Experimental investigation of EM noise environment surrounding detector systems in Swedish railways

The close environment of railway tracks is heavily polluted by electromagnetic noise from the railway system itself. The reliability of railway signalling, communication, and control systems depends on good immunity to electromagnetic noise. There are sometimes false detector signals indicating non-existing flat wheels and ghost trains. A possible reason for detector failures is interference by transient voltage peaks in the detector system. Thus characterisation has been made of the electromagnetic environment around the detector system located at the track. The investigation shows that the typical electromagnetic environment is a combination of broadband low-level noise, and rare fast transients of potentially harmful amplitudes.