The design of modern railway systems involves ever challenging issues related to the demand for more and more high performances, as well as to the need for rolling stock interoperable over the European countries (where different versions of supply systems are used). From the engineering viewpoint, in recent years the design of traction systems and, in general, of the railway-system apparatus has implied the increasing introduction of high powered electronic equipment, micro-controllers, and electronic devices. Due to this trend, Electromagnetic Compatibility (EMC) and human-exposure to electromagnetic fields within the railway environment have become potentially critical issues. Basically, the importance of EMC aspects within the rail environment arises from the need to employ high powers for electric traction in conjunction with small signals for signalling, telecommunications, and control purposes. Therefore, from the electromagnetic standpoint, railway systems are complex and harsh environments in which numerous interference and interaction phenomena play a role in a very wide frequency range.
In recent years, the European Union (EU), aware of the fact that critical aspects related to EMC issues regard both the design and the implementation of modern rail transportation systems, has developed mandatory requirements that should be fulfilled by the railway systems and their apparatus. The EU Standards for EMC of railway systems outline and clarify all the general aspects related to emission and immunity verifications, but (as almost every EMC Standard) omit design-related aspects, aimed to develop tools and criteria oriented to EMC and eco-efficiency of railway systems of modern generation.
In this framework, this research project has considered the requirements and indications provided by the European Standard EN 50121 as a starting point for a quantitative analysis of the main electromagnetic interference/interaction phenomena, the development of optimized procedures and setups for EMC assessment, and the identification of EMC-oriented design strategies for the modern and future generation of railway systems.
The combined effect of the electromagnetic emission sources (conducted and radiated) of rolling stock and infrastructure determine the EMC level of a railway system to the outside world, whereas the electromagnetic interaction between different parts of a transport system determine the internal EMC level of that system. Identification, modelling, and experimental evaluation of such phenomena are therefore of paramount importance with regard to the quantitative evaluation of the whole EMC and, particularly, with regard to the development of intrinsically EMC-oriented design criteria.
In this context, this research project was aimed to define measurement procedures and setups for railway transportation systems of new generation in order to:
- ensure repeatability and to provide well-defined experimental evaluations of electromagnetic emission/interference levels and performance comparison of rolling stock or infrastructure of different kind;
- allow quantitative verifications of functional-safety levels and environmental-safety (human exposure to electromagnetic fields);
- relate EMC assessments to the design process by introducing EMC-oriented design strategies;
- conduct feasibility and performance analyses oriented to the design of innovative systems/subsystems for data transmission on board of rolling stock, devoted to future generation services.
Specific objectives of this project were to:
- improve the theoretical and experimental characterization of electromagnetic interference phenomena in the rail environment;
- develop methodologies, prediction models, measurement procedures, and setups helping EMC-oriented design of modern railway systems.
The methodology adopted in this research project was based on the identification of the most relevant EMC issues for the rail environment and investigation of the dominant effects related to the involved interference phenomena.
Particularly, the three principal EMC sub-problems (TOPICS) listed in the following were identified and investigated:
TOPIC 1: Electromagnetic emissions radiated by a railway system:
Characterisation of the external and internal (i.e., inside rolling stock) electromagnetic environments; characterisation of the contribution of rolling stock to radiated emissions and analysis of the impact of the infrastructure.
The main task within this TOPIC was the analysis of the electromagnetic emissions radiated by a railway system to the outside world, targeted to characterize the infrastructure impact on the radiation of the electromagnetic emissions generated by rolling stock. This analysis was addressed at:
- theoretical investigation of the radiation properties of the infrastructure;
- identification of a “standard infrastructure” with controlled characteristics, to be used as a test site for experimental verification of the radiated emission levels due to rolling stock.
TOPIC 2: Intra-system Electromagnetic Compatibility of the railway system: modelling of interference sources and electromagnetic interactions between rolling stock and infrastructure. The main task within this TOPIC was to study the main interference phenomena which determine the level of internal EMC of the railway system. This activity was addressed at:
- modelling of the main emission sources;
- modelling of phenomena and dominant coupling paths: emissions injected into the feeding line, radiated emissions, interaction with other on-board systems, with the signalling system, with infrastructure apparatus and with nearby infrastructures;
- development of measurement procedures.
TOPIC 3: Innovative systems (wired and wireless) for data transmission on-board of rolling stock: feasibility analysis, performance and EMC analysis.
The main task within this TOPIC was to carry put a performance analysis and characterization in terms of EMC of different techniques for data transmission on board of rolling stock. To this aim, both wired [traditional and
The following key results were obtained:
- Design and implementation of innovative time-domain measurement systems for the characterization of electromagnetic emissions on board rolling stock.
- Identification of optimal detection and estimation techniques for evaluation of the ICNIRP safety index associated with the radiated electromagnetic emissions in the rail environment.
- Development and implementation of a simulation tool (based on transmission line theory) for the analysis of noise current distribution along the railway line conductors. This tool allows for the identification/characterization of possible resonance phenomena and for investigation of the radiation properties of the railway infrastructure.
- Development and implementation of a simulation tool for the evaluation of the electromagnetic coupling onto the signalling system, and between systems based on different technologies (wired, wireless).
- Development of innovative calibration procedures for conducted susceptibility testing of onboard data-buses, based on bulk current injection (BCI).
- Design of an innovative communication system based on broadband powerline communications (PLC) technology for onboard data transmission.
T1: This project has proposed new measurement procedures/systems for the assessment of EMC and human exposure to electromagnetic fields. These procedures can be applied for a systematic and effective characterization of EMI phenomena in the rail environment and to assure interoperability of rolling stock of modern generation over the EU Countries.
T2: The innovative communication systems for onboard data-transmission developed by this project have great potential with respect to the development of future generation onboard services.
P1: Assessment of EMC levels of modern railway systems and verification of human exposure to electromagnetic fields in the rail environment are tasks of paramount importance, inherently related to a) the system performance and reliability, b) the functional safety of the system itself and of other equipment within or external to its border, c) the environmental impact (i.e., safety and well-being of individuals and societies). For these reasons all Member States should continuously update measurement procedures for the characterization of EMI phenomena and enhance system performance and services. As proposed by this project, this can be done by spinning in novel promising technologies and new results, as they are made available by the EMC community.