EMC aspects in railway systems often involve prediction of current flow in the distributed transmission line system formed by the rails and a number of other conductors. For this purpose the matrices characterizing the transmission line system has to be accurately known. For surface track configurations simplified analytical and numerical models exist.
The object of a recent study in this field was the question whether the surface track models can also be applied to tunnel configurations. A boundary element method was used to perform a parametric study on the configuration of the new dual-rail Botlek tunnel forming part of the Betuwe Route. The figure shows the current distribution in the soil surrounding the tunnel.