General Information on Track Circuits - RGS Online

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Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page D14 of 20 <strong>General</strong> <strong>Information</strong> on Track Circuits Only One Bonded Fishplate Joint Permitted 13 METRES MAX. If X Or Y >13m Then Additional Cross Bonds To The Stock Rails Will Be Required Figure D9 D14 RAILTRACK Y X 13.5 Series Bonding Simplification If series bonding becomes complex, it imposes penalties on both reliability and maintenance. The option of cut sections should then be considered. A maximum of four point ends or fifteen IRJs (including boundary joints) per track circuit is strongly recommended. 13.6 Applications of Bonding Configurations Type of Track Non–electrified Lines A.C. Electrified Lines D.C. Electrified Lines Plain Line DRDS or CR DRDS or SR DRDS or SR♣ S & C DRSS * SR SR Complex S & C Figure D10 Notes: Withdrawn Document Uncontrolled When Printed CR # SR SR * Where DRDS is impracticable. # Where DRDS and DRSS are impracticable. ♣ Maximum permitted length is 200m. 13.7 IRJs Between Differing Track Circuit Types IRJs must be provided in both running rails at the point where differing track circuit types abut. Special cases will be discussed in the relevant sections. 13.8 IRJs at Signals Where a signal is replaced to danger by occupation of the first track circuit ahead, the IRJs will generally be positioned between 5m - 20m beyond the signal. For further information see SSP 62. 13.9 Jointed Track Circuits Abutting Non–track Circuited Line In order to detect defective IRJs where a jointed track circuit adjoins a non–track circuited section, a short circuit bond must be provided immediately beyond the IRJs, as shown in Figure D11. This bond shall be a standard bond on non– electrified lines, or a traction standard bond on electrified lines.
Withdrawn Document Uncontrolled When Printed <strong>General</strong> <strong>Information</strong> on Track Circuits Figure D11 AA 13.10 IRJs at Electrified/Non–electrified Boundary Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page D15 of 20 13.10.1 Running Lines At the boundary between electrified and non–electrified lines, initial isolation IRJs must be provided in both running rails at a sufficient distance beyond the end of the catenary/conductor rail to prevent an overrunning train from injecting traction current into the rails on the non–electrified side of the joints. The collector shoes on d.c. multiple units are interconnected within each multiple unit set. Therefore, it is the length of the longest multiple unit which will dictate the position of the initial isolation IRJs in d.c. traction areas. All track circuits within 800m of the initial isolation IRJs on the non–electrified side must be immune to the traction system and provided with double rail IRJs. Where there are no track circuits on the non–electrified side of the initial isolation IRJs, a second set of isolation IRJs must be provided in each rail 800m beyond the initial isolation IRJs. If any siding occurs within the above 800m areas, a second set of isolation IRJs must be provided in each rail of the siding immediately clear of the running line. 13.10.2 Sidings Off Electrified Lines In electrified traction areas, two sets of IRJs are to be provided in both rails at least 27m apart. These are to be provided beyond the last track circuit in private sidings leading to stores or depots containing flammable or explosive substances, and in other sidings where isolation from electric traction is required. In d.c. electrified areas, the traction return bonding must be extended by the Electric Traction Engineer onto track circuited non–electrified lines and sidings for at least 120m beyond the conductor rail or the tips of the points. Track circuits beyond this distance must be fully isolated with double rail IRJ’s or the traction return bonding must be continued for at least another 335m. This ensures that an electric traction unit inadvertently entering a non–electrified area will not lose its negative return whilst any shoe is still in contact with a conductor rail. On lines where Eurostar operations are authorised, the above distances will need to be extended accordingly. If the line concerned connects with a d.c. electrified line at more than one point, it must have continuous traction bonding throughout in order to prevent traction return current passing through the couplings of a train which is bridging two traction portions of a siding. 13.11 A.C. and D.C. Electric Traction Areas Abutting Where there is a requirement for inter–running with trains operating on differing electrification systems, IRJ separation between the differing traction systems cannot generally be achieved. In these areas, a suitable “buffer” zone of dual immunisation must be provided. As a general guide, for track circuit applications, immunisation against 50Hz electrification should be maintained for a distance of 3km beyond the extremity RAILTRACK D15
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