Assessment of Locomotive Receivers’ Sensitivity Using Test Loop with Crossing

Abstract

Main technical and operational characteristics of the locomotive receiver of the automatic locomotive signalling system, which is part of all types of core locomotive safety devices, comprise its sensitivity. This characteristic makes it possible to estimate by indirect methods the signal/noise ratio at the input of the locomotive receiver, and, therefore, to evaluate the noise immunity of its operation at the nominal parameters of amperage and current frequency of signals of automatic locomotive signalling system in the track circuit under operating conditions.Thanks to correct adjustment of the sensitivity of the locomotive receiver, it is possible to significantly reduce the number of failures in operation of the main locomotive safety devices. Checking the sensitivity of the locomotive receiver and other parameters of safety devices is carried out at control points, usually equipped in depots, using stationary test loops that simulate the electromagnetic field generated by the signal current flowing in the track circuit. Sensitivity measurement results are influenced by various factors, primarily the position of the receiving coils along the test loop performed with crossings, as well as the distance between adjacent crossings. The influence of these factors may lead to the impossibility of checking the correct operation of locomotive safety devices at nominal signal parameters, as well as to an incorrect assessment of sensitivity.The objective of this work is to evaluate the influence of these factors on the results of measuring the sensitivity of a locomotive receiver. A model developed as part of the work and based on the well-known methods of analysis and synthesis and the Biot−Savart− Laplace law describes the inductive connection «test loop−coil». Several characteristic dependencies have been also obtained. The results have been compared with the existing requirements for the position of the coils relative to the test loop performed with crossings.To ensure the most accurate results of measurements of the sensitivity of the locomotive receiver, it is proposed to place the receiving coils of the locomotive safety devices at an equal distance from adjacent crossings of the test loop.