Measurements and analysis of electromagnetic interferences in the Swedish railway systems

Sammanfattning: Presently, the existing failure reporting system at Banverket (the Swedish Rail Administration), which handles reports on the failures of the railway infrastructures and possible causes of failure, is not optimum (or most suitable) when it comes to analysis of electromagnetic compatibility (EMC)- related failures and causes. This failure reporting system is reliant on correct reporting into the system, so that the right information can be sent back to the users, the maintenance and service personnel, in real time. In general railway infrastructure operates in a complex and non-homogeneous environment where low power electronics has to function in the same environment as large voltages and currents from trains. The environment close to the railway tracks is heavily polluted by electromagnetic (EM) noise from the railway systems themselves. The reliability of railway signalling, communication, and control systems depends on the degree of galvanic isolation from EM noise. When new technologies are implemented into old installations, the complexity of the system increases, leading to new challenges which necessitate new forms of skill and competence to deal with these issues and challenges. The new technologies which are to be integrated into the old systems, or which are to be applied to build new systems, must meet the requirements for EMC in order to obtain a high degree of system reliability and ensure the problem-free operation of such systems. The complexity of the infrastructure is not easy to simulate or calculate, and consequently it is important to observe the real systems and their characteristics in real situations. Therefore, measurements were performed on real systems in operation. To perform an audit of the problems in the railway systems leading to EM noises and failures, investigations were made by studying the real systems in operation and using the existing failure (and inspection) reporting system of Banverket. A large number of measurements were made on site at detectors and signalling systems and installations. By studying and analyzing the measured data and failure reports from the databases, an effort was made to understand the causes of faults related to EMI (Electromagnetic interferences). Thereafter, visual inspection was carried out in the engineering constructions, i.e. signal and detector boxes, to verify if the recurring faults are caused by poorly designed installations and their physical environment. The visual inspections were concentrated on EMC and to the areas from where the power and communication cables entered the locations selected for study, by examining the areas where the sensitive equipment was placed. Through the visual inspection it was found that there could be improvements in two problem areas, namely installations and instructions from the suppliers of equipment, which often result in wrong installations. During this study, measurements were performed at sites which had extensive EMC and EMI problems. The measurements clearly show the erratic characteristics of the equipment and systems used in signalling and detector installations, mainly leading to EMC and EMI problems. For example, the measurements from detectors show that random transients appear even when a train is not present, and the measurements in the signal box show a completely different behaviour where the measuring equipment showed a reading of over -100 volts in a 27 V system. These measurements and the results from the subsequent analyses show EMI characteristics which are totally unexpected. The detailed analysis of the failure reporting systems and databases shows that most of the failure causes are related to EMC problems. The fault reporting system is not configured to identify the failure causes as EMC or EMI problems. Therefore, this has to be investigated to identify the cause so that corrective actions can be initiated to restore the system to an operating condition. The research study has helped in understanding the function of railway signalling and detector installations from an EMC and EMI point of view. The knowledge generated will be of assistance in designing new signalling and detector equipment which will have a higher level of reliability, leading to a smaller number of failures and EMC problems. The study has made a contribution towards an understanding of the EMC and EMI characteristics of the signalling and detector infrastructure of the railway system. These characteristics often lead to failures resulting in train delays.