Indian Railways AC Traction Manual Volume 1 PDF

CHAPTER IV SAFETY PRECAUTIONS ON ELECTRIFIED SECTIONS 10400 Induction Effects of 25 kV ac 50 Hz Single Phase Traction 1. The attention of all railway staff is drawn to the fact that under 25 kV ac 50 Hz single phase traction, there is heavy induction on all metallic structures and conductors in the...

CHAPTER IV SAFETY PRECAUTIONS ON ELECTRIFIED SECTIONS 10400 Induction Effects of 25 kV ac 50 Hz Single Phase Traction 1. The attention of all railway staff is drawn to the fact that under 25 kV ac 50 Hz single phase traction, there is heavy induction on all metallic structures and conductors in the vicinity of the track. The induction is two-fold: a) Electro-static, which results from the high potential of 25 kV on the OHE system. b) Electro-magnetic, which is proportional to the currents passing from the sub-station to the OHE to the locomotives / EMUs and back partly through the track and partly through the earth. 2. Those who have been used to work on dc traction are liable to overlook taking adequate precautions required to guard themselves against the dangerous inductive effects of 25 kV ac system. Attention is therefore specially drawn to the need for taking adequate precautions. 3. The voltage induced is quite appreciable on overhead conductors running parallel to the tracks depending ,on the length of parallelism. This explains why most of the overhead telecommunication lines are replaced by underground cables. Special protective measures are required to reduce the adverse effects of induction. 4. In a railway yard, voltage of the order of 200 volts may be induced on yard lighting mains situated 8 m away from the centre of a double-line track, if it runs parallel to the 25 kV lines for a distance of about 270 m., it could be several thousand volts when parallelism is much longer. In such a case, a dangerous voltage due to induction will exist even after power supply to the line has been switched off. No one shall therefore attempt to work on any overhead line running alongside the electrified tracks without taking special precautions of earthing on both sides of the work. Before a section is electrified, the necessary modifications to distribution lines in all stations and yards should be carried out, so as to limit the induced voltage within permissible values, but this by no means obviates the need of earthing the lines on both the sides of the working party. Earthing should be done individually by each working party as close to the work-spot as possible. The distance between the two earths shall not exceed 1 km. 5. Such inductive effects occur on large metallic structures such as fencings, structural steelwork of platforms running parallel to the track. They will therefore have to be earthed suitably to afford safety. 6. Inductive effects also show themselves on any metallic conductor, such as metallic clothes-lines, powerlines and lines belonging to private parties running parallel and close to the electrified tracks. Wide publicity should be given to the effects of induction so that special precautions are taken by the private parties. I. WORKING OF STEAM AND DIESEL LOCOMOTIVES IN ELECTRIFIED SECTIONS 10401 Prevention of Smoke Pollution Pollution of OHE insulators due to smoke on account of operation of steam locomotives causes appreciable operating and maintenance difficulties. To reduce pollution to the minimum, the following precautions shall be taken : 1. No steam locomotive should be left standing with the chimney under an OHE insulator. Stabling of steam locomotives with chimneys under traction structure is prohibited. 2. Continuous blowing of safety valves, sudden opening of blower and priming through exhaust steam should be avoided as they cause flashover of insulators resulting in severe consequences. Sudden starting of a steam engine shall also be avoided as it may cause slipping of wheels which would result in priming through exhaust steam, which in turn may cause flashover. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME (34) 10402 Standing on Boiler Shell or Tender Staff are warned of the danger of standing on the boiler shell or tender when stabled under live OHE as it may result in electrocution. 10403 Working the Fire-Spraying, Advancing of Fuel and Handling of Tools 1. Special care must be taken while firing coal or raking fire to ensure that the TOOLS DO NOT GET WITHIN THE DANGER ZONE of the OHE.. Spraying of coal with water under electric overhead lines is forbidden. 2. The firing tools must be handled with great care, and special care should be taken to see that THESE TOOLS ARE NEVER LIFTED OR RAISED TOWARDS THE OHE. Tools must always be placed in their respective positions after use. 3. A jet from a hose should never be directed towards the OHE. The jet of water should only be directed horizontally far away from the live OHE and not vertically. 10404 Loading of Fuel 1. The loading of coal or fuelling of the locos shall only be carried out in yards outside the Electrified zones. 