BRITISH STANDARD BS EN 50238 2003 Railway applications — Compatibility between rolling stock and train detection systems ICS 29 280; 45 060 10 ?? ? ??????? ? ??????? ? ??? ? ?????????? ? ?????? ? ?? ?[.]
Overview
The parties concerned in the acceptance process are shown in Figure 2:
Acceptance Railway infrastructure authority No 1
Figure 6 – The parties concerned in the acceptance process
Responsibilities
The responsibility for ensuring compatibility among rolling stock, train detection, and traction power supply systems is a shared duty between the parties managing the railway infrastructure and the rolling stock Clear delineation of specific responsibilities, including the lead role for each compatibility case, is essential Documentation of these compatibility cases must be submitted to an accepting body and reviewed whenever modifications occur.
For a defined route (the application of interest), the railway infrastructure authority should characterise all train detection systems and the traction power supply system
The rolling stock operator should characterise the interference which may be generated and propagated by the rolling stock
The accepting body shall review submitted documents and as a result issue a certificate of acceptance
As part of this process, the accepting body should ensure that the compatibility case is reviewed by experts who are qualified to assess and evaluate it.
Acceptance process
The acceptance process is summarised in Figure 3:
Modify rolling stock ? Theoretical analysis
Additional information and/or measurements
Acceptance with temporary restrictions ? No
Economic and technical comparison of available solutions : selection of optimum solution
Description of power supply system
Can a compatibility case be made ?
No Acceptance with permanent restrictions ? certificate No Yes mandatory action optional action
Test plan approved by accepting body ?
Characterisation of train detection system gabarit
Compatibility case 1 1
A compatibility case shall be prepared, including but not limited to, the following:
− characterisation of train detection systems;
− characterisation of traction power supply system;
The compatibility case shall be submitted to an accepting body for approval.
Quality management 1 1
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, along with maintenance processes and schedules, must be documented in the compatibility case Any changes to these configurations will necessitate a review of the compatibility case's ongoing validity.
The testing organization must demonstrate its ability to perform measurements in a traction environment and should ideally be certified to EN ISO/IEC 17025 Additionally, it is essential for the organization to have a documented quality system that complies with a recognized standard.
To ensure objectivity during testing, especially when a manufacturer tests its own equipment, the testing organization must undergo an audit by the accepting body.
Route identification 1 1
To accept specific rolling stock for a designated route or network, it is essential to identify the various types and applications of train detection and traction power supply systems on the route and any adjacent routes that could be impacted Furthermore, alternative routes that may be necessary during traffic disruptions should also be taken into account alongside the primary operational routes.
Characterisation 1 1
The characteristics of the identified systems shall be obtained in accordance with the following clauses:
Tests 1 2
A test plan shall be prepared in accordance with 6.4
Tests shall be conducted in accordance with the test plan and a test report produced in accordance with Clause 6.
Compatibility analysis 1 2
The rolling stock characteristics for generated and propagated interference must align with the train detection system's specifications under specified operating conditions, including degraded modes, as illustrated in Figure 4 The information flow can vary in direction based on the system that requires modification.
Permissible interference per on-board source
Total interference from on-board sources
TRAIN DETECTION SYSTEM SUBSTATION ROLLING STOCK
Figure 8 – Relationship between gabarit and permissible interference
Additionally, the physical characteristics of the rolling stock shall be demonstrated to be compatible with the train detection systems
The compatibility analysis is mandatory and shall explain the technical principles which assure compatibility, including (or giving reference to) all supporting evidence e.g., calculations, test plans and results etc
The analysis method for fault modes must be mutually agreed upon by the parties specified in section 4.2 For complex systems, it may be necessary to refer to the "risk" and "risk analysis" clauses outlined in EN 501 26.
