BS EN 50617-2:2015 Railway Applications – Technical parameters of train detection systems for the interoperability of the trans-European railway system Part 2: Axle counters

BS EN 50617-2:2015 pdf free.Railway Applications – Technical parameters of train detection systems for the interoperability of the trans-European railway system Part 2: Axle counters.
6.1.4 Maintainability
The following information and definitions are derived from EN 50126 and EN 50129.
The proper function of the axle counter system depends on correct installation, initial adjustment, preventive and corrective maintenance of the cabling, connections to the rail and position of the sensors.
The maintainability of the axle counter system shall be seen in the context of the complete integrated system including the ACD, the communication links, the evaluator unit and the power supplies.
The maintenance cycle shall have a frequency lower than or equal to once a year per ACO. The cycle for indoor equipment shall be described in the product specific user’s guide. This guide shall be checked for validation.
The scope and frequency of the maintenance cycle of the axle counter shall be described in the product specific user’s guide. A validation of these documents shall be done.
The supplier shall provide the information related to equipment failure modes and their rates of occurrence. This will enable infrastructure managers to estimate the corresponding MTTR and clarify the implications for their maintenance specification. Aspects to be taken into consideration on the trackside maintenance:
– Axle counter sensor has been damaged or knocked off the rail,
– Sensor sensitivity requires readjustment due to a deterioration of rail conditions (e.g. worn rail surface),
– Train wheel conditions changed (introduction of a new type of vehicle),
– Cabling is incorrectly connected to the sensor and or the connection box,
– Short circuit of two or more wires in the outdoor cable. Other aspects
In-House equipment – If there are any then they have to be described in the product specific user’s
guide,
– Cabling/wiringlconnection boxes,
– Time without train runs (refer to 6.1.5.2).
6.1.5 Safety
6.1.5.1 General
The following information and definitions are derived from EN 50126, EN 50128 and EN 50129.
The safe movement of the trains on railways relies on the train detection equipment. The following levels of safety integrity may be assigned.
NOTE THR is a term used in evolving safety related standards and means a specific calculable failure rate, which can be converted to a defined SIL level.
The safety integrity shall be validated based on the safety case of the axle counter system. It shall be shown in the safety case that the safety integrity level required is achieved. Requirements are described in EN 50126, EN 50128 and EN 50129.
Examples of applications with different safety requirements:
Lower safety integrity levels
For systems designed with the lowest level of safety integrity, the equipment is not safety relevant. There is no level of automatic train protection that can be achieved with these systems. In such circumstances, the train driver is responsible for the safe train movement. Based on the reaction time of drivers, the train speed shall be restricted to ensure safe operation. A set of “drive on sightTM rules shaI be defined. These types of low safety integrity train detection are applicable for example to manually operated trams which share the track with normal road traffic vehicles.
• Another application is where tracks are designed to transport freight only or with a very limited number of passengers per day. In this case the risk of injuries is limited to an acceptable level. A degree of safety integrity level is required to protect the train and the driver. Examples of such applications may be found in freight yards and depots where driverless train movements are permitted.
• Highest safety integrity level (SIL 4).
• On lines used to transport passengers and designed for speeds > 80 kmlh or where the direct line of sight is not always assured (e.g. in tunnels) the safety cannot be left to the responsibility of the drivers, and additional protection shall be provided. This scenario will occur on interoperable and on main lines with mixed passenger and freight traffic. In this case usually a safety integrity level of SIL 4 for the complete train detection system is required within the context of its application.
6.1.5.2 Maximum time between trains
This subclause defines the maximum time allowed between two train runs — the “maximum time without train runs”.
To alleviate any remaining hazards, it is recommended to specify a maximum time between trains of one year. This requirement for a SIL4 train detection system is deemed reasonable because no additional operating expenses are to be expected. Furthermore, an annual check run’ is considered more practicable from a maintenance point of view.
NOTE Train runs, where a fault occurs are not applicable as TMcheck runsTM for the purposes of this definition. The check run constitutes a physical train movement over the train detection section, to prove intended operation.
Typically the maximum time allowed without any train runs between two train wns is an input parameter for safety case and fault tree analysis. Validation is successful if
• the hazard rate (HR) of the overall axle counter system <tolerable hazard rate.
Failures that can only be revealed through a train run influence the hazard rate by increasing the risk when extending the duration of time between train runs. The limit for the maximum time is reached when:
• the hazard rate (HR)  tolerable hazard rate (THR).
6.2 Immunity against magnetic fields — in-band and out-of-band
6.2.1 General
ACD can be influenced in different ways. Within the frequency range of the ACD, the influence of magnetic fields generated by rolling stock is dominant. As a result of these fields, spurious wheel pulses may be generated in the ACD, potentially creating unreliability which can lead, in the worst case, to a safety risk.
To ensure proper compatibility between rolling stock and ACDs, electromagnetic emission of rolling stock has to be taken into account. Therefore it is necessary to test the immunity levels of ACDs to verify their conformity. The emission limits for rolling stock have been defined in the FrM and are the basis for deriving the immunity levels of the ACDs.
The following parameters are associated with the immunity of the ACD:
• immunity level to magnetic fields within the working frequency range:
o continuous magnetic fields;
o discontinuous (transient) magnetic fields;
• sesponse bandwidth (3 dB and 20 db);
• immunity to current in the rail;
• immunity to magnetic fields outside the working frequency range:
• immunity to magnetic field generated by the ETCS vehicle antenna.
The following subclauses describe the requirements for the axle counter immunity. The limits effectively encompass interference from magnetic fields of all sources which may occur at rail level, either generated by rail current or equipment on the vehicles, or both.
The associated measurement procedures for the determination of the magnetic field immunity levels of ACDs in all three directions X, Y and Z are described in Annex C.
6.2.2 Derivation of immunity requirements
The immunity requirements for the axle counters shall be derived from the FrM as specified in the CCS TSI Index 77.
The FrM defined in the CCS TSI Index 77 specifies the reserved frequency bands for the ACD with the corresponding emission limit values for rolling stock. The FrM defines three frequency bands for axle counters:
– 27 kHz to 52 kHz for band 1;
– 234 kHz to 363 kHz for band 2;
– 740 kHz to 1 250 kHz for band 3.
In addition, out-of-band limit levels are defined in the FrM, covering the range between the reserved frequency bands and in the frequency range from 10 kHz to 27 kHz.
In the complete frequency range from 10 kHz to 1,3 MHz rolling stock manufacturers are required to fulfil the specified magnetic field limits (in-band and out-of-band), applying specified evaluation parameters (e.g. filter bandwidth, filter order and integration time) as listed in Annex B.BS EN 50617-2 pdf download.
BS EN 50617-2:2015 Railway Applications – Technical parameters of train detection systems for the interoperability of the trans-European railway system Part 2: Axle counters