Overhead Equipment Maintenance Guide (PDF)

Chapter III OVERHEAD EQUIPMENT 20300 Introduction 1. This chapter is divided into five Sections as under:- Section I - Organization : A broad description of the duties of 3 important categories of staff in OHE Section is given. Here also, in territorial distrib...

Chapter III OVERHEAD EQUIPMENT 20300 Introduction 1. This chapter is divided into five Sections as under:- Section I - Organization : A broad description of the duties of 3 important categories of staff in OHE Section is given. Here also, in territorial distribution of work, the CTFO in charge have all activities under his control, and TFOs next in command will be in charge of functional activity. Section II – Guiding Notes on Maintenance : The important points to be borne in mind in the maintenance of the main items of OHE are enumerated. Section III – Maintenance Schedules for OHE : A recommended schedule of maintenance for OHE is given. Section IV – Safety Rules for OHE : The essential safety rules applicable to OHE staff are given. Section V - Forms and Registers : The records to be maintained in regard to OHE maintenance and recommended performance for these are given. 2. The following relevant documents have been incorporated as Appendices to this Volume. 2.1 “Principles for Layout Plans and Sectioning Diagram for 25 kV ac Traction” issued by RDSO (Appendix I). 2.2 “Code for Bonding and Earthing for 25 KV ac 50 Hz. Single Phase Traction System” issued by RDSO (Appendix II)\ 2.3 “Regulations for Power Line Crossing of Railway Tracks “ issued by Railway Board (Appendix IV) 2.4 “Guidelines for Provision of Maintenance Depots, Tools and Plants and Transport Facilities (Appendix VI) 2.5 Model Circulars” (Appendix VII) 2.6 “List of Specifications and for Equipments and Materials for Railway Electric Traction” issued by RDSO (Appendix IX) 2.7 “Diagrams of General Arrangement and Fittings” a reference booklet issued by RDSO (Appendix X). 1. ORGANISATION 20301 Duties of Chief Traction Foreman – CTFO (OHE) He is the senior supervisor working under the control of Sr. DEE/DEE (TRD) and directly responsible for the proper maintenance of OHE including the 25 KV feeders and return feeders from the traction sub-stations to the feeding posts. He should be fully conversant with the layout and sectioning of OHE in his jurisdiction as also the rules and procedures laid down for efficient maintenance of OHE and safe working on OHE. In particular he shall: 1. supervise the maintenance of installations under his charge in accordance with the prescribed schedules, to keep them fully serviceable and in a state of good repair. 2. Plan in advance the requirement of power blocks for OHE maintenance based on the work to be done in consultation with his section supervisors and ensure the completion of the work within the time allotted. INDIAN RAILWAYSAC TRACTION MANUAL VOLUMEIIPART1 3. Carry out detailed inspections of OHE under his control by push trolley or motor trolley to cover the entire section once in 3 months. 4. Scrutinize daily the reports on foot patrol and other defects on OHE, as well as reports from section supervisors and inspection reports of officers and arrange prompt rectification of defects pointed out and report compliance to Sr. DEE/DEE/AEE (TRD) 5. Check the work by sectional gangs under him to ensure that quality work is done and that compliance with prescribed schedules is adhered to. 6. Keep the organization for attending to breakdowns in constant readiness to act promptly and expedite restoration whenever there is a breakdown. 7. Instruct and train staff under him in the correct methods of maintenance with special reference to safety precautions. 8. Arrange to send his staff for training courses as required. 9. Ensure that special testing instruments, tools and equipment including the OHE inspection cars and breakdown vehicles, provided for maintenance of OHE are properly cared for and maintained in proper condition. 10. Keep a watch on availability of spare parts and stores required for maintenance of OHE and initiate timely action to recoup stocks. 11. Ensure proper accounting and periodical verification of the stores and tools under his charge. 12. Submit the prescribed periodical returns to DEE/AEE(TRD) and carry out their instructions issued, if any, on the basis of such returns. 13. Keep his superior officers fully informed of each and every important development and seek their guidance when required. 14. Carry out such other duties as may be allotted to him by his superior officers; and 15. Carry out inspections as indicated at Annex. 3.01. 20302 Duties of Field Supervisors. The field supervisors in charge of OHE (ATFO, chargeman, inspector etc.) will be under the CTFO(OHE) and each supervisor will be responsible for the following. 1. maintenance of the OHE and allied installations in his jurisdiction in accordance with the prescribed schedules. 2. Submission of the requirements of power blocks for OHE maintenance, in co-ordination with permanent way maintenance as far as possible, so as to take maximum advantage of traffic blocks. 3. Detailed inspection of OHE under his charge by push trolley or on foot as indicated in para 20322 and 20323. 4. Scrutiny of daily foot patrol and other reports of defects and take prompt action to remedy the defects brought out. 5. Close supervision of the maintenance gang under his control to ensure a high standard of work and compliance with prescribed schedules. 6. Keeping the organisation under his control in readiness to deal with breakdowns. 7. Guidance to the maintenance staff for the proper execution of work in accordance with standing instructions. 8. Ensuring that tools and equipment under his charge are properly cared for and maintained in proper condition 9. Keeping watch and taking necessary action to recoup stores and spares required for his jurisdiction. 10. Preparation and submission of periodical reports and returns to superior officials as laid down: 11. Keeping CTFO(OHE), AEE(TRD),DEE(TRD) and Sr. DEE(TRD) informed of all important developments and seeking their guidance when required. 12. Carrying out any other duties allotted by superior officials. 13. Carrying out inspection indicated at Annex. 3.01. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 20303 Linesman 1. All linesmen should have requisite educational qualifications to enable their working independently – to take power blocks from TPC, deal with messages in connection with power blocks and also to submit written reports to their supervisor in regard to patrol and inspection work assigned to them. However, until it is possible to have all Linesmen with the requisite educational qualifications, it will be necessary to authorize only selected linesmen to deal independently with taking of power block and issue of messages. Literate Linesman to be authorized to take power blocks independently should be trained and certified. 2. Every linesman should be conversant with the safety rules pertaining to his work and be capable of independently attending to minor repair and adjustment work on OHE. For this purpose he would be required to carry his tool box, telephone etc. with him wherever needed. 3. A linesman should be able to carry out operation at switching stations on local control in an emergency under instructions from the TPC. 4. Linesman shall look for the common types of defects on OHE when they are deputed for patrol work and to report on defects noticed during such patrols to the Section Supervisor (Para 20322) 5. Every linesman should develop the ability to carry out temporary repair in the event of breakdowns so as to restore traffic as quickly as possible and to deal with repairs necessary for all types of breakdowns of OHE. II GUIDING NOTES ON MAINTENANCE 20304 Introduction 1. For better utilization of traction assets, outage of any traction equipment from service should be minimum without compromising on safety of the equipment and personnel. Monitoring of condition of the equipment by reliable means is essential for following the system of need based maintenance i.e. directed maintenance. However, till such time reliable condition monitoring techniques are introduced, the present system of preventive maintenance has to continue. 2. Recommendations of Original Equipment Manufacturer (OEM) and Guidelines issued by RDSO, from time to time, shall be kept in view while defining the scope and periodicity of the schedules. 3. The tightening torque for fasteners of various sizes is given in the Annexure 2.08. 20305 Out of Plumb Masts Inspite of the care taken in design and erection, OHE masts do sometimes get out of plumb. This occurs largely on embankments, due to erosion of earthwork on the outer side of the mast on account of poor drainage or excavations in the vicinity or due to sinking of foundations onnew embankments. The extent of earthwork initially provided at the back of foundations on embankments is shown in Structure Erection (SEDs). OHE maintenance staff should, during patrolling and inspections, make a particular check of the condition of earthwork has been or is likely to be eroded away, the Engineering Department should be approached to strengthen the embankment, and the matter pursued until it is satisfactorily completed. Masts which appears to be out of plumb should be checked with a plumb bob. Since the normal height of the contact wire is 5.60 m above rail level, the extent of deflection of the masts at this height can be conveniently found by measuring the deflection at a height of 1.85 m above rail level and multiplying this figure by 3. If the mast is out of plumb, by more than 3 cm upto 5 cm, it should be kept under watch after making sure that there is enough earthwork all round. To identify such masts requiring watching, a yellow bend of width 5 cm should be painted at a height of 1.85 m from rail level. Masts which are out of plumb in excess of 5 cm can be set right by releasing the OHE and pulling the mast by a “Tirfor”. To facilitate this, the foundation must first be exposed on the side to which the mast is to be pulled by the Tirfor., and the rear under side of the foundation should be packed and rammed with pieces of stone until the foundation is fully supported. If necessary the newly packed part may be strengthened by pouring in cement INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI Any other method considered appropriate as per site conditions may be adopted. RDSO’s report No. ETI/OHE/55 on Tilting of OHE masts, Causes and Remedies may also be referred to. 20306 Rail Level and Setting Distance Structure Erection (SEDs) show setting distance or implantation of the OHE masts i.e. distance of the nearest part of mast from the centre line of the nearest track as well as the height of the contact wire from rail level at each location. These are with reference to alignment and level of the track at the time of erection of OHE. Before electrification work is taken up, it should be ensured that the track alignment and level are finalized. This is particularly so in the case of yards under remodeling. Any change in alignment due to slewing of tracks will affect the setting distance and consequently the stagger of the contact wire. At locations where the setting is critical i.e. close to the minimum permissible value, slewing of track may result in infringement of the moving dimensions with consequent danger of accidents. Change in rail level due to variation in ballast cushion or packing up or packing down of the track will also result in change in contact wire height. Though provision exists in the cantilever assembly for adjustments of the stagger and height, such adjustment are not to be made unless absolutely necessary. It is best to maintain the position of OHE and tracks as in the SEDs. General Rule (1976) 17.06 stipulates as under: Alteration to track “Before any alteration to alignment or level of electrified track is commenced, due notice shall be given to