APPENDIX I

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)



1.0 Introduction

1.1 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, principles have been evolved to standardize designs and to speed up the work. The principles could be relaxed in special' 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.

2.0 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:

2.1 Bond

An electrical connection across a joint in or between adjacent lengths of rail:

1) 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) Bond, 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 building, to which the traction overhead equipment is attached and the track return.

2.2 Cantilever (assembly)

It is an insulated swivelling 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 from 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 from this member by catenary suspension bracket and catenary suspension clamp.

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.

2.3 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 track(s) whether electrified or not for transmission of electrical energy.

ii) Crossing OHE - Crossing of two conductors of OHE crossing without physical contact.

2.4 Dropper

A fitting used in overhead equipment construction for supporting the contact wire from catenary.

2.5 Electrical Clearance

The distance in air between live equipment and the nearest earthed part.

2.6 Encumbrance 

The axial distance on vertical plane between the catenary and the contact wire at support.

2.7 Feeder

A conductor connecting (a) a substation with a feeding post, or (b) a feeding post with the OHE.

2.8 Height of contact wire

The distance from rail level to the under side of contact wire.

2.9 Interruptor

It is a single phase Vacuum SF6/oil circuit breaker used as load switch to close the circuit on fault but does net open on fault. It is operated either by remote control or manually at site. Different methods of connection of interruptors are:

a) Bridging Interruptor - 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.

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.

2.10 Jumper .

A conductor or an arrangement of conductors for electrical continuity not under tension, which forms electrical connection between two conductors or equipments.

2.11 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.

2.12 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.

2.13 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.

2.14 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. Bectrical continuity is provided by an isolator, interruptor or booster transformer.

2.15 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.

2.16 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.

2.17 Return Conductor

A conductor which carries return current from the tracks to "the sub-station in the booster transformer system.

2.18 Regulating Equipment

A device for maintaining the tension of OHE conductors constant under all ambient temperature conditions. Note: Such OHE is called regulated OHE.

2.19 Setting Distance (Implantation)

The horizontal distance from the nearest face of traction mast to the centre line of the track.

Fig. A 101

2.20 Suspension Distance

The horizontal distance from the centre of the eye of catenary suspension bracket to the face of the mas for a single cantilever assembly or to the face of cross arm channel in case of multiple cantilever assembly (Ref: Fig. A1.01).

2.21 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.

2.22 Stagger

Stagger of the contact wire is the horizontal distance of the contact wire from the vertical plane through the centre of pantograph pan at the contact surface.

The stagger of the catenary is the horizontal distance of the eye of the catenary suspension bracket from the vertical plane through the centre of the track.

2.23 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.

2.24 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 a 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.

2.25 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.

2.26 Tension Length

Length of conductor which is stretched between the two anchor points.

2.27 Versine

The versine is the maximum offset of the rail on which spans have been measured (Para 5.1) of the curved track from the chord connecting two points, each opposite adjacent masts.

3.0 Electrical Clearance

3.1 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) Minimum vertical distance between any live part of overhead equipment or pantographs and parts of any fixed structures (earthed or otherwise) or moving toads:

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 structure (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.

3.2 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 2m. Where the clearance is not obtained the structure shall be protected by earthed metallic screens or prescribed warning boards (Refer para 22.2 and 22.3).

4.0 Wind Pressure

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 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

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 2/3 rd 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.

5.0 Spans

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.

5.2 Standard span

Standard spans shall be determined in accordance with:

i) Drg. No. ET1/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).

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.

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 giver in the span and stagger chart (ETI/OHE/G/00202). taking into account the stagger at the common support and the stagger at the extreme supports (See para 8).

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 catenan 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).

iv) The lengths of spans loaded with section insulators may require to be restricted (See para II).

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.

5.6 Overlaps

The spans at insulated and un-insulated overlaps should be designed in accordance with Drg. Nos. ETI/OHE/G/ 02131/Sheet 1 and RE/33/G/02121 Sh. 1 respectively. '

Note: If feasible, overlap shall be avoided under overhead power line crossings.

5.7 Neutral sections

The spans at neutral sections should conform to Drg. No. ETI/OHE/G/02161 Sheet No. 1 and no deviations are normally permissible.

6.0 Masts, Portals, Head Spans and Foundations

6.1 Types of masts . 

OHE conductors are suspended from swivelling cantilever assembly generally erected on individual masts.

6.1.1 Nine types of masts are used. These are designated as 150x150 BFB, 200x150 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. ET1/C/0071) masts can be used In lieu of K-Series masts.

