SIST EN 50123-1:2003

Railway applications - Fixed installations - D.C. switchgear -- Part 1: General

The EN 50123 series specifies requirements for d.c. switchgear and controlgear and is intended to be used in fixed electrical installations with nominal voltage not exceeding 3 000 V d.c., which supply electrical power to vehicles for public guided transport, i.e. railway vehicles, tramway vehicles, underground vehicles and trolley-buses.
Part 1 specifies general requirements.
The other parts are covering
Part 2   D.C. circuit breakers,
Part 3   Indoor d.c. disconnectors, switch-disconnectors and earthing switches,
Part 4   Outdoor d.c. disconnectors, switch-disconnectors and earthing switches,
Part 5   Surge arresters and low voltage limiters for specific use in d.c. systems,
Part 6    D.C. switchgear assemblies,
Part 7 1   Measurement, control and protection devices for specific use in d.c. traction systems – Application guide,
Part 7 2   Measurement, control and protection devices for specific use in d.c. traction systems –  Isolating current transducers and other current measuring devices,
Part 7 3   Measurement, control and protection devices for specific use in d.c. traction systems –Isolating voltage transducers and other voltage measuring devices

Bahnanwendungen - Ortsfeste Anlagen - Gleichstrom-Schalteinrichtungen -- Teil 1: Allgemeines

Applications ferroviaires - Installations fixes - Appareillage à courant continu -- Partie 1: Généralités

Železniške naprave – Stabilne naprave električne vleke – Stikalne naprave za enosmerni tok – 1. del: Splošno

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 50123-1:2003 - Railway applications - Fixed installations - D.C. switchgear - Part 1: General

Relations

• Revised: SIST EN 50123-1:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 1: General
• Effective Date: 13-May-2010
• Replaces: SIST EN 50123-1:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 1: General
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 50123-1:1998 - Railway applications - Fixed installations - D.C. switchgear -- Part 1: General
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 50123-1:2003
01-maj-2003
1DGRPHãþD
SIST EN 50123-1:1998
äHOH]QLãNHQDSUDYH±6WDELOQHQDSUDYHHOHNWULþQHYOHNH±6WLNDOQHQDSUDYH]D
HQRVPHUQLWRN±GHO6SORãQR
Railway applications - Fixed installations - D.C. switchgear -- Part 1: General
Bahnanwendungen - Ortsfeste Anlagen - Gleichstrom-Schalteinrichtungen -- Teil 1:
Allgemeines
Applications ferroviaires - Installations fixes - Appareillage à courant continu -- Partie 1:
Généralités
Ta slovenski standard je istoveten z: EN 50123-1:2003
ICS:
29.130.99 Druge stikalne in krmilne Other switchgear and
naprave controlgear
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST EN 50123-1:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 50123-1:2003

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SIST EN 50123-1:2003
EUROPEAN STANDARD EN 50123-1
NORME EUROPÉENNE
EUROPÄISCHE NORM February 2003

ICS 29.120.60; 45.020 Supersedes EN 50123-1:1995


English version


Railway applications –
Fixed installations – D.C. switchgear
Part 1: General


Applications ferroviaires –  Bahnanwendungen –
Installations fixes – Ortsfeste Anlagen –
Appareillage à courant continu Gleichstrom-Schalteinrichtungen
Partie 1: Généralités Teil 1: Allgemeines






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 50123-1:2003 E

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SIST EN 50123-1:2003
EN 50123-1:2003 – 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 formal vote and was approved by CENELEC as EN 50123-1 on
2002-09-01.
This European Standard supersedes EN 50123-1:1995. It has been prepared taking into account
IEC document 9/578/FDIS (61992-1) in order to align technically as much as possible this EN 50123-1
and IEC 61992-1. These documents are to be considered as technically equivalent except for those
references and peculiarities which are due to the European standardisation 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

