IEC 62427:2024
(Main)Railway applications - Compatibility between rolling stock and train detection systems
Railway applications - Compatibility between rolling stock and train detection systems
IEC 62427:2024 describes a process to demonstrate compatibility between rolling stock (RST) and train detection systems (TDS). It describes the characterization of train detection systems, rolling stock and traction power supply systems.
It is worth noting that the demonstration of technical compatibility between the rolling stock and infrastructure with respect to physical dimensions is not detailed in this document.
This document is not generally applicable to those combinations of rolling stock, traction power supply and train detection system which were accepted as compatible prior to the publication of this document. However, as far as is reasonably practicable, this document can be applied to modifications of rolling stock, traction power supply or train detection systems which can affect compatibility. The detailed process can be used where no rules and processes for compatibility are established.
This second edition cancels and replaces the first edition published in 2007. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) generic compatibility process, which is broken into a two-stage process depending on whether there are established compatibility limits or not;
b) rules for characterization of train detection systems;
c) rules for characterization of rolling stock;
d) rules for characterization of the power system;
e) informative references are provided in notes to established CENELEC standards for compatibility;
f) terminology is updated.
Applications ferroviaires - Compatibilité entre le matériel roulant et les systèmes de détection des trains
IEC 62427:2024 Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) procédure de compatibilité générale à deux niveaux (selon que les limites de compatibilité établies sont respectées ou non);
b) règles de caractérisation des systèmes de détection de train ;
c) règles de caractérisation du matériel roulant ;
d) règles de caractérisation de l'alimentation de traction ;
e) ajout de références normatives aux normes CENELEC établies dans les notes pour la compatibilité ;
f) mise à jour de la terminologie.
La présente version bilingue (2025-11) correspond à la version anglaise monolingue publiée en 2024-12.
Le présent document décrit une procédure qui permet de démontrer la compatibilité entre le matériel roulant (MR) et les systèmes de détection de train (SDT). Il fournit également des informations sur la caractérisation des systèmes de détection de train, du matériel roulant et des alimentations de traction.
Il est à noter que le présent document ne couvre pas la démonstration de compatibilité technique entre le matériel roulant et l'infrastructure en termes de dimensions physiques.
Le présent document ne s'applique généralement pas aux ensembles matériels roulants, alimentations de traction et systèmes de détection de train qui ont déjà été reconnus compatibles avant la publication du présent document. Toutefois, le présent document peut être appliqué, dans des limites raisonnables, aux modifications du matériel roulant, de l'alimentation de traction et des systèmes de détection de train qui sont susceptibles de compromettre la compatibilité. La procédure décrite dans le présent document peut être utilisée lorsqu'aucune règle ni procédure de compatibilité n'ont été définies.
Cette seconde édition annule et remplace la première édition parue en 2007. Cette édition constitue une révision technique.
General Information
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Standards Content (Sample)
IEC 62427 ®
Edition 2.0 2024-12
INTERNATIONAL
STANDARD
Railway applications – Compatibility between rolling stock and train detection
systems
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IEC 62427 ®
Edition 2.0 2024-12
INTERNATIONAL
STANDARD
Railway applications – Compatibility between rolling stock and train detection
systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 45.060.01 ISBN 978-2-8327-0024-2
– 2 – IEC 62427:2024 © IEC 2024
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms, definitions and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 10
4 Compatibility process . 10
4.1 Overview. 10
4.2 Detailed compatibility process . 10
4.3 Building the compatibility argument . 11
4.4 Quality management . 12
4.5 Route identification for introduction of RST (new or changed) . 12
4.6 Introduction of infrastructure elements (new or changed) . 12
4.7 Characterization. 13
4.8 Compatibility analyses . 13
4.8.1 General terms . 13
4.8.2 Transfer function . 14
5 Characterization of train detection systems . 15
5.1 Objective of procedure . 15
5.2 Track circuit systems – Standards, regulations and technical specifications . 16
5.3 Axle counter systems – Standards, regulations and technical specifications . 16
