OHE-34-96 PDF - Principles for Layout Plans and Sectioning Diagrams for 25 KV AC Traction

PRINCIPLES FOR LAYOUT PLANS AND SECTIONING DIAGRAMS FOR 25 KV AC TRACTION (This is a reproduction of RDSO document No. ETI/OHE/53 issued in June, 1988) 3.0 Introduction These principles for preparation, checking and finalization of overhead equipment layout plans, have been framed for standardization and guidance of Railways / Railway Electrification Projects. In some cases, the principles are obligatory and should be followed. In other cases, after studying individually the implications to arrive at the best solution both from economical and technical points of view. The fundamental aim of design of overhead equipment is to install the contact wire at the requisite height and to keep it within the working range of the pantograph under all circumstances. 3.1 Definitions The technical and other terms used in this book, shall have the same meaning as defined in General and Subsidiary Rules / ac Traction Manual, unless there is any thing repugnant to the subject or context: 3.1.1 Bond An electrical connection across a joint in or between adjacent lengths of rail. i) Bond, continuity : A rail bond used for maintaining continuity of the rail circuit at crossings and junctions. ii) Bond, Cross – A rail bond used for connecting together two rails of a track or rails of adjacent tracks. iii) Bond, Impedance : A special rail bond used to bridge an insulated rail joint in ac track circuited sections in areas equipped for electric traction. iv) Boand Rail – An electrical connection across a joint between two adjacent lengths of rail as part of the track return. v) Bond, Structure – An electrical connection between the steel work of track structures, bridge or station bulking, to which the traction overhead equipment is attached and the track return. 3.1.2 Cantilever (Assembly) It is an insulated swiveling type structural member, comprising of different sizes of steel tubes, to support and to keep the overhead Catenary system in position so as to facilitate current collection by the pantograph at all speed without infringing the structural members. It consists of the following structural members. i) Stay arm – It comprises of dia. 28.4/33.7 mm (Small) size tube and an adjuster at the end to keep the bracket tube in position. It is insulated form mast by stay arm insulator. ii) Bracket tube – It comprises of dia 40/49 mm (large) or dia 30/38 mm (standard) bracket tube and insulated by bracket insulator. Catenary is supported form this member by Catenary suspension bracket and Catenary suspension clamp. Over Head Equipments Page 34 iii) Register Arm – It comprises of dia 28.4 x 33.7 mm tube to register the contact wire in the desired position with the help of steady arm. iv) Steady arm assembly : It is 32 x 31 mm BFB section made of aluminium alloy to register the contact wire to the required stagger and to take the push up of contact wire. It is always in tension. 3.1.3 Crossings The electrically live member / conductor passing over another electrically live member / conductor, without physical contact. i) Power line crossing – An electrical overhead transmission or distribution line or underground cable placed across railway tracks whether electrified or not for transmission of electrical energy. ii) Crossing OHE – Crossing of two conductors of OHE crossing without physical contact. 3.1.4 Dropper A fitting used in overhead equipment construction for supporting the contact wire from Catenary. 3.1.5 Electrical Clearance The distance in air between live equipment and the nearest earthed part. 3.1.6 Encumbrance The axial distance on vertical plane between the Catenary and the contact wire at support. 3.1.7 Feeder A conductor connecting (a) a substation with a feeding post, or (b) a feeding post with the OHE. 3.1.8 Height of contact wire The distance from rail level to the under side of contact wire. 3.1.9 Interrupter It is a single phase Vacuum SF / oil circuit breaker used as load switch to close the circuit on fault but does not open on fault. It is operated either by remote control or manually at site. Different methods of connection of interrupters are: a) Bridging Interrupter: An interruptor which is provided at the neutral section to extend the feed from one substation to the overhead equipment normally fed by the other substation in emergencies or when the latter is out of use. This normally remains in the open position. Over Head Equipments Page 35 b) Sectioning Interruptor: An interruptor which connects adjacent sub-sectors together to maintain continuity of supply. This normally remains in closed position. c) Paralleling Interruptor : An interruptor which connects overhead equipments of two different tracks. This normally remains in closed position to reduce the voltage drop. 3.1.10 Jumper A conductor or an arrangement of conductors for electrical continuity not under tension, which forms electrical connection between two conductors or equipments. 3.1.11 Mast A single vertical post embedded in the foundation or otherwise rigidly fixed in vertical position to support the overhead equipment with cantilever assembly. It may be rolled section or fabricated. The uprights of portals and TTCs are also called masts. Note : Pre-stressed concrete spun poles for traction overhead equipment are under development. 3.1.12 Neutral Section A short section of insulated dead over head equipment which separates the sectors fed by two adjacent substations which are normally connected to different phases. 3.1.13 Overhead Equipment (OHE) The electrical conductors over the track together with their associated fittings, insulators and other attachments by means of which they are suspended and registered in position. All overhead electrical equipment, distribution lines, transmission lines and feeders may be collectively referred to as overhead lines. 3.1.14 Overlap An arrangement of overhead equipment over a track where two sets of traction conductors are run parallel to each other for short distance over span(s) providing a smooth passage for the pantograph of an electric rolling stock. In the un-insulated overlaps two sets of conductors are separated by 200 mm and connected by a jumper. In Insulated overlaps the two sets of conductors are separated by 500 mm in air. Electrical continuity is provided by an isolator, interruptor or booster-transformer. 3.1.15 Over-line structure Any fixed structure provided over the track. The prescribed clearance is normally provided as laid down in the Schedule of Dimensions for unrestricted movement of rolling stock. 3.1.16 Pantograph A collapsible device mounted on and insulated from the roof of an electric engine or motor coach for collecting current from the overhead equipment. Over Head Equipments Page 36 3.1.17 Return conductor A conductor which carries return current from the tracks to the sub-station in the booster transformer system. 3.1.18 Regulating Equipment A device for maintaining the tension of OHE conductors constant under all ambient temperature conditions. Note : Such OHE is called regulated OHE. 3.1.19 Setting Distance (implantation) The horizontal distance from the nearest face of traction mast to the centre line of the track. Over Head Equipments Page 37 3.1.20 Suspension Distance The horizontal distance from the centre of the eye of Catenary suspension bracket to the face of the mast for a single cantilever assembly or the face of cross arm channel in case of multiple cantilever assembly. (Ref. Fig. 3.01) 3.1.21 Span The distance between the centre line of the adjacent supporting masts for overhead equipment / lines. Clear span in case of portal structure, is the distance between the inner faces of portal uprights. 3.1.22 Stagger Stagger of the contact wire is the horizontal distance of the contact wire from the vertical plane through the centre of track. 3.1.23 Section Insulator A device installed in the contact wire for insulating two elementary electrical sections from each other while providing a continuous path for the pantograph without break of current. 3.1.24 Supply Control Post It is general term which refers to an outdoor assembly of control gear, such as interruptors, isolators, potential transformers, auxiliary transformers, etc including remote control equipment installed in a cubicle, for controlling power supply to overhead equipment. a) Feeding Post (FP) – It is a supply post where the incoming 25 kV feeder lines from substation are terminated and connected to the overhead equipment through interruptors. b) Sectioning and Paralleling Post (SP) - It is the supply control post situated mid-way between two feeding posts at the neutral section and provided with bridging and paralleling interruptors. c) Sub-sectioning and Paralleling Post (SSP) – It is a supply control post where sectioning and paralleling interruptors are provided. d) Sub-sectioning Post (SSP) – (for single line section) : It is a supply control post where a sectioning interruptor is provided. 3.1.25 Sector A section of Overhead equipment of a track which can be energized by closing a feeder circuit breaker at the substation. a) Sub-sector – The smallest section of overhead equipment which can be isolated remotely by opening of interruptors. b) Elementary Section – The smallest section of overhead equipment which can be isolated from the rest of the system by manual operations. Over Head Equipments Page 38 3.1.26 Tension Length Length of conductor which is stretched between the two anchor points 3.1.27 Versine The versine is the maximum offset of the rail on which spans have been measured (para 3.5.1) of the curved track form the chord connecting two points, each opposite adjacent masts. 3.2 Electrical Clearance 3.2.1 Clearance The clearance between 25 kV live parts and earthed parts of fixed structures or moving loads shall be as large as possible. The electrical clearances to be maintained under the worst conditions of temperature, wind, etc are given below: a) Maximum vertical distance between any live part of overhead equipment or pantographs and parts of any fixed structures (earthed or otherwise) or moving loads: i) Long duration 320 mm ii) Short duration 270 mm b) Minimum lateral distance between any live part of overhead equipment or pantographs and parts of any fixed structures (earthed or otherwise) or moving loads: i) Long duration 320 mm ii) Short duration 220 mm Note : I) These clearances may be reduced to 250 mm (long duration) and 200 mm (short duration) with the personal approval of the Chief Electrical Engineer in very difficult locations (Rly Board’s letter No. 76/RE/240/1 dated 27.3.80). II) A clearance study should be made for every over-line structure / tunnel and, if required, should be referred to RDSO for advice. 