Annexes designated “normative” are part of the body of the standard.
Annexes designated “informative” are given for information only.
In this standard, Annexes A, B and C are normative and Annexes D and E are informative.
_____________

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SIST EN 50123-1:2003
– 3 – EN 50123-1:2003
Contents

1 Scope.4
2 Normative references .4
3 Definitions .6
3.1 General terms.6
3.2 Performance characteristics.9
3.3 Components .13
3.4 Terms relating to d.c. circuit breakers, switch-disconnectors and associated relays .17
4 Service conditions and requirements.22
4.1 Environmental conditions .22
4.2 Insulation levels .22
5 Standard features and conventional assumptions.24
5.1 Standard features and conventional parameters for the main circuit .24
5.2 Standard features for auxiliary and control circuits.26
6 Temperature-rise limits.26
7 Tests .27
7.1 General .27
7.2 Test tolerances .28
7.3 Tests on movable devices.28
7.4 Temperature-rise test .30
7.5 Dielectric tests .32
7.6 Short circuit and load switching conditions .32
7.7 Verification of the behaviour during short-time withstand current test.34
7.8 Verification of the manual control device for sturdiness and position indicator
reliability.34
Annex A (normative) Diagrams for tests.36
Annex B (normative)  Environmental conditions for indoor installations .38
Annex C (normative) Search of critical currents for d.c. circuit breakers and switches.40
Annex D (informative) Recommended creepage distances .42
Annex E (informative) Determination of maximum energy fault location .43
Bibliography.46
Figure A.1 - Diagram of the test circuit for checking the making and breaking capacities
in short-circuit and load/overload switching conditions .37
Figure A.2 - Typical calibrations and interruption under short-circuit and load/overload
switching conditions .38
Figure E.1 - Equivalent circuit of a d.c. traction system .46
Figure E.2 - Ratio of I /I to T /T .46
maxE ss s c
Table 1 - Insulation levels.24
Table 2 - Test circuit parameters for maximum circuit energy .25
Table 3 - Preferred voltages for auxiliary and control circuits [V] .27
Table 4 - Temperature-rise limits for insulated coils.27
Table 5 - Temperature-rise limits for various components.28
Table 6 - Test tolerances.29
Table 7 - Recommended quantities and dimensions of copper bars .32
Table 8 - Values of forces or torques for the tests.36
Table B.1 - Limits of sinusoidal vibrations.40
Table D.1 - Material group identification .43
Table D.2 - Recommended creepage distances, in mm/kV (base U ).43
Nm

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SIST EN 50123-1:2003
EN 50123-1:2003 – 4 –
1 Scope
The EN 50123 series specifies requirements for d.c. switchgear and controlgear and is intended to be
used in fixed electrical installations with nominal voltage not exceeding 3 000 V d.c., which supply
electrical power to vehicles for public guided transport, i.e. railway vehicles, tramway vehicles,
underground vehicles and trolley-buses.
Part 1 specifies general requirements.
The other parts are covering
Part 2 D.C. circuit breakers,
Part 3 Indoor d.c. disconnectors, switch-disconnectors and earthing switches,
Part 4 Outdoor d.c. disconnectors, switch-disconnectors and earthing switches,
Part 5 Surge arresters and low voltage limiters for specific use in d.c. systems,
Part 6 D.C. switchgear assemblies,
Part 7-1 Measurement, control and protection devices for specific use in d.c. traction systems –
Application guide,
Part 7-2 Measurement, control and protection devices for specific use in d.c. traction systems –
Isolating current transducers and other current measuring devices,
Part 7-3 Measurement, control and protection devices for specific use in d.c. traction systems –
Isolating voltage transducers and other voltage measuring devices
2 Normative references
This European Standard series 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 series only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
EN 50119 2001 Railway applications – Fixed installations – Electric traction overhead contact
lines
EN 50121 Series Railway applications – Electromagnetic compatibility
EN 50122-1 1997 Railway applications – Fixed installations – Part 1: Protective provisions relating
to electrical safety and earthing
EN 50124-1 2001 Railway applications – Insulation coordination – Part 1: Basic requirements –
Clearances and creepage distances for electrical and electronic equipment
EN 50125-2 2002 Railway applications – Environmental conditions for equipment – Part 2: Fixed
electrical installations
EN 50126 1999 Railway applications – The specification and demonstration of Reliability,
Availability, Maintainability and Safety (RAMS)
EN 50163 1995 Railway applications – Supply voltage of traction systems (IEC 60850:2000)
EN 60099-1 1994 Surge arresters – Part 1: Non-linear resistor type gapped surge arresters for a.c.
systems (IEC 60099-1:1991)