NOTE In accordance with the new organisation defined by EC Directive 91 /440, it could be necessary to define a new
“infrastructure gabarit” including both the train detection system gabarit and the substation characteristics
The accepting body shall review the compatibility case and issue a certificate of acceptance
Characterizing the interference caused by rolling stock is often a lengthy process that necessitates extensive testing during service operations to fine-tune its characteristics To expedite this, temporary acceptance may be granted if the associated risks are deemed acceptable, enabling the identification of overlooked factors in the compatibility assessment before full acceptance is achieved.
Any temporary acceptance shall be time limited and be provided for a specific agreed purpose, whilst additional measures to identify interference and mitigate against possible hazards should be implemented
If an assessment reveals non-compliance with the current gabarit or an increase in susceptibility that renders previously accepted rolling stock non-compliant, the Railway Infrastructure Authorities and rolling stock operators must collaboratively decide on necessary modifications to the infrastructure or rolling stock and initiate acceptance processes as needed Should modifications be unfeasible or not implemented, permanent restrictions will be enforced.
5 Characterisation of train detection systems
Objective of procedure 1 3
To ensure the correct operation of train detection systems, their physical and electromagnetic properties shall be checked against those of the rolling stock and the traction power supply system.
Physical compatibility 1 3
Physical compatibility, including but not limited to the following aspects, shall be considered:
− response time of track circuits;
− shunt values of track circuits;
− shunt impedance of trains, and reliability of shunting in all service conditions;
The reliable detection of wheels may be influenced by factors including but not limited to the following:
− equipment which may be mistaken for a wheel, e.g track brakes or metal assemblies which are mounted close to the rail head
Axle counters and treadles are generally specified to detect reliably wheel types used on main line vehicles Other vehicle types may require special settings of the wheel detectors
Equipment mounted within the immediate vicinity of the rail may interfere with the reliability of wheel detection either by fouling mechanically or due to their electromagnetic properties (see Annex A)
This aspect of compatibility shall be assessed by testing.
Electromagnetic compatibility 1 4
This subclause outlines the measurement of the train detection system's gabarit, establishing a general approach while acknowledging the unique details of each installation It emphasizes that the compatibility case must encompass all plausible configurations and parameters, with examples provided in Annex A.
The required measurements are as follows
5.3.1 The sensitivity of the train detection system equipment (see 5.3.3.1 for track circuits; 5.3.4.1 for wheel detectors).
The transfer function, denoted as F, describes the relationship between the interference signal detected by the train detection system and the interference produced by the rolling stock For detailed information, refer to sections 5.3.3.2 regarding track circuits and 5.3.4.2 concerning wheel detectors.
Let the interference signal at the train detection system equipment be denoted by I TDS
Let the interference signal generated by the rolling stock be denoted by I RS
The interference signal is then:
The maximum allowable interference signal for the train detection system, denoted as I TDSmax, is dictated by the sensitivity of the system The total permissible interference produced by rolling stock is represented as I RStot.
Where multiple sources may contribute to the total interference signal, the permissible interference per source shall take this into account (see 5.8)
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);
A right-side failure in the train detection system can lead to incorrect indications of occupancy, even when the track is clear It is essential to assess the impact of this reliability issue on the interlocking logic to ensure safe and efficient train operations.
5.3.3.1 Sensitivity and susceptibility of equipment alone
The sensitivity of track circuit equipment must be assessed, with the receiver's susceptibility typically being more critical than that of the transmitter This receiver sensitivity will largely dictate the acceptable level of interference, although it is also important to evaluate the transmitter's susceptibility.
Where the sensitivity of the track circuit is adjustable, it shall be measured for all the relevant settings and in particular for the worst case settings
The susceptibility shall be determined as follows
The parameters, including amplitudes, frequencies, and durations of voltages, currents, or electromagnetic fields, can energize the receiver even without a signal from the transmitter, leading to a "track circuit unoccupied" indication.
Certain track circuit receivers designed for amplitude modulation can also be activated by a mix of unmodulated frequencies Similarly, some receivers intended for frequency modulation may respond to one or more amplitude modulated frequencies.
