Compatibility between Rolling Stock, Signalling Systems, and Traction Power Supply Systems; A Study for Portuguese Railways

A railway system is a transport system on which high requirements are imposed with respect to reliability and safety. A railway system consists of a large number of subsystems, with mutual interactions, such as: Traction Power Supply Systems, Signalling Systems; Telecommunication Systems and Rolling Stock These systems are owned by various parties such as train operating companies and infrastructure managers, which increases the complexity. This leads to a large distributed system, for which it not only must be proven that electromagnetic compatibility exists between all systems, but at the same time the reliability, safety and availability must be at a high level. Due to the increasing use of power electronics in rolling stock, the emissions of harmonic currents of the rolling stock is increasing, not only in magnitude, but also higher frequencies are present. As the Eigen frequencies of the Traction Power Supply System are relatively low the higher switching frequencies of modern traction converters can lead to resonances in the Traction Power Supply System, which can lead to costly major malfunctions. At the same time compatibility must exist between the rolling stock and the train detection layer. This necessitates a careful fine tuning of the various system elements. As the railway system as a whole is a legacy system, in which for instance a large number of different systems are used for train detection, this is a complex and time consuming task, of which the importance is growing, illustrated for instance by the start of the EU STREP (Specific Targeted Research Project) Railcom. In Portugal the introduction of new rolling stock has lead to severe resonance problems in (traction) power supply systems. Before the introduction of a new switching frequency of the power invertors in the rolling stock it must be ascertained that not only no new problems with respect to resonances of the traction power supply system, but also with respect to the train detection layer (a safety critical system!) are introduced. A mutual project between REFER and Movares, with co-operation of CP (Comboios de Portugal), has been started to determine a solution, which is a technical and economical optimal solution. The project consists of 3 parts, homologation of the modified rolling stock with signalling and telecommunication installations, development and evaluation of a measurement system and modelling of traction power supply system. Two separate measurement campaigns are used to measure the compatibility with the train detection layer, a third measurement campaign for validation of the measurement system. The entire traction power supply network of Portugal (21 substations and 1430 km of line) has been modelled in the frequency range 100 Hz - 10 kHz. Using modelling it is possible to study the effect of the change in switching frequency and the different configurations of the traction power supply system more easily and more economical than using measurements. The simulation results compare well with the measurements performed. Using modern simulation tools and measurement techniques it is possible to reach compatibility between all elements of the railway system and prove that the RAMS (Reliability, Availability, Maintainability, Safety) requirements are met.