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Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page D10 of 20 13 Insulated Rail Joints and Bonding Withdrawn Document Uncontrolled When Printed <strong>General</strong> <strong>Information</strong> on Track Circuits 13.1 Definition of Bonding Types When bonding sections of rail together to form track circuits, equipment of differing performance has to be used depending upon the type of track circuit and the type or absence of electrification; eg. a jumper bond or fishplate bonding may vary in design depending upon: • whether or not it is part of a traction rail system; • whether or not it is proved intact via series bonding.; • whether or not it is part of a non–series “safety–through–diversity” system. In order to avoid repetition of bonding equipment detail in each section of this handbook, a method of classifying bonding types has been developed in which fishplate bonding is identified separately from jumper bonding, the ‘family tree’ being shown in Figure D6. Standard Jumper Bond(ing) Figure D6 Jumper Bond(ing) Traction Jumper Bond(ing) Yellow Standard Bond(ing) Bonding Yellow Traction Bond(ing) Standard Fishplate Bond(ing) Fishplate Bond(ing) Traction Fishplate Bond(ing) 13.1.1 Fishplate Bonding This type of bonding is used to improve the reliability of the electrical connection between pieces of rail which are already in casual electrical contact by virtue of their construction. Whilst the most obvious item in this category is the un– insulated fishplate, this method of bonding extends to elements of S & C, such as crossings, wing rails etc, where the components are also bolted together without intervening insulation. Fishplate bonding is not shown on bonding plans. There are two types of this bonding: Standard Fishplate Bonding Used to bond all fishplate rail joints on non–electrified lines and a.c. only electrified lines. On d.c. or dual a.c./d.c. electrified lines, this bonding is only used on the insulated (signal) rail of single rail track circuits. The most common method is two galvanised iron bonds attached to the rail at each end with driven taper pins. It is installed by the Signal Engineer in all cases. Traction Fishplate Bonding Used to bond all fishplate rail joints on d.c. or dual a.c./d.c. electrified lines which form part of the traction current system. It is the responsibility of the Electric Traction Engineer. 13.1.2 Jumper Bonding This covers jumper cables which bond together sections of rail for track circuit and/or traction purposes; those sections may themselves be formed from many D10 RAILTRACK
Withdrawn Document Uncontrolled When Printed <strong>General</strong> <strong>Information</strong> on Track Circuits Railway Group Approved Code of Practice GK/RC0752 Issue Two Date December 1998 Page D11 of 20 individual pieces of rail which are bonded together with fishplate bonding. There are four types of jumper bonding: Standard Jumper Bonding A jumper bond between sections of rail which is proved intact as part of fail–safe series bonding and does not form any part of a traction current system. It is a light current cable installed by the Signal Engineer. Yellow Standard Bonding Used on non–electrified lines or long spurs of insulated (signal) rail on electrified lines. A jumper bond between sections of rail which is not proved intact by fail–safe series bonding. Safety is assured by installing at least three alternative jumpers, such that two jumper disconnections are not, by themselves, unsafe. It is a mechanically robust light current cable installed by the Signal Engineer and identified either by a yellow sheath or a yellow sleeve at its termination. Its mechanical strength allows its electrical integrity to be inferred from regular visual inspection. Traction Jumper Bonding Traction rated bonding attached to the traction rail of electrified lines but which is not relied upon for the integrity of track circuit operation. Yellow Traction Bonding Provided in accordance with the same design principles as Yellow Standard Bonding, except that it is traction current rated. It is installed by the Electric Traction Engineer (except impedance bond end connections which are connected by the Signal Engineer). 13.2 Design Principles for Yellow Bonding The design principles whereby the need for yellow bonding is identified are the same for both non–electrified and electrified lines. Electrification only affects the rating of bond to be installed and the organisation responsible for its installation and subsequent maintenance. Yellow bonding shall ensure that a single or double disconnection will not result in an unsafe condition. See GK/RT 0252. 13.2.1 Yellow Bonding Where separate sections of rail are required to be electrically interconnected in parallel, each section is to be bonded to the adjacent section at each point of abutment using a yellow bond. Each spur extremity is to be bonded to another part of the same electrically common network, which is not itself a part of the same spur, using a yellow bond. In addition to any switch reinforcement yellow bond, each section must have at least three yellow bonds attached to it in different physical locations, which should be a minimum of 20m apart. Additional yellow bonds are to be installed to achieve this and, wherever possible, the additional bonds must connect to a different section from those already fitted. In the case of non–electrified multiple track plain line, the common rails of parallel tracks must be cross bonded together using yellow bonds at the site of feed/relay ends and at least 1km intervals. Yellow bonds are to be clearly identified on bonding plans as shown in Part C. RAILTRACK D11
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