The parameters, including amplitudes, frequencies, and durations of additional voltages, currents, or electromagnetic fields, can potentially de-energize the receiver or affect the transmitter's output signal, leading to a "track circuit occupied" indication.
Information regarding the track circuit equipment must be sourced from the suppliers In instances where this information is unavailable, such as with obsolete designs, laboratory measurements should be conducted to obtain the necessary data.
5.3.3.2 Transfer function of track circuit as installed
The transfer function of the installed track circuit with regard to interference current shall be determined as follows
To determine the electrical equivalent circuit of the track circuit and its interaction with the traction power supply system, it is essential to consider all relevant conductors, including catenaries, conductor rails, cross-bonded running rails, return conductors, impedance bonds, booster transformers, earthed structures, and earth paths Typically, the "worst case" transfer function will be associated with the maximum length of the track circuit.
5.3.3.2.2 Set up the equivalent circuit using a real test site or a hardware or software model If a model is used it shall be verified by means of comparative site tests
To measure the voltage or current at the terminals of track circuit equipment caused by the current generated by rolling stock, the transfer function is defined as the ratio of the voltage at these terminals to the interference current.
NOTE 1 The value of the transfer function will depend on the position of the train with respect to the track circuit The worst case value shall be determined
If a train is equipped with multiple on-board power sources, consists of electric multiple unit stock, or uses the rails for the return current path for auxiliary power supplies, it may require representation by more than one current source.
Conduct tests under fault conditions, such as broken rails, cross-bonds, and return conductors, as illustrated in Annex A (see 4.9) The "worst case" transfer function is defined as the ratio of the maximum interference voltage observed at the track circuit equipment terminals during these fault conditions to the interference current(s).
The transfer function of the installed track circuit concerning electromagnetic fields should be assessed similarly to interference currents; however, practical site tests are likely to yield more relevant results than computer modeling An example illustrating this process can be found in Annex A.
The wheel detector circuits used in axle counting systems are usually galvanically decoupled from currents flowing in the rails
Axle counters can be influenced by electromagnetic interference that is transmitted through wheel detectors, making their sensitivity largely dependent on the electromagnetic susceptibility of the wheel detector employed Additionally, the configuration of the system may lead to interference along the transmission path between the trackside and the evaluation unit located in the interlocking room.
The return current (d.c or a.c.) in the rail can interfere with permanent-magnetic or inductively operating wheel detectors
− directly, through its effect on the sensors,
− indirectly through its effect on the permeability of the rail
Direct coupled interference is expected to be most severe at the operating frequency of inductive sensors Harmonics of rail current shall be considered
Electromagnetic interference fields from equipment on the rolling stock can also affect the wheel detectors Major sources of interference include:
− transformers and converters, especially when fitted under the vehicle close to the rails Harmonic content of interference shall be considered;
Factor of safety 1 7
To account for potential inaccuracies in measurements and simulations, the sensitivity of the train detection system must be enhanced by a safety factor This safety factor should be adequate to accommodate the estimated uncertainties involved.
Interference due to DC substation ripple may need to be taken into account in the factor of safety.
Track circuit susceptibility 1 7
5.5.1 Permissible interference signal for right side failure
The allowable interference signal for right side track circuit failures is assessed without considering faults in the traction return system, as track circuits are not anticipated to function reliably when such faults are present.
Let the transfer function in this case be denoted by F norm
Let the interference signal which causes the track circuit to show occupied while clear be denoted by
Then the total permissible value of interference I RStot, occ for this case is given by:
I RStot, occ = I TDSocc / F norm for all combinations of amplitude, frequency and duration of the interference signal
5.5.2 Permissible interference signal for wrong side failure
For wrong side failures the worst case fault in the traction return system, resulting in the “maximum” transfer function F max, shall be assumed
Let the interference signal which causes the track circuit to show clear while occupied be denoted by
Then the total permissible value of interference I RStot, clear for this case is given by:
I RStot, clear = I TDSclear / F max for all combinations of amplitude, frequency and duration of the interference signal.
