Modelling for electromagnetic interference assessment in electric railway traction systems

Electromagnetic field and circuit simulation models are described which enable a railway traction system with substations, traction drives, track signalling equipment, track and traction line to be assessed for low and audio frequency electromagnetic interference. The novel features are the derivation of frequency-dependent track and traction line impedance by the finite-element method of electromagnetic field analysis and the representation of the frequency dependency in circuit simulation by current-dependent voltage sources. Example interference spectra are given for cab signal current with audio frequency track signalling on a 3 kV DC traction system with 12-pulse rectifier substations and an inverter-fed traction drive