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SIST EN 50123-1:2003
– 5 – EN 50123-1:2003
EN 60099-4 1993 Surge arresters – Part 4: Metal-oxide surge arresters without gaps for a.c.
systems (IEC 60099-4:1991)
EN 60129 1994 Alternating current disconnectors and earthing switches
+ A1 1994 (IEC 60129:1984 + A1:1992 + A2:1996)
+ A2 1996
EN 60243-1 1998 Electrical strength of insulating materials – Test methods – Part 1: Tests at
power frequencies (IEC 60243-1:1998)
EN 60269 series Low-voltage fuses (IEC 60269 series)
EN 60298 1996 AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV
and up to and including 52 kV (IEC 60298:1990 + corr. April 1995 + A1:1994)
EN 60507 1993 Artificial pollution tests on high-voltage insulators to be used on a.c. systems
(IEC 60507:1991)
EN 60529 1991 Degrees of protection provided by enclosures (IP Code) (IEC 60529:1989)
EN 60694 1996 Common specifcations for high-voltage switchgear and controlgear standards
(IEC 60694:1996)
EN 60721 series Classification of environmental conditions (IEC 60721 series)
EN 60947-1 1999 Low-voltage switchgear and controlgear – Part 1: General rules
(IEC 60947-1:1999, mod.)
EN 60947-2 1996 Low-voltage switchgear and controlgear – Part 2: Circuit breakers
+ A1 1997 (IEC 60947-2:1995 + A1:1997)
HD 214 S2 1980 Method for determining the comparative and the proof tracking indices of solid
insulating materials under moist conditions (IEC 60112:1979)
HD 380 S2 1987 Test methods for evaluating resistance to tracking and erosion of electrical
insulating materials used under severe ambient conditions (IEC 60587:1984)
HD 588.1 S1 1991 High-voltage test techniques – Part 1: General definitions and test requirements
(IEC 60060-1:1989 + corr. March 1990)
IEC 60050-441 1984 International Electrotechnical Vocabulary (IEV) – Chapter 441: Switchgear,
controlgear and fuses
IEC 60050-446 1983 International Electrotechnical Vocabulary (IEV) – Chapter 446: Electrical relays
IEC 60050-605 1983 International Electrotechnical Vocabulary (IEV) – Chapter 605: Generation,
transmission and distribution of electricity – Substations
IEC 60050-811 1991 International Electrotechnical Vocabulary (IEV) – Chapter 811: Electric traction
IEC 60466 1987 A.C. insulation-enclosed switchgear and controlgear for rated voltages above
1 kV and up to and including 38 kV
IEC 61245 1993 Artificial pollution tests on high voltage insulators to be used in d.c. systems