Note: Sometimes 200x200 (8"x8") BFB have been imported. These are used in lieu of 200x150 RSJ as specified in mast employment schedules.

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 mm2 Cd-Cu catenary and 107 mm2 copper contact wire):

Light wind pressure:(75 kgf/m2) Drg. No. ET1/C/0702, Sheet 1 to 5.
Medium wind pressure:(112.5 kgf/m2 Drg. No. ETI/OHE/G/00153 and 00154, Sheet 1 to 4.
Heavy wind pressure:(150 kgf/m2) Drg. No. ETI/C/0726, Sheets 1 to 4, ETI/C/0727;0728 and 0729.


b) Composite OHE (comprising of aluminium alloy catenary and 107 mm2 copper contact wire with 1000 kgf tension in each conductor).

Light wind pressure:(75 kgf/m2) Drg. No. ETI/C/0721 Sheet
1 to 4 & ETI/C/0722,0723, & 0724.
Medium wind pressure: (112.5 kgf/m2) Drg No. ET1/C/0717 
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/OHE/ 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.

6.1.2.1 On long (more than 150 m) bridges and within 100 m from their abutments on either side and on banks where the height of the catenary above surrounding meaft 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 kgf/m2

Medium (yellow) wind pressure zone       - 150 kgf/m2

Light (green) wind pressure zone           - 100 kgf/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 for medium (yellow) pressure zone.

6.2 Two Track Cantilever

In the yards and sidings when the mast can not be erected near the track to be equipped, it may be erected spanning one or two tracks using a two-track cantilever (Drg. No. ETI/C/009, Sheet 1). This is generally used for supporting OHE near rumouts and X-overs. This arrangement 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.

6.3 Portals

On multiple track sections, where adequate track centres are not available and tracks cannot be slewed, portals 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.

6.3.1 Three types of portals have been standardized. 'N' type portal is used for clear spans of 10m - 20 m (4 tracks maximum). O' type portal is for clear spans of 20 m.-30 m (for 6 tracks maximum) and 'R' type portal with spans of 30 m -40 m (for 8 tracks maximum).

6.3.2 Where the upright of standard portals cannot be erected, due to limited track centres, P' type portal may 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 '0' type respectively. In exceptional cases, BFB uprights of 152 mm width (Drg. No. ET1/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 where 'N' type portals cannot be used. ,

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 intermediate tracks are provided on the drop-arms suspended from the boom (ref para 1-9.6).

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 arrangements are not used normally.

6.5 Foundations ,

6.5.1 Volume charts

The foundation bending moment codes (FBM) for each location are obtained from the mast employment schedules 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 due 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. ET1/C/0058) on the basis of FBM code, type and bearing capacity of soil/shoulder width and the extent of projection above ground level.

6.5.2 Type of foundations

The following types of foundations are for OHE mast and portals: 

(1) For Masts:  
i) (A) Side bearing (Type B) Drg. No. ETI/C/0058 Sh.1
(B) Side gravity (type : BG) -do-
(C) Pure gravity (Type: G) -do-
(D) Pure gravity for black cotton soil (Type: WBC) -do-
ii) New Pure gravity (Type : NG) -do- Sh. 2A.
iii) NBC type foundation for dry black cotton soil (16500 & 11000 kgf/m2) 3.0 m depth. -do- Sh. 3A.
iv) New pure gravity for different soil and site conditions (500 mm exposed) (Type-. NG or SPL) -do- Sheet 4 
v) New pure gravity for black cotton soil (for 8000 kgf/m2 sojl pressure. 2.5 m depth. (Type : NBC) -do- Sheet 5
vi) Foundations in soft rock (bearing capacity 45000 Kgf/m2 Drg. No. ETI/C/0059 
vii) Foundations in hard rock (bearing capacity 90,000 kgf/m2). Drg. No. ETI/C/0060.


,ommmmm

FIG. A 1.03

 

(2) For portals: .

i) In ordinary soil :                     Drg. No. ETI/C/0005/68

ii) In dry black cotton soil :         Drg. No. ETI/C/0063

6.5.2.1 In the case of OHE foundations in deep rock cutting the foundations should be below the drain.

6.5.2.2 For ail future constructions of pure gravity foundations drawing No. ET1/C/0058 Sheet -2A only shall be followed.

6.5.3 Selection of foundations

Side bearing foundations are used for masts where the soil bearing capacity is 11.000 or 21,500 kgf/m2 and 300mm 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. ET1/C/0023). (Ref. Fig. A1.02).