those responsible for the overhead equipment so that the overhead equipment may be adjusted to conform to the new conditions:” If follows, therefore, that any alterations of the alignment of the track on electrified sections shall only be made with the prior knowledge and concurrence of the Sr. DEE(TRD) so that he may arrange to correct the SEDs to the extent required. No alterations to the track affecting OHE parameters may be carried out without obtaining specific approval from Sr. DEE(TRD). Whenever any permanent changes are effected, the SEDs should be revised and a note made of the circumstances and the authority under which the revision has been made. To facilitate periodical checking, rail level and setting distance should be painted at the base of each OHE mast face soon after commissioning, preferably in black letters. A horizontal line would indicate the rail level. The setting should be marked in correct to the second decimal place. Repainting of the these markings will ordinarily be required once in two years. Where pollution due to brake shoe dust etc. is severe, repainting may be required more often. During yearly maintenance of OHE, rail level and setting distance should be checked and compared with the original figures. Any variations above 30 mm is setting distance and 20 mm in rail level should be advised to the PWI for correction. No change in setting distance and rail level should be allowed if such change results in infringement of moving dimensions. It is essential to have a joint annual check of rail level and setting distance by the Chargeman/OHE and APWI. In addition to the marking on the masts, a register should be maintained by CTFO(OHE) to record the annual measurements of implantation at critical locations over his jurisdiction. A similar register should be maintained by each Chargeman for his own section (see proforma 03-8 in Section –V) Limits for mast setting distances are indicated in Appendix I. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 20307 Contact Wire Hard Spots and Wear Hard spots are points on the OHE where contact wire wear is likely to be higher than at normal locations, due to less flexibility in the OHE. Smoke pollution aggravates wear at hard spots. The usual spots where the contact wire is likely to show more wear are – 1. Support points at curves. 2. Section insulators. 3. Splices 4. Turn outs 5. Central mast of 2 span uninsulated overlaps of unregulated OHE> 6. At approaches to tunnels and over line structures. 7. Locations where smoke pollution is pronounced, namely, tunnels with steam traction and at the ends of platforms where steam locos halt for a long time under OHE. 8. Pull offs At such hard spots, it is important to keep a watch on wear of contact wire by measuring and keeping a record of contact wire thickness periodically. It is essential to concentrate on these spots during annual measurement of contact wire wear. 20308 Sparking During Current Collection Sparking occurs when there is loss of contact ( or improper contact) between the pantograph and the contact wire. The common causes attributable to the OHE are: 1. Incorrect tension in regulated OHE due to maladjustment or sluggish operation of regulating equipment; 2. Inadequate tension of contact wire in the case of unregulated OHE; 3. Deposit of soot on contact wire due to steam and diesel traction and the resulting roughness of contact face during current collection; 4. Kinks in contact wire. If OHE on the main line is unregulated the tension in the contact wire should be checked and adjusted if need be once in 2 years. The speed being low in yards and sidings, the adverse effect of incorrect tensioning will be less pronounced and re-tensioning at longer intervals of 3-4 years will be adequate (para 20330) Deposits of soot on account of steam and diesel traction may cause trouble due to sparking at points where steam engines halt for long periods. Particular note should be made of such locations and cleaning done at shorter intervals. The importance of cleaning of contact wire before introduction of electric traction is dealt with in Chapter IX. Kinks detected during patrolling and inspection should be straightened or/removed without delay. After re-tensioning it is particularly necessary to inspect the section for kinks. The periodic current collection tests (para 20324) would reveal points where sparking takes place. Apart from investigating and rectifying the cause of such sparking, it is also important that the roughened surface of the contact INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI wire be attended to, failing which, there will be further deterioration, with successive passage of pantographs resulting in reduced life of contact wire. 20309 Contact Wire Wear Hard drawn grooved copper contact wire of 107 mm 2 cross sectional area when new is used in the 25 kV electric traction system. With a proper maintenance of the OHE the contact wire is expected to have a life of about 30 years, with average traffic density and conditions of pollution. The thickness of new contact wire is 12.24 mm. It will be necessary to replace the contact wire when it has worn to a thickness of 8.25 mm corresponding to a cross sectional area of approximately 74 mm2. At this point 2 mm clearance shall be available between the bottom most point of the dropper clip, parallel groove clamp as well as contact wire splice and the pan of pantograph. Any further reduction in cross sectional area will result in the current density in the contact wire splice and the pan of pantograph. Any further reduction in cross sectional area will result in the current density in the contact wire under certain conditions exceeding the permissible limit of 4.7 A/mm2 apart from reduced factor of safety under tension. In siding and lines with a low traffic density, a lower thickness limits of 8 mm may be adopted. It is important to measure and record the wear of contact wire at the known hard spots (para 20307) and at a few selected locations where heavy wear may be expected, so as to keep a watch on the rate of wear. Observations have indicated the wear of contact wire between starter and advance starter is high where the train picks speed, specially in suburban sections. In addition to the known hard spots, the wire thickness may be measured at one or two points between each pair of stations where speed is maximum. These measurements should be taken at the time of yearly maintenance and recorded in a register. When the average wire thickness has reached approximately 10 mm, the number of points where measurement is taken may be increased and one location in each tension length may be covered in addition to the known hard spots. Measurements of contact wire thickness in the vertical direction should be made with a micrometer, preferably one fitted with a ratchet screw adjustment to ensure that the pressure between the jaws when taking measurement does not exceed a particular value. Considerable care is required in using the micrometer. The measurement will be meaningful only if in successive years the thickness is measured at the same point at each location. It is only then that the values recorded can be directly compared. A 75 mm wide band may be painted on the mast fact with black paint. If the location is identified in this manner and a convention followed that measurement should be taken say 20 mm before the swivel clip in the direction of motion. It can be ensured that in successive years, measurement will be taken at identical points. The measurements must be taken personally by a supervisor well acquainted with the use of micrometer. Registers should be maintained in the office of the ATFO(OHE) for his jurisdiction and CTFO(OHE) for the entire division in proforma 03-4 given in Section V. If any isolated point the contact wire reaches the condemning limit of thickness, a splice should be introduced at the point. 20310 Splice Fittings The splice in OHE becomes necessary when a small length requires replacement as a result of excessive wear or restoration after breakdown. The splice fittings commonly in use are – 1. splice for single contact wire to identification No. 1080 or 1080-1 2. splice for double contact wire to identification No. 1280 3. splice for Catenary to identification No. 1090 4. splice for feeder wire to identification No. 1100 The main components are made of aluminum bronze and the studs of contact wire splice are of stainless steel. Samples of splices from each batch of supply are required to be subjected to special tensile tests in addition to the normal tests for quality of material, in view of the need for ensuring reliability of these important fittings. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI A splice should, as far as possible, be located at a distance of not less than 5 m from the support in the direction of traffic to avoid a hard spot on the OHE. Not more than 15 splices shall be used in one tension length. The distance between adjacent splices should, as far as possible, be more than 100 m. In new construction normally no splice shall be provided. Under exceptional circumstances a maximum of two splices may be permitted. The main points requiring attention during inspection of splice fittings are – 1. Careful examination for cracks or other casting defects or abnormalities. 2. In case of Catenary splice fitting tightness of the right hand and left-hand joint sockets. 3. Check to see if any slipping of the ends of two contact wires has taken place. When viewed through the top window, there should be no gap between the two contact wire ends. 4. Tightness of the stainless steel studs. Contact wire splices should not ordinarily be re-used. If they are re-used at all, new brass ferrules for contact wire splice to Id No. 1080 should invariably be used to ensure that worn serrations of the ferrules do not result in insufficient grip on the contact wire. Over-tightening of the stainless steel studs of contact wire splice fittings is harmful. Tightening should only be done to the extent possible with a standard spanner. No extra leveraile by means of a pipe etc. should be used. Registers should be maintained in the Offices of Sr. DEE(TRD), AEE(TRD), CTFO(OHE), TFO/ATFO(OHE) and OHE Section Chargeman showing the location and date of installation of all splice fittings under their jurisdiction. These registers should be brought up-to-date by taking an inventory of splice fittings during yearly maintenance and POH. 203011 Section Insulator Assembly 1. Section Insulators assembly is used to provide electrical isolation between two elementary sections which are otherwise continuous. They are used mainly on cross overs, diamond crossings and turnouts for loops and sidings to isolate section from main line. They may be used on main lines to form neutral sections in heavily graded sections, suburban sections and at inspection pits on secondary lines as well as lines for sheds for maintenance and inspection. Rules regarding the location of section insulators are contained in Appendix I; the speed permissible at these locations is also indicated therein. 2. The section insulator assembly is shown Fig. 3.02. The assembly comprises of a strain insulator with two runners connected to one of contact wires. The bottom of the runners is at the same height as the contact wire on the other side, and so shaped as to allow a smooth passage of the pantograph underneath it. The two runners overlap with the contact wire on the other side for a short length to ensure that there is no interruption in the current drawn by the locomotives as it passes underneath the section insulator. The flexibility of the OHE is reduced where a section insulator assembly is provided. 