5.4 Wheel detectors (treadle applications) . 16
5.4.1 General . 16
5.4.2 Wheel detectors based on inductive technology . 16
5.5 Loops. 17
5.5.1 General aspects . 17
5.5.2 Interfering mechanisms. 17
5.5.3 Characterization . 18
6 Characterization of rolling stock . 18
6.1 Objective . 18
6.2 General procedure . 18
7 Characterization of traction power supply systems . 19
7.1 Objective . 19
7.2 DC traction power supplies . 19
7.3 AC traction power supplies . 19
7.4 Test procedures . 20
8 Test report . 20
8.1 General . 20
8.2 Introduction to the report . 20
8.3 Test organization . 20
8.4 Configuration . 20
8.5 Reference documents . 20
8.6 Application of the test plan . 21
8.7 Test results . 21
8.8 Comments . 21
8.9 Archive of test results . 21
Annex A (informative) Guidelines for the determination of susceptibility of train
detection systems . 22
A.1 Examples of system configurations . 22
A.2 "Normal" configuration . 22
A.3 Interference mechanism with broken signal rail . 22
A.4 Interference mechanism with broken return rail . 23
A.5 Double rail track circuits . 24
A.6 Voltage between axles of rolling stock . 25
A.7 Effect of resistance between coupled vehicles . 26
A.8 Radiated interference . 28
A.9 Sensitive zone of wheel detector . 28
A.10 Factor of safety . 29
A.11 Multiple interference sources . 29
Annex B (informative) General characterization of rolling stock . 30
B.1 Objective of procedure . 30
B.2 Description of rolling stock and factors affecting its characteristics . 30
B.3 Configuration (design status) . 30
B.4 Test plan . 30
B.4.1 General . 30
B.4.2 Test site . 31
B.4.3 Instrumentation . 31
B.4.4 Test procedure . 31
Annex C (informative) Factors affecting rolling stock characteristics and compatibility . 33
Annex D (informative) DC traction power supplies . 36
D.1 General . 36
D.2 Interference currents generated by the rolling stock . 36
D.3 Interference currents generated by the traction power supply system . 36
Annex E (informative) Compatibility parameters for loops (European example) . 39
E.1 General . 39
E.2 Principles of operation – Electrical background . 39
E.3 Vehicle metal construction . 39
Bibliography . 42
Figure 1 – Sources of electromagnetic interference . 7
Figure 2 – The compatibility process . 11
Figure 3 – Relationship between compatibility limits and permissible interference . 15
Figure A.1 – Interference mechanism with rails intact . 22
Figure A.2 – Interference mechanism with self-revealing broken rail . 23
Figure A.3 – Interference mechanism with unrevealed broken rail . 23
Figure A.4 – Double rail track circuit . 24
Figure A.5 – Double rail track circuit with broken rail . 24
Figure A.6 – Interference mechanism due to voltage between axles – Case 1 . 25
Figure A.7 – Interference mechanism due to voltage between axles – Case 2 . 25
Figure A.8 – Effect of inter-vehicle current . 26
Figure A.9 – Equivalent circuit for Figure A.8 . 26
Figure A.10 – Example of radiated interference . 28
– 4 – IEC 62427:2024 © IEC 2024
Figure C.1 – Electrical bonding . 34
Figure D.1 – Rolling stock with DC supply . 37
Figure D.2 – Circulation of interference current generated by rolling stock . 37
Figure D.3 – Circulation of interference current generated by the substation . 38
Figure E.1 – Example of loop installation . 39
Figure E.2 – Vehicle layouts . 40
Figure E.3 – Example longitudinal beams with cross connection in section (a) . 40
Figure E.4 – Example short circuit rings in section (a) . 40
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS –
COMPATIBILITY BETWEEN ROLLING STOCK
AND TRAIN DETECTION SYSTEMS
FOREWORD
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IEC 62427 has been prepared by IEC technical committee 9: Electrical equipment and systems
for railways. It is an International Standard.
This document is based on EN 50238-1:2019.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) generic compatibility process, which is broken into a two-stage process depending on
whether there are established compatibility limits or not;
b) rules for characterization of train detection systems;
– 6 – IEC 62427:2024 © IEC 2024
c) rules for characterization of rolling stock;
d) rules for characterization of the power system;
e) informative references are provided in notes to established CENELEC standards for
compatibility;
f) terminology is updated.
The text of this International Standard is based on the following documents:
Draft Report on voting
9/3115/FDIS 9/3142A/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
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• reconfirmed,
• withdrawn, or
• revised.
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INTRODUCTION
This document defines a process to demonstrate compatibility between rolling stock operating
on an area of use or network and train detection systems installed in this area of use or network.
