Abstract
The South African railway company makes use of a train wheel detection system to
monitor the trains present on a particular track, noting their lengths, positions and
speeds. Interference due to distorted traction currents cause havoc with this system
rendering the information gathered unreliable. To combat this interference two paths
are available to reduce the detection systems susceptibility. These paths include the
addition of shielding between the railway track and the wheel detectors, which form
the functional entities of the train wheel detection system, and the installation of a
cable running parallel to the railway track with connections to it some distance before
and after the position of the wheel detector. To verify these paths, high frequency
experiments were performed in the lab as well as FEM simulations. To perform the
high frequency experiments a source capable of producing the high frequency current
needed was designed and constructed, along with a well shielded measurement system
to enable the mapping of the flux density within the region occupied by and
surrounding the wheel detector. The results of both the experimental measurements
and simulations yielded that the interfering magnetic field could indeed be reduced
through the use of the two available paths, when they are both applied separately and
in combination. To obtain the greater reduction in the interfering field within the area
occupied by and surrounding the wheel detector the paths should be used in
combination. Therefore through the use of a shield that is constructed from a magnetic
material and the installation of a parallel cable the train wheel detection system can be
made more robust.
Prof. W.A Cronjé
Prof. I.W. Hofsajer