3. The essential points to be checked during periodical maintenance are as under- a) The weight of the section insulator should be fully taken up by the droppers so that the runners are at the same height as the adjacent contact wires both longitudinally and transversely. Fasteners are provided, at both the contact wire ending clamps, at the ends of the contact wire and link assembly and section insulator cross beam assembly, for effecting the adjustment accurately. When correctly adjusted, there should be no sparking when a pantograph negotiates it. The runners if bent or damaged should be either replaced or straightened out. The runners as well as the contact wire should be smoothened by filling off globules of copper which might have formed due to arcing. The distance between the contact wire and the runner on either side should be not less than 220 mm. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI and application of silicone grease should be decided based on the extend of smoke pollution in the area ( para 20314) b) The PG clamps holding the stiffeners at both ends should be checked to ensure that the stiffeners do not work loose. 20312 Short Neutral Sections Assembly. 1. Short neutral sections assembly incorporating light weight contact wire insulator of composite type ) resin bonded glass fibres core protected with wear resistant ceramic beads) has now been adopted as standard. Ease of installation even on flat curves and difficult locations, substantially reduced maintenance and other advantages are gained by introducing short neutral section. Conversion of existing overlap type neutral sections to short neutral sections may be done where it is not yet done. Short neutral sections should also be introduced in lieu of insulated overlaps opposite to the feeding posts at sub-stations. (Board’s Ref. 86/RE/501/1N/S) dt. 16/22.7.1987.) 2. The general construction, design and other requirements of short neutral sections shall conform to RDSO’s Drg. Nos. (I) ETI/OHE/SK/551-Arrangement of Neutral Sections for Conversion with Short N.S. (ii) ETI/OHE/SK/552-Arrangement of short N.S. at Existing Feeding Post. 3. The essential points to be checked during periodical maintenance are as under: a) cracked beads. b) Electrical erosion of coating c) State of cleanliness of insulators. d) Burning of arcing horns and arc traps e) Pantograph hit marks on the under side of compression ferrules and end sleeves of the contact wire insulators to ascertain need for adjustment to be runners. f) Freedom of movement of telescopic anti torsion droppers. g) Elastomeric bellows for cracks h) Insulation resistance. 20313 Jumper Connections. The following types of jumper connections, using standard copper conductors and PG clamps, are in common use in 25 KV OHE. 1. In-span jumpers of approximately 50 mm2 cross section for electrical continuity between contact and Catenary wires, at intervals not exceeding 400m. 2. Potential equalizer jumpers of approximately 50 mm2 cross section at insulated over laps and neutral sections to keep the portion of OHE between the cut in insulators and the nearer anchorage at the same potential as the adjacent run of OHE. 3. Continuity jumpers of cross section 105 mm2 to provide electrical continuity between the two portions of OHE at uninsulated overlaps and between the main line OHE and turn out/cross over OHE at turn outs/cross over. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 4. Jumpers of cross section 105 mm2 or 150 mm2 between feeders and OHE at feeding points. 5. Jumpers of cross section 50 mm 2 provided between out of run. OHE and anticreep wire as an anti theft measure. Jumper connections play a vital part in maintaining continuity of supply. On account of the up and down movements of the contact wires, the jumper connections are bent to some extent every time a pantograph passes through. With repeated bendings the strands of the flexible jumper connections are liable to get broken in course of time on account of fatigue. To guard against this possibility, special attention should be devoted to the jumpers during periodical maintenance. The essential requirements for reliability of jumpers are – 1. Sufficient length and adequate looping to provide flexibility so as to prevent failure on account of repeated up and down movements and movements on account of elongation and contraction of OHE due to temperature variations. 2. Adequate cross section to carry the normal currents and possible overloads due to shut downs on adjacent lines, as well as faults. 3. Proper bonding and in soldering of the ends. 4. Proper seating and tightness of connections at PG clamps. Failure of continuity jumpers will result in discontinuity of the OHE and consequent serious interruption of traffic. Though failures of potential equalizer jumpers may go unnoticed, such failures can result in electrical accidents. Also, unscheduled attention to such jumpers will necessitate power-block on both the adjacent elementary sections, which may be quite difficult to arrange without repercussion to traffic. Proper attention to jumpers during scheduled maintenance is, therefore, very important. Jumpers, particularly continuity jumpers, with broken strands should be invariably replaced, failing which the reduced cross-section may cause overheating and eventual failure. Broken strands are most likely at the point of entry into PG clamps, possibly due to sharp edges in the clamp. PG clamps should have properly rounded off edges to prevent the cutting of strands. The clamps should be checked for signs of overheating and proper tightness. It should, however, be remembered that a PG clamp should not be interfered with unless there are signs of overheating or damage. 20314 Environmental Effect on OHE Atmospheric Pollution The atmospheric pollution has caused a large number of insulators flash over in certain areas such as Howradh and Assansol in Eastern Railway. Ahmedabad, Vadodara,. Surat and Valsad sections of Western Railway and Madras-Gudur section of Southern Railway. The flash over mainly occur in the early morning in winter before sun rise and in the pre monsoon period, specially when monsoon are delayed. The pollutants provide a creepage path resulting into flash over of insulators and consequent tripping of the 25 Kv and EHV circuit breakers. Pollution can be classified, broadly into the following categories. I_) Saline Pollution : caused by salt deposits in coastal areas. The adverse effect get magnified in foggy, humid and light rain conditions, resulting in series of flashovers. ii)_ Chemical and Industrial Pollution : Waste gases from industries – hydrochloric acid, sulphuric acid, hydrofluoric acid fumes etc. and minute particles of urea, cement etc. affect insulators of the electrified tracks in the vicinity of these industries. These conditions not only effect the insulators, but also affect the steel parts including mast, which corrode rapidly and need frequent attention. Special steps are required to be taken throughout the year, suitably modifying the insulator cleaning schedules to ensure trouble free service. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 1. Insulators Although insulators supporting OHE are by the side of supporting masts, they are subject to settlement of carbon deposits, smoke pollution due to steam trains, oily deposits on account of diesel engine and cement or other industrial dust as mentioned earlier. If these deposits are not removed at regular intervals, they are liable to become hard and difficult to remove in course of time, and by reducing the insulation of the OHE greatly, lead finally to a flashover. Further, a dirty insulator of a section insulator can result in a dangerous potential in a section made dead. The remedy lies in cleaning the insulators at regular intervals. Where there is no pollution, cleaning need be done only once a year or even at longer intervals. Where pollution is not appreciably high, the interval may be three months or longer depending upon the degree of pollution in the area. Generally in heavy industry areas more frequent cleaning of insulators may have to be done. Cleaning is done by wiping the surface with a piece of dry cloth. A wet cloth may be necessary if the coating is hard. If the deposits are oily, petrol may be used for cleaning. If this too in ineffective where encrustation has become hard due to continued neglect, the coating may have to be removed by rubbing with a wet coir rope using a suitable detergent. After removing the deposits, the surface of the insulator should be washed well with water, wiped with dry cloth and polished until the normal glaze is restored. The periodicity of cleaning of insulators in polluted locations should be laid down by local instructions. The affected section should be divided into various zones based on the degree and nature of pollution And periodicity of insulator cleaning fixed suitably. The cleaning will be required more frequently in foggy weather compared to dry or rainy season. The periodicity may be reviewed based on effect of special measure, Other steps for reducing flashovers due to pollution _ i) Application of High Voltage Insulting Silicone Compound The frequency of manual cleaning can be substantially reduced by application of silicone grease or similar anti tracking compounds. Application of high dielectric strength anti acidic varnish has also been found to be useful under certain conditions. The surface of the insulator is cleaned and then a light coat of the material is applied so that a dust and water repellent surface is produced. ii) Use of longer creepage path insulators Use of Insulators of longer creepage path will reduce frequency of cleaning. The problem can be tackled in many ways mainly to reduce the frequency of cleaning, which can be established by constant endeavor in trying out what is best for a specific section over a period of 2 to 3 years. 2. OHE Structure and Fittings. Due to effluents discharged by the factories which are close to the railway tracks, the atmosphere gets surcharged due to presence of corrosive fumes in the effluents. Such cause corrosion of steel structures and OHE parts. In order to safeguard against this problem, remedial action as under should be taken. a) Matter should be taken up with the factories and the Board of Control of Pollution of that area, they should ensure that the discharge of the factories is well within the limits laid down by the Board. b) A special check at regular intervals should be conducted to see that the corrosion does not affect the performance of the components. c) Chlorinated paints may be tried on the steel structures to off set the effect of pollution on the steel structures. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 20315 Clearances in Tunnels and Other Overline Structures. If the OHE construction as well as the tunnels and over line structures are not modified subsequent to the electrification, the clearances provided at the time of erection will remain unaltered. It is, however, important to check the clearances during the annual maintenance, compare the values given in as erected and take corrective action as required. 