Currently, general rules for the maximum levels of interference allowed, and maximum
susceptibility levels (or minimum required immunity levels) are not established in every country.
This is due to the great diversity of rolling stock, power supply and return current systems, and
train detection systems installed in each country. This diversity leads to consideration of
compatibility of rolling stock and train detection systems on a "route by route" or "network by
network" basis, to avoid unnecessarily restrictive specifications.
The compatibility process described in this document is generic. The process refers to all types
of train detection systems (TDS), which may be influenced by electromagnetic emissions of
rolling stock or traction power supply systems, (e.g. axle counters, track circuits, wheel
detectors, loops).
Compatibility is determined by both physical and electromagnetic considerations. With regard
to the electromagnetic compatibility, the need is not for general values for maximum levels of
interference permitted, and maximum susceptibility levels (or minimum required immunity levels)
but for convenient methods by which to specify the level of interference allowed for operation
on routes or a network.
Main interference sources are considered to be:
– rail currents and voltage sources;
– electromagnetic fields;
– differential voltage between adjacent axles of the train;
as shown in Figure 1.
Figure 1 – Sources of electromagnetic interference
In practice, the susceptibility of the system is determined by:
– the sensitivity of individual components of the system and the type of interference it is
susceptible to;
– the application of the components, i.e. the configuration of the system.
– 8 – IEC 62427:2024 © IEC 2024
Therefore the problems concerning TDS are considered separately for each type.
• National rules or standards, including agreements among stakeholders, define compatibility
limits for track circuits;
• National rules or standards, including agreements among stakeholders, define compatibility
limits for axle counters and wheel detectors;
• National rules or standards, including agreements among stakeholders, define the testing
method of rolling stock for electromagnetic compatibility with axle counters;
• Compatibility with other types of wheel detectors (mechanical or magnetic) is described in
5.4;
• Compatibility with loops can be established following the guidance in 5.5;
• Compatibility with any other type of TDS not explicitly covered by this document can also
be established following the generic process in this document.
NOTE 1 In Europe, CLC/TS 50238-2, CLC/TS 50238-3 and EN 50592 provide compatibility limits for track circuits,
compatibility limits for axle counters and wheel detectors, and the testing method of rolling stock for electromagnetic
compatibility with axle counters, respectively.
For determining the susceptibility of signalling systems, laboratory/simulation testing methods
and in situ tests on the "real railway" are proposed. Modelling enables worst-case conditions to
be simulated. In addition, particular test sites are selected because, from experience, they are
expected to provide the test evidence required.
Then, taking account of the experience of the railways, it is possible to establish a general
method for determining the susceptibility of train detection systems, described in this document.
NOTE 2 In Europe, general requirements on how to establish immunity have been defined in EN 50617-1 and
EN 50617-2.
Before assessing the electromagnetic emissions of rolling stock, sufficient knowledge of the
electric circuit diagram of the power equipment is important, including switching frequencies of
on-board power converters, type of regulation used for power converters, resonant frequency
of each filter, operating limits under high and low supply voltages, degraded modes of operation.
RAILWAY APPLICATIONS –
COMPATIBILITY BETWEEN ROLLING STOCK
AND TRAIN DETECTION SYSTEMS
1 Scope
This document describes a process to demonstrate compatibility between rolling stock (RST)
and train detection systems (TDS). It describes the characterization of train detection systems,
rolling stock and traction power supply systems.
It is worth noting that the demonstration of technical compatibility between the rolling stock and
infrastructure with respect to physical dimensions is not detailed in this document.
This document is not generally applicable to those combinations of rolling stock, traction power
supply and train detection system which were accepted as compatible prior to the publication
of this document. However, as far as is reasonably practicable, this document can be applied
to modifications of rolling stock, traction power supply or train detection systems which can
affect compatibility. The detailed process can be used where no rules and processes for
compatibility are established.
2 Normative references
There are no normative references in this document.
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1.1
competent body
body responsible for the independent evaluation of the compatibility case
Note 1 to entry: This can be an accredited conformity body or an independent safety assessor. This role is not
limited to external parties, unless mandated under the applicable legislation.