2. The height of the coal in the tender must not be more than 4.28 m above the rail level on BG and 3.65 m above rail level on MG. 10405 Watering of Steam Locomotives Whatever may be the height of the contact wire, NO ONE SHOULD CLIMB ON THE TENDER to open the cover of the water tank or to insert the funnel of the water column. Water columns have been suitably modified for operation from ground level. Only the operating rods provided should be used for this purpose. 10406 Crane Working No crane shall be worked on or near traction overhead equipment unless an authorised representative of the OHE section is present. When so working, care shall be taken to avoid hitting or damaging OHE structures. 10407 Decorative Fittings No decorative or extension pieces be attached to the chimney of a steam locomotive that would raise its effective height. 10408 Engines Owned by Outside Parties The safety precautions mentioned above are equally applicable to locomotives owned by Steel Works or other factories in the neighborhood of electrical sections that are likely to work in electrified sidings for shunting or other purposes. The special safety rules to be observed in electrified sections should be advised by Sr. DEE (TrD) to parties owning such locos and their written assurance obtained that their operating staff have been made familiar with these rules. II. WATERING OF CARRIAGES IN ELECTRIFIED SECTIONS 10409 Watering Arrangements - Basic Precautions With electrification, 'side filling' arrangements for coaches have been introduced Asia long term measure, in lieu of overhead filling arrangements which necessitate shut down of power for watering and other precautions. Since all carriages have not yet been provided with side filling arrangement, special arrangements have been made for INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME (35) Overhead watering of carriages in some electrified stations. The following precautions must be observed in such interim arrangements: 1. If the carriages are standing on lines having overhead traction wires, nobody shall get on to the roofs of the carriages unless the overhead traction wires above are made dead and earthed. 2. Staff getting on to the roofs of the carriages for watering, after the overhead traction wires above such carriages are made dead, should be warned against carrying long poles or any other articles which may come within the danger zone, that is within 2 m of the live traction wires on the adjoining lines. They should also be warned about the risk of extending the water hoses or any part of their body or directing water jets within the danger zone i.e. Within 2 m of live overhead traction wires. 10410 Watering Section 1. For the purpose of isolation and earthing the OHE, wires above the watering arrangements for each platform will form a separate elementary section i.e. different platforms will have different watering sections. This is to ensure that isolation of each platform can be done independently. The limits of each watering section shall be marked by danger limit board (Fig. 4. 0 1) hanging from the catenary at either end. These constitute the limits within which, alone watering of the carriages may be done. In Fig. 4.02 CD is the watering section. Separate interruptors or isolators shall be provided for controlling supply to each watering section. Keys for such interruptors/isolators shall be provided with metal tags on which the numbers of the interruptors/isolators are punched. 2. A neutral section about 12 m long bounded by section insulators is provided at -, either end of each watering section. The purpose of the neutral section is to afford additional protection to the watering section against approach of any electric locomotive or any other type of "feeding in" from the live sections on either end. In Fig. 4.02, BC and DE are the neutral sections. 10411 Controlling Switches 1. 'L' is the locally operated interruptor/isolator at the end of the platform in a separate enclosure. The Key for the enclosure is with the ASM on duty. 2. S 1 and S 2 are manually operated isolators - one at each end of the watering section, the purpose being to switch off power from the respective small neutral sections and to earth the two ends of the watering section. For this purpose the two isolators are provided with earthing heels. 3. Elernentary sections AB and EF are normally live. 4. A feeder line for maintaining continuity (shown dotted in Fig 4.02) is carried on the OHE structure having supermasts. 10412 Sequence of Interlocking and Operation The following are the interlocking arrangements and the sequence of operations:- 1. The enclosure to interruptor/isolator 'L' is locked and its key is with the ASM on duty. When required, the ASM issues it to the lineman, only against a receipt on the register kept for the purpose. 