20316 Regulating Equipment 1. There are three types of regulating equipment in use at present viz. The winch type, pulley block type and 3 pulley type. With all the three types of equipment the chief task of maintenance is to ensure that the counter weight is free to move up and down in the guides without any chafing or obstruction. If the movement of the counterweight is obstructed, the tension of the OHE will not be correctly regulated resulting in poor current collection. The counterweight should not come down so low so as to touch the muffing in summer, nor should if strike the guide fixture at the top during winter. During yearly maintenance of the pulley block type of equipment dimension ‘X’ (i.e. the distance between the centres of the movable and fixed pulleys) and ‘Y’ (i.e. the distance between the bottom of the counterweight and the top of the muffing) should be checked against prescribed values and adjusted as required according to the tension length of the OHE and prevailing temperature. Small adjustment can be effected by using the adjusters provided. In the event of appreciable stretching of the contact and catenary wires, particularly a few months after installation, it will be necessary to cut small lengths of contact and catenary wires at the terminations to get correct alignment and adjustment. In the winch type equipment, corresponding to dimension ‘X’ in the pulley block type dimension ‘Z’ i.e. the distance between the centres of the movable pulley and the winch drum is required to be measured. To facilitate checking, the position of the bottom of the counterweight corresponding to the lowest and highest temperature should be marked on the masts by means of black bands of width 20mm. The position of the counterweight at ambient temperature of 35 degree C may be marked by a red band which can be seen during trolley inspection readily. The bottom of counter weight should coincide with the band mark. 2. The usual defects to be looked for in the pulley block type of equipment are – a) damage to pulley grooves by the stainless steel rope due to misalignment of the equipment and the catenary wire being not vertically above the contact wire at the termination; b) seizing of the needle bearings due to drying up of lubricant and consequent jamming of the pulleys; c) jamming of guide pulley due to lack of lubrication and consequent grooving of the pulley. This can be checked by pushing up the counter weight and allowing it to descent due to its own weight; d) damage to neoprene washers provided between pulleys resulting in ingress of dirt and water into the needle bearings; e) bent sliding rods obstructing the movement of the movable pulley; f) blocking of grease nipples. These defects except for replacement of the guide pulley and attention to blocked grease nipples are not capable of being attended to in-situ. The complete equipment should be replaced with a spare one and the removed equipment taken to the workshop for attention. The main pulley and guide pulley bearings of the pulley block type equipment should be lubricated using approved type of grease which will be able to withstand 60 degree C without drying. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI Another important check required for the pulley block type equipment is to see that that the stop nuts provided at the end of the guide rods are intact. These are provided to prevent the movable pulley coming off the guide rods in the event of breakage of the stainless steel rope. 3. The common defects to be looked for in the winch type equipment are : a) Over riding of stainless steel rope and grazing of grooves. b) Breakage of strands of stainless steel wire rope. c) Seizure of pulley bearing. d) Tilting of anti falling device. Stainless steel ropes should be examined periodically with a magnifying glass for putting and other signs of corrosion. Regulating equipments should be checked periodically for free movement with the help of a spring balance. If pull required for a visible movement of counter weight exceeds 10 kgf. The regulating equipment should be overhauled. Whenever a panto/OHE entanglement takes place the regulating equipments of all the concerned OHEs should be checked thoroughly, particularly if any of them was overhauled more than two years earlier. Until such time a grease capable of retaining the properties for 4 years becomes available, all regulating equipments should be overhauled every two years. Priority should be given to those which cover the more vulnerable locations. During overhaul of regulating equipment special attention should be paid to the shape and dimensions of the winch frame arms (right and left) as they have a direct influence on the angle of incidence of the stainless steel wire rope on the winch drum. Whenever a regulating equipment is dismantled, the condition of the bearing grease should be checked. If it is found to have lost its oil content and exhibits the consistency of hard soap, the source and type of grease used initially should be investigated. The condition of rubber or felt seals provided to prevent the ingress of water into bearings should be checked and if they have deteriorated, the quality and source should be investigated and remedial steps taken. All seals should invariably be replaced during periodical overhaul unless their condition is found to be good enough to work satisfactorily for another four years. 4. Most of the points mentioned above are also applicable to pulley type regulating equipment which is now standard. 20317 OHE Inspection Car (Tower Wagon) 1. OHE inspection car has a key role in the maintenance of OHE and for attending to break downs. The satisfactory upkeep of the car is, therefore, or utmost importance. ATFO (OHE) should ensure that the car under his control is maintained satisfactorily and is available at all times for attending to OHE and for use in the event of break downs. Each car should carry necessary tools for maintenance of OHE and attending to breakdowns, such as tackles, straining screws, clamps, ropes a minimum of two ladders as well as an adequate stock of insulators, lengths of contact and catenary wires and other OHE fittings. An approved list of tools and equipments to be carried in each care should be issued by DEE(TRD). ATFO(OHE) should ensure that tools and equipment as per the approved list are always available in the car. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 2. A monthly mechanical inspection of the bogies and running gear of each car shall be done by a nominated TXR of the Mechanical Department, headquartered close to the OHE depot where the car is normally stabled. For each car on a Zonal Railway, the TXR responsible for monthly mechanical inspection will be nominated and a joint circular to this effect issued by CME and CEE laying down his duties. The ATFO(OHE) in charge of the car will advise the TXR concerned the date on which it is required to be inspected and running repairs carried out. Such advise shall be given at lest 48 h. in advance. ATFO(OHE) should ensure that this monthly advise is issued regularly and the car is offered for inspection and attended to every month. The TXR will arrange for examination of bogies., running gear, underframe, under gear fittings and axle boxes only, in accordance with IRCA rules, Part-III. He will also arrange for stenciling the date of monthly examination on the sole bar of the car. The POH of the car shall be done at an interval of 3 years in an EMU shop/electric loco shed/Electric workshop, as decided by CEE. (Ref. Board’s letter No. 84/Elec/140/4 Vol. I dt. 1.3.90) 3. The day to day maintenance of the diesel engines and driving gear of the car will be the responsibility of the ATFO(OHE) concerned. The OHE inspection car drivers should carry out the daily maintenance. Specialist staff conversant with the maintenance and overhaul of diesel engines and driving gear should be available on each division for attending to monthly and six monthly maintenance of the diesel engines and driving gear. If it is more convenient and depending upon the work load, two or three divisions may be grouped together for the purpose of posting such specialist staff. 4. Taking into account the total number of OHE inspection cars and the need for relief of such cars for purpose of POH etc. in each Zonal Railway, one or more spare OHE inspection cars may be provided as necessary. 20318 Salient Features of OHE Inspection Cars. The salient features of the OHE inspection cars presently in use of on Indian railways are as under – 1. Mark II 4 wheeler manufactured by Kanchrapara Workshop/E. Rly. i) Diesel engine 83 HP (Simpson make) ii) Axle load 6.8 tonnes iii) Pay load 3 tonnes iv) Speed potential 40Km/h v) Transmission Gear box system vi) Brake system Vacuum 2. Mark III 4 wheeler manufactured by Jamalpur workshop/E.Rly. i) Diesel Engine 185 HP ii) Axle load 16 tonnes iii) Speed potential 75 Km/h iv) Transmission Hydraulic/Hydro mechanical v) Brake system Compressed Air Brakes. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI 3. OHE Inspection Car – 8 wheeler i) Diesel engine Single 530 HP or twin 285 HP ii) Transmission Volt’s Hydraulic Transmission iii) Axle load 16 tonnes iv) Pay load 10 tonnes v) Speed potential 110 Km/h on level tangent track 30-40 km/.h on 1 in 60 t rising gradient while hauling a loaded bogie flat wagon of 60t vi) Brake system Compressed air brakes vii) Paying out facility on one drum each of contact and catenary wires viii)Small workshop fitted with drilling machine etc. ii) Two staff cabins with toilet iii) A small kitchen ,storable space for tools,spares, and traction mast etc. iv) Adjustable lifting and swivelling platform v) Observation dome To watch pantograph and contact wire interaction during motion. 20319 Rules for Operation of OHE Inspection Car. General i) Authorization: No OHE inspection car may be operated by any person unless he is specifically authorised to do so after he has been trained and examined for his knowledge of the rules prescribed ( chapter XII) ii) Scope The following rules shall govern the working of an OHE inspection car fitted with a pantograph for the purpose of inspection of OHE either during commissioning of completed sections of OHE or during periodical inspections carried out by the OHE inspection car maintenance staff. All staff in charge of operation of OHE inspection are shall make themselves fully conversant with and act according to the special instructions given below: iii) Movement The movement of OHE Inspection Cars on tracks will be governed by all the rules governing movement of trains. Driving j) OHE Inspection Car shall be driven only by an authorized person, and no person shall be so authorized unless he has knowledge of the section (Road and Signals) on which the car is to operate and is conversant with the operation and maintenance of car. He should also be in possession of competency certificate for the purpose. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI ii) The OHE Inspection car shall be driven at a speed not exceeding 10 km/h when checking contact wire level and stagger. This shall be done by running on the first gear. Riding on the clutch for this purpose is prohibited. iii) If the OHE inspection Car is driven for other than recording operations, the speed should not exceed the designed speed subject to the speed restrictions imposed in the section. iv) In every depot, at least two OHE staff shall be trained and issued with competency certificate to drive an OHE Inspection Car in the event of an emergency. Panto graph Operation. i) The pantograph mounted on the roof of the OHE Inspection Car is electrically bonded to the underframe by means of a cable connection. This cable connection should be checked before starting any operation for checking and adjustment of OHE. ii) The pantograph should normally be kept in the fully lowered position and clamped securely by means of the special clamp provided for the purpose. No string, cord, etc. shall be used for the purpose. iii) Before any person goes up to the roof of the OHE Inspection Car for commencing inspection and adjustment, the section of the OHE concerned shall be made dead and earthed on either sides. Additional earths shall be provided where necessary. After earthing the OHE, an additional earth shall be provided near the OHE Inspection Car on the OHE of the track on which it is standing. An authorized person not lower in rank than a linesman shall then go up on the roof and remove the clamps to release the pantograph. iv) Under no circumstances should the OHE inspection car be worked with the pantograph raised without an earth on either side of it on the section of the OHE in which it is to be worked. v) In order to ensure that the pantograph does not enter a section where the OHE is live the OHE inspection car shall be protected on both the sides with banner flags and other signal flags. The Driver shall always stop the OHE Inspection Car ahead of all turn outs, cross overs, insulated overlaps and section insulators first and then proceed only after ensuring that the section ahead is dead and earthed. Banner flags shall then be removed for the purpose of admitting the OHE inspection car into the section ahead. vi) At the end of the Inspection and checking, the pantograph, shall be lowered and clamped by an authorized person not lower in rank than a linesman working on the roof after earthing the OHE of the track on which the OHE inspection car operating. The earths on the OHE near the OHE Inspection Car shall then be removed after all persons working on the roof have come down. Operation of Lifting and Swivelling Platform a) The lifting and swivelling platform shall ordinarily lie in the fully lowered position along the length of the OHE Inspection Car. ii) The swivelling platform shall be raised or lowered only when the OHE Inspection Car is stationary. iii) The platform shall be moved out of the normal position only when the OHE Inspection Car is stationary. iv) The OHE Inspection Car shall be moved only after the platform has been put back in the normal position. v) If the OHE Inspection Car is to be moved with the platform raised, it may be done at a speed not exceeding 5 km/h. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI  III MAINTENANCE SCHLEDULES FOR OHE 20320 Schedule of Inspections 1. In order to achieve high reliability and ZERO DEFECT OHE, and to ensure effective checks on the maintenance work a minimum schedule of inspections to be carried out each month by the officers and Senior Subordinate in charge of operation and maintenance of OHE and associated system, is indicated at Annexure 3.01. 2. The schedule of inspections is the minimum quota for each official and should be independent of other tasks. They will not be of routine nature but shall be carried out in depth to identify. b) Deficiencies and short comings. ii) Lack of skill amongst staff. iii) Inadequacies in maintenance facilities iv) Constraints experienced v) Conditions of environment leading to poor quality of work. 3. The inspecting officials should programme their inspections in such a manner as to cover the widest areas in their jurisdiction over the year and so stagger the inspections as to avoid over inspections of the same section repeatedly, in a very short time while neglecting other areas. A check in brief for various inspections is indicated at Annexure. 3.02 20321 General The OHE is subject to dynamic oscillations due to the constant contact and movement of the fast moving pantograph coupled with wind pressure. It is necessary to maintain the OHE in perfect condition through proper checks on its geometry and all parameters adopted in the design. The following schedules of maintenance for the OHE are required to be followed to ensure good current collection as well as safety of installations and personnel – I) Foot Patrolling ii) Trolley inspection iii) Current collection Tests iv) Special checks v) Annual Maintenance and OHE Inspection Car Checks. vi) Periodical Overhaul vii) Re-tensioning of Unregulated OHE. 2.The importance of OHE arises from the fact that it is extensive, with a very large number of insulators, fittings and other parts; failure of any one of which may result in dislocation of train services for appreciable periods until the defect/breakdown is rectified. The adjustment work is particularly important at cross overs and at overlaps spans since any departures from the standards laid down could cause entanglement of the pantograph with the OHE, with serious repercussions. The need for a thorough detailed inspection of every part of the installation, mast by mast need not therefore be over-stressed. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI  3. The periodicity of schedules laid down below apply to the majority of installations. The periodicity may however, be modified by CEE, where local condition so warrants. 4. As regards new equipments, if schedules, have not been drawn up, tentative schedules may be evolved based on the Original Equipment Manufacturer’s guidelines and RDSO’s recommendations, keeping in the view the local conditions also and followed with the approval of CEE. 20322 Foot-Patrolling of OHE The object of foot-patrolling is to made visual inspection of every part of OHE (including feeder line) so that any defect and abnormalities noticed are recorded and reported to the maintenance gangs for attention. 2.An experienced OHE linesman (accompanied by a Khalasi if deemed necessary by local conditions) should be deputed to patrol the section on foot by day, so as to cover every part of the section including years once a fortnight and suburban sections once a week. If this patrolling is done thoroughly, many of the defects will be noticed at the incipient stage, before they develop into major defects. ATFO or Chargeman should foot patrol the section once in six months. 3. The Linesman on foot patrol should be equipped with signal flags, an emergency telephone instrument and essential tools required for attending to defects on the spot e.g. spanners for tightening bond connections. 4. The Linesman on patrol duty should particularly look for the following – a) Chipped or damaged insulators. b) Displaced fittings and droppers c) Excessive sagging or hogging of contact wire d) Whether equalizing plate is tilted e) Free movement of auto tensioning device and position of counterweight with reference to upper and lower limits of movement marked on the mast. f) Presence of protective screens, caution and warning boards and Anticlimbing devices. g) Structural soundness of height gauges at level crossings. h) Bird nests and pieces of stray wire likely to cause short circuits and branches of trees likely to infringe the OHE.. i) Defective bonds and earth connections. j) Defects in return conductor connecting booster transformers and its connection to rails. Oil leakage if any from BT and AT. k) Any obstructions including tree branches in the way of free movement of pantograph and trains. l) Signs of heavy sparking when trains pass. m) Isolators blades being fully in and for signs of sparking or overheating of isolators as also condition of locks n) General condition of switching stations en-route. INDIAN RAILWAYS –AC TRACTION MANUAL-VOLUMEII PARTI o) Tilting of masts especially on high banks and masts with sand core foundations. p) Number plates q) Any other abnormal/unusual situation 5. Major defects noticed by the Linesman which endanger safety shall be reported forthwith to TPC through the nearest telephone. Full details should be given to enable the TPC to decide on the course of action to the taken and if required to regulate train movements in the affected section. 6. The Linesman should himself attend to and rectify such of the minor defects (e.g. loose bond connections) which can be rectified by him on the spot without special assistance. To facilitate this, he shall carry with him a few essential tools. Other minor defects should be noted by him in his diary and entered by him in a Register (see para 20351) maintained for the purpose in the depot/sub depot. The roster of patrolling Linesmen should be so arranged that they will be able to return to the depot sub-depot for submission of report as above before going off duty for the day. Where this is not convenient, the Linesman must report the defects on telephone to the depot/sub- depot followed by a written report in the register on the next day. The supervisor in charge of the depot/sub-depot will carefully scrutinize the Register and take prompt action to rectify defects reported, making suitable entries in the Register. 7. Testing of Emergency Telephone Sockets: During patrol duty, the Linesman will speak to TPC from every emergency telephone socket in route. Such calls from patrolling Linesmen should be recorded in a Register by the TPC indicating the date, time and serial number/location of the socket tested. Defective sockets should be reported promptly to the S&T Department for rectification. A proforma for Linemen’s Foot Patrol Report is given at Annexure3.03 20323 Trolley Inspection of OHE Inspection of OHE by push trolley is essential except in sections where use of trolley is prohibited. The object of such inspection is to enable supervisors and officers in charge of OHE maintenance to observe closely the OHE under their charge and should be carried out during day time. The depot in charge (TFO or ATFO)_ should inspect his entire section once a month. CTFO/AEE(TRD) should inspect their respective sections once in 3/6 months respectively by push trolley or motor trolley as convenient. Sr. DEE/DEE(TRD) also should cover his entire section at least once a year by push trolley or motor trolley. 2. Apart from trolley inspection as above, officers and senior subordinates shall travel by the cabs of locomotives and EMU trains as often as possible but atleast once a month to observe the general condition of OHE and to get a first hand knowledge of operating conditions. 20324 Current Collection Tests It is necessary to carry out periodic tests to detect points at which contact between the contact;Are and pantograph is unsatisfactory resulting In sparking. Such current collection tests are performed at night. A mirror can be fixed in front of the look-out glass of the rear cab of a locomotive and adjusted so as to get a reflection of the rear pantograph which is normally in service. A person travelling in the cab can then observe through the mirror any sparking which may take place. The location where the sparking is observed and the severity of the sparking should be immediately noted down and the OHE at the location got checked up as soon as possible to find out and eliminate the cause of sparking. The current collection tests as above should be carried out by the depot-in-charge (TFO or ATFO) once in 3 months over his entire section. The CTFO/AEE (Trd) should accompany the depot-in- charge during such tests alternately so as to cover their sections once in 3/6 months respectively. DEE (trod) should accompany the depot-in-charge so as to cover his jurisdiction once a year. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 1 The form in which a record is to be maintained Is indicated in para 20349. 20325 Special Checks While the majority of items require attention only during Annual Maintenance and Periodical Overhaul, items listed below will require more frequent attention as indicated against each - 1. Insulators: Generally insulators need cleaning once a year along with the annual maintenance schedule. At locations subject to smoke pollution on account of steam locus or pollution due to industrial dust, the frequency of cleaning will have to be fixed based on the extent of such pollution. Where pollution is heavy, cleaning may have to be done more frequently. With the application of silicone grease, the interval for cleaning at such locations can be extended significantly. 2. Section Insulators: Section insulators on the main lines such as at neutral sections and passenger yards should be attended to as under once in three months - (a) Clean insulators and replace badly chipped or even slightly cracked insulators. (b) Check runners for flash-marks. (c) Check level of the assembly and adjust as required. (d) Check foe excessive contact wire wear near anchor clamps. (e) Tighten properly the PG clamps of droppers and stiffeners. (f) Check that pantograph passes underneath the section insulator smoothly. 3 Isolating switches at Yards/Loading sidings: The continuity and soundness of earth connections should be checked once a month. 4. Bi-metallic clamps: These should be checked for tightness and signs of overheating once in 3 months. 5. Earth Connections: Apart from general inspection of bond and earthing connections during foot- patrolling, all such connections should be specially checked for continuity and soundness of connections once in six months. Particulars of all earthing connections (other than structure bonds) should be entered in a Register station-wise for each section and the dates of six-monthly inspection entered therein (see para 20351). 