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SIST EN 50123-1:2003
EN 50123-1:2003 – 6 –
3 Definitions
For the purpose of this European Standard series, the definitions given in IEC 60050-441, IEC 60050-446,
IEC 60050-605, IEC 60050-811, EN 50124-1, EN 60099-1, EN 60099-4, EN 60298 and EN 60947 apply
together with the following:
3.1 General terms
3.1.1
switchgear
general term covering switching devices and their combination with associated control, measuring,
protective and regulating equipment; it covers also assemblies of such devices and equipment with
associated interconnections, accessories, enclosures and supporting structures
NOTE For the sake of simplicity in this standard the term “switchgear” means “switchgear and controlgear”.
3.1.1.1
d.c. switchgear and controlgear assembly
combination of one or more d.c. switching devices together with associated control, measuring, signalling,
protective, regulating equipment, etc., completely assembled under the responsibility of the supplier, with
all the internal electrical and mechanical interconnections and structural parts
NOTE 1 Throughout the Standard, the abbreviation switchgear assembly is used for a d.c. switchgear and controlgear assembly.
NOTE 2 The components of the switchgear assembly may be electromechanical or electronic.
NOTE 3 An enclosure, but not an integral enclosure, when housing a switching device and some associated controlgear, may be
considered as a switchgear assembly.
3.1.2
switching device
device designed to make or break the current in one or more electric circuits
[IEV 441-14-01]
3.1.3
d.c. circuit breaker
switching device capable of making, carrying and breaking direct currents under normal circuit conditions
and also making, carrying (up to a specified limit and for a specified time) and breaking currents under
specified abnormal conditions, such as those of short-circuit
3.1.4
d.c. disconnector
mechanical switching device, which provides, in the open position, for safety reasons, an isolating
distance in accordance with specified requirements
NOTE 1 The disconnector is capable of opening and closing a circuit when either negligible d.c. current is broken or made, or
when no significant change in the voltage across the terminals of the disconnector occurs. It is also capable of carrying d.c.
currents under normal circuit conditions and carrying, for a specified time, currents under abnormal conditions such as those of
short-circuit.
NOTE 2 A disconnector is not suitable for making or breaking load current, fault current or other current arising from the effects of
lightning or transient phenomena.
NOTE 3 A disconnector is only able to make or break current of very limited magnitude such as those arising from electrostatic
charging or discharges across undamaged insulation. The ability to make or break minimum currents due to eventual marginal
transient conditions of the network is subject to agreement between purchaser and supplier.

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SIST EN 50123-1:2003
– 7 – EN 50123-1:2003
3.1.5
switch-disconnector
mechanical switching device capable of making, carrying and breaking currents in normal circuit
conditions and, when specified, in given operating overload conditions. In addition, it is able to carry, for a
specified time, currents under specified abnormal circuit conditions, such as short-circuit conditions.
Moreover, it complies with the requirements for a disconnector (see 3.1.4)

When specified, a switch-disconnector may be designed for making short-circuit currents, but not for
breaking the same.
NOTE Outdoor switch-disconnectors, in given special conditions, may be required to be suitable for breaking overload currents of
specified amplitude.
3.1.6
earthing switch
mechanical switching device for earthing parts of the circuit, capable of withstanding for a specified time,
currents under abnormal conditions such as those of short-circuit, but not required to carry currents under
normal conditions of the circuit
NOTE An earthing switch may have a short-circuit making capacity (see 3.2.23).
[IEV 441-14-11]
3.1.7
low-voltage limiter
device intended to be in parallel in those parts of a traction system where overvoltages are expected
having the function of limiting the voltage to predetermined values
3.1.8
d.c. sensor
device used for detecting a current or a voltage in d.c. main circuit, which produces an output signal,
proportional to and linear (over a range) with the primary input, for connection to a secondary device
which acts on the signal
3.1.9
d.c. shunt
device connected in the primary circuit, usually composed of metal grids, that provides a millivolt output
proportional to the current following in the primary circuit
3.1.10
isolating transducer
device which is interposed between the output of a sensor in the main circuit and the input of a secondary
device used for measurement or protection, and used to provide an output isolated from the main circuit
and, usually, at lower voltage
3.1.11
hall effect sensor
type of sensor which fits around the main circuit current carrying conductor and uses a single or multiple
Hall effect cells situated in the magnetic field of an iron circuit and which is energised by the current in the
main conductor
3.1.12
divider
bank of resistors connected across the main supply with a footing resistor used as the output, which gives
a voltage proportional to the main supply. This output is connected either directly or indirectly through an
isolation transducer to the voltage terminals of the secondary device