2. If an interruptor is provided, on its frame is mounted the opening key which is accessible only after the enclosure to the interruptor is opened. This ensures that no one can open the interruptor, without taking the key of the lock of the enclosure from the ASM. The tripping key is normally back locked in the lock on the interruptor frame. It can be extracted from the lock only after the interruptor is opened to switch off supply to the watering section. Similarly, when an isolator is provided it can be opened only by the linesman on receipt INDIAN RAILWAYS AC TRACTION MANUAL VOLUME 1 (36) BRASS BADGES FOR AUTHORISED PERSONS FIG. 4.03 INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME (37) of its key from the ASM on duty. For opening the (main) isolator 'L' the additional precautions detailed in the Chapter VI of Vol. 11 of this Manual shall be observed. 3. Each of the isolators 'S1' and 'S2' is provided with a double lock. The opening key extracted as above from interruptor'L'when inserted in S1 and turned, releases the operating handle of S1. If the isolator S1 is now opened or closed, a key K 1 (normally back-locked in the double lock on S 1) is released, simultaneously locking the operating handle as well as the opening key. This ensures that once the key KI is in the hands of the operator, the interruptor 'L'as well as isolator S1 cannot be operated. The key Kl as obtained now is known as the isolator Interlocked key. 4. Key K1 is taken to the other end of the platform and inserted into the double lock of S2. This releases the operating handle of S2 and if isolator S2 is now opened another key K2 normally back-locked in lock of S2 is released. This key is handed over to the TXR in charge by the authorised person as an assurance that the supply to the watering section is cut-off and made dead and earthed. Key K2 is known as the "permit-to-work" key. 5. The details given above and in subsequent paras are mainly for watering sections controlled by interruptors. The same principles however apply for watering sections controlled by manually operated isolating switches, though the details vary somewhat between installations at different stations. 10413 Persons Authorised to Open Interruptors and Isolator Switches No staff of rank lower than a linesman working under the Traction Foreman (OHE) is authorised to open or close the interruptors or isolators controlling power supply to the overhead traction wires in the watering section., A list of names of the authorized linesmen duly signed by the Traction Foreman (OHE) shall be exhibited prominently in the office of the ASM and the TXR of the station concerned. Each such linesman should also carry an identity card with photograph or specimen signature. It will be the duty of the linesman concerned to report to the ASM on duty at least half an hour before the scheduled arrival of a train. No linesman on duty shall leave his place of duty until he has been properly relieved by his reliever and that too after his reliever has been introduced by him to the ASM on duty at the time. 10414 Custody of Keys 1. The keys of the interruptor enclosures and isolators shall be inscribed with the distinguishing marks and locked in glass-fronted Key box and kept in the personal custody of the ASM on duty. The keys should never be kept in a bunch, but hung on individual pegs provided for each. The description of each key shall be painted above each peg to avoid confusion. 2. When the watering section of a particular platform is required to be made dead and earthed for watering of carriages, the ASM on duty shall give the key of the lock of the enclosure of the controlling lnterruptor/ isolator of the platform to the linesman on duty and getting his acknowledgment in a "Key Register" to be provided for the purpose at the station. This key shall be handed over immediately on arrival of the passenger train concerned, if hauled by an electric loco. If, however, the train, the carriages of which are to be watered, is not hauled by an electric locomotive, the key may be handed over to the linesman even prior to the arrival of the train, in question so as to save time, provided the earlier isolation of the watering section does not interfere with the movement of the other train. (It is to be understood that the handing over of the key of the interruptor enclosure to the linesman amounts to the requisition for a power block). 3. The ASM shall ensure that no electric locomotive with raised pantograph is allowed to enter a watering section till the watering linesman returns the key back to the ASM and signs in the Key Register. 