3.3 Working clearance Minimum clearance between live conductor / equipments and such earthed structure / live parts of different elementary sections where men are required to work shall be 2 m. where the clearance is not obtained the structure shall be protected by earhed metallic screens or prescribed warning boards (Refer para. 3.22.2/3) 3.4 Wind Pressure 3.4.1 Wind Load Wind pressures for design of all masts and determination of spans are based on IS-875-1964 – “Code of Practice for Structural Safety of Buildings – Loading Standards”. Vide an amendment issued in 1971 to this specification, wind pressures for structures of height less Over Head Equipments Page 39 than 30 m were reduced by 25%. Accordingly, the standard wind pressures adopted are as follows for all new works for different zones as indicated in the specification. I) Green zone (light) 75 kg/m2 II) Yellow zone (medium) 112.50 kg/m2 III) Red zone (heavy) 150 kg/m2 3.4.2 Loading calculation For working out the wind loading the total projected area for the rolled sections. 150% of the projected area for fabricated structures, and 2/3rd of the projected area for conductors and other circular member is taken into account. Note: The safety of masts and portals is checked for two conditions. a) at 35° C temperature and full wind pressure b) at 4° C temperature and 20% of the governing wind pressure. 3.5 Spans 3.5.1 Measurement Spans shall be accurately measured by means of a steel tape. On curves, these measurement shall be taken on the outer rail of the middle track in the case of an odd number of tracks and in the case of an even number of tracks on the inner rail of the first outside track (from the centre of the formation). On single track, measurements shall be made on the outer rail. 3.5.2 Standard span Standard spans shall be determined in accordance with i) Drg. No. ETI/OHE/G/00202 for conventional OHE ii) Drg. No. ETI/OHE/G/04201 for regulated tramway OHE, and iii) Drg. No. ETI/OHE/SK/375 for composite OHE (Aluminium – alloy Catenary and copper contact wire). 3.5.3 The spans shall be as large as practicable, but should enable the contact wire to be erected with permissible stagger. For a stipulated maximum stagger, the length of the span is governed by curvature, blow-off of overhead equipment, sway of pantograph and deflection of the mast under wind condition. Standard spans shall be used to maximum extent possible. 3.5.4 Mid span stagger Where the two adjacent spans are located on curves of different radius or when the two versines are in opposite directions, the spans shall be determined so as to keep the mid-span stagger in the two spans within the limit given in the span and stagger cart (ETI/OHE/G/00202), taking into account the stagger at the common support and the stagger at the extreme supports (See para. 3.8) Over Head Equipments Page 40 3.5.5 Restrictions The following restrictions are applicable I) On main tracks, the lengths of two consecutive spans shall not normally differ by more than 18 m. II) The lengths of spans with unequal encumbrances shall be such that the axial distance between the Catenary and the contact wire at the minimum dropper is not less than 150 mm. For example, the length of the span with 1.4 m and 0.9 m encumbrances at the two ends shall not exceed 67.5 m. This restriction is applicable to the two spans on each side of the structure, equipping a turnout for the main OHE. III) Spans in the vicinity of over line structures with restricted head room shall be determined with reference to the electrical clearances available (see para 3.3) IV) The lengths of spans loaded with section insulators may require to be restricted (See para 3.11) V) Non-standard spans may be adopted in difficult locations, e.g. in rocky cuttings, on through girder bridges, for locations of masts on bridge piers and within station limits. VI) With crossed type equipment with actual crossings of OHEs at facing turnouts, the anchor spans shall be restricted to 54 m. VII) Where earth wire is provided, the maximum span over level crossings should be 58.5 m. 3.6 Masts. Portals, Head Spans and Foundations 3.6.1 Types of masts OHE conductors are suspended from swiveling cantilever assembly generally erected on individual masts. 3.6.1.1 Nine types of masts are used. These are designated as 150 x 150 BFB, 200 x 150 RSJ, K-100, K-125, K-150, K-175, K-200, K-225 and K-250. The first two are rolled sections and remaining seven are fabricated masts. B-series (Drg. No. ETI/C/0071) masts can be used in lieu of K-Series masts. Note: Sometimes 200 x 200 (8” x 8”) BFB have been imported. These are used in lieu of 200 x 150 RSJ as specified in mast employment schedules. 3.6.1.2 Selection of masts The masts for standard applications viz. masts for single OHE, anti-creep and overlaps should be selected from the mast employment schedules. Separate mast employment schedules have been made for each wind pressure zone as under : a) Conventional OHE (65 mm 2Cd-Cu Catenary and 107 mm2 copper contact wire): Light wind pressure : Drg. No. ETI/C/0702, (75Kg/m2) Sheet 1 to 5. Medium wind pressure Drg. No. ETI OHE/G/00153. (112.5 kgf/m2 ) and 00154 Sheet 1 to 4 Over Head Equipments Page 41 Heavy wind pressure Drg. No. ETI/C/0706, (150Kg/m2) Sheet 1 to 4, ETI/C/0727, 0728 and 0729. b) Composite OHE (comprising of aluminium alloy Catenary and 107 mm2 copper contact with 1000 tension in each conductor). Light wind pressure : Drg. No. ETI/C/0701, (75Kg/m2) Sheet 1 to 4 & ETI/C/0722, 0723 & 0724.. Medium wind pressure Drg. No. ETI/c/0717. (112.5 kgf/m2 ) Sheet 1 to 4 & ETI/C/0713, 0719 & 0720. The mast employment schedules are prepared only for standard setting distance as given in Drg. No. ETI/IHE / G/00111 Sh. 1. For higher implantations and other locations like masts for turnouts, diamond crossings, umbrella type OHE etc., the load on the mast should be calculated separately for every location and safety of the mast checked in accordance with Drg. No. ETI/OHE/G/00141 Sheet 3. The permissible bending moments of the masts are given in Drg. No. ETI/SK/C/122. 3.6.1.2.1 On long (more than 150 m) bridges and within 100 m from their abutments on either side and on the ban where the height of the Catenary above surrounding mean retarding surface is more than 30 m 25% reduction in wind pressure (para 4.1) should not be taken into consideration. These masts should be designed for full wind pressure i.e., Heavy (red) wind pressure zone 200 kg/m2 Medium (yellow) wind pressure zone 150 kg/m2 Light (green) wind pressure zone 100 kg/m2 The maximum span should be restricted to 54 m for heavy wind pressure zone and 63 m for medium wind pressure zone. In case of curves on the banks of such bridges, the span should be 4.5 m less than the max. span permitted by relevant span and stagger chart, but should not exceed 54 m for heavy (red) wind pressure zone and 63 m medium (yellow) pressure zone. 3.6.2 Two Track Cantilever In the yards and sidings when the mast cannot be erected near the track to be equipped, it may be erected span one or two tracks using a two-track cantilever. (Drg. No. ETI/C/009, Sheet 1). This is generally used for supporting OHE near turnouts and X-overs. These arrangements should not be used for supporting OHE of two main lines. The OHE can be supported upto a distance of 10.5 m from the upright with this arrangement. 3.6.3 Portals On multiple track sections, where adequate track centres are not available and tracks cannot be slewed, port are used. Each portal consists of two fabricated uprights and one fabricated boom consisting of with or without one central piece and two end pieces. 3.6.3.1 Three types of portals have been standardized. ‘N’ type portal is used for clear spans of 10 m – 20 m tracks maximum). ‘O’ type portal is for clear spans of 20 m – 30 m Over Head Equipments Page 42 (for 6 tracks maximum) and ‘R’ type portal with spans of 30 m – 40 m (for 8 tracks maximum). 3.6.3.2 Where the upright of standard portals cannot be erected due to limited track centres. ‘P’ type portal not to be used in place of ‘N’ type and ‘G’ type may be used in place of ‘O’ type. The width of upright of these portals is 300 mm and 250 mm as against 450 mm of ‘N’ type and 550 mm of ‘O’ type respectively. In exceptional cases BFB uprights of 152 mm width (Drg. No. ETI/C/0026, Sheet 1) may also be used with ‘N’ type portal boom Special BFB portals with 3 legs (Drg. No. ETI/C/0027, Sheet 1) may also be used in exceptional cases when ‘N’ type portals cannot be used. 3.6.3.3 The cantilevers for the extreme tracks are provided on the uprights of the portals in accordance with para 19. The cantilevers for the immediate tracks are provided on the drop arms suspended from the boom (ref. Para 19.6) 3.6.4 Head Spans In yards where un-regulated- regulated OHE is used head span may also be used to cover more than 6 tracks. Standard head span arrangement is given in Drg. No. ETI/OHE/G/03201. The head span arrangement at not used normally. 3.6.5Foundations 3.6.5.1 Volume Charts The foundation bending moment codes (FBM) for each location are obtained from the mast employment schedule or by actual calculations (para 6.1.2). Bearing capacity of the soil is determined at the outer toe of the bottom of foundation at a representative number of locations. Where foundations are placed on the slope of banks do to increase in setting distance, the bearing capacity of the soil should be determined on the slope. Bearing capacities determined thus would be considerably less than those determined on the top of formation. Selection of the type and size of foundation is done from the volume chart (Drg. No. ETI/C/0058) on the basis of FBM code, type and bearing capacity of soil/shoulder width and the extent of projection above ground level. 