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SIST EN 50123-1:2003
EN 50123-1:2003 – 8 –
3.1.13
operation
motion of the moving contact(s) from one position to another position, for example open to close or open
to earth
NOTE 1 This may be a closing operation or an opening operation.
NOTE 2 If a distinction is necessary, the terms "electrical operation" (for example make and break) and "mechanical operation"
(for example closing and opening) should be used.
NOTE 3 The position of a switching device where the continuity of the main circuit is assured is indicated as "close" position.
NOTE 4 The position of a switching device where the prescribed distance between the contacts of the switching device is assured
is indicated as "open" position.
3.1.14
operating cycle (of a mechanical switching device)
succession of operations from one position to another and back to the first position through all other
positions, if any [IEV 441-16-02]
3.1.15
dependent manual operation (of a mechanical switching device)
operation solely by means of directly applied manual energy, such that the speed and force of the
operation are dependent upon the action of the operator [IEV 441-16-13]
3.1.16
stored energy operation (of a mechanical switching device)
operation by means of energy stored in the device itself prior to the completion of the operation and
sufficient to complete it under predetermined conditions
NOTE This kind of operation may be subdivided according to
a) the energy storage mode (spring, weight, etc.);
b) the origin of energy (manual, electric, etc.);
c) the energy releasing mode (manual, electric, etc.).
[IEV 441-16-15]
3.1.17
independent manual operation (of a mechanical switching device)
stored-energy operation where the energy originates from manual power, stored and released in one
continuous operation, in such a way that the speed and force of the operation are independent from the
action of the operator [IEV 441-16-16]
3.1.18
independent power operation
operation by means of energy where the energy originates from an external power source and is released
in a single continuous operation, in such a way that the speed and force of the operation are independent
from the action of the operator
3.1.19
switching device with interlock preventing opening and/or closing operations
switching device in which an operation (closing and/or opening) is prevented by interlocking means
reflecting given system conditions
3.1.20
utilisation category (of a switching device)
combination of specified requirements related to the condition in which the switching device fulfils its
purpose, selected to represent a characteristic group of practical applications [IEV 441-17-19]
NOTE The specified requirements may concern, for example the values of the making capacities, if applicable, breaking
capacities and other characteristics, the associated circuits and the relevant conditions of use and behaviour. The term "duty" used
elsewhere in the standard corresponds to a particular aspect of the utilisation category.

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SIST EN 50123-1:2003
– 9 – EN 50123-1:2003
3.1.21
unidirectional switching device
switching device (for example a circuit breaker), the purpose of which is to interrupt d.c. current which is
flowing in a prescribed direction through that device, and which is identified accordingly
3.1.22
bidirectional switching device
switching device (for example a circuit breaker), the purpose of which is to interrupt d.c. current which
flows in either direction through that device, and which is identified accordingly
NOTE Proof of bidirectional ability is included in the interrupting type tests.
3.2 Performance characteristics
3.2.1 Voltages
3.2.1.1
nominal voltage (U )
n
voltage by which an installation or part of an installation is designated
3.2.1.2 Limits of system voltages
3.2.1.2.1
highest system voltage (U )
max
highest value given for the voltage in the continuous operating conditions U specified in EN 50163
max1
3.2.1.2.2
lowest system voltage (U )
min
lowest value given for the voltage in the continuous operating conditions U specified in EN 50163
min1
3.2.2
rated insulation voltage (U )
Nm
maximum value of the d.c. voltage for which the equipment is designed in respect to its insulation
3.2.3
rated voltage (U )
Ne
voltage value, given by the manufacturer, which, combined with rated service current, determines the
utilisation of the equipment and to which the corresponding tests and utilisation categories, if any, relate
NOTE The rated voltage may differ from the nominal voltage by a quantity within permitted tolerances.
3.2.3.1
rated auxiliary and control supply voltage
voltage measured at the circuit terminals of the apparatus during its operation, including, if necessary, the
auxiliary resistors or accessories supplied or required by the manufacturer to be installed in series with it,
but not including the conductors to the electrical supply
3.2.3.2
rated voltage of a gapped arrester (U )
r
maximum d.c. voltage value between terminals at which the surge arrester is designated to withstand
continuously
3.2.3.3
rated voltage of a gapless arrester (U )
r
the maximum d.c. voltage value between terminals at which the surge arrester is designated to operate
correctly under temporary overvoltage conditions as established in the operating duty tests (see 4.7.5 of
EN 50123-5). The rated voltage is used as a reference parameter for the specification of the operating
characteristics