6. Feeders: Foot-patrolling of 25 kV feeders should be carried out every month. During this check, the Linesman shall also check that safety guards provided under the feeders properly earthed, if the clearances are adequate and caution notice boards are in position. 7. OHE supported on steel girder bridges should be examined as frequently as possible depending upon traffic conditions. 8. Bird nests: Vigil should be exercised especially during the nesting season and the nests removed as soon as possible. 9. Pre-monsoon checks : Some of the items to be attended are - i. Checking condition of insulators specially that of section - Insulators at major yards having mixed type of traction; ii. Over-line structures for any water leakage on the OHE and PVC insulators at major yards having mixed type of traction; iii. Trimming of trees branches; iv. Condition of embankments with respect to stability of masts; Rod gaps. v. Rod gaps INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART 20326 Annual Maintenance and Checks by OHE Inspection Car 1. This schedule must be carried out by Inspection Car. During the schedule, fittings are not generally dismantled, but all fittings which are found defective must be replaced. In addition clearances, heights, staggers etc. should be checked and corrected. 2. The details of work to be carried out during this schedule are as under- (a) Masts, portals and cantilever supports: (i) Check rail level and setting distance against markings on the masts and entries in the Register. Variation above 3Omm in setting distance and 2Omm in rail level should be notified to the PWI for correction. Variations, even within the above limits, should not be permitted if the Schedule of Dimensions are infringed. (ii) Check all steel parts and remove rust, if any, from painted steel work. Rusted portions, after cleaning, must be given two coats of zinc chromate primer followed by aluminum paint. (iii) Check all anchors for tightness of bolts, nuts and checknuts and pins, Lubricate all turn buckles/adjusters and pulleys. (iv) Examine the base of each structure to ensure that muffs permit drainage of water. Clean the muffs removing any muck or dirt. Cracked or damaged muffs must be recast. (v)Check all bonds thoroughly. Defective bonds must be rectified and missing bonds provided, (Vi) Check and tighten all G.I.bolts and nuts. (vii) Check all galvanized pipes and fittings. Where galvanization is found to be chipped off, the fitting of pipe should be replaced. Minor chippings may be repaired using 'cold galvanizing paint'. (viii) Examine register arm and all hooks and fittings for cracks. Check for cracks on steady arm tube also. (ix) Clean all insulators and carefully check for cracks and broken sheds. If more than 2 sheds are broken or there is any crack on the core the insulator should be replaced. (X) Check and adjust heights and staggers on the basis of setting distance and rail level marked. Close co- ordination with Permanent Way Inspectors is required for keeping the permanent way at the correct location. (Xi) Check presence and condition of caution notice boards, number plates, coasting boards, etc. Paint the boards as required. Ensure that they are all well secured. (xii) Ensure that the drain holes in the tubes are free and not clogged. (b)Contact and Catenary Wires: (i)Check carefully condition of contact and catenary wires, particularly for kinks and twists in contact wire and broken strands of catenary wire. Any stranded conductor (catenary wire etc.) should be spliced if more than 20 per cent of the strands are broken. (ii) Check condition of PG clamps and jumpers after opening the clamps and tighten properly. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 1 (c) Droppers: (i)Check droppers and tighten bolts wherever required. (ii)Make droppers vertical. (d)Turn outs (i) With OHE Inspection Car running on main line check up if pantograph glides smoothly under the loop line OHE.. (ii)With OHE Inspection Car running on loop line check up if pantograph glides smoothly under the main line OHE. (iii) Check stagger of both the OHEs at turn cuts. (It shall not normally exceed 300 mm). (iv) Check that the main line OHE of overlap type turn out is about 50 mm below that of the turnout OHE. (v) Check up cross contact bar, if any, for displacement and distortion. Check up for hit marks, if any. (vi)Check up for hit marks ,if any. (vii) Check up rail level and setting of the obligatory mast. (viii) Check up for hard spots near rigid droppers, if any. (e) Section Insulators Assemblies: (i) Clean insulators and replace chipped or cracked insulators. (ii)Check runners for flash-marks, hit marks and proper adjustment. (iii)Check for excessive contact wire wear near anchor clamps. (iv)Check the level of the assembly and adjust if necessary. (v)Tighten PG clamps of droppers and stiffeners. (e) Isolators: (i) Check number plates for cleanliness and security. (ii) Check number plates for cleanliness and security. (iii)Check correctness of operation, alignment of contacts and arcing horns. Check earth continuity where applicable. (iv)Lubricate moving parts and locks. (v)Check interlocks where provided. (vi) Check that the distance between male and female contacts in open position is 38Omm to 50omm depending upon the type of isolator. INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART [80 ] (g) Short Neutral Section Assemblies Carry out all checks as indicated in para 20312. (h)Overlaps: (i) Check height and stagger of OHE In the overlap section. (ii) Check whether the normal minimum clearance of 500mm is available between the two OHEs In an insulated overlap and 200mm in an uninsulated overlap. (iii) Check whether the lifting of out-of run OHE is correct. (iv) Check that parallel running of contact wires In the overlap for a minimum 2m In the panto sweep region (i)Contact Wire thickness: Measure and record thickness of contact wire as detailed in para 20309. (k)Neutral Sections: Carry out all checks as for an insulated overlap in case of overlap type neutral sections and as for section insulators in the case of section insulator type neutral section. (l)Overline, Structures/Tunnels (i) Check and record horizontal and vertical clearances and adjust OHE as required. (ii) Check for any flash-marks on the under side of the bridge structures. (iii) Check that the prescribed height of contact wire is available, (iv) Check that the gradient of contact wire on either side does not exceed 3mm/m. (v) Check that smoke screens are properly secured and have adequate clearance from OHE. If not, get these attended to by Engineering Department. (vi) In tunnels get necessary repairs done by Engineering Department. (vii) Check rail level mark on sides of tunnels. (m)Level Crossings (i) Check height and gradient of contact wire. (ii) Check condition of road surface and clearance of height gauge (a black band may be marked on the uprights at a distance of 4m from bottom face of the boom to facilitate measurement of clearance.) Regulating Equipment: (i) Check 'X' and 'Y' dimensions in the case of pulley block type equipment and 'Z' and 'Y' dimensions in the case of winch type equipment against prescribed values for the temperature at the time of checking. Make use of turn-buckles to adjust as required. (ii) Check that the compensating plate is vertical. If not, adjust as required. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 1  (iii)Lubricate pulleys and other moving parts. (iv)Check if 20mm wide bands in black colour are painted on the mast to indicate upper and lower limits of movement of counter weight. (v)Check condition of stainless steel wire rope for any signs of corrosion and breakage of strands. (vi) Check condition of grooves on the drum of winch type regulating equipment. (o) Bonds & Earthing Connection. (i) Check all bonds and replace defective or missing bonds. Paint all bonds. (ii) Inspect earths and record earth resistance. Earths having resistance of over 10 ohm should be attended to. (P)Masts: Check verticality of all masts with plumb-bob and take remedial action as required (see para 20305). (q)Sites affected by accidents: Such sites should be specially checked and attended to. (r)Feeder Lines: (i)Check guard wires at road crossings, if any. (ii)Check earthing of towers. (iii)Measure and record earthing resistance of towers. (iv)Clean insulators and replace those which are cracked or chipped. (v)Check the jumper connections, strain clamps, PG clamps and bi-metallic strip. PG clamps: (i) Check and clean oxide from surface. (ii) Apply corrosion inhibiting compound. (iii) Tighten to the prescribed torque. 30327 Integrated Blocks The annual maintenance schedules can best be organized by adopting the system of Integrated Blocks. In this. scheme, a 3 to 6 km block (Jumbo Block) is taken by introducing single line working in the off peak traffic hours between any two stations. Simultaneous work is carried out by permanent way, signal OHE/PSI staff during day light hours. This saves considerable time for taking and returning blocks, which forms a sizeable proportion of a short duration block. Effective use of available man-power can also be made by using extra gangs depending upon the nature of work. Such work may be organized for 2 or 3 days a week in selected sections and instructions issued in advance by appropriate planning. 20328 Re-tensioning of Unregulated OHE The re-tensioning of unregulated OHE in accordance with the tension-temperature chart should be done ordinarily at the end of 6 months from the date of erection and again at the end of 12 months. Thereafter the tension should be checked up once in 2 years and retensioning done as required. INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART (82) 20329 Periodical Overhaul 1. The aim of POH is to recondition and restore the installation in the condition it was when it was first commissioned, whereas preventive maintenance has for its objective to take care of the wear and tear during norma l service and forestalling possible failures by regular inspection and prompt attention. The POH should be thorough and cover every part of the installation. The tests to be done at the time of commissioning of new OHE have been detailed in Chapter IX. The work involved during 4-year POH is somewhat greater in scope than the pre-commissioning tests, since after years of service many parts would have suffered wear and tear, of which necessary adjustments will have to be made or repairs done to make good the wear, or the irreparable items replaced. The POH of OHE should be planned on a programmed basis so that every part of the installation receives detailed attention, repair and overhaul at an interval of 4 years. For programming POH, the entire section in each Division should be divided into smaller sections. POH gangs may be provided with camps at convenient locations so that heavy materials do not have to be carried from depot or sub-depot every day. Gangs can move to the site of work in convenient trains or by other means of transport. As far as possible, gangs for the work should be earmarked so that a uniform standard of is achieved. All POH work should be done under the direct supervision of a supervisor not lower in rank than an ATFO/TFO. To summarize, the object of POH is to make a thorough inspection of the OHE and to replace such of the worn- out or damaged parts by those, which have been reconditioned earlier in the maintenance depots and kept ready. The parts removed are sent to the maintenance depots for dismantling, thorough examination, re-conditioning if possible and re-assembly for use again as required. Maintenance charts, prepared in different colours may be made indicating the type of schedule each section has to undergo. The same chart can be used to indicate the progress of work and special works to be done to exercise check over the tasks and targets. 