3.6.5.2 Type of foundations The following types of foundations are for OHE mast and portals: (1) (A) Side bearing Drg. No. ETI/C/058 Sh.1 (Type B) (B) Side gravity -do- (Type : BG) (C) Pure gravity -do- (Type: G) Over Head Equipments Page 43 (D) Pure gravity for black cotton soil -do- (Type:WBC) ii) New pure gravity -do- Sh.2A (Type: NG) iii) NBC type foundation for dry -do- Sh.3A black cotton soil (16500 & 11000 kgf/m2) 3.0 m depth. iv) New pure gravity -do- Sh.4 for different soil and site conditions (500 mm exposed ) (Type: NG or SPL) v) New pure gravity -do- Sh.5 for black cotton soil (for 8000 kgf/m2 soil pressure. 2.5 depth (Type :NBC) vi) Foundations in soft rock Drg. No. ETI/C/0059 (bearing capacity 45000 kg/m2) vii) Foundations in hard rock Drg. No. ETI/C/0050 (bearing capacity 90000 kg/m2) Over Head Equipments Page 44 (2) For portals i) In ordinary soil Drg. No. ETI/C/0058/68 ii) In dry black cotton soil Drg. No. ETI/C/0063 1. In the case of OHE foundations in deep rock cutting the foundations should be below the drain. 2. For all future constructions of pure gravity foundations drawing No. ETI/C/0058 Sheet – 2A only shall be followed. 3.6.5.3 Selection of foundations Side bearing foundations are used for masts where the soil bearing capacity is 11,000 or 21,500 kg/m2 and 300 mm wide shoulder is available on the banks. However, for overlap inter masts and masts on the inside of curves. 550 mm wide shoulder is necessary (Drg. No. ETI/C/0023). (Ref. Fig, A3.02) 3.6.5.4 New pure gravity foundations may be used for masts where soil bearing capacity is 5500, 8000 and 11000 kg/m2 or where adequate shoulder width as mentioned in para 6.5.3 is not available. In such cases, it should be ensured that foundation is not exposed. 3.6.5.5 Side gravity foundations may be used for masts where soil bearing capacity is 8000 and 11000 kg/m2 or adequate shoulder width is not available. No portion of the foundation should be exposed. 3.6.5.6 Pure gravity foundations (Type-G) are used for independent masts where soil surrounding the foundations is loose and can not exert passive pressure on the foundations. G-type foundations have been designed for soil bearing capacity of 5500, 8000 and 11000 kg/m2. Pure gravity foundations (Type P) are used for portals and are designed for soil bearing capacity of 8250 and 11000 kg/m2. 3.6.5.7 Foundations in black cotton soil 1. The foundation of the black cotton should be done preferably in dry season i.e., from November to May. Excavations should be avoided as far as possible in case f unexpected rains in dry season also. 2. In black cotton soils. WBC and NBC type of foundations are used. Primarily WBC foundations are to be adopted where swelling / shrinkage is not expected to take place at the founding level and NBC foundations have to be provided where swelling / shrinkage is expected to occur. 3. The safe bearing capacity should be determined in accordance with IS-6403. 4. When in doubt regarding classification of BC soil as to dry or wet, it is preferably to make NBC type foundation. Over Head Equipments Page 45 3.6.5.8 Where foundations are constructed on the slope of banks, the foundations should be so located that generally no part of it is exposed. The top of foundation may then be brought to the desired level (rail level- 500 mm) by providing a super block of length and breadth equal to the top dimension of foundations. The increase in bending moment due to increased setting distance should be calculated and the designation of foundation to allow for this BM should be selected. The arrangement is shown in the fig. No. A3.03. 3.6.5.9 The top of foundation should be 50-100 mm above the surrounding ground level. The length of mast below rail level should be minimum 1850 mm for regulated OHE and 1750 for un-regulated OHE. A 135 mm embedment of mast in concrete is necessary. Concrete cushion of 150 mm below the bottom of mast is also necessary. Wherever necessary, these may be achieved by providing a super block of length and width equal to the top dimension of foundation. However, portion of existing pure gravity foundations to Drg. No. ETI/C/0058 Sheet – 1 corresponding to a depth of 500 mm of embankment having slope of 1:2 may be exposed. 3.6.5.10 Giving due consideration to the above, the most economical type of foundation should be adopted. 3.7.0 Contact Wire Height 3.7.1 Standard height Normally the height of contact wire (under side surface) above the track plane shall not be less than 5.50 m at any point in the span under the worst temperature conditions. To ensure this, the normal height at the suspension point shall be as under: Type of OHE Normal height of contact wire at the support point j) Regulated a) Normal with 10 cm pre-sag 5.60 m b) Old electrification 5.55 m works with 5 cm pre-sag Note : 5 cm pre-sagged OHE was provided upto 1968. For new works 10 cm pre- sagged OHE shall normally be provided. However, OHE with 5 cm pre-sag may be provided in long tunnels and through girder bridges to achieve the minimum electrical clearance. ii) Unregulated a) Unregulated OHE designed for areas with a temp range of 4° C to 65°C 5.75 m b) Unregulated OHE designed for areas with a temp. range of 15° C to 65°C 5.65 m Over Head Equipments Page 46 3.7.2 The height may be reduced under over line structures after a clearance study. The minimum height shall be 4.92 m for the broad gauge and 4.02 m for the metre gauge to permit movement of “C” class ODCs without physical lifting of wires. In case “C” class ODC movement is not required, the height could be reduced to 4.80 m (BG). Height may be further reduced to 4.65 m if rolling stock higher than 4.265 m are not allowed on such lines. (Ref. Fig. A. 3.04) 3.7.2.1 At electric locomotive sheds and loco inspection pits; the minimum height shall be 5.80 m for the broad gauge and 5.50 m for the metre gauge. 3.7.2.2 At level crossings, the minimum height shall be 5.50 m for both broad and metre gauges. 3.7.3 Erection tolerance A tolerance of 20 mm is permissible on the height of contact wire as measured at a point of support except on either side of an over bridge where a tolerance of 10 mm will be allowed. But the difference between the heights of contact wire at two adjacent supports shall not exceed 20 mm. In spans with gradient of contact wire, this difference of 20 mm is measured over and above the approved gradient. Over Head Equipments Page 47 3.7.4 Contact wire gradient Any change in the height of the contact wire should be made gradually and the slope should not normally exceed 3 mm / m on main lines and 10 mm/m on sidings. In no case shall the relative gradient of the contact wire in two adjacent spans be greater than 1.5 mm/m on main lines and 5 mm/m on sidings. 3.7.5 Provision for future track raising The rail level may go up in future by 275 mm (max) due to use of concrete sleepers and strengthening of track structure. Provision should be made for possible lifting of track by 275 mm (max). (Correction Slip No. 10, Schedule of Dimension (BG/Metric) 1973). OHE arrangement indicated in Drg. NO. ETI/OHE/G/02102, Sheet 3 should be used for the areas where track raising is contemplated. The areas where track is proposed to be raised may be ascertained before commencement of works. No track raising is normally contemplated near overline structure unless additional head room has been provided. 3.8.0 Stagger 3.8.1 Tangent track On tangent track, the contact wire is normally given a stagger of 200 mm at each support alternately on the side of the centre of the track. This is relaxed in special cases for ensuring requisite clearances in difficult locations such as in the vicinity of signals, subject to stagger at mid span not exceeding the permissible values given in Drg. No. ETI/OHE/G/00202. 3.8.2 On tangent track, the catenary stagger is zero for masts supporting a single equipment. The catenary is fixed vertically over the contact wire at all supports at which more than one equipment is supported, at flexible head spans and at supports with reduced encumbrance, on tangent as well as curved tracks. 3.8.3 Curved track On curves, the stagger of the contact wire at supports should not exceed 300 mm. the stagger of the catenary on curved track shall be determined with reference to Drg. No. ETI/OHE/G/00202. The standard values adopted are 0, +200 and –200. Note: For maximum permissible stagger refer para 4 of Chapter V-A of Schedule I; BG Metric Schedules of Dimensions – 1973. 3.8.4 Turnouts and diamond crossing At turnouts, the stagger of the contact wire on the main running line shall be in accordance with Drg. No. ETI/OHE/G/00202. The stagger of contact wire of the branching line shall not exceed 300 mm at any point in the span. This is achieved by selecting a suitable location for the mast near the centre of the turnout in the case of overlap type equipment, or by suitably adjusting the point of crossing of the two contact wires in the case of crossing type equipment. Over Head Equipments Page 48 3.8.5 Un-insulated overlaps At un-insulated overlaps, the stagger should confirm to Drg. No. RE/33/G/02121 sheet 1. On non-uniform curves or at other locations where staggers different from those indicated in these drawings are adopted the following points should be observed. i) The stagger of the in-running contact wire does not exceed 200 mm on tangent track and 300 mm on curve track at any support, at which only one contact wire is in-running. ii) In any span at the centre of which only one of the contact wires is in-running (as in a 4-span overlap), the mid-span stagger of the in-running contact wire does not exceed the values given in Drg. No. ETI/OHE/G/00202. iii) The two contact wires run parallel to each other between the intermediate supports at a distance of 20 mm from each other. 3.8.6 Insulated overlap At insulated overlaps stagger should confirm to Drg. No. ETI/OHE/02131 sheet 1. On non-uniform curve and at other locations where stagger different from those shown in this drawing are adopted, the points mentioned against un-insulated overlap spans also apply with the difference that between the intermediate masts the two contact wires run parallel at a distance of 500 mm from each other. 3.8.7 Neutral Sections The stagger at overlap type neutral sections should confirm to Drg. No. ETI/OHE/G/02161, Sheet No. 1. 3.8.7.1 The stagger at section insulator type neutral section should be so adopted that the stagger at the section insulator assembly is within the limit of + 100 mm (See para 11.1 (iii)) 3.8.7.2 PTFE type neutral section shall be erected on tangent track only. The stagger shall be zero at support. 