3.1.2
compatibility case
set of documents which records the evidence demonstrating the degree of compatibility
between rolling stock, traction power supplies and train detection systems for a specific route
or specific railway network
[SOURCE: IEC 60050-821:2017, 821-03-47]
– 10 – IEC 62427:2024 © IEC 2024
3.1.3
degraded modes, pl
modes of operation in the presence of faults which have been anticipated in the design of the
signalling system or the rolling stock
[SOURCE: IEC 60050-821:2017, 821-01-52]
3.1.4
traction power supply system
part of the overall electricity energy supply system, not extending beyond the dedicated feeder
stations on the rail network
Note 1 to entry: IEC 62313 applies at the interface to the national electricity supply network.
3.1.5
wheel detector
sensor which detects the passage of a wheel
Note 1 to entry: A wheel detector can be used as part of an axle counter or as a treadle.
[SOURCE: IEC 60050-821:2017, 821-03-53]
3.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms apply.
AC Alternating current
DC Direct current
IM Infrastructure manager
MVA Megavoltampere
NTR National technical rule
RINF Register of infrastructure
RST Rolling stock
TDS Train detection system
WSF Wrong side failure
4 Compatibility process
4.1 Overview
The party which introduces a new element or introduces a change of an existing element or
system is responsible for demonstrating compatibility between rolling stock, train detection,
traction power supply systems and neighbouring infrastructure, if applicable. The party is
responsible for initiating the compatibility process. The relevant data shall be made available
to the party responsible for constructing and/or amending the compatibility case. If data are not
available or not sufficient, alternative arrangements can be made by both the responsible party
and the affected party to demonstrate compatibility, for example by carrying out specific
compatibility tests. It is recommended that a competent body evaluates the compatibility case
if the stakeholders consider the modification to be a significant change. In 4.2 to 4.8, the specific
tasks to demonstrate compatibility are listed and explained.
4.2 Detailed compatibility process
The compatibility process is summarized in Figure 2.
Figure 2 – The compatibility process
4.3 Building the compatibility argument
A compatibility case in compatibility analysis shall be prepared, following the process depicted
in Figure 2, including but not limited to the:
a) definition of the scope of the compatibility case, including:
• new element to be introduced;
• identification of the route or area of use (network) if applicable;
• operational conditions;
b) description of the overall rail system including:
• infrastructure:
– train detection system (frequency-wide immunity limits if available);
– track parameters relevant for the train detection system (e.g. earthing and bonding);
– traction power supply and line parameters;
– 12 – IEC 62427:2024 © IEC 2024
• rolling stock in any configuration, including degraded modes:
– relevant operational conditions e.g. power limitations;
– factors affecting rolling stock characteristics and compatibility as listed in Annex C,
identification of disturbance sources, their behaviour and/or applicable summation
rules;
• adjacent infrastructure and other rolling stock, if applicable;
c) theoretical analysis (e.g. simulation) against requirements of the scope including
assumptions:
• derive the permissible interference per on-board source using the analysis in 4.8;
d) test plan taking account of the results of the theoretical analysis;
e) test reports – see Clause 8;
f) assessment of theoretical analysis and test reports against requirements:
• related compatibility cases;
• check of validity of assumptions;
• check if restrictions may be lifted or relaxed;
g) quality management plan and evidence.
If a competent body is appointed, then it is recommended to involve them at each step of the
compatibility case.
It is recognized that characterization of interference generated and propagated by rolling stock
can be a time consuming process, which may require a significant amount of testing during
service operations in order to refine the characteristics. Therefore, provided that the risks to all
parties can be demonstrated to be acceptable, temporary operational conditions may be
imposed prior to full compatibility being established.
Hereunder specific aspects of the compatibility case will be further outlined.
4.4 Quality management
Quality management systems shall be in place. The importance of configuration management
should be noted.
The configuration state of the relevant infrastructure and rolling stock (including maintenance
processes and schedules) shall be recorded and referenced within the compatibility case. Any
subsequent changes to these configurations shall lead to an examination of the continued
validity of the compatibility case.
4.5 Route identification for introduction of RST (new or changed)
In order to accept a particular rolling stock in respect of a particular route or network, the
different types and applications of train detection systems and traction power supply systems,
if applicable, on the network or on the route and on adjacent routes which can be affected shall
be identified. In addition to the intended operational route(s), alternative route(s), which may
be required in the event of disruption to traffic shall also be considered.
