The article is devoted to the issues of increasing the stability of the operation of
track circuits under the influence of interference from alternating traction current. Track
circuits are widely used on railways around the world to monitor the occupation by rolling
stock and the integrity of rails on a railway section. In modern multilevel systems of
interval regulation of train traffic using digital radio channels and satellite navigation,
track circuits are also used.
It was found that the appearance of asymmetry of the longitudinal and / or transverse
resistances of the rails is only the root cause of the asymmetry of the traction current. The
mutual inductance of the rails in the rail line increases the value of the asymmetry of the
traction current by several times. The degree of this increase depends on the temperature
of the rails and the value of the traction current in them.
The mutual inductance of the rails of the rail line with the parallel rails of other track
circuits can both increase and decrease the asymmetry of the traction current depending
on the nature of the distribution of the traction current along the rails of the adjacent track
circuits. The mutual inductance of rails with longitudinal power supply lines located on
the supports of the contact network can noticeably affect the value of the asymmetry.
The degree of distortion of the signal current sinusoidality is determined by the
harmonics of the asymmetry current. The harmonic composition of interference from
traction current can quickly change over time and depends on the number, series and
operating modes of traction equipment of electric locomotives moving in the area between
traction substations. It is shown that electric filters used in track circuits do not always
provide the required interference filtering efficiency.