10415 Watering of Carriages On receipt of the "permit-to-work" key of the concerned watering section, the TXR-in-charge of watering shall personally check that the key received by him bears the correct number and relates to the concerned. INDIAN RAILWAYS AC TRACTION MANUAL \/OLUME 1 (38) watering section on which the carriages to be watered are standing. The TXR-in-charge shall also ensure that the train is standing within the limit of the watering section bounded by the danger limit boards on the overhead traction wires. He will then arrange to fix yellow flags (or yellow lights by night) on either end of the train high enough to be visible from the carriage roof. He will at the same time hand over to each of his men who are to go up on the roof of the carriages, a number badge of the legend and description shown in Fig. 4.03 as the authority to go on the carriage roof for the watering. Only the staff holding the badges mentioned above are authorised to go to the roof of the carriages and water the same. The badges when not in use, shall be kept in the personal custody of the TXR- in-charge of watering under lock and key. Any loss of the badge shall be notified immediately and the badge cancelled. The TXR shall ensure that his staff deputed for watering are conversant with the following precautions: 1. Watering operation shall be confined to the limits specifically marked by "Danger Limit Boards" hanging from the catenary wire of the OHE above the concerned watering section. 2. The hydrants shall not be opened till the other end of the hose pipe has been inserted in the overhead tank of the carriage. 3. The hose pipes shall not be withdrawn from such overhead tank, till the hydrant has been closed. Precautions 2 and 3 above are necessary to avoid accidental contact of a water jet with the live overhead traction wires of the adjacent tracks. Each platform adjoining the watering section shall have a small area marked with the legend "Watering Gang". Each of the staff deputed for watering shall be instructed to assemble in this area as soon as watering is completed or they are signalled to stop watering and get down from the roof of the carriages. On completion of the watering, the TXR-in-charge of watering shall collect the authority badges given to his men and ensure that all the badges have been returned and there are no men on the top of the carriages in the watering section. The TXR shall also ensure that no material has been left on the carriage roof and that all the watering hoses have been brought down and the watering hydrants closed. 10416 Restoration of Supply On receipt of the permit-to-work key the linemen on duty shall proceed to restore supply as under:- He shall insert the "permit-to-work key" in the double lock of the isolator switch S2 and turn the same. This will release the isolator switch handle which shall then be operated to close the isolator. After this operation the isolator interlock key shall be extracted from the double lock and taken to isolator Sl and inserted in its double lock and turned. This will release the operating handle of isolator S1 which shall then be closed, thus back-locking the Isolator interlock key. The interruptor opening key may then be taken out and inserted in the key hole of the interruptor lock and turned after which operation the interruptor should be closed. The interruptor enclosure shall then be closed and locked and the key returned to the ASM on duty. The returning of the key to the ASM on duty signifies that the power block has been cancelled. The linesman on duty returning the key shall sign the Key Register entering the time at which the key is returned. The ASM on duty shall also sign the register in acknowledgment of having got the key back. On receipt of the key the ASM shall arrange to start the train. INDIAN RAILWAYS AC TRACTION MANUAL - VOLUME (39) 10417 Key Register Each watering station shall have a key register for recording the interchange of keys between the ASM on duty and the linesman. This key register will have the following columns: 1. Date 2. Description of the key 3. Watering Section No. 4. Train No. 5. Time made over 6. Signature of the linesman 7. Time returnd 8. Signature of the linesman 9. Brief reasons for delay if any. 10. Signature of ASM on duty. Safety depends essentially on the proper exchange of the keys and correct record of the same. All exchange of keys shall take place directly between the persons concerned and not through messengers. The custody of any key shall be the responsibility of the person possessing the same at the time. 10418 Loss of Key In case of loss or damage to any key controlling the switching arrangements to the watering section, the same should be reported at once to the TPC over phone and by XXR message addressed to the Sr. DEE(TrD), Sr. DOM and Chief Controller of the Division. The Sr. DEE(TRD) shall make immediate arrangements for the provision of a new locking system requiring a different set of keys. During such period the TXR-in-charge of the watering shall personally be responsible for making dead and earthing the overhead traction wires of the watering section concerned. He shall arrange to lock the operating handles of the interruptor'L' and isolator switches S 1 and S2 by his own padlocks, the keys of which shall be in his personal custody-till the watering is completed and the brass badges authorizing his staff to go on the top of the carriages for watering are returned to him. III. LOADING AND UNLOADING OF PETROLEUM PRODUCTS II. 10419 Precautions to be Observed In order to avoid any sparking during loading or unloading of petroleum products at the petroleum siding, electrical continuity must be maintained between the earth systems of petroleum installations, the track and electric overhead traction installation. The loading zone should be insulated from the rest of the railway net work during loading and unloading operations. The following precautions / arrangements would be necessary. Arrangements 1. Provision of an equipotential link between the earth system of petroleum siding installations and the track via a switch. INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME I (40)  2. Setting up of neutral zones (insulating joints) in the track to avoid any risk of propagating stray current. 