4.6 Introduction of infrastructure elements (new or changed)
In order to accept a particular infrastructure change (e.g. TDS or traction power supply) in
respect of a particular route or network, the different types of RST, TDS and traction power
supply systems on the network or on the route and on adjacent routes, which may be affected,
shall be identified.
4.7 Characterization
The characteristics of the identified systems shall be obtained in accordance with the following
clauses:
For train detection systems: Clause 5;
For rolling stock: Clause 6;
For power supply systems: Clause 7.
4.8 Compatibility analyses
4.8.1 General terms
It shall be demonstrated that the rolling stock characteristics for generated and propagated
interference comply with the train detection system limits, under defined operating conditions,
including degraded modes.
NOTE 1 EN 50617-1, EN 50617-2, EN 50592 are available for operating conditions in Europe.
The relationship between rolling stock and infrastructure is shown in Figure 3. The information
flow may be in either direction depending on which system is to be changed.
NOTE 2 Compatibility is now based on worst-case conditions. This results in very severe requirements for rolling
stock interference limits, while in practice the tolerable interference level is much higher due to overall degradation
of older systems and interference produced by the current collecting system. Despite this situation, the cases with
hazards caused by interference are very rare. It is obvious that a perspective of risk calculation will ease the
interference current requirement by probably a decade.
The safety margin is applicable for safety related tests, where train detection technology implies
WSF. The availability margin is applicable for availability related tests.
NOTE 3 All applicable parameters for compatibility cases of track circuits and axle counters in Europe can be
identified from EN 50617-1 and EN 50617-2 respectively.
The compatibility analysis is mandatory and shall explain the technical principles which ensure
compatibility, including (or giving reference to) all supporting evidence, e.g., calculations, test
plans and results.
The method of analysis of fault modes shall be agreed between the parties listed in 4.3.
The scenario for compatibility including the worst case shall be described with the following
parameters:
– transfer function between interference sources (rolling stock and infrastructure) and
sensitivity level of the used TDS in the specified frequency band;
– characteristics, operating modes and conditions of rolling stock (normal and degraded
modes of RST and maximum torque, speed or other operating conditions);
– characteristics and operating conditions (normal and degraded modes) of traction power
supply, including substation parameters and traction return path;
– safety and/or availability margin taking account of the above modes and conditions. Track
circuit sequencing is considered when safety or availability margins are agreed.
NOTE 4 Testing during operation in service on one vehicle will establish a probability for generated interference,
e.g. a level down to once per 1 000 h during several months of testing. This is only sufficient for the basic level of
generated interference current.
Both on-board systems and/or infra-side systems can be used to monitor the probability of
occurrence of high levels of interference currents, provided they remain compatible with the
various immunity levels of the propagation and detection systems.
– 14 – IEC 62427:2024 © IEC 2024
4.8.2 Transfer function
The "transfer function" expresses the relation between the received interference signal at the
train detection system equipment and the total interference signal generated by rolling stock.
Let the transfer function be denoted by F.
Let the interference signal at the train detection system equipment caused by a single train
and/or multiple trains at the electric section be denoted by I .
TDS
Let the interference signal generated by the rolling stock be denoted by I .
RS
The interference signal is then:
I = F × I
TDS RS
The maximum permissible interference signal at the train detection system equipment I
TDSmax
is determined by the sensitivity of the train detection system equipment. Let the total permissible
interference generated by rolling stock be denoted by I . Then:
RStot
I = I / F
RStot TDSmax
Where multiple sources (rolling stock and substations) may contribute to the total interference
signal, the permissible interference per source shall take this into account.
NOTE 1 Line resonances and phase sensitive receivers can be part of the evaluation of compatibility.
NOTE 2 In Europe, CLC/TS 50238-2 provides possible guidance on the application of the transfer function
considering multiple sources.
Note that the permissible interference signal will have two values determined by the following
criteria:
– the signal which may cause the train detection system to show clear when it is in fact
occupied (a wrong side failure, i.e. a matter of safety);
– the signal which may cause the train detection system to show occupied when it is in fact
clear (a right side failure, i.e. a matter of availability). The effect on interlocking logic shall
however be considered.
The process of application of the summation rules can be applied in both directions as depicted
in Figure 3.
Figure 3 – Relationship between compatibility limits and permissible interference
5 Characterization of train detection systems
5.1 Objective of procedure
To ensure the correct operation of axle counter systems, wheel detectors and track circuit
systems, their physical and electromagnetic properties are defined in the detailed standards
and regulations (see 5.2, 5.3 and 5.4 for details) as well as the measurement methodology and
how to report the compatibility with these standards.