Wheel detector susceptibility 1 7
Due to the principle of discrete detection of wheels passing a wheel detector, transient and continuous interference may be considered as equivalent
The susceptibility of wheel detectors shall be determined under laboratory conditions as follows:
5.6.1 Set up a wheel detector arrangement as in the field with worst case geometrical conditions (e.g worn wheels, small wheel diameter, worn rail profiles).
Inject a specified interference current into the rail using the mounted wheel detector, or apply a defined interfering electromagnetic field that simulates the rolling stock, including traction current and harmonics Measure the resulting changes in the internal signal—such as current, voltage, or frequency—that are crucial for the wheel detector's switching function.
The frequency of harmonics shall include the operating frequency of the wheel detector
The value of external interference signal causing an unwanted reaction of the wheel detector, both with and without a wheel passing, shall be measured
Axle counters must demonstrate that their counting reliability remains intact despite anticipated interference, and it is not necessary to distinguish between counting failures on the right side and wrong side caused by this interference.
Train detection system gabarit 1 8
The train detection system gabarit is the maximum permissible value of interference signal determined above, reduced by the factor of safety (see A.1 0).
Interference signal generated by rolling stock and substations 1 8
The interference signal generated by rolling stock and substations is a function of the following:
− the interference signal generated by each source;
− the rules adopted for the summation of interference signals from different sources
5.8.1 Interference signal generated by each source: track circuits
Track circuits are affected by the following sources of interference current:
− the current drawn by the rolling stock
− with the rolling stock considered as passive impedances, and
− with the traction power supply interference voltages superimposed on the supply voltage
The currents are constrained by establishing a minimum impedance value for the rolling stock and controlling the interference level produced by the substation In certain situations, the rolling stock's impedance may interact with the power supply's impedance, leading to additional interference that cannot be solely attributed to either source.
− the current generated by the rolling stock powered with a “pure” voltage (d.c or undistorted sine wave a.c.) This current includes:
− the interference current generated by the traction equipment;
− the interference current generated by on-board converters for auxiliary power supplies (note that the return current from these may flow through the rails beneath the train);
− unwanted coupling from the transmitter(s) of other track circuit(s)
5.8.2 Interference signal generated by each source: wheel detectors
The major sources have been defined in 5.3.4 The effect of multiple source interference shall be considered in the particular case
Test report 1 9
The tests and the context in which they were performed shall be presented in a report, the main text and appendices of which should include the following
A general presentation of the systems under test
A statement of who performed the tests and the contact address
The design status of the train detection system encompasses both hardware and software components, as detailed in the documentation This status is crucial for understanding the factors that influence the system's characteristics and overall performance.
This includes the test plan, the description of the train detection system and the document listing the factors affecting its characteristics
With specific reference to compromises or amendments to the test plan which were found to be necessary, including
− test conditions - technical characteristics of the test site,
− instrumentation - a block diagram of the equipment used, the location of the measuring instruments, the interconnections between them, their accuracy, response characteristics, sensitivity, signal scalings, etc.,
− test procedure - calibration, verification of environmental noise, operational conditions of the system under investigation during tests
− the sensitivity of the train detection system alone,
− the transfer function of the train detection system as installed,
− the electrical equivalent circuit of the train detection system and traction power supply system,
− description of model (if used),
− verification of model (if used),
− results of tests; “normal” and “maximum” transfer functions,
− list of possible fault conditions considered,
− gabarit of train detection system,
− summation rules (for use by rolling stock operator)
An evaluation of the results, their validity (e.g why the site was chosen) and comparison with expected results
Measurements typically involve gathering extensive recordings, which may not always be feasible to reproduce and distribute with a report However, it is essential to ensure these recordings are archived, and the test report should include information on how authorized access to this documentation can be obtained.
Objectives of procedure
Tests shall be made on rolling stock to verify the interference generated and also for the following reasons:
− to acquire additional information concerned with the characterisation of the train power system;
− to compare measured levels of interference with those predicted to confirm the understanding of the train power system
Tests should be clearly defined, conducted, and documented to ensure clarity and prevent unnecessary retesting if a new route for the rolling stock is considered in the future.