3. Setting up neutral zones/ sections in the contact and catenary wires similar to loco inspection pits. 4. Provision of longitudinal bonds on both the rails as well as transverse bond ( 30 m intervals) on the track. All masts and metallic structures in the vicinity of the track/siding should be provided with structure bond. 5. Provision of 10 Ohm earths connected to the petroleum siding on each side at the insulated joint. Precautions 1. No oil tanker is permitted to stable under live OHE for inspection purpose. 2. Fueling to be done by side filling arrangements only. 3. Pipelines in the vicinity of the track should be properly earthed. 4. Minimum 2 m electrical clearance from live OHE of the adjacent track or any other equipment nearby must be maintained. 5. During service operations, the continuity of track and the contact wire should be set up at the same time the link between the track and petroleum facility should be opened. 6. The isolators at the neutral section of OHE should be kept open, OHE made dead and earthed. IV RULES APPLICABLE TO PERMANENT WAY STAFF 10420 General These instructions have already been included in the supplement to Part ‘J’ of Chapter II of the Indian Railways Permanent Way Manual. These instructions lay down precautionary measures to be observed by railway personnel working in the vicinity of the tracks equipped with 25 Kv ac OHE. These have already been included in the supplement to Para ‘J’ of Chapter II of the Indian Railway Permanent Way Manual which are reproduced below:- 10421 Need for Precautions Precautions are required to be taken on account of the following : a) Proximity of a live conductor: The risk of direct contact with live OHE is ever present while working in electrified sections such as for painting of steel work of through spans of bridges and platform covered sheds. b) Build up of potential due to return current in rails : The return current in the rails may cause a potential difference. g) between rail and the surrounding mass of earth; ii) between the two ends of a fractured rail ; iii) between the two rails at an insulated joint; iv) between earth and any other metallic mass. INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME1  c) Building up of potential due to induction in metallic bodies situated close the OHE. It is important to note that dangerous voltages may be inducted in metallic masses such as fencing posts in the vicinity of traction conductors. To avoid possibility of shock due to such voltages the metallic structures are bonded together and earthed. 10422 General Precautions. The precautions laid down below must be followed under all circumstances in sections equipped for 25 Kv ac single phase, 50 Hz. Traction in addition to those referred to in Indian Railway Permanent Way Manual. 1. No work shall be done above or within a distance of 2 m from the live OHE without a ‘permit to work’ 2. No part of tree shall be nearer than 4 m from the nearest live conductor. Any tree or branches likely to fall on live conductor should be cut or trimmed periodically to maintain this clearance. Cutting or trimming should be done by engineering staff in the presence of authorized staff of the OHE section. 3. No fallen wire or wires shall be touched unless power is switched off and the wire or wires suitably earthed. In case the wires drop at a level crossing, the Gate-keeper shall immediately make arrangements to stop all road traffic and keep the public away. 4. As far as possible closed wagons shall be used for material trains. In case open or hopper wagons are used, loading and unloading of such wagons in electrified tracks shall be done under the supervision of an Engineering Official not below the rank of a Permanent Way Mistry who shall personally ensure that no tool of any part of the body of the worker comes within the ‘danger zone’ i.e. within 2 m of the OHE. 5. Permanent way staff should keep clear of the tracks and avoid contact with the rails either when approaching or reaching the work-spot when an electrically hauled train is within 250 m. 6. When unloading rails along side the tracks, it should be ensured that rails do not touch each other to form a continuous metallic mass of length greater than 300 m. 10423 Continuity of Track During maintenance or renewal of track, continuity of the rails serving electrified tracks shall invariably be maintained. For