the voltage of the control circuits;
• the kind of current (d.c. or a.c.);
• the current frequency, in case of an a.c. current.
The voltage of the supply source and its frequency are the values on which the performances,
the thermal behaviour and the insulation characteristics are based.
Unless otherwise required, the voltage shall be in accordance with 5.2 of EN 50123-1 and
rated insulation voltage shall be in accordance with EN 50124-1.
The supply voltage shall be within a range between 80 % and 110 % of the voltage in
accordance with 5.2 of EN 50123-1.
Where the control voltage is the same as in the main circuit, the same variations as in the main
circuit apply.

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The manufacturer shall indicate the value(s) of the current drawn by the control circuits at the
rated voltage. In the case of control circuits which draw current intermittently, the duration of
the current flow shall be given.
5.5 Auxiliary contacts and circuits
Auxiliary circuits are mainly defined by the number of contacts provided, by their rating
(thermal current and voltage) and by their characteristics (NO, NC or commutation). Unless
otherwise required, the rated voltage shall be in accordance with 5.2 of EN 50123-1, and the
rated insulation voltage shall be in accordance with EN 50124-1.
The purchaser shall specify the minimum number of auxiliary contacts required.
The auxiliary wiring connected to a circuit at 1 000 V a.c. or at 1 500 V d.c. or above shall be
physically separated from those connected to a circuit at a voltage below said limits.
For other characteristics of the auxiliary circuits, the requirements of 5.4 apply.
5.6 Releases
NOTE  The following requirements apply for direct or indirect releases which are part of the circuit breaker.
5.6.1 Type
Classification of the releases comprises
• series (direct or indirect) overcurrent releases,
• shunt releases,
• under-voltage releases,
• other releases.
5.6.2 Characteristics
A release may be instantaneous, time-lagged or time-dependant, or a combination of all three.
Other characteristics are as follows:
a) for overcurrent (d.c.) releases:
• type (overcurrent direct or indirect);
• rated current;
• the setting current (or setting range);
• the direction of the main carrying current in case of a unidirectional circuit breaker;
• characteristics of the operating time which the release gives the circuit breaker as a
function of the rate of rise of the current.
The release shall be capable of withstanding this current under the test conditions
specified in clause 8, without the temperature-rise exceeding the values specified in
clause 6 of EN 50123-1.
For circuit breakers provided with interchangeable or adjustable releases, the current
setting (or the setting range, if applicable) shall be indicated on the release or on its
setting scale. The indication may be either in ampere or in multiples of the current
indicated on the release. The purchaser shall specify the required setting range. The ratio
of the minimum and maximum values shall not exceed 1:2 in normal conditions.

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EN 50123-2:2003 - 12 -
b) for the shunt release:
• the rated voltage;
• the power taken at the rated voltage for a specified time.
5.7 Arc voltage
The manufacturer shall specify the maximum value of the arc voltage Û caused by the
arc
operation of the circuit breaker when it is tested in accordance with clause 8.
NOTE  This maximum voltage is the peak voltage measured during any test duty and is not necessarily seen
with maximum current.
This value shall not exceed both that of the rated impulse withstand voltage of the equipment
and four times the nominal voltage. If lower arc voltages are required, these shall be specified
by the purchaser.
6 Construction
6.1 General
All apparatus and connections required for the safe and satisfactory operation, control and
protection of the equipment concerned shall be provided, whether or not specifically
mentioned, unless otherwise agreed between the circuit breaker manufacturer and the
switchgear assembly manufacturer. Unless otherwise specified, the equipment shall be
earthed, insulated, screened or enclosed as may be appropriate to ensure the protection of the
equipment and safety of those concerned in its operation and maintenance.
Control and auxiliary circuits and contacts shall comply with the requirements of 5.2 of
EN 50123-1.
6.1.1 Materials
No materials containing asbestos shall be used in the construction of the circuit breaker.
NOTE  Special attention is to be paid to the ability of the material used to resist moisture and fire: materials
used should be of the self-extinguishing type, such that the risk of propagation of fire from one cubicle to
another is minimised. See Annex B of EN 50123-1.
6.1.2 Arcing contacts
Arcing contacts, if any, which are liable to be consumed during arc interruption shall be easy
to replace.
6.1.3 Clearances and creepage distances
Clearances and creepage distances shall not be lower than those indicated in Table 1 in
EN 50123-1 and in Annex D of EN 50123-1 respectively.
NOTE  Clearances and creepage distances may be increased to take into account the presence of foreign
substances after the number of operations, in normal and short circuit conditions, that occur during the normal
life-span between cleaning procedures.

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Where applicable, ribs shall be provided in order to break the continuity of conducting deposit
which occurs during operation.
6.1.4 Primary connections
The circuit breakers shall be equipped with fixed, removable (bolted or clamped) or plug-in
coupling connections.
6.1.5 Location of the primary connections
For non-withdrawable circuit breakers, the terminals for the primary connections shall be
accessible with the circuit breaker in its normal operating position. The position of the
terminals shall be agreed between purchaser and supplier, unless covered by a European
standard.
For withdrawable circuit breakers, the terminals for the primary connections shall be
accessible in the conditions detailed in EN 50123-6.
6.1.6 Earthing terminal
The frames, the structure and the fixed parts of the metallic enclosures shall be connected to
each other and to a suitable earthing terminal, placed in an accessible position, in order to
allow earthing.
NOTE 1  This condition may be fulfilled by normal construction elements, ensuring an adequate electric
continuity.
For withdrawable circuit breakers, the earth connection shall be made before the shutters are
opened, and the shutters shall be closed before the earth connection is disconnected.
NOTE 2  The purchaser may require a dedicated earth connection for this purpose. For a non-dedicated earth
connection, where bolts or similar fixings are used for earth continuity, the maintenance instructions should state
the requirements for cleaning the surfaces and ensuring tightness.
The earthing terminal shall be protected against corrosion. The standard earth symbol shall be
permanently marked.
The earth terminal shall be capable of carrying the rated earth fault current I for 0,25 s.
Ncwe
6.1.7 Manual operation for maintenance
NOTE  A handle m
...