Previously accepted rolling stock may not need additional testing on new routes if the characteristics of these routes are similar to those of existing ones, such as when extending a line with comparable train detection and traction supply systems.
Electrical multiple unit trains must undergo testing as a complete fixed formation, while locomotives are tested independently from the coaches they pull Each type of passenger coach being towed is required to be tested separately, following the guidelines set forth in UIC 550 For information on summation rules for harmonic currents, refer to section A.1 1.
Description of rolling stock and factors affecting its characteristics
The manufacturer or operator must define and document the factors influencing the compatibility of rolling stock and signaling, ensuring that all relevant modifications to the rolling stock are included Additionally, it is essential to clearly identify safety-critical components.
Annex C lists known factors which can affect the rolling stock / signalling compatibility.
Configuration (design status)
Measurements must be conducted on representative samples of the rolling stock intended for acceptance The equipment should be in a fully developed and modified operational state, with the status of hardware and software—critical factors influencing rolling stock and signaling compatibility—clearly documented and understood.
Test plan
The test plan is a crucial document that must receive approval from the relevant authority to effectively measure the characteristics of rolling stock It should reference specific criteria to ensure comprehensive evaluation.
Measurements must be conducted with rolling stock on track sections that closely represent the intended routes It is essential to assess the suitability of using a less-than-fully representative test site to explore the range of tests outlined in section 6.4.3.
Rolling stock shall be tested on lines electrified with the different types of traction power supply with which the rolling stock can operate
To ensure clarity in results, it is essential to consider the interference levels contributed by the characteristics of the traction power supply, as well as those generated by the rolling stock being tested.
Measurement and testing equipment shall be specified and agreed (in particular transducers, spectrum analysers, selective voltmeters)
The selection and arrangement of instruments must ensure that measurements can be accurately interpreted in relation to the reference gabarit(s) It is essential to take specific factors into account during this process.
− quantification of systematic errors; e.g noise, intermodulation effects, etc.,
− system response to evaluate signals within both frequency and time domains,
− measurement of modulation between frequencies or other gabarit specified criteria,
− recording of speed, location, traction power supply parameters and other factors which may have an influence on the level of interference currents generated,
Annex B details ways in which the above have been addressed historically
Tests will be carried out across a variety of conditions that may arise during normal operations, ensuring a sufficient number of tests to reveal the true characteristics of the rolling stock The most extreme scenarios will be analyzed in detail Testing should occur under the specified operational conditions.
− the full extent of the effort-speed characteristics in motoring and braking (including regenerative braking);
− constant speeds up to the maximum (regulated by speed control or the driver);
− operation at reduced efforts as determined by the position of the driver's power controller;
− sequences of motoring, coasting and braking;
− normal and degraded modes of operation;
− typical variations or disturbances in the supply voltage (e.g due to other trainsets on the system, a substation cut out, line gaps, poor contact of current collection equipment etc.);
− environmental conditions which can affect the rolling stock equipment operation (e.g wheelslip, wheelslide etc.);
− regular known transients (e.g circuit breaker opening / closing, particular rolling stock equipment starting / stopping)
Test report
The tests and the context in which they were performed shall be presented in a report, the main text and appendices of which should include the following
A general presentation of the systems under test (rolling stock, power supply system and train detection system)
A statement of who performed the tests and the contact address
A definition of the design status of the rolling stock, including the status of hardware and software listed in the documentation of the factors affecting the rolling stock’s characteristics
This includes the test plan, the description of the rolling stock and the document listing the factors affecting rolling stock’s characteristics
With specific reference to compromises or amendments to the test plan which were found to be necessary, including
− test conditions - technical characteristics of the test site,
− instrumentation - a block diagram of the equipment used, the location of the measuring transducer, the interconnections between instruments, their accuracy, response characteristics, sensitivity, signal scalings, etc.,
− test procedure - calibration, verification of environmental noise, number of test runs, operational conditions of the system under investigation during tests
An analysis and summary of the measurements made with typical examples of recordings
An evaluation of the results, their validity and comparison with expected results.