3.9.0 Encumbrances 3.9.1 Normal The encumbrance shall normally be 1:40 m Over Head Equipments Page 49 3.9.2 Reduced encumbrance The preferred values of reduced encumbrance for erection of overhead equipment under over-line structure are Span under overline Recommended Largest permissible structure (m) encumbrances for span adjacent spans. (m) under over-line structure (m) 1 2 3 63.0 0.9 67.5 58.5 0.9 67.5 54.0 0.75 67.5 49.5 0.6 63.0 45.0 0.6 63.0 40.5 0.5 58.5 36.0 0.40 54.0 31.5 0.40 49.5 27.0 0.30 45.0 Applicable where the encumbrance cannot be increased to 1.40 m in a single span from the value given in column 2. the normal encumbrance of 1.40 m should be provided in subsequent spans. In such cases, the encumbrance may be adjusted in such a way that the lowest point of the catenary does not fall between first dropper and the support. See para 3.8.9. Note: I) The above values are applicable only to regulated OHE with 10 cm nominal pre-sag of contact wire II) Special droppers may be required in spans under and adjacent to over-line structures. 3.9.3 Minimum Encumbrance Normally, the axial distance between the catenary and the contact wire at the minimum dropper should not be less than 150 mm. Smaller droppers may be adopted in exceptional cases. If the shortest dropper is loop type and more than 150 mm, no speed restriction is called for. But if the dropper is without loop or of rigid type of less than 150 mm, the overhead equipment is deemed suitable upto 90 km/hr speed. 3.9.4 If section insulators are to be installed in spans under over-line structures, special designs will have to be evolved. 3.10.0 Droppers 3.10.1 The standard arrangement of droppers assembly shall be as per drawing No. ETI/OHE/P/1190. 3.10.2 The general distribution of droppers on an OHE span shall be as per drawing No. ETI/OHE/G/00161. The arrangement of OHE span should be designed in such a way that standard droppers are used. Over Head Equipments Page 50 3.10.3 Special dropper arrangement The special arrangement of dropper as shown in Drg. No. ETI/OHE/P/1400 may be followed in exceptional cases wherever unavoidable. 3.10.3.1 The arrangement of the dropper to be adopted on the through girder bridges as shown in Drg. No. ETI/OHE/P/1410, where the OHE is supported on member of girder bridge. 3.10.4 Rigid dropper Adoption of rigid dropper (made of contact wire only) should be avoided as far as practicable. It should not be adopted, at all on main running lines. 3.11.0 Section Insulators 3.11.1 Location Sectional Insulators should be so located that the following conditions are fulfilled. i) At location of section insulator, the axial distance between the catenary and contact wire shall not be less than 450 mm in the case of single-wire section insulator and 600 mm in the case of a double wire section insulator without increasing the encumbrance at the supports beyond 1.40 m. ii) The section insulator is to be located beyond the point where the centre distance between the two tracks is equal to or more than 1.65m. If the section insulator is erected with the free ends of the runners away from the centre of the turnout this distance may be reduced to 1.45 m. iii) The stagger of the contact wire at the location of the section insulator should normally be zero, but in no case should exceed + 100 mm. iv) On loops, the section insulator shall, as far as possible, be located close to the first support of the overhead equipment for the loop. v) The preferred location of section insulator on main running track is 2 to 10 m from the support in the direction of traffic through its provision on the main line should be avoided. vi) In double line section, the runners should be in the trailing direction. 3.11.2 Permissible Speeds 3.11.2.1 On double line sections, with runners trailing, the section insulator assembly using porcelain sectioning insulators are fit for speeds upto 120 km/h provided it is installed within the first one-tenth and one-third of the span. Over Head Equipments Page 51 3.11.2.2 In case the runners of the section insulator are facing or it is not installed within 1/3rd of the span the speed should be restricted to 80 km/h (Ref. Fig. 3.05) 3.12.0 Arrangement of Jumpers 3.12.1 In span jumpers In span jumpers between the contact and catenary wires are provided at suitable equidistant intervals as indicated in Drg. No. ETI/OHE/G/05101. 3.12.2 Turnout jumpers The arrangement of connections at turnouts and at diamond crossings is indicated in Drg. No. ETI/OHE/G/05103 and 05106 respectively. 3.12.3 G jumpers The arrangement of jumpers at un-insulated overlaps is indicated in Drg. No. ETI/OHE/G/05102. 3.12.4 Potential equalizing jumpers The arrangement of potential equalizer jumpers is indicated in Drg. No. ETI/OHE/G/05104. 3.12.5 Anti-theft jumpers The arrangement of anti-theft jumpers should be as indicated in Drg. No. ETI/OHE/SK/432. Over Head Equipments Page 52 3.13.0 Tension Lengths 3.13.1 Regulated equipment With regulated overhead equipment every tension length is equipped with an automatic tensioning device at each end and an anticreep located approximately midway between the tensioning devices. The distance between the anticreep and the anchor mast / structures on either side should not exceed 750 m or 15 supporting masts. 3.13.2 Half tension lengths Half tension lengths of regulated overhead equipment, not greater than 750 m between anchorages, may be adopted where necessary. The equipment is fixed at one end and provided with an automatic tensioning device at the other, the fixed end being determined to suit convenience of erection. The half tension length on either side of the neutral section should not exceed 600 m when the whole or a part of it is located on a curve. The distance of the axis of a 4-span insulated overlap from the anti-creeps / fixed terminations on either side shall not exceed 600 m. 3.13.3 Bridges and tunnels Where the catenary is anchored on the face of an overline structure, the anchor shall be the anticreep point. Termination of overhead equipment or provision of an anticreep, should be avoided, as far as possible, inside the tunnels and on the mast set on bridge piers. 3.13.4 Masts with three brackets In the case of masts with three brackets supporting regulated equipment, anticreeps or fixed terminations of the overhead equipments should be arranged so as to keep the relative movement between brackets as low as possible so that the brackets do not foul with each other. 3.13.5 Unregulated equipment With unregulated equipment, tension lengths of upto 2000m between anchors may be adopted on tangent as well as curved track. 3.13.5.1 Unregulated OHE shall not take off from main running lines. 3.13.6 Linkage of wire-runs Wire-runs linking two or more main line wire-runs shall be as short as possible. For example, the same wire run may not ordinarily be used for equipping an emergency cross-over and a loop line. 3.13.7 Anti-creep Over Head Equipments Page 53 Anticreep arrangement: Anticreep is located approximately in the centre of a tension length. The standard arrangement should be in accordance with Drg. No. ETI/OHE/G/02111. 3.13.7.1 Boom type anticreep arrangement (Drg. No. ETI/OHE/G/02113) may be provided on multiple track sections or in other areas where portals have been provided on account of other design considerations. Portals should not be provided specifically for provision of boom type anticreep. 3.14.0 Anchor Height 3.14.1 Crossing of anchoring spans Crossing of equipments of different elementary electrical sections in the anchoring span should be avoided as far as possible. 3.14.2 Crossing of regulated and unregulated equipments should be avoided. This may, however, be permitted if there is sufficient mechanical clearance between the crossing contact wires under all conditions. 3.14.3 Anchoring near signals Anchoring spans in the vicinity of signals, water columns and other fixed structures should be avoided as far as possible. 3.14.4 Back to back anchors Back to back anchoring of two equipments on the same mast may be adopted if both the terminations are of the fixed type (without counter weights). 3.14.5 Anchor near buffers In order to equip the full length of a buffer end siding, the scheme of anchoring as indicated in Fig. A.306 may be adopted. Over Head Equipments Page 54 3.14.6 Anchor height Where the contact wire is of unregulated equipment and raised from the contact plane and anchored in a single span, the anchor height shall be fixed within limits decided on considerations indicated below. The maxi9mum height shall be such that with the contact wire tension at its maximum, the contact wire of the anchor OHE does not leave the contact plane in the one where it is required to be in-running. The minimum height shall be such that with the contact wire tension as its minimum, there is no possibility of the contact wire sagging too much below the contact plane where it is out of running and getting entangled with the pantograph. In both cases, the anchor height is to be determined with respect to the anchor span if there is no crossing of the two contact wires, and with respect to the distance between the anchor mast and the point of crossing if there is crossing of the wires. 3.14.7 IN case of regulated equipment, when the equipments to be anchored on a single span, anchor height shall be the standard one to get the regulation of the overhead equipment within the limited travel zone of counter weight assembly. However, single span anchoring should be avoided as far as possible. 3.14.8 Anchor near buildings No live anchor or equipment shall be provided near or over any hut / goomty and building. In such cases the overhead equipment should be isolated by providing cut- in-insulator and earthed by connecting it mechanically to the anchor mast without providing the insulator in the anchor assembly. 3.14.9 Termination The anchoring arrangement of OHE are given in Drg. No. RE/33/G/03121. In polluted areas, e.g. tunnels, areas near sea-coast, neighbourhood of chemical / fertilizer / cement plants, near loco sheds, ash, pits, water columns, etc long creepage path (1050 mm) Insulator should be used on the anchoring arrangement. 