– 16 – IEC 62427:2024 © IEC 2024
For other train detection systems not covered by standards, their relevant properties shall be
defined by the infrastructure manager in collaboration with the manufacturers. Relevant
information shall be described by the manufacturers in the product documentation.
5.2 Track circuit systems – Standards, regulations and technical specifications
Parameters for track circuits are provided by national rules or standards, including agreements
among stakeholders. All requirements to be fulfilled by a track circuit system are listed and
defined there in detail.
NOTE 1 In Europe, EN 50617-1 directly includes the requirements for physical and electrical aspects (e.g. axle
resistance, ballast resistance, broken rail behaviour) as well as the electromagnetic parameters (e.g. behaviour to
interferences and immunity limits), the measurements to be executed and the reporting to show the compatibility with
this document.
NOTE 2 The methodology defined in Europe in EN 50617-1 can be used where practically applicable.
NOTE 3 Guidance to establish compatibility limits is contained in Annex A. Some known track circuit compatibility
limits in Europe are published in CLC/TS 50238-2.
5.3 Axle counter systems – Standards, regulations and technical specifications
An axle counter system is the whole system including the axle counter detector with its sensor,
and the evaluation unit.
If the characterization is to be performed on the axle counter (wheel detector) alone, rather than
on the axle counter system, refer to 5.4.
Parameters for axle counter systems are provided by national rules or standards, including
agreements among stakeholders. All requirements to be fulfilled by an axle counter system are
listed and defined there in detail.
NOTE 1 In Europe, EN 50617-2 directly includes the requirements in accordance with physical and electrical
aspects (e.g. axle distances, fastenings to the rail, environmental conditions) as well as the electromagnetic
parameters (e.g. behaviour to interferences and immunity limits), the measurements to be executed and the reporting
to show the compatibility with this document.
NOTE 2 The methodology defined in Europe in EN 50617-2 can be used where practically applicable.
NOTE 3 Some known axle counter compatibility limits are published in Europe in CLC/TS 50238-3.
5.4 Wheel detectors (treadle applications)
5.4.1 General
Treadle applications are mainly switch on/off functionalities, direction detection or speed
measurement.
NOTE Requirements for wheel detectors applied as treadles in Europe are not explicitly described in EN 50617-2
because they are not used for axle counter systems.
5.4.2 Wheel detectors based on inductive technology
Owing to the principle of discrete detection of wheels passing a wheel detector, transient and
continuous interference limits may be considered as equivalent to the limits defined for axle
counter detectors or axle counter sensors.
NOTE 1 In Europe, EN 50617-2 can be taken into account where applicable for wheel detectors based on inductive
technology with respect to the physical, electromechanical and electromagnetic interface.
Owing to the inherent difficulties of designing a sufficiently complete electrical equivalent circuit
for an inductive wheel detector, field testing or alternatively laboratory tests injecting
interference currents into the rail and applying external electromagnetic fields shall be used for
measuring the susceptibility of wheel detectors.
To allow for uncertainties in the accuracy of measurements and simulations, the susceptibility
of the train detection system as determined above shall be increased by a factor of safety
(margin). The uncertainties shall be estimated and the factor of safety shall be sufficient to
allow for them.
It is possible that it will be necessary to take into account interference due to DC substation
ripple (e.g. harmonics of the substation voltage source) in the factor of safety.
NOTE 2 Wheel detectors based on other technology (e.g. mechanical or optical) are not described in detail in this
document.
5.5 Loops
5.5.1 General aspects
Loops are mainly used for level crossing applications, to command the lowering or raising of
barriers. A loop application based on the principle of continuous detection of a large metal mass
has a different influencing mechanism compared to axle counter sensors and track circuits
which shall be taken into account.
Loops have a greater area to be influenced by trains than wheel sensors, on the other hand the
sensitivity of a loop against rail currents is not directly linked because the loops are not
connected to the rails. Because of this, induction is the main interference mechanism. Loops
for communication tasks and/or automatic train protection applications are not within the scope
of this document.
For reliable train detection with loops, the definition of compatibility requirements with the train
shall be taken into account as shown in the example in Annex E, for a specific type of loops.
Loops are usually used as o
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