2. In addition to the items detailed under annual maintenance, the following items should be attended to during POH: (a) Masts, portals and cantilever supports: (i) least one complete cantilever assembly per 10 track-km (this may be modified by CEE if considered necessary) should be removed and taken to the,workshop for dismantling and detailed examination of various components after thorough cleaning. This test check would reveal the extent to which other cantilever assemblies have to be examined. (ii) All regulating equipment should be replaced by previously overhauled ones and the removed equipment should be sent to the workshop for overhaul. (iii) As the bracket is articulated, check the position with reference to the axis of the mast. The position will vary with temperature and distance from anti-creep. The register arm and steady arm should as far as possible be in the same plane as the bracket. (iv) Check adjustments of cantilever assemblies, their slope and displacements at every structure for compliance with the 'as erected' SEDs. (b) Catenary and Contact Wires: (i) Dismantle all jumper connections, clean the conductors, (with emery paper in case of copper or bronze conductors and metallic brush in case of aluminium conductors) clips etc. If the pieces show signs of overheating, this may be because either they are not tightened properly or the clips are deformed and INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 1 contact surface is insufficient. In the latter case they should be replaced. In case of the contact wire, it is the groove that has to be cleaned with either a fine metallic brush or emery paper. The use of scraper or file is forbidden. Replace frayed or damaged jumpers. (i)Remove kinks if noticed. (c) Insulated and Uninsulated Overlaps: (i) Check the position of contact wire respect to tracks to comply with SEDS. (ii)Ensure that insulators of anchoring wires are crossing the plane of OHE in correct position as per plan. (d) Overline Structures: Check the height and gradient of the contact wire and tally the same with 'as erected'. (e)Tunnels: (1) Check the height and gradient of the contact wire and adjust as per SED. (ii)100 per cent OHE fittings In tunnels should be replaced with new or previously over-hauled fittings and the removed fittings taken to the Workshop for detailed examination. (f)Turn outs: Check the position of the contact wires with respect to the track for compliance with SED. (g)Overhead Cross-feeders, Return Conductors and 25 kV Feeders: (1) Examine wires for frayed strands, overheating, pinching or corrosion, especially at suspension clamps and PG clamps. Tighten junction sleeves. (ii)While tightening PG clamps ensure that all joints are properly coated with veseline. (iii)Check tension in wires and adjust if necessary. (iv)Other overhead wires such as bypass feeders and earth-wires should be inspected. The insulator attachments should be dismantled, overhauled and put back in position. The insulators should be cleaned at the same time. (h)General: (i)During POH, fittings, which do not provide prescribed margin of adjustment and proper fitting should be replaced. (ii)All fittings on masts should be checked against "as erected" drawings and any variation should be recorded. and reported to Sr. DEE for changing the drawings. (iii)The position of splice should be recorded in the relevant lay out plans. (i)Work to be done in Workshops: (i) Aluminium bronze fittings, bolts and nuts should be cleaned and carefully examined if necessary with a magnifying glass. Particular care should be taken to see that the threads are in good condition. Fittings which have developed cracks should invariably discarded. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART (ii) All G. I. fittings and pipes should be examined for deterioration of galvanization. Minor chippings may be repaired by using cold galvanizing paint. (Sand or emery paper should never be used for cleaning). (iii) in case of a major OHE break down, it is advisable to remove the bracket assemblies in about 8 to 10 spans on either side and examine them critically for cracks, twists, bends or other defects which may cause failures later on. (iv)The regulating equipment should be dismantled and every part should be cleaned. Bearings should be fitted back after lubricating. Rubber washers/rings should be replaced where necessary. Any grazing or rubbing on pulleys should either be repaired if possible or the damaged equipment should be replaced. All lubricating holes should be free for passage of grease. The stainless steel rope should be closely examined for damage to the strands. Particular attention should be given to the end fittings on the stainless steel rope. Only approved type of lubricant should be used for regulating equipment components. 20330 Rehabilitation of OHE Depending upon the condition of the fittings, rehabilitation of the OHE may be undertaken after a period of 20 year. CEE may decide the assemblies to be replaced after a special drive for condition monitoring. 20331 Transmission Lines 1. General The overhead lines should be inspected periodically to detect any faults and necessary repairs should be done immediately. 2. Patrolling of Overhead Lines from the Ground Patrolling of all overhead lines should be done before and after the monsoon. The frequency of patrolling of the overhead lines for the rest of the period will depend on local conditions. The patrollers should write the inspection notes and pass them on to the maintenance gang for carrying out repairs. The patrollers, should be equipped with Inspection books, , tape and binoculars. The main points to be noted while patrolling are as follows: a) Structures:- Leaning structures; deformed members; buckled structures; missing fasteners and members; accessories removed; protective coatings like galvanizing or paints disappeared; suspension and strain insulator attachments damaged. b) Foundations - Signs of external damage; settled and washed out soil below normal ground level over foundations within uplift frustum perimeters; tilted stubs; cracks or breaks in chimney top; slippage oil stubs from encasing chimney concrete; uneven settlement of footings; disappearance of gravel blanket protection; backfill embankment and its covers (rip-rap or revelment); damage to retaining walls, abutments and breast walls and disappearance of external earth backing retaining walls below designed lines. c) Insulators and Fittings:- Damage to insulators, heavy surface pollution, missing locking devices like nuts, washers and pin, burnt out fittings, deflected strings, damage to protective coatings. The cracked insulators, bird droppings, dense spider webs, kites with threads hanging on the insulators string. d) Conductors and Jumpers:- strands cut and opened up; loose jumpers out of shape and causing infringement of clearance of live wire to earthed metal parts, dead birds, fallen branches or fallen trees on conductors. e) Earthing Equipment:- Damaged, broken or missing earthing strips. f) Right of Way and Clearance:- Shrubs and trees within right-of -way causing obstruction and infringe- INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART rnent of clearance of bottom conductor to ground ; objects within line clearance excavation. In no circumstances, however, clearance measurements should be taken from live line. 3.Foreign Objects:- Construction works near lines causing infringement in line safety or electrical clearance; birds' nests on structures; use of structure for applying permanent support or pull to other objects; huts newly constructed underneath lines, and embankments/fencing. - 3. Inspection of Overhead Lines from Tower Tops Many breakdowns including slipping of conductor due to loose clamps, cracks in insulator porcelain, defects in insulator fittings, conductor, earthwire and accessories and their attachment points on structures can only he dispensed or seen by going on top of every structure. This inspection should be carried out by taking a shutdown of the line at least once in six years. Along with such inspection, repairs should also be carried out. Any replacement as required should also be made. 4. Special and Emergency Inspection A special inspection of the overhead lines should be carried out after severe wind/hail storms, quakes, snowfalls, forest fires, floods or heavy rains. Such inspection should be done after sabotage too. The purpose of such inspection is to detect any damage or breakage on line and to effect necessary repairs. When an overhead line is subject to fault often, it should be inspected to ascertain the nature of fault, such as too much sag, tree branches touching the line, etc. and to find out remedial measures required with a view to avoiding their recurrence. 5. Maintenance Tests and Measurements Insulation resistance of line should be measured at convenient interval particularly at the time when the line is shutdown for repairs or maintenance. In regard to measurements of earth resistance of metal structures, it should normally be carried out annually, however, local circumstances and experience may dictate increase or decrease in this interval but it should not be less than once in two years. The clearance and shape of the jumpers should be checked at an interval not exceeding 3 years. 6. Line Repairs Tools The following special tools, apart from tools required for maintenance of civil works of the lines, should be kept handy and in working order: a) Conductor jointing tools, c) Bolted come-along clamps, c) Winches, d) Aerial trolleys e) Aerial rollers, f) Thermometers, g) Dynamometers, h) Level and theodolite, i)Measuring tapes k) Linesman's ratchet, INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART [861 m)Pull-lift device of adequate capacity, n)Wire ropes, and p) Spanners IV. SAFETY RULES FOR OHE 20332 General 1. The following rules are supplementary to the General and Subsidiary Rules and the instructions contained In Volume 1. 2. Printed boards containing instructions regarding treatment of persons suffering from electric shock should be exhibited in every OHE maintenance depot, equipment room, switching station, cabin, OHE Inspection Car shed, loco shed, OHE Inspection Car and wiring train and also in offices of SM, ASM, CYM, AYM and HTXR. 3. First Aid Boxes should be kept at every switching station, maintenance depot, in OHE Inspection Car, breakdown vehicle and wiring train. 1 4. Ropes, come-along clamps, tirfor etc. should be tested once in six months at least, in the presence of an ATFO, and record of such tests maintained in each depot. 20333 Documents to be kept with OHE Supervisors for Work on OHE 1. The ATFO (OHE) or other official supervising OHE work shall have with him a complete set of structure erection drawings, lay out plans, sectioning' diagram and general supply diagram etc. pertaining to the overhead equipment under his charge. He shall also have with him Station Working Rules for the stations between which he is working. He shall, in addition, keep with him all useful information regarding the running of trains over his section. 2. It shall be the responsibility of the TFO/ ATFO (OHE) or in his absence the senior-most official in-charge of the work to ensure that all safety rules prescribed are actually observed by the staff when carrying out work on traction installations. It shall be the duty of the supervisor to remind the staff periodically of the various safety rules to be observed at work site. 20334 Permit to Work Before commencing work on any part of the dead OHE or within 2m of live OHE, a permit-to-work shall be obtained from TPC or other authorized person as detailed in Chapter VI. 20335 protection of Staff against Traffic Movements and Protection of Trains 1. The supervisory official in-charge of work on OHE shall observe relevant provisions of GR and SR for protection of trains before work on OHE is commenced and for the whole time the work is in progress. 