6.5.4 New pure gravity foundations may be used  For masts where soil bearing capacity is 5500,8000and 11000 kgf/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.

6.5.5 Side gravity foundations may be used for masts where soil bearing capacity is 8000 and 11000 kgf/m2, or adequate shoulder width is not available. No portion of the foundation should be exposed.

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 kgf/m2. Pure gravity foundations (Type P) are used for portals and are designed for soil bearing capacity of 8250 and 11000 kgf/m2.

6.5.7 Foundations in black cotton soil 

6.5.7.1 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 of unexpected rains in dry season also.

6.5.7.2 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.

6.5.7.3 The safe bearing capacity should be determined in accordance with IS:6403.

6.5.7.4 When in doubt regarding classification of BC soil-as to dry or wet, it is preferable to make NBC type foundation.

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. A1.03.

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 mm for un-regulated OHE. A 1350 mm embeddment 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.

6.5.10 Giving due consideration to the above, the most economical type of foundation should be adopted.

7.0 Contact Wire Height

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 

i) Regulated

a) Normal with 10 cm pre-sag 5.60 m
b) Old electrification works with 5 cm pre-sag.  5.55 m

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 4C to 65C. 5.75 m
b) Unregulated OHE designed  for areas with a temp. range of 15C to 65C. 5.65 m

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 4.02m 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 4.26b m arc not allowed on such lines. (Ref. Fig. A1.04).

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.

7.2.2 At level crossings, the minimum height shall be 5.50 m for both broad and metre gauges.

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.

Note : All Dimensions are in mm

FIG. A 1.04

7.4 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.

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 ma3e 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 over-line structures unless additional head room has been provided.

8.0 Stagger

8.1 Tangent track 

On tangent track, the contact wire is normally given a stagger of 200 mm at each support alternately on either 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 midspan not exceeding the permissible values given in Drg. No. ETI/OHE/G/00202.

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.

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 1, BG Metric Schedules of Dimensions - 1973.

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.

8.5 Un-insulated overlaps

At un-insulated overlaps, the stagger should conform 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 curved 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 200 mm from each other.

8.6 Insulated overlap

At insulated overlaps, stagger should conform to Drg. No. ETI/OHE/G/02131 sheet 1. On non-uniform curves 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 500mm from each other.

8 7 Neutral Sections

The stagger at overlap type neutral sections should conform to Fig. No. ETI/OHE/G/C2161, Sheet No. 1.

8.7.1 The stagger at section insulator type neutral section should be adopted that the stagger at the section insulator assembly is within the limit of 100mm (See para 11.1)

8.7.2 PTFE type neutral section shall be erected or talent track only. The stager shall be zero at support.

9.0 Encumbrance

9. 1 Normal

The encumbrance shall normally be 1.40 m.

9.2 Reduced encumbrance

The preferred values of reduced encumbrance for erection of overhead equipment under over-line structure are:

Span under over line structure Recommended encumbrances for span under for span under over-line structure Largest permissible adjacent spans
(m) (m) (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 docs not fall between first dropper and the support

"See para 5.5(1)

Note: i) The above values are applicable only to regulated 10 cm nominal pre-sag of contact wire.

ii) Special droppers may be required in spans under line structures

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 or less than 150 mm, the overhead equipment is deemed suitable upto 90km/h speed.

9.4 If section insulators are to be installed in spans under over-line structures, special designs will have to be evolved.

10.0 Droppers

10.1 The standard arrangement of droppers assembly shall be as per drawing No. ET1/OHE/P/1190.

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.

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.

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.

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.

11.0 Section Insulators

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 1.65 m. 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 it 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, though its provision on the main line should be avoided.

vi) In double line section, the runners should be in the trailing direction.

11.2 Permissible Speeds

11.2.1 On double line sections, with runners trailing, the section insulator assembly using porcelain sectioning insulators are fit for speeds upto 120km/h provided it is installed within the first one-tenth and one-third of the span.

11.2.2 In case the runners of the section insulator are facing or it is not installed within first 1 /3rd of the span the speed should be restricted to 80km/h. (Ref. Fig. A1.05).

FIG. A 1.05


12.0 Arrangement of Jumpers

12.1 In span jumpers

In span jumpers between the contact and catenary wires are provided at suitable equi-distant intervals as indicated in Drg. No. ETI/OHE/G/05101.

12.2 Turnout jumpers

The arrangement of connections at turnouts and at diamond crossings is indicated in Drg Nos. ET1/OHE/G/ 05103 and 05106 respectively.