3.15.0 Location of Overlap 3.15.1 Platform lines Overlaps serving platform lines should not be located opposite platform to avoid location of tensioning devices on the platforms. It is unavoidable, half tension length may be adopted to avoid the provision of the regulating equipment on the platform. 3.15.2 Protection by signals In the station area insulated overlaps on main running lines should be located after the stop signals. (Refer to sectioning arrangement of OHE – para) 3.15.3 Cross-over In the case of emergency cross-over insulated overlaps in the direction of the trailing end should permit the longest train to be accommodated between the lock bar of the Over Head Equipments Page 55 crossover switch and the first intermediate mast of the overlap with a minimum margin of 50 m. This distance may be taken as 850 m. The overlap in the rear should be located as close as possible (Refer to sectioning arrangement of OHE –para 3.20) 3.15.4 Span Location of insulated and uninsulated overlaps should be decided in such way that the maximum span can be adopted to achieve parallel path of not less than 2 m for smooth change over by the pantograph. 3.15.5 The arrangement of overlaps should be as per standard drawings (see para) 3.15.6 Feeders to overlaps Feeding overlaps should be sufficiently away (see para 3.42) from the stop signals to facilitate coasting of trains with pantograph lowered in the event of extension of feed from either side. Feeders may be run, if required, from the substation which is usually located in the station areas. 3.16.0 Neutral Section 3.16.1 Overlap type The conventional overlap type neutral section (Drg. No. ETI/OHE/G/02161, Sheet-1) shall be used except in suburban and heavily graded sections. 3.16.2 Short Neutral Section of Section Insulator Assembly type In heavy graded section and suburban section where adoption of overlap type neutral section is not feasible, short neutral section of 5 m length, comprising of conventional section insulator assembly may be adopted. The arrangement is shown in the Drg. No. ETI/OHE/G/02161, Sheet 2. Speed under such neutral sections shall be restricted to 100 km/h if the runners are in trailing direction, otherwise to 70 km/hr (Para 3.11.2) Note: Short neutral section should be provided on half tension length not exceeding 500 m. 3.16.2.1 Adoption of short neutral section with section insulators assembly should be avoided on main running lines due to heavy weight, restricted speed and frequent maintenance requirement. 3.16.3 Short Neutral section of PTFE type If adoption of short neutral section on main line is unavoidable, short neutral section of ceramic beaded resin bonded glass fibre rod insulators be provided. This is lighter and is considered fit for speeds upto 130 km/h. Note: Ceramic beaded rod insulator type neutral section equipments have not yet been developed indigenously and are still under trial. Standard drawings will be issued after the indigenous product proves successful. 3.16.4 Neutral section shall be located away from stop signals, level crossing and shall be on tangent track and on level to the possible extent. Over Head Equipments Page 56 3.16.4.1 If neutral section is provided after a stop signal, the distance between signal and neutral section shall be such that after stopping, the train shall be able to pick up enough speed to coast the neutral section without any risk of stalling. 3.16.4.2 If neutral section is provided before a stop signal, the distance between neutral section and signal shall be such that the train shall not cross the signal in an effort to coast the neutral section. Note: The distance should be preferably 1600 m away on section with gradient upto 1 in 300 and 2500 m with higher gradient upto 1 in 200, if unavoidable. 3.16.5 The PTFE type short neutral section shall be located on level tangent track at least 400 m after the stop signal and 200 m before the stop signal. Where, however, modifications require to comply with these guide lines are difficult or entail heavy investment, the Chief Electrical Engineer of the Railway may direct any other arrangement to be followed consistent with safety and reliability, and for location on graded section according to para 16.4.1 and 16.4.2 (Ref Fig. A3.07) 3.16.6 Location of ‘OPEN DJ’ and ‘CLOSE DJ’ boards. The indication boards to indicate the approaching neutral section and ‘OPEN DJ’, ‘OPEN DJ’ boards shall be provided according to drawing No. ETI/OHE/G/02161, Sheet 3. 3.16.6.1 Separate ‘CLOSE DJ’ boards are required for EMUs and loco hauled trains. 3.17.0 Points and Crossings 3.17.1 General arrangement The equipment at points and crossings should preferably be of the overlap type. In unavoidable circumstances it may be of crossed type. 3.17.1.1 The general arrangement of regulated overhead equipment at turnouts and cross-overs is shown in Drg. No. ETI/OHE/G/02141 and 02151. For high speed running, the overlap type should be provided. 3.17.1.2 The general arrangement of regulated overhead equipment at turnouts and cross-overs is shown in Drg. No. ETI/OHE/G/03151and 03152, Sheet 1&2. Over Head Equipments Page 57 3.17.1.3 The leading dimensions of standard turnouts and crossings are given in Drg. No. RE/33/G/01104, sheet 1 and 01105, Sheet 1 for the broad gauge and in Drg. No. RE/33/G/01104, sheet 2 and 01105, sheet 2 for the metre gauge. 3.17.2 Overlap type In the case of turnouts for high-speed running a mast is located near the centre of the turnout and the contact wire of the secondary track is raised in one or more spans (exclusive of the anchor span) after the centre of the turnout, before it is anchored. A cross over is equipped in the same manner as two ordinary turnouts. Note: Overlap type overhead equipment at turn out taking off from main line shall be provided. 3.17.2.1 A diamond crossing with or without slips is equipped as two turnouts, the turnout centres being coincident. The mast located near the common centre is, therefore, equipped with three bracket assemblies (see Drg. No. ETI/OHE/G/02151). 3.17.3 Crossed type The crossed type equipment for turnouts is normally adopted on secondary tracks but may be used on main tracks, where speeds are less than 100 km/h. The overhead equipment of the secondary track normally crosses the overhead equipment of the main track or does not have any overlapping span before anchorage. The two contact wires are clamped together to prevent relative vertical displacement. For this type of equipment, no support is necessary near the centre of turnout. 3.17.3.1 In case of diamond crossings with double slips, if crossed type of equipment is provided, doubling of contact wire is necessary (See Drg. No. ETI/OHE/G/03152, Sheet 2). Doubling of contact wire is, however, not essential in the case of diamond crossings with single slip. In either case, no mast is necessary at the centre of the crossings. 3.18.0 Arrangement of Masts 3.18.1 Location of Masts Masts should generally be arranged as far as possible in the same line parallel to the track and in the same line transverse to the track. Normally, no masts should be located between any two main running tracks. 3.18.2 Umbrella type Masts may be fitted with bracket assemblies on each side to serve adjacent tracks if the overhead equipment of the tracks belong to the same elementary electrical section. 3.18.3 Restrictions 3.18.3.1 Masts serving track of different elementary sections should not normally be located between them and in the same line. If two masts serve tracks belonging to two different elementary electrical sections and are located between them, the masts Over Head Equipments Page 58 should normally be staggered by 9m, though a minimum stagger of 4.5 m is permissible in exceptional cases (Ref. Fig. A3.08(i)) 3.18.3.2 If one of the masts mentioned in an anchor mast, and the anchor falls between the two masts, they should be staggered by 13.5 m minimum (Ref. Fig. A3.08(i)) 3.18.3.3 If both the masts mentioned are anchor masts and both anchors fall between the masts, they should be staggered by 18 m (Ref. Fig. A3.08(i)) 3.18.3.4 If one of the masts is an anchor mast and the anchor falls away from the masts and the out-of-run equipment runs close to the second mast, the spacing of masts should be such that sufficient working clearance is available between the two overhead equipment and the second mast. (See para. 3.32 Cut in insulators or special anchor arrangements may be adopted in special cases (Ref. Fig. A3.08(iv) 3.18.4 If masts are located on both sides of a track, they shall be staggered by 4.5 m (Ref. Fig. A3.08(iv)) 3.18.5 Masts for turnouts and diamond crossing should be located at the theoretical centre. If unavoidable, 2 metres is the permissible displacement on either side of the theoretical centre of turnout. Over Head Equipments Page 59 3.18.6 Wiring of loops in future Masts should generally be located and designed to permit wiring of unwired loops and extension of electrification in yards and sidings, in future, conveniently. Wherever, such provisions is made, future wire-runs should be shown in dotted lines on the layout plans to ensure selection of correct type of masts and foundations. 3.18.7 Masts with counterweights should be avoided on platforms 3.18.8 Ash-pits & water columns Masts should not be located within 15 m of ash-pits and water columns. Steam engines standing at water columns and ash-pits blow off steam which may cause flash-over of insulators. Over Head Equipments Page 60 3.18.9 Masts shall not be located in front of station entrances. 3.18.10 Masts shall not be located opposite to trolley refuges, close to culverts, subways and on bridges of length less than 50 m. 3.18.11 No masts shall be located beyond a signal post at a distance less than 10 m. In case the OHE mast is located in the front of the signal the distance between the OHE mast and signal post should not be less than 30m. (Ref. Fig. A3.10) 3.18.12 Masts should be located sufficiently far away from level crossings and back of abutments of bridges. The distance between the mast and the end of the level crossing / abutment shall not normally be less than 10m. 3.18.13 The sections having more than two tracks, independent masts should be provided if adequate track centres are available or if the tracks can be slewed. Where adequate track centres are not available portals will normally be adopted and they should be located in such a way as to facilitate provision of drop arm/s and bracket assembly. 