2. Measures laid down in the Chapter VI shall be observed by all concerned to prevent accidental energization of the section under power block on account of electric train movements. 20336 Earthing before Commencement of Work 1 All metallic parts within reach (either directly or through tools etc.) shall be earthed, after they are made dead. 2. Each working party shall be protected by at least two independent earths, one on each side of a working party. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 3. If the distance between the working parties exceeds 100m intermediate earths shall be provided in such a manner as to ensure that the distance between earths does not exceed 100m. 4. Even when earthing is provided by isolator switches with earthing heels, additional temporary earths as above shall also be provided. 20337 Procedure for Providing Temporary Earths The following sequence of operations shall be carried out while providing temporary earths on OHE 1. Men shall be posted on both sides of the site of work to warn the working party of any approaching train on the same track and adjacent track(s). 2. The permit-to-work shall be obtained prior to commencing work to make sure that power supply has been switched off. 3. For providing temporary earth on the OHE or other equipment after it has been made dead, only discharge/ earthing pole assembly specially designed for this purpose alone should be used. The cable shall be flexible and should have adequate cross-section (40 mm') to be able to withstand short circuit currents. 4. Fix the earthing-clamp securely to a mast at least one span away on one side of the work site after making sure that the mast-to-earth rail bond of this mast is intact. Alternatively, the clamp may be fixed to the bottom flange of one of the traction rails, taking the cable under the rails. In single-rail track-circuited sections, the earthing clamp should be fixed to the traction rail i.e. non- track-circuit rail; on double-rail track-circuited sections the earthing clamp should be fixed to the mast. The mast-end or rail-end clamp of the discharge /earthing pole assembly should be checked for tightness just before connecting the top clamp on to the OHE as the earthing clamp fixed to the rail or mast in advance could have worked loose. 5. Hook securely with a snap action the top clamp of discharge/ earthing pole assembly to the OHE conductor close to the mast/structure and tie the earthing pole to the mast/structure. Never hook on the top hook of the earthing cable to the OHE, till the other end has been first connected to earth. 6. The earthing clamps should always be fixed to the traction rail or mast / structure first and then the top clamp should be hooked to the OHE to be earthed. 7. Repeat operations 4 and 5 for the second temporary earth on the other side of the working party. 8. After temporary earths have been fixed on the OHE on both sides of the work site, staff may proceed with the maintenance work. 9. After work is completed and men, materials and tools have been removed and the OHE is clear, the above earthing rods may be removed in the reverse order i.e., first remove the hook on the OHE and then the clamp fixed to the rail or mast/structure. After warning all staff that supply will be restored and that they should keep away from live equipment, the permit-to-work may be returned and supply restored. 20338 Precautions in Regard to Discharge/Earthing Pole Assembly 1. The continuity of the cable connection between the top clamp and the earthing clamp should be checked once a fortnight. Cable should be renewed if more then 20% strands are broken. During use, cable should be continually examined for fraying and breakage of strands. INDIAN RAILWAYS - AC TRACTION MANUAL VOLUME 11 PART 1 Discharge/Earthing pole assembly should be Inspected by TFO/ATFO once a month. 2. During accidents when slewing the OHE and in similar circumstances, the discharge/ earthing pole assembly should be provided at a location where it is not likely to be interfered with during crane working or due to work on the permanent way. 20339 Work on OHE or any Conductor having a Sectioning Point When work is to be carried out on OHE or conductors, which are not electrically bonded, following additional precautions are required. i) The two sections of conductors or ends of conductor which may have snapped may be at different potentials. Each end should, therefore, be separately earthed at two points after switching off supply to both parts,of the OHE or conductor. 11) This precaution should also be observed when working on or in the vicinity of a sectioning point and cut-in insulators. 3. Neutral Sections should be treated as live equipment and earthed separately at two points on either side of the work party before commencing work. 4. , When work is to be carried out on an isolator, both sides of the isolator should be earthed at two points or more conveniently, isolator jumpered temporarily. 20340 Protective Helmets At the work-site, staff are advised to wear helmets to protect their heads against any tools or equipment which may drop down accidentally, as well as to minimize head injury in case of accidental fall from a height. 20341 Safety Belt Staff working on structures or a ladder are advised to protect themselves against an inadvertent fall by wearing a safety belt for supporting themselves by a rope sling. 20342 Rules for use of Ladders 1. It shall be the responsibility of the supervisor to ensure that ladders are stored in a protected enclosure, properly maintained and reconditioned as often as required. A ladder should never be in such a position so as to likely to fall on a live part. 2. Ropes used with ladders should be of cotton or jute. Use of metallic ropes is prohibited. A ladder should be held by one person on the ground to prevent slipping, while the top end should be tied to the supporting structure or conductor to keep.lt in position and prevent it sliding away. 3. Ladders should never be allowed to fall on or rest against the contact wire. 4. If the nature of the work involves risk of the conductor breaking into two parts (due to opening out of sleeves or splices) the ladder shall not be rested against the conductor. Trolley ladders shall be used in such cases. 5. More than one person shall not normally be allowed on a ladder as far as possible. 6. Climbing on a ladder with wet or slippery foot-wear is forbidden. 7. Ladders should not be used for transporting materials. 8. A rope should be used to pass tools or any equipment to the men working on a ladder. INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART 9. No one should stand directly below a work spot under a ladder. 20343 Other Important Precautions to be taken while Carrying out Works on OHE 1 The useful cross section of a conductor shall not he reduced while making joints. 2. Any contact with conductors, which are not specifically earthed, is forbidden. 3. The strength of the anchoring rope should be not less than that of the cable to be anchored. 4. Temporary anchoring of conductors should only be done by using stranded flexible steel cable at least of the same tensile strength as the cable to be anchored. Use of two cables of different strengths joined together is prohibited. Use of cotton, jute or other non-metallic ropes for anchoring is forbidden. 6. Structure bonds and cable connections of the structure to earth shall be maintained in proper condition. No heavy materials should be stacked on the rail bonds; transverse bonds between two rails of the same track as well as rails of different tracks shall also be maintained in proper condition. 7. Where rails to which structures are connected are replaced, the structure shall be connected to the new rail immediately after it has been laid. 20344 Procedure for Effecting Shut-Down for Work on Auxiliary Transformers Power supply to auxiliary transformers is effected through fuse-switches on the 25 kV side and the LT Side is controlled through fuses or double-pole iron-clad switch-fuses. Isolating fuse switches should be opened out and fuses removed both on the HT and LT sides and the transformer earthed before starting work. 20345 Work on Overhead lines Running Parallel to Electrified Tracks No work on any span of any overhead line (LT power line or other line) running parallel to an electrified track where the minimum distance between the nearest conductor of the overhead line and the centre-line of the nearest electrified track is less than 8m, should be done without switching off power from the 25 kV traction line (in addition to making dead and earthing the overhead line on which work is to be carried out, in the normal manner) excepting for the following specific items for work : 1. Replacement of lamps, if below line. 2. Painting of structures / poles upto a distance of 2m from the live wires of the power line. 3. Reinforcement of foundations where such reinforcement does not involve any prior weakening of the foundation at any time during the work. 4. Replacement of aerial fuses. 20346 Isolation of Booster Transformers To isolate a booster transformer for maintenance or other work, the following sequence of operations should be carried out 1. Where no isolator is provided a permit-to-work should be obtained for both the elementary sections, the BT should be disconnected from the OHE and the OHE made through by jumpering. 2. When an isolator is provided to disconnect the BT primary winding from 25 kV lines, power must be switched off from both the elementary sections to which the BT is connected after which the isolator should be opened to disconnect the BT from the OHE and to make the OHE through. 3. The secondary winding of the BT should be disconnected from the return conductor and the return conductor made through by jumpering. 4. The return conductor should be earthed at the location where the BT has been disconnected; and the mid- INDIAN RAILWAYS - AC TRACTION MANUAL - VOLUME 11 PART point rail links on both sides of the BT should be opened so that booster cells on either side will extend over a longer section temporarily. 5. With the OHE and return conductors made through, 25 kV power supply may be restored It should be noted that during the period when a BT has been disconnected from service, the interference on adjacent communication circuits will be enhanced. In view of this the defective BT should be replaced with a good BT with the least possible delay. 20347 Isolators Isolating Switches on the 25 kV system shall not be opened or closed when current is passing through them. Normally, isolators should only be opened or closed, after power supply to the section has been switched off by opening the appropriate interruptor (see para 20600 & 20601). 20348 Petroleum Sidings The following arrangements/precautions would be necessary: - Arrangements i) An equipotential link between the petroleum sidings installation earth and the track via a switch ii) Setting up of neutral zones (insulating joints) in the track to avoid any risk of propagating stray current. iii) Setting up of neutral zones/sections in the contact wire similar to loco inspection pits. iv) The tracks must be provided with longitudinal bonds on both the rails as well as transverse bond (30 m intervals). All masts and metallic structures in the vicinity of the track/ sidings should be provided with structure bonds. Copper rivets should be used for bonding. v)10 ohm earths must be connected to the petroleum siding on each side at the insulated joint. Precautions c) No oil tanker Is. permitted to stable under live OHE for inspection purpose. ii) Fuelling to be done by side filling arrangement only. iii) Pipe lines in the vicinity of the track should be properly earthed. iv) Minimum 2 m electrical clearance from live OHE of the adjacent track or only other structure nearby must be maintained. v) During filling/loading and unloading of petroleum products the isolators at the neutral section of OHE should be kept open to ensure that the OHE is dead and earthed.