bridging gaps which may be caused during removal of fish plates or rails, temporarily metallic jumpers of approved design shall be provided as under :- a. In case of a rail fracture, the two ends of the fractured rail shall be first temporarily connected by a temporary metallic jumper of approved design (Fig. 4.04). In all cases of discontinuity of rails, the two parts of the rail shall not be touched with bare hands. Gloves of approved quality shall be used. b. In the case of track renewals, temporary connections shall be made as shown in Fig. 4.05. c. In the case of a defective or broken rail bond, a temporary connection shall be made as mentioned in (a) above. d. Before fish plates are loosened or removed, temporary connections shall be made as in (a) above. 10424 Permanent Way Tools Permanent Way tools alongwith the gloves shall be used in the manner as approved by the Chief Engineer of the Railway. INDIAN RAILWAYS – AC TRACTION MANUAL – VOLUME I (42) FIG 4.05 INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME-I  10425 Track-Circuited Rails. In track-circuited areas where the rail/s has/have insulated joints, such joints shall not be bridged with bare hands or any metallic article. Similarly simultaneous contact with an insulated section of rail/s and non-insulated section of rail/s of the same or other tracks shall be avoided. 10426 Care in Handling Pipes etc. Use of rails as a foot path, a seat or for such other purposes is strictly prohibited. Particular care shall be taken when carrying or handling long pipes, poles, overhanging on the shoulder or otherwise to avoid all possibility of such objects and work pieces coming inadvertently in contact with or within 2 m of live equipment. 10427 Steel Measuring Tapes not to be used. In electrified tracks, steel tape or metallic tape or tape with woven metal reinforcement should not be used. 10428 Traction Structure Foundation 1) The top of foundation block of track structures shall be kept clear of all materials and kept tidy. 2) While excavation the foundations not be exposed and there should be no risk of sinking of the foundations. V. RULES FOR S&T INSTALLATIONS 10429 Effect of 25 KV ac, 50 Hz, Single Phase Traction on S&T Equipment 1. Any circuit in the vicinity of 25kv ac OHE is influenced by electrostatic and electromagnetic induction. The electrostatic induction is practically eliminated by transferring S&T circuits into underground cables protected with metal sheath. The electromagnetic induction causes various currents and voltages to develop in conductors parallel to the track. These include the rails, traction return conductor where provided, cable sheath, any other conductors in the vicinity and S&T circuits. The voltages that occur in the conductors appear a potential gradients. The value of induced voltage depends on various factors such as: a) Length of parallelism between the cable conductor and electrified track. b) Soil conductivity. c) Screening efficiency of cable sheath where existing. d) Return current through the rails and return conductor where provided. e) Mutual inductance between catenary and cable conductors. f) Current in the OHE. Appropriate precautions to overcome the effects of the induced voltages therefore have to be taken by S&T department. Other aspects in which S&T equipment is affected are: i) OHE structures and fittings affect visibility of signals to some extent and may come in the way of a signal; INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME1 ii) Restrictions come in the path of traction return currents on section provided with track circuits. 2. Essential precautions to be taken while working on signalling and telecommunication installations as described. Reference may also be made to Chapter XVII of the Indian Railways Telecommunication Manual. 10430 Precautions in the Event of Breakage of Wires. Should a catenary or contact wire snaps and falls on the running track, it is possible that the fault current may damage signalling equipment. The following precautions shall, therefore, be taken. 1. The Section Controller on receipt of an advice of a break in traction overhead lines shall immediately advise, by the quickest possible means, the signal maintenance and operating staff of the section where the catenary/contact wires have broken. 2. If abnormal working of any equipment is noticed, its working shall be immediately suspended and necessary action under the rules shall be taken. 3. On receipt of the intimation from the Section controller the staff responsible for the maintenance of signaling of the section shall immediately proceed to the site and test all signaling circuits and allied equipment paying particular attention to the outdoor signaling gear to check if any damage has taken place. An authorized representative of the Signal Department shall submit a certificate that everything is working all right and send it to his superiors along with a detailed test report as soon as possible. 10431 Works on Signal Posts and Fittings. 