3.18.14 In case of bad formations, if it is possible to locate the masts on either side of a track, preference should be given to the side with better stability. 3.18.15 Support for OHE in tunnels In the lined tunnels, slubs for supporting OHE cantilever assembly should be provided on both sides of the tunnel, opposite each other. This would facilitate restoration of OHE in the event of damage to slubs on one side. 3.18.16 Masts on bridges Core holes for erecting masts on bridges should be provided as per Drg. No. RE/31/0590/63 on both sides of all the piers. Holes on piers which are not used for foundation should be filled with dry and covered with a concrete slab. 3.18.17 In case of wiring a petroleum siding special precaution shall be adopted as laid down. 3.19.0 Cantilever Arrangement 3.19.1 Overhead equipment is supported from the masts by cantilever bracket assembly made of galvanized steel tubes. The bracket assembly shall be of the swiveling type. 3.19.2 Cantilever arrangement The arrangement of cantilever depends upon the height of contact wire, encumbrance, suspension distance, stagger and super elevations. Standard cantilever arrangements are given in Drg. No. ETI/OHE/G/02106, Sheets 1 and 3. 3.19.2.1 Platform location The arrangement of cantilever on platform shall be as per Drg. No. ETI/OHE/G/02104, Sheet 2. Over Head Equipments Page 61 3.19.3 Allowance for adjustment The bracket assembly shall be such as to permit easy adjustment of the whole equipment after erection to catenary for displacement of track during maintenance to the extent of 100 mm on either side of the track centre. 3.19.3.1 Adjustment on bracket tube It shall be ensured at the time of selection of bracket assembly that the free length of the bracket tube beyond the catenary suspension bracket fitting is at least 150 mm to facilitate future adjustment. 3.19.3.2 Adjustment on stay tube The selection of stay tube at any location shall be such that its adjuster is free for adjustment of minimum 90 mm in either direction. 3.19.3.3 In case of curve track when the rail level is raised or the super elevation is changed due to strengthening of track structure, the pantograph axis will be shifted. If this shift is not within the possible adjustment limit of bracket assembly as specified in Clause 3.19.3.1 and 3.19.3.2 above, new cantilever may have to be provided taking care that at no stage the contact wire is beyond the specified stagger. 3.19.4 Size of tubes The size of stay tube and register arm tube is 28.4/33.7 mm dia for all cantilever arrangements. The size of bracket tube is either 30/38 mm or 40/49 mm designated as standard or large respectively depending upon the location (See Drg. No. ETI/OHE/G/00158 sheet 1,2 and 3 and 00159 sheet 1,2&3). 3.19.5 Back to back arrangement More than one cantilevers (on the same side) are provided on the masts for overlap, turnouts, cross over and diamond crossings. The cantilever may be symmetrical (50 cm on either side of the mast) or asymmetrical (65 cm on one side and 35 cm on the other side of the mast). Note: (i) Adoption of more than three bracket assembly is not possible on a single cross-arm. (ii) Cantilever assemblies can be provided on both sides of the mast, if the OHE of the two tracks are of the same elementary section. This is called ‘Umbrella’ construction. 3.19.6 Bracket assembly on drop-arm On portals, bracket assembly for the intermediate track/s is erected on drop arms. Wherever the track centre is inadequate (i.e. suspension distance less than 1.60 m), the equipment should be supported on drop arm of reduced length so that the bracket assembly does not infringe with the swept zone of pantographs. The arrangement is shown in Drg. No. ETI/OHE/G/02108. 3.19.7 Bridge & Tunnels Bracket assembly of special design may be adopted on bridges and tunnels after making clearance study. Over Head Equipments Page 62 3.19.8 Bracket chair Bracket assembly can be designed upto suspension distance of 3.5 m only. If the suspension distance is more, bracket chair to Drg. No. ETI/OHE/P/3050 and RE/33/P/3100 shall be used. 3.19.9 Insulator for Bracket Assembly In polluted areas, e.g. tunnels, areas near sea coast, neighbourhood of chemical / fertilizer / cement plants, near steam loco sheds, ash pits, water columns etc long creepage path (1050 mm) insulators should be used on the cantilever assemblies. 3.20.0 Setting of Masts 3.20.1 Tangent track The standard setting i.e., the normal distance of the nearest part of the traction mast from the centre line of tangent track shall be 2.50 m for the broad gauge and 2.35 m for the metre gauge. The setting may be reduced to a minimum of 2.36 m for the broad gauge and 2.14 m for the metre gauge only in special circumstances such as yards, cuttings and bridges etc. with the approval of the Chief Electrical Engineer of railway concerned. In case of portal uprights, masts carrying more than one OHE and head span masts, the setting should not normally be less than 3.00 m for the broad gauge and 2.50 m for the metre gauge. 3.20.2 Curved track The minimum setting distance of masts including portals, head span masts etc on curves is obtained by adding the curve allowance and 150 mm slewing allowance to the setting distance specified for tangent track in para 20.1. For trunk routes and main lines where the speed may be increased in near future, curve allowance should be taken as per Table III. For other routes, branch lines and yards where there is no prospect of increase in above 105 Km/h in near future, the curve allowance should be taken as per Table-I for Board gauge and Table-II for Meter gauge. Normally, the standard setting distance on board gauge main lines on curves should not be less than the values given below: a) On outside curves Standard settings (m) i) Radius curvature 2.80 greater than or equal to 875 m. ii) Radius of curvature less 2.95 than 875 m. b) On inside curves i) Radius of curvature 3.20 greater than or equal to 3500 m. ii) Radius of curvature 3.35 greater than or equal to 2350 m. but less than 3500 m. iii) Radius of curvature 3.55 greater than or equal to 1150 m. but less than 21350 m. Over Head Equipments Page 63 iv) Radius of curvature 3.60 greater than equal to 300 m. but less than 1150 m. TABLE – I Curve allowance for maximum speed Upto 105 km/h – Broad Gauge. Degree of Radius of Max. Super Extra clearance between curvature curvature permissible elevation adjacent track (mm) (meter) speed (km/h) (mm) Inside Outside curve curve 1 1747 105 50 130 - 1½ 1164 105 75 220 - 2 875 105 100 310 10 3 583 96 120 390 30 4 434 80 125 420 40 5 350 72 120 420 60 6 292 65 105 390 80 7 250 56 125 470 90 8 219 48 140 540 110 9 194 48 140 550 130 10 175 40 120 500 140 Note : See Drg. No. ETI/OHE/G/00111 Sheet 1, also for this reference. Over Head Equipments Page 64 TABLE – II Curve allowance for Metre Gauge Degree of Radius of Max. Super Extra clearance between curvature curvature permissible elevation adjacent track (mm) (meter) speed (km/h) (mm) Inside Outside curve curve 1o 1747 72 15 50 - 2o 875 72 30 120 - 3o 583 72 45 200 20 4o 438 96 120 390 30 5o 350 80 125 420 40 6o 292 72 120 420 60 7o 250 56 75 370 70 8o 219 48 85 420 80 9o 194 48 90 460 100 10o 175 40 75 410 110 11o 159 40 80 440 120 12o 146 32 55 360 140 13o 134 32 60 390 150 14o 125 32 65 420 160 15o 116 25 40 340 180 16o 109 25 40 350 190 Note: See Drg. No. ETI/OHE/G/00111 Sheet: 2 also for reference. Over Head Equipments Page 65 TABLE – III Curve allowance for Meter Gauge Degree of Radius of Max. Super Extra clearance between curvature curvature permissible elevation adjacent track (mm) (meter) speed (mm) (km/h) Inside Outside curve curve o 1/2 3492 200 71 191 - (160) (40) (89) 3/4o 2328 200 133 40 - (160) (60) (159) 1o 1747 190 185 575 - (160) (100) (295) 1 1/2o 1164 155 185 585 - 2o 875 135 185 590 10 3o 583 110 185 605 30 o 4 438 95 185 620 40 5o 350 85 185 640 60 o 6 292 80 185 655 80 Note : i) Figures in bracket indicates super elevation and curve allowance for 60 km/h speed. ii) See Drg. No. ETI/OHE/G/00111 Sheet 1, for reference. Reproduced from Railway Board’s letter No. 68/WDO/SC/1 dated 15.4.1968. 3.20.2.1 In yards, where there is no super elevation of track on curves, the extra clearance indicated may be reduced suitably in locating masts between tracks. 3.20.3 Masts with counter weights In the case of masts with counter weights, the term “Setting” refers to the minimum distance of the counter-weight from the track centre in the worst condition. For this purpose, the displacement of the counter-weight due to wind transverse to the track may be taken + 50 mm. 3.20.4 Platform masts The setting of masts on platforms shall not be less than 4.75 m on the broad gauge and 4.0 m on the metre gauge. As far as possible, masts shall be located in line with other masts or obstructions on platform and shall be of minimum possible dimensions and fit in with the architectural pattern prevailing in the vicinity. Locations of masts opposite to public entrances, exits, staircases, gang ways shall be avoided. No live conductor should be run over platforms. 3.20.5 Masts near signals The visibility of signals should be kept in mind while deciding the setting up masts in their vicinity. The following principles should be observed for deciding the setting of masts near signals. Over Head Equipments Page 66 3.20.5.1 Colour light signals located all tracks a) Colour light signals without route indicators. i) Where no approach signal is provided. The minimum setting of mast before signal should be 3.25, 3.10, 3.05, 2.90 and 2.75 m for distance upto 80 m, beyond and upto 110 m, beyond and upto 190 m, beyond and upto 270 m beyond and upto 400 m respectively. ii) Where approach signal is provided and for signals other than distant signals. The minimum setting of mast before signal should be 3.25, 3.10, 3.05, 2.90 and 2.75 m for distance upto 85 m, beyond and upto 70 m, beyond and upto 115 m, beyond and upto 160 m beyond and upto 240 m respectively. b) Colour light signal with route indicators: i) With horizontal route indicator: The minimum setting of mast before signal should be 3.72, 3.50, 3.25,3.05, 2.90 and 2.75 m for distance upto 60 m, beyond and upto 125 m, beyond and upto 170 m, beyond and upto 215 m beyond and upto 250 m, beyond and upto 310 m, respectively. ii) With other than horizontal route indicator: The minimum setting of mast before signal should be 3.50, 3.25,3.05, 2.90 and 2.75 m for distance upto 70 m, beyond and upto 130 m, beyond and upto 170 m, beyond and upto 215 m, beyond and upto 280 m, respectively. Note : 1. See Drg. No. ETI/OHE/G/00112 also. The setting may be reduced in special cases, confirming to figs 6 to 9 of ibid. 2) Setting distance may be reduced for starter signals of loop lines and yard lines. 