Rail Engineer • March 2016
SIGNALLING AND TELECOMS
38
Frauscher axle counter sensor.
Axle counter lineside location.
Train detection Atkins offered an innovative new product, not previously used on the UK network, as an efficiency saving under the CASR scheme at time of tender. Frauscher digital axle counters (FAdC) with type RSR123 wheel sensors have been installed throughout the CASR area. Although axle counter products are common in resignalling schemes, the wheel sensor RSR123 has the advantage that it is fitted to the rail by a clamp so it can be fitted on-site in a matter of minutes since drilling the rail is eliminated. No trackside interface module is required further reducing staff time on-site, and it has a comprehensive diagnostic support system.
The clamp installation feature also provided the team with a solution for the Cardiff west station throat. A very cramped four-way divergence with eight sets of double slips, much bespoke point operating iron work in the S&C, which is not being renewed at this stage, meant that drilling the rails was not an option. A plan was drawn up at the single option development stage (GRIP 4) for the installation of 109 track circuits in the station area which would involve a lot of rail drilling for bonding and the fitting of rail end-post insulations with a significant installation time. There was a lot of concern about maintaining robust track circuit electrical separation within the bonding and rails of the moving point operating rods and stretcher bars. After further consideration, Network Rail and Atkins concluded that the Frauscher axle counters, with their much smaller interference area around the head, more compact design, and clamp-on feature, was the ideal solution for the station area. Overall, CASR uses 832 Frauscher wheel sensors (a total of about 600 train detection sections), of which 252 are in the Stage 5 area. Sensors consist of two detector coils which enable direction to be determined. A single RSR123 may act both as exit counter for the rear section and as entry counter for the forward section.
Sensors are connected into ring transmission circuits, which are linked via nodes into the Fixed Telecomms Network (FTN), communicating with IP protocol utilising Westermo ethernet switches and modems. Thus, if the system detects a fault with part of the lineside cabling, messages are automatically re-routed. A handshake, via the evaluation boards of adjacent sensors, determines the clear/occupied status of the section which is fed into the signalling system via standard Solid State Interlocking (SSI) Track Function Modules (TFM) in an adjacent location case. All the ring circuits are connected into the South Wales Control Centre (SWCC) where the diagnostic support system provides technicians with detailed information on the condition of all sensors and train detection status to facilitate efficient faulting.
Points and signals - ‘Plug and Play’ Many existing point operating devices will remain and be recontrolled by the new signalling with the exception that surviving older Westinghouse Type M3 point machines will be replaced. Points will be operated by a mixture of Alstom HW2000 machines, which are AC-immune DC machines for 110V operation; the comparatively