VRIOGS 010.7 RevA - Public Transport Victoria

20 VRIOGS 010.7 Revision A6.5 Tram and Train Interfaces at Road Crossings (Tramway Squares)1. Where tram and train lines interface (tramway square areas) there must bebonding at and around the square for both the 1500 volts DC traction fortrains and the 600 V DC power for trams.2. All rails of the actual tramway square for either tram or train are electricallybonded together utilising 300 mm 2 aluminium flexible cables and 35 mm 2head of rail bonding.3. The outer extremities of the tramway square are physically isolated by theuse of IRJs joints in all rails.4. The negative return cables either side of the tramway square are routed to aNegative Return Cable Connection Box and then to a heavy duty electricalswitch that is manually or electrically controlled and operated, for the passageof either a train (1500 V) or tram (600 V) to ensure the correct voltage isavailable for the passage of either the tram or train and in the correctsequence. The cables from the switch are then connected to the actualtramway square for the return of negative traction power for tram and train.5. The actual position of the negative return switch is both controlled andindicated to an identified and controlled location or area. The negative returnswitch is such that a clean break between tram and train position during theoperation of the switch must be achieved.6.6 Train Detection Equipment1. Train detection using the same rails as those carrying the traction returncurrent requires that interference from the traction current should not allow aloss of detection. Since the current carrying rails need to provide acontinuous path to the substation return busbar the usual signalling practiceof using IRJs must be reconsidered.2. Track circuits used in conjunction with electric traction must provide anunbroken, low-resistance path for traction current to flow from train tosubstation, while the maintaining the sectioning of tracks to provide a meansof determining the location of a train.3. All track circuits within the electrified area shall be DC immune.4. Axle counters do not depend on continuous rail, therefore no breaks in thetraction current return conductor need occur. Indeed it is possible to bondadditional conductors in parallel with the rails if necessary.6.6.1 Axle CountersWhere axle counter equipment has been type approved for use within DC electrifiedareas the installation design usually requires local earthing of the trackside boxes.Care must be taken to ensure that no dangerous voltage potential can build upbetween the parts electrically connected to the rails and those connected to the localearth. Where axle counters are utilised with no other form of train detection, crossbonding shall be in accordance with this specification and the same as for non trackcircuited areas.NOTE: This document is controlled only when viewed on the DOT Engineering Standards website.Any other copy of this document is uncontrolled, and the content may not be current.