Archive of test results
Measurements typically necessitate gathering extensive recordings While it may not be feasible to include all these recordings in a report, it is essential to ensure they are archived properly The test report should indicate how authorized individuals can access this documentation.
7 Characterisation of traction power supply systems
Objective
The objective is to determine the influence of the power supply system upon the characterisation of the rolling stock
Relevant factors include but are not limited to the following:
− impedance of catenary or conductor rail(s);
− normal and degraded modes of operation
Information about power supply characteristics are defined in EN 501 63
Interference frequencies can arise from either the substation or the rolling stock, leading to potential confusion regarding their origin It is essential to clarify and resolve this ambiguity.
Resonances and oscillations shall also be considered.
D.C traction power supplies
D.C traction power supplies, due to their rectifiers, are prone to generating interference currents that can impact track circuits Annex D provides a brief overview of how these interference currents interact with both rolling stock and the d.c traction power supply.
7.2.1.1 Substations equipped with diodes only
The voltage ripple is mainly due to the rectifier bridge and to phase unbalance in the high voltage supply
To begin, voltage ripple measurements should be taken on the rolling stock near the substation with the traction power system disabled If there is significant uncertainty, voltage ripple should be assessed on a power resistive load, contingent upon an agreement between the railway infrastructure authority and the testing organization.
7.2.1.2 Substation equipped with regulated converters
Voltage ripple can arise from imbalances in the converter control system and should be characterized under both no-load conditions and with a power resistive load.
A.C traction power supplies
Guidelines for the determination of susceptibility of train detection systems
Here are some simplified examples of train detection system configurations, which do not include structures connected to the traction return rail It is important to note that these configurations are not exhaustive; they serve merely as illustrations of the various scenarios that should be taken into account.
Figure A.1 2 – Interference mechanism with rails intact
The voltage drop along the length of traction return rail included within the track circuit appears across the track circuit receiver when the track circuit is occupied
A.3 Interference mechanism with broken signal rail
With a break in the signal rail the track circuit will show occupied (a “self-revealing” fault) The circuit is as shown:
Figure A.1 3 – Interference mechanism with self-revealing broken rail
The voltage at the receiver is influenced by the voltage drop between the vehicle and the feeder station, with the ballast resistance of the broken rail in series with the track circuit receiver's input This broken rail condition leads the track circuit to indicate an occupied status, a scenario that should occur rarely.
A.4 Interference mechanism with broken return rail
In the case of an unrevealed break in a traction return rail, the circuit becomes:
Traction current I Track circuit receiver
V=Vab+Vbc+Vcd+Vde+Vef
Figure A.1 4 – Interference mechanism with unrevealed broken rail
The longer return path for traction current to the feeder station, with some current flowing through the earth, results in increased interference voltage at the receiver This return path length is influenced by the spacing of the cross-bonds and the length of the track circuit.
A typical configuration for a double rail track circuit is shown:
Figure A.1 5 – Double rail track circuit
In typical operations, the traction return current in each rail is nearly equal, leading to minimal voltage at the track circuit equipment terminals However, if a rail is broken or an impedance bond fails, the return current becomes significantly unbalanced, causing a transverse voltage to develop.
Figure A.1 6 – Double rail track circuit with broken rail
A break in the track circuit typically results in the circuit indicating it is occupied; however, certain types of track circuits may allow for false energization due to interference prior to the train's arrival, potentially enabling the train to proceed Consequently, the track circuit may incorrectly display as clear even when a train is present.
A.6 Voltage between axles of rolling stock
Figure A.1 7 – Interference mechanism due to voltage between axles – Case 1
When a voltage is generated between a train's axles, a portion, denoted as α, can be detected by the track circuit receiver If the length of the train is comparable to that of the track circuit and the spacing of the cross-bonding, α can be close to one.
