NR RT/E/C/50009 ISSUE 1 PDF

This document covers FS2600 track circuits installed in double rail configuration on d.c. electrified Railtrack controlled infrastructure.

Methodology is based on level alone for simplicity of demonstration. This is achieved by:

• Providing a characterisation of the track circuit components.

• Providing a characterisation of the infrastructure.

• Providing a methodology to define the susceptibility for worst case scenarios.

Combining these elements will allow an analytical investigation to find the maximum permissible interference for trains in d.c. electrified areas, with double rail FS2600 circuits applicable to Railtrack infrastructure. The minimum levels found from the susceptibility analysis are taken as the maximum permissible interference levels. Methods are included to analyse intact and faulty infrastructure for single and double track configurations.

The FS2600 track circuit has been designed to be 'traction immune', so that it cannot be energised by any single interference frequency or transient. This is achieved by using Digital Signal Processing (DSP) to monitor the signal it receives from the track. The use of DSP enables the validity of the signal to be checked in terms of its frequency content and amplitude at the same time. This overcomes the traditional problem encountered with separate level and code checking systems which can be erroneously activated by small genuine signals with a higher general noise signal overlaid. Energisation of the receiver requires a train to produce a modulated current which gives an FFT signature similar to that of the FS2600 transmitter. This is unlikely to occur in practice. Hence the results of this analysis are highly pessimistic.

Purpose

The purpose of this document is to provide a methodology to demonstrate compatibility with FS2600 track circuits on Railtrack 750V d.c. electrified railway.