1. No staff shall work on any portion of a signal post or its fittings falling within a distance of 2 m from a 25 Kv live OHE or a metal part electrically connected to this OHE unless such portion is protected with a metallic screen in accordance with approved instructions. 2. If for any reasons the protective metallic screen is not provided, the staff shall not undertaken any work on those portions of the signal or its fittings falling within 2 m of 25 Kv live OHE, unless power to the 25 Kv live OHE has been switched off and a ‘permit to work’ has been obtained. To draw the attention of the staff in such cases a red band 10 cm wide shall be painted all around the signal post at a height of 3 m above the rail level. 3. The inspectors of the Signal Department and the Station Masters shall explain these instructions to the staff working under them and ensure that they are correctly understood. 10432 Precautions against build up of Potential due to Return Current in Rails. 1. The flow of return current in the rails may cause a potential difference to build up between: a) two rails at an insulated joint of the track circuit at an ordinary joint in case the fish plates are broken. b) two ends of a fractured rail; c) an insulated rail and the rail used for the traction return current ; and d) the rail and the surrounding mass of earth. 2. Whenever staff have to work on installations which are in direct contact with the rails, they shall : a) use tools of the type approved for the purpose by the Chief Signal and Telecommunication Engineer of the Railways ; and b) observe the provisions of Chapter II of the Indian Railways Permanent Way Manual. INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME1 10433 Precautions against Induction Potential in Metallic Bodies. Voltage will be induced in signalling and telecommunication circuits when the length of the parallelism to the track is appreciable, due to normal load currents or short circuit current in the event of a fault on the traction system. Dangerous potentials may also develop in circuits with earth connection if the earth connection gets broken for any reason. Consequently every time staff have to work on signalling and telecommunication circuits along with 25 Kv ac electrified lines, they shall take precautions to protect themselves and the equipment as prescribed by the S&T Department. Some of the important precautions are however given below: a) Rubber gloves and tools with insulated handles should be used. b) When the work to be done is of such a nature that rubber gloves cannot be used, splitting of the circuits into sections to reduce the length of parallelism and earthing them to ‘drain out’ the voltage should be adopted. Both the steps should be taken simultaneously. If these protective measures cannot be applied, staff must get insulated from ground by using rubber mats or other approved form of protection. c) The line wires of the electric block instruments are likely to get heavy induced voltages and every time the staff handles the line wire terminals of the block instruments, they must observe the provisions of paras (a) and (b) above. Line wire terminals should be painted red to remind the maintenance staff of the danger. The maintenance inspectors shall explain the meaning of this painting to the maintenance staff and ensure that it is correctly understood by them. d) Before cutting the armour or the lead sheath of a cable or the wires in the cable, an electrical connection of low ohmic resistance should be established between the two parts of the armour or the sheathing and the wires that are to be separated by cutting. VI OVER-DIMENSIONED CONSIGNMENTS 10434 Definition of Over-Dimensioned Consignments (ODC) When a consignment whose length, width and height are such that one or more of these infringe Standard Moving Dimensions at any point during the run from start to destination, then the consignment is called an Over-dimensioned consignment (ODC). It is also known as out-of -gauge load. If any consignment exceeds the following dimensions, it is to be treated as ODC or over dimensioned consignment. BG MG a) Length 13716 mm 12192 mm b) Height i) at centres 2743 mm 2540 mm ii) at corners 2134 mm 2134 mm c) Width 2997 mm 2540 mm d) Top width 610 mm 610 mm INDIAN RAILWAYS-ACTRACTION MANUAL-VOLUME1 (46) 10435 Classification of ODCs ODCs are classified as under: ‘A’ class ODC having clearance (i.e. clearance measured under stationary conditions) as 228.6 mm and above from the fixed structures but infringes the standard moving dimensions. ‘B’ class ODC having gross clearance of 152.4 mm ‘C’ class ODC having clearance of less than 152.4 mm but more than 76.2 mm. 10436 Precautions for Movement of ODCs in25 Kv ac Electrified Sections. The following precautions must be observed for transport of ODCs in the electrified sections: 1. Movement of ODC shall undertaken only after sanction of competent authority has been obtained. 