Figure A.1 8 – Interference mechanism due to voltage between axles – Case 2
If two trains contribute to the interference, the combined effect is similar to that for one train
A.7 Effect of resistance between coupled vehicles
X = vehicle bonding (if fitted) resistance
Figure A.1 9 – Effect of inter-vehicle current
This can be re-drawn (ignoring rail resistance):
Figure A.20 – Equivalent circuit for previous figure
If all r are equal and R ằ r and X → ∞ (either disconnected or not fitted) then VR → I × r
If the maximum tolerable VR is 200 mV and I is 1 20 A then rmax = 1 ,7 m Ω if X → ∞ or rmax = 5 m Ω if X ≈ r
These values are quite low
Loops within magnetic field generated by rolling stock
Rolling stock with chopper or converter
Track circuit without insulated joints
Track circuit with insulated joints
Loops within magnetic field generated by rolling stock
Figure A.21 – Example of radiated interference
A.9 Example of sensitive zone of wheel detector
Figure A.1 1 below shows the area in which mechanical parts of vehicles may have an influence on wheel detectors
Figure A.22 – Sensitive zone of wheel detector
The impact of an unsafe failure in a train detection system is influenced by how the system's indications (track occupied or clear) are utilized within the interlocking Implementing sequential proving of track section occupation in the interlocking can significantly mitigate the consequences of a false clearance.
The value of the factor of safety will be chosen according to the following considerations:
− accuracy of known information (e.g track layouts, number of trains);
− accuracy of predictions (e.g computer models);
− “safe” or “unsafe” failure of the train detection system;
− the way the train detection system indication is processed in the interlocking;
The appropriate factor of safety cannot be predetermined; it must be established and justified within the compatibility case for each specific application (refer to Clause 4).
In countries where a fixed factor of safety is normally applied, this should be adopted, unless the compatibility case shows that a higher value is required
Recommendations for factors of safety are given in UIC 737-3
The maximum number of interference sources impacting a train detection system must be established based on operational factors Additionally, summation rules should account for the interdependence among various equipment.
ORE B1 08/1 outlines the guidelines for distributing interference currents from traction equipment and auxiliary converters based on the train's position relative to the track circuit These general guidelines are replaced by the specific transfer function defined in this procedure.
Guidelines for the measurement of rolling stock characteristics
B.1 An example of a conceptual block diagram of a system used to measure interference currents
Figure B.2 – Example of system for measurement of interference currents
The choice of the interference current measuring depends on the type of rolling stock:
For electrical locomotives and multiple units, measurements should be conducted as near as possible to the current collection equipment, such as the pantograph or third rail shoegear In exceptional cases, measurements may be taken at other points in the current path, provided it can be theoretically or practically demonstrated that the results will not differ significantly.
− for diesel locomotives, the measurements are made on the high voltage auxiliary train line;
Measurements for trailer equipment, such as static inverters or battery chargers, are conducted either on the High Voltage auxiliary train line when multiple elements are connected in parallel or directly at the equipment input when a single element is involved.
Transducers used for measurement must be compatible with the supply type, whether single-phase AC or DC, and should be specified with adequate precision to effectively cover the relevant frequency range The response characteristics of the measuring transducer are determined through calibration testing.
The equipment used in the instrument system processes the signal from the transducer to simulate the characteristic response of the susceptible track circuits In particular:
− all relevant signals are recorded in a mass memory medium such as magnetic tape;
To achieve optimal dynamic range for the frequencies and levels under investigation, the system's gain and pre-filtering are carefully adjusted, considering the limitations of the recorded signals' dynamic range.
The interference current is processed by specialized instruments designed to replicate the characteristics of the track circuit, with the results displayed on a graphic recorder or plotter This signal processing can utilize analog, digital, or a combination of both techniques, and may include specific analyses such as frequency modulation, as outlined in the relevant specifications.
− the interference current is signal processed as function of frequency and recorded with one or more spectrum analysers;