3.20.5.2 Colour light signals located between tracks: a) Signals without route indicators: No OHE mast should, as far as possible be located in the same lane as the signal for a distance of at least 600 m before a signal. Drop arms of portals should also not normally be located in the lane where signal are located, at least for a distance of 600 m before the signal. Where this is not possible, for any reason, the signal should be mounted on an off-set bracket. In addition, a spectra study should be made in each such case in respect of three drop arms before the signal, to see whether the drop arms can be off-set from the centre line of the lane in a direction opposite to the off-set of the signal or alternatively whether it is possible to shorten the drop arms. Reduction in the signals height may also be examined. b) Signals with route indicators: The principles mentioned under para 20.5.2(a) should be observed in these cases also. Note: 1. No part of a colour light signal without a route indicator should, as far as possible, be higher than 5.2 m above rail level. Great care should be exercised in deciding the locations of colour light signals with route indicators so that the necessary minimum clearances are available between the signals and live out of run conductors, or pantograph sway zone. 2. On single-line sections, signals (colour light as well as semaphore) should, as far as possible, be located on the side of the track opposite to the OHE masts. Over Head Equipments Page 67 3.20.5.3 For semaphore signals located outside the track: The minimum settings of masts before the signal should be 3.05, 2.90 and 2.75 m for the first second and next three masts respectively. Note: For details, see Drg. No. ETI/OHE/G/00112. 3.20.6 Masts on bridge piers The setting of masts on piers of bridges will be as large as possible and indicated by the Railway. 3.20.7 Turnouts The setting of masts located near theoretical centres of turnouts and diamond crossings should be 3.0 m from the nearest track for the broad gauge and 2.75 m for the metre gauge. (Ref. Fig. A1.09) 3.20.8 Portals Wherever portals are proposed to be used, they shall be selected with standard clear spans (distance between face of the uprights) indicated in the tables IV and V. for this purpose the clear span for any location obtained by adding the proposed setting of the two columns to the centre-to-centre distances of the tracks spanned by the portal shall be rounded off to the next higher standard span indicated in the tables. The setting of the uprights of the portal shall then be adjusted to suit the standard span selected with a minimum setting distance as specified in para 20.2. TABLE – IV Standard Clear Spans for ‘N’ type portals (Spans in metres) Nominal range : 10.0 m to 20.0 m 9.91 9.96 10.01 10.06 10.11 10.41 10.46 10.51 10.56 10.61 10.91 10.96 11.01 11.06 11.11 11.41 11.46 11.51 11.56 11.61 11.66 11.71 11.76 11.81 11.91 11.96 12.01 12.06 12.11 12.16 12.21 12.26 12.31 12.41 12.46 12.51 12.56 12.61 12.66 12.71 12.76 12.81 12.91 12.96 13.01 13.06 13.11 13.16 13.21 13.26 13.31 13.41 13.46 13.51 13.56 13.61 13.66 13.71 13.76 13.81 13.91 13.96 14.01 14.06 14.11 14.16 14.21 14.26 14.31 14.41 14.46 14.51 14.56 14.61 14.66 14.71 14.76 14.81 14.91 14.96 15.01 15.06 15.11 15.16 15.21 15.26 15.31 15.41 15.46 15.51 15.56 15.61 15.66 15.71 15.76 15.81 15.91 15.96 16.01 16.06 16.11 16.16 16.21 16.26 16.31 16.41 16.46 16.51 16.56 16.61 16.66 16.71 16.76 16.81 16.91 16.96 17.01 17.06 17.11 17.16 17.21 17.26 17.31 17.41 17.46 17.51 17.56 17.61 17.66 17.71 17.76 17.81 17.91 17.96 18.01 18.06 18.11 18.16 18.21 18.26 18.31 18.41 18.46 18.51 18.56 18.61 18.66 18.71 18.76 18.81 18.91 18.96 19.01 19.06 19.11 19.16 19.21 19.26 19.31 1941 19.16 19.51 19.56 19.61 19.66 19.71 19.76 19.81 19.91 19.96 20.01 20.06 20.11 20.16 20.21 20.26 20.31 Over Head Equipments Page 68 TABLE – V Standard Clear Spans for ‘O’ and ‘G’ type portals (Spans in metres) Nominal range : 20.0 m to 30.0 m 20.05 20.10 20.15 20.20 20.25 20.55 20.66 20.65 20.70 20.75 21.05 21.10 21.15 21.20 21.25 21.55 21.60 21.65 21.70 21.75 21.80 21.85 21.90 21.95 22.05 22.10 22.15 22.20 22.25 22.30 22.35 22.40 22.45 22.55 22.60 22.65 22.70 22.75 22.80 22.85 22.90 22.95 23.05 23.10 23.15 23.20 23.25 23.30 23.35 23.40 23.45 23.55 23.60 23.65 23.70 23.75 23.80 23.85 23.90 23.95 24.05 24.10 24.15 24.20 24.25 24.30 24.35 24.40 24.45 24.55 24.60 24.65 24.70 24.75 24.80 24.85 24.90 24.95 25.05 25.10 25.15 25.20 25.25 25.30 25.35 25.40 25.45 25.55 25.60 25.65 25.70 25.75 25.80 25.85 25.90 25.95 26.05 26.10 26.15 26.20 26.25 26.30 26.35 26.40 26.45 26.55 26.60 26.65 26.70 26.75 26.80 26.85 26.90 26.95 27.05 27.10 27.15 27.20 27.25 27.30 27.35 27.40 27.45 27.55 27.60 27.65 27.70 27.75 27.80 27.85 27.90 27.95 28.05 28.10 28.15 28.20 28.25 28.30 28.35 28.40 28.45 28.55 28.60 28.65 28.70 28.75 28.80 28.85 28.90 28.95 29.05 29.10 29.15 29.20 29.25 29.30 29.35 29.40 29.45 29.55 29.60 29.65 29.70 29.75 29.80 29.85 29.90 29.95 30.05 30.10 30.15 30.20 30.25 30.30 30.35 30.40 30.45 3.21 Over line structure 3.21.1 Clearance The requisite minimum electrical clearances (See para 3) should be maintained under over-line structures such as over-bridges, signal gantries, platform sheds and tunnels. The location of structures and spans under these structures is, therefore, determined to suit the clearances. A clearance study shall be made for all existing over-line structures. Efforts should be made to provided as large clearance as possible. 3.21.2 Where adequate clearance is available, the catenary should be erected so as to have maximum clearance from the over-line structure to reduce the possibility of birds perching on the catenary wire and coming in contact with earthed parts. 3.21.3 The catenary is normally passed freely under over-line structures. Where this is not possible, on account of restricted clearances, the following alternatives may be adopted. i) The catenary may be suspended from the two faces of the over line structures. ii) Suspension from over-line structure. The catenary may be suspended from the over-line structure at an intermediated point. Over Head Equipments Page 69 iii) The catenary may be anchored on to the over-line structure on either side or on to special anchor structures. The anchor point should normally be the anticreep. iv) Special designs may be adopted inside covered station areas and on through girder bridges, employing even regulated tramway type equipment (contact wire only), where it is feasible. Note: At over-line structures, the span should preferably be centrally located as far as possible and generally should not exceed 54.0 m. 3.21.4 Polluted one Double insulation or insulator for polluted zones shall be used in the following cases: i) In tunnels (see 3.19.9) ii) For insulators located on the axis of the track in areas where steam traction would be in extensive use or where smoke is likely to accumulate. 3.22.0 25kV Feeders 3.22.1 Suspension Where a 25 kV feeder is run longitudinally on traction masts, it shall be carried on the masts as shown in Drg. No. ETI/OHE/G/05143. The feeder may be run on either side of a mast. Two 25 kV feeders, or one return conductor and one 25 kV feeder, may be carried on a single mast, if necessary, with one feeder on each side of the mast. Note: If the 25 kV feeder and OHE are of different elementary sections, ‘Restricted clearance’ board shall be provided. 3.22.2 Clearances from overhead equipment Where a 25 kV feeder crosses overhead equipment belonging to a different elementary electrical section, the clearance between the feeder and the overhead equipment shall not be less than two metres under any conditions. 3.22.3 Clearance from the line side structures Normally, no feeder should be erected over huts, cabins, goomties, platforms shed or other covered structures. If unavoidable the clearance between the highest point of a covered structure and a 25 kV feeder passing over an over-line structures which is not covered, a suitable metallic screen shall be provided on the structure underneath the feeder. The clearance between the feeder and the highest point of the screen shall be adequate. A clearance of 2 m is desirable between the 25 kV feeder and any part of an earthed structure for facilitating maintenance work on the structure. Over Head Equipments Page 70 3.23.0 Cross-Spans at Switching Stations 3.23.1 Cross span arrangement All the switching stations have gantry with two or more main vertical supports. Cross span wires / feeders are provided on the gantry to connect the various sections of overhead equipment by jumper connections. The general arrangement is shown in Drg. No. ETI/OHE/G/05124. 3.23.2 Setting distance The minimum setting distance of the gantry upright which is normally aligned parallel to the track shall be 4.30 m. 3.23.3 Multiple track The general arrangement of connections at the switching stations on double track and multiple track section are shown in Drg. No. ETI/OHE/G/05125 and 05126 respectively. 3.24.0 Tramway type overhead equipment 3.24.1 Regulated Equipment In tramway type equipment only contact wire is provided and is auto-tensioned at the anchor by weight. The contact wire is supported by swiveling type of brackets on individual masts as indicated in Drg. No. ETI/OHE/G/04204. Generally, the principles applicable to normal overhead equipment are also applicable to regulated tramway equipment except as specified below: 3.24.1.1 Usage The regulated tramway type equipment is to be adopted for loop lines, sidings, yards and spur lines excluding the main running line and first loop or lines taking-off from the main running line. 3.24.1.2 Span The maximum span is restricted to 63 m. The general arrangement is shown in Drg. No. ETI/OHE/G/04203. 3.24.1.3 Section Insulators Where a section insulator assembly is to be provided, the provision of a structure to support the assembly is obligatory. The arrangement is shown in Drg. No. ETI/OHE/G/04207 Sheet 1&2. 