2. In all cases where ODC is to be moved, staff accompanying the ODC shall remember that the OHE is ‘live’ except when a power block has been obtained from the traction officials. Even when a power block has been obtained, all lines other than those for which the power block has been granted are to be treated as ‘live’ at 25 Kv. 3. The following are the prescribed clearances from contact wire for the passage of ODCs through electrified sections and the special restrictions required: a) Special speed restriction is not required when the gross clearance is more than 390 mm. b) Speed must be restricted to 15 km/h when the clearance is between 390 mm and 340 mm. c) Speed must be restricted to 15 km/h and power to OHE must be switched off when the clearance from the contact wire is less than 340 mm. 4. No consignment with less than 100-mm clearance from the overhead contact wire will be permitted in a 25 KV electrified section. 5. A representative of the OHE section should accompany all ODCs having clearance as specified in items 3(b) and 3(c) of item (3) above, to supervise safe movement of the ODC at locations where clearance from the contact wire is critical. 6. A representative of the OHE section should also accompany ODCs having width more than 1981 mm for BG (and 1910 mm for MG) from centre line of track. 7. Section Controller and Traction Power Controller must coordinate while an ODC moves in electrified section in order to ensure that OHE masts are not damaged at locations where the clearance is critical. 8. A list of structures where the clearance are restricted in the electrified section and also the clearance, available under the over-bridges should be with the Section Controller and TPCs. 9. To facilitate checking of clearance from the Contact wire for over-dimensioned consignments, the Operating and Engineering branches at the Divisional and Headquarter level should have with them up-to-date charts showing location of the minimum height of contact wire and clearances of OHE structures in the electrified section. The Operating Department may permit movement of ODCs on the basis of clearance checked with the help of the above mentioned charts subject to the speed restrictions. However, when sanction of CRS is required to be obtained for movement of any particular INDIAN RAILWAYS-AC TRACTION MANUAL-VOLUME1  ODC, a specific reference should be made to CEE and a certificate obtained from him in the following form. Certified that the minimum height of contact wire on the section over which the consignment is to move is not less than except at the following locations where restrictions are indicated below should be observed:- Section Location Height of Power ‘ON’ Speed Restriction Contact wire or ‘OFF’ in km/h 1 2 3 4 5 10437 Power Blocks for Movement of ODC When an ODC is permitted to be moved in an electrified section with the OHE power off, it will be the responsibility of the Section Controller to arrange with the TPC for power to be cut off before admitting the ODC into the section. An authorised representative of the Traction Distribution Branch will obtain confirmation from TPC by message supported by private number that power has been switched off and then issue a memo to the Guard of other traffic official in charge of the train to the effect that power has been switched off over the specified section. Only on receipt of such memo may the train carrying the ODC be allowed to enter the section. Note: Since such a memo is not a “permit to work”, earthing of the OHE is not necessary. VII. OTHER PRECAUTIONS 10438 Movement of Rubber Tyred Vehicles on Railway Wagons. All metallic parts of rubber tyred vehicles which are transported on railway wagons through 25 KV electrified areas, shall be earthed to avoid the effect of induction. 10439 Hoarding Boards. Hoarding boards provided in the vicinity of electrified tracks should be located at a safe distance from the track so that the event of their supporting structures being damaged during agitation or storms it should not fall on the OHE or infringe the track. For this purpose, CCS and CPRO will ensure that while granting approval for erection of hoardings boards, it must be ensured that not only these are located at the safe distance from the track but also their structural arrangements are properly secured. VIII COMPETENCY CERTIFICATE 10440 Competency Certificate and Courses for Assistant Station Masters/Guards of EMUs. All staff who are required to work in electrified territory must have undergone a course in Electric traction so that they are made familiar with the working rules in the electrified sections. ASMs are also sometimes required to operate isolators at the station premises for which necessary training is to be imparted. Similarly, the guards of the EMUs are also required to undergo an operational course for the working of EMUs and are to undergo a refresher course at regular intervals of 6 months at Electrical Training Schools. Operating department will ensure that only that staffs who have undergone the course in Electric traction are posted in electrified areas. INDIAN RAILWAYS-AC TRACTIO MANUAL-VOLUME 1