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SIST EN 50123-1:2003
EN 50123-1:2003 – 10 –
3.2.3.4
rated voltage of a low-voltage limiter (U )
r
the maximum d.c. voltage value between terminals which the low-voltage limiter is designed to withstand
continuously
3.2.3.5
maximum continuous operating voltage of a gapless arrester (U )
c
voltage which corresponds to U defined in 3.2.1.2.1
max
3.2.3.6
protective voltage level of a gapped arrester (U )
p
crest value, declared by the supplier, higher than the maximum of the three voltage values between the
surge arrester terminals: residual voltage at I , maximum standard lightning impulse sparkover voltage,
n
maximum front of wave impulse sparkover voltage, the latter divided by 1,15
3.2.3.7
protective voltage level for gapless arrester (U )
p
impulse protection level of the arrester covering the maximum residual voltage for the nominal discharge
current I
n
3.2.3.8
maximum withstand voltage of a low-voltage limiter (U )
w
maximum peak voltage value between terminals at which the current in the voltage limiter is zero or
limited to specified values (leakage current)
3.2.3.9
maximum sparkover voltage of a low-voltage limiter (U )
s
maximum voltage value between terminals at which a gapped voltage limiter is designated to make a
connection between terminals such as to limit the difference of potential between the same to a safe value
3.2.3.10
rated supply voltage in a switchgear
voltage measured at the circuit terminals of the apparatus itself during its operation, including, if
necessary, the auxiliary resistors or accessories supplied or required by the manufacturer to be installed
in series with it, but not including the conductors from the connection to the electrical supply
3.2.4
rated impulse withstand voltage (U )
Ni
the peak value of an impulse voltage of prescribed form and polarity which the equipment is capable of
withstanding to, without failure, under the specified test conditions
3.2.5
power-frequency voltage withstand level (dry and wet) (U )
a
power-frequency test voltage level which, when withstood by the equipment, proves the integrity of its
insulation in operating conditions
3.2.6
Transient voltages
3.2.6.1
recovery voltage
voltage which appears across the terminals of a switching device after the breaking of the current
[IEV 441-17-25]
3.2.6.2
maximum arc voltage (Û )
arc
maximum voltage appearing across the switching device during arcing

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SIST EN 50123-1:2003
– 11 – EN 50123-1:2003
3.2.7
prospective current
current that would flow in the circuit if the device was replaced by a conductor of negligible impedance
[IEV 441-17-01]
NOTE The prospective current may be qualified in the same way as a real current: prospective broken current, peak value of the
prospective current, etc.
3.2.8
conventional free-air thermal current (I )
th
current which may be used for the temperature-rise test of an equipment in free-air (see notes 1 and 2).
This value is equal to or greater than the maximum value of the rated service current I of the equipment
Ne
NOTE 1 Free-air is the indoor air existing in normal conditions, reasonably free from dust and external radiations.
NOTE 2 A free-air device is a device supplied by the manufacturer without an enclosure (see 3.3.16) or a device supplied by the
ma
...