3.24.1.4 The arrangement of tramway equipment at anti-creep and points and crossings are shown in Drg. No. ETI/OHE/G/04205 and 04208 respectively. Over Head Equipments Page 71 3.24.2 Unregulated equipment The general arrangement of tramway equipment to be adopted for head span and cantilever type construction is shown in Drg. No. ETI/OHE/G/04101. The principles applicable to normal OHE are applicable to this type of unregulated equipment except as specified below: 3.24.2.1 The maximum span is restricted to 30 m. In station areas, where this type runs side by side with conventional equipment with contact and catenary wires, the maximum span may be increased to 31.5 m. 3.24.2.2 Where a section insulator is to be provided the provision of a structure becomes obligatory. 3.25.0 Booster Transformers 3.25.1 100 kVA Booster Transformers wherever necessary for suppression of inductive interference of P&T communication lines running in close vicinity and parallel to 25 kV OHE may be provided separately for each running tracks. The primary winding of the booster transformer is connected in series with the OHE at insulated overlaps. The arrangement of mounting and connection is shown in RDSO Drg. No. ETI/PSI/115. 3.25.2 The Booster transformers are located at an approximately spacing of 2.66 km between each other. 3.25.3 The location of the booster transformer should be decided considering the following aspects. a) At feeding posts and sectioning and paralleling posts the booster transformers should be located equidistant on either side so that the mid-point falls in front of these switching stations. b) In exceptional circumstances where the booster transformers are not placed equidistant from the feeding post or sectioning post, it must be ensured that the distance of the booster transformer from FP or SP does not exceed 1.33 km. c) The booster transformer should not be located: - In the vicinity of the stop signals to avoid bridging of insulated overlap by locomotives pantograph. - Within the station limits except for very big stations. 3.26.0 Return Conductors 3.26.1 Route In deciding the route of return conductors the obstructions en-route should be taken into consideration. Besides, adequate physical and electrical clearances should be maintained from fixed structures. The general objectives is to run the return conductor as close as possible to the associated overhead equipment so as to secure maximum compensation. Subsidiary lines such as sidings, loops etc are not provided with return conductors. Over Head Equipments Page 72 The return conductor will be normally run on the traction masts on the same side as the overhead equipment. The arrangement is shown in Drg. No. ETI/OHE/G/05307. The clearance between the return conductor and the overhead equipment should not be less than 400 mm under the worst conditions. 3.26.2 Clearance The static and dynamic clearance to any part of the return conductor from an earthed structure should be 150 mm and 80 mm respectively. 3.26.3 Return conductors at over-bridges At over-bridges return conductors may be run straight through, if possible, as on normal structures. 3.26.4 Return conductors in complicated areas. In station areas, having complicated track layout. It may not be practicable to position the return conductor sufficiently close to the associated overhead equipment to secure the required compensation. In such cases, the route of the return conductor should be decided on the merits of each case. Care being taken to avoid running of return conductor over platforms. 3.26.5 Tension lengths of return conductors Return conductors are normally terminated at the masts where the return conductors are connected to the rail. They may be anchored back to back at such masts. 3.26.6 Connections to booster transformers At all booster stations, the return conductors for each track should be provided with a cut-in-insulator. The return conductor is connected in series with the secondary winding of the booster transformer and the connections of the return conductor to the booster transformer should be carried out in accordance with Drg. No. ETI/OHE/G/05413. 3.26.7 (i) The mid-point of return conductor shall be connected to the buried rail as per RDSO’s Drg. No. ETI/OHE/G/05306 and ETI/PSI/611. The mid-point is defined as a mid point between two consecutive booster transformers. (ii) Mid-point of the return conductor before feeding posts shall be connected to the buried rail on either side of the insulated overlap and in case of sectioning posts shall be connected on either side of the neutral section. (iii) In exceptional circumstances, where mid-point does not fall in front of feeding posts and sectioning posts, the two rail links between return conductor and rail should be provided in front of feeding posts and sectioning post on either side of the insulated overlap / neutral section. In these cases, mid-point should not be connected to rail. Over Head Equipments Page 73 3.27.0 LT Supply Transformer 3.27.1 Low tension power supply 230 V single phase power supply required for operation of substation equipment e.g. circuit breakages, interruptors etc lighting of the station yard, tunnels and working of colour light signals, is obtained through 25 kV / 230 V, 10 kVA 50 Hz single phase LT supply transformer. It is provided at substations feeding and switching post stations, block-huts and at other outdoor locations e.g. level crossings with gate signals. 3.27.2 Capacity LT supply transformers are of 10 kVA capacity. More than one transformer are provide at large station, yard etc. 3.27.3 Protection LT supply transformers are protected only by a 25 kV, Amp, dropout fuse on the primary side and 63A fuse (wire able dc type with 20 SWG tinned copper wire) on the secondary side. 3.27.4 Mounting arrangement The LT supply transformer is mounted on steel platform erected on the OHE mast and connected to the 25 kV OHE through rigid aluminium bus-bar or 50 mm2 copper jumper wire. The general arrangement of mounting and connection is shown in Drg. No. ETI/PSI/036. 3.27.5 Substation LT Supply At substation, in order to provide power to single phase transformer oil centrifuging / filtration plant, 100 kV, 25 kV/ 230V, 50 Hz single phase transformers are provided. The general arrangement of mounting and connection is shown in Drg. No. ETI/PSI/0312. 3.28.0 Mast and Rail Bonds 3.28.1 Structure Bonds All traction masts shall be bonded to a non-track circuited rail as shown in Drg. No. ETI/OHE/P/ 7000 (see para 3.29.1). In the case of portals, only one uprights of the portals, and in the case of head spans, both masts of the head spans, shall be bonded to non-track circuited rails. 3.28.2 Rail Bonds The Rail bonds to connect the running rails longitudinally across rail joint shall be in accordance with Drg. No. ETI/OHE/P/ 7030. Over Head Equipments Page 74 3.28.3 The cross bonds connecting two rails of track o rails of adjacent track shall in accordance with Drg. No. ETI/OHE/G/ 05251. 3.29.0 Earth Wires 3.29.1 Sectioning and earthing In sections where a non-track circuited rail is not available, as in double-rail-track- circuited sections, all traction masts shall be connected together by a continuous serial earth wire supported by the traction masts. The earth wire shall be divided into electrical sections not exceeding 1000 m in length by means of cut-in-insulators. Each section of earth wire shall be bonded to traction mast which should be connected to an earthing station (Drg. No. ETI/OHE/P/ 7020). With two separate earth electrodes in such a way that the interval between the earthed structures does not normally exceed 500 m as shown in Drg. No. ETI/OHE/G/ 05201. 3.29.2 In Tunnels In case of tunnels, all the traction support structures shall be connected together by a continuous earth wire, which may be supported from tunnel surface. The earth wire shall be made into discontinuous sections not exceeding 1000 m and shall be connected to earth electrodes provided not more than 500 m apart and traction rail at both ends of the tunnel. 3.29.3 Layout No earth wire shall cross any track. Where masts required to be connected to an earth wire are located on opposite sides of a track, separate wire-runs shall be used for connecting the masts. In complicated areas, masts may be connected to individual earthing stations. 3.29.4 Anchoring Earth wires need be anchored only at termination of wire-runs. 3.30.0 Sections Arrangement 3.30.1 Necessity of sectioning OHE is divided into electrically isolated sections by provision of interruptors or isolators at overlaps and with section insulators at turnouts. Sectioning is provided to permit isolation of OHE in small sections for maintenance or to isolate damaged OHE in case of breakdown / accident and to permit diversion of trains from up line to down line and vice-versa. However, the sectioning should be kept to the minimum consistent with operational requirements. Over Head Equipments Page 75 3.30.2 Protection of isolated sections Protection by signal of the isolated sections: Normally a stop signal is provided before the insulated overlap, i.e., isolator so that approaching train is stopped from entering the isolated section. Although the distance between the stop signal and the sectioning points have not been specified in the rules, it is desirable to provide 120 m between the stop signal and the centre line of the insulated overlap / section insulators i.e., the sectioning point. 3.30.3 Sectioning arrangements for different types of stations: Since most of the electrified routes are on the double line section, only double line stations have been considered. Since most of the electrified routes are on the double line section, only double line stations have been considered. 3.30.3.1 Stations having no emergency cross-over. The isolation is provided to take a block. The trains are stopped by the stop signal. The sectioning point should be provided 120 m away from the starting signal. This arrangement enables the trains to be received at the station Fig.A.3.11 shows the layout. 3.30.3.2 The first loop line adjacent to the main is normally pro

OHE-34-96 PDF - Principles for Layout Plans and Sectioning Diagrams for 25 KV AC Traction

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