12.3 G-Jumpers

The arrangement of jumpers at un-insulated overlaps is indicated in Drg No. ET1/OHE/G/05102.

12.4 Potential equalizing jumpers

The arrangement of potential equalizer jumpers is indicated in Drg. No. ETI/OHE/G/05104.

12.5 Anti-theft jumpers

The arrangement of anti-theft jumpers should be as indicated in Drg. No ETI/OHE/SK/432.

13.0 Tension Lengths

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.

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.

13.3 Bridges and tunnels

Where the catenary is anchored on the face of an over-line 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.

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.

13.5 Unregulated equipment

With unregulated equipment, tension, lengths of upto 2000 m

between anchors may be adopted on tangent as well as curved track.

13.5.1 Unregulated OHE shall not take off from main running lines.

13.6 Linkage of wire-runs

Wire-runs linking two or more mainline 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.

13.7 Anti-creep

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.

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.

14.0 Anchor Height

14.1 Crossing [misprint]- anchoring spans

Crossing of equipment of different elementary electrical sections in the anchoring span should be avoided as far as possible-

14.2 Cro [misprint]- unregulated equipments should be avoided. This may, however, be permitted if there is sufficient [misprint]- earance between the crossing contact wires under all conditions.

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.

14.4 Back to back anchors

Back to back anchoring of [misprint]-pments on the same mast may be adopted if both the terminations are of the fixed type (without counter weu[misprint]-

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. A1.06 may
be. adopted.

FIG. A 1.06

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 maximum 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.

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.

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 metalically to the anchor mast without providing the insulator in the anchor assembly.

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/fertiliser/cement plants.near loco sheds, ash pits, water columns, etc. long creepage path(1050 mm) insulator should be used on the anchoring arrangement.

15.0 Location of Overlap

15.1 Platform lines.

Overlaps serving platform lines should not be located opposite platform to avoid location of tensioning devices on the platforms. If it is unavoidable, half tension length may be adopted to avoid the provision of the regulating equipment on the platform. 

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 30.).

15.3 Cross-over

In the case of emergency cross-overs insulated overlaps in the direction of the trailing end should permit the longest train to be accommodated between the lock bar of the crossover switch and the first Intermediate mast of the overlap with a minimum margin of 50m. This distance may be taken as 850 m. The overlap in the rear should be located as dose as possible (Refer to sectioning arrangement of OHE -para 30).

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.

15.5 The arrangement of overlaps should be as per standard drawings (see para 5.6).

15.6 Feeders to overlaps

Feeding overlaps should be sufficiently away (See para 16.2) from the stop signals to facilitate coasting of trains (with pantograph lowered In the event of extension of feed from either side. Feeder may be run, If required, from the substation which Is usually located in the station areas.

16.0 Neutral Section

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.

16.2 Short Neutral Section of Section Insulator Assembly type

In heavily 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/h (Para 11.2.1).

Note: Short neutral section should be provided on half tension length not exceeding 500 m.

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.

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.

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.

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.

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.

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. A1.07).

FIG. A 1.07


16.6 Location of 'OPEN DJ' and CLOSE DJ' boards.

The indication boards to indicate the approaching neutral section and "OPEN DJ', 'CLOSE DJ' boards shall be provided according to drawing No. ETI/OHE/G/02161, Sheet 3.

16.6.1 Separate 'CLOSE DJ' boards are required for EMUs and loco hauled trains.

17.0 Points and Crossings

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.

17.1.1 The general arrangement of regulated overhead equipment at turnouts and cross-overs is shown in Drg. Nos. ETl/OHE/G/02141 and 02151. For high speed running, the overlap type should be provided.

17.1.2 The general arrangement of unregulated overhead equipment at turnouts and cross-overs is shown in Drg No. ETI/OHE/G/03151 and 03152, Sheet 1 & 2.

17.1.3 The leading dimensions of standard turnouts and crossings are given in Drg. Nos. RE/33/G/01104, sheet 1 and 01105, sheet 1 for the broad gauge and in Drg Nos. RE/33/G/01104, sheet 2 and 01105, sheet 2 for the metre gauge.

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 rum out taking off from main line shall be provided.

17.2.1 Adiamond 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. ET1/OHE/ G/02151).

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.

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.

18.0 Arrangement of Masts

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.

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.

18.3 Restrictions

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 should normally be staggered by 9 m, though a minimum stagger of 4.5 m is permissible in exceptional cases (Ref. fig. A1.08 (i).

18.3.2 If one of the masts mentioned is an anchor mast, and the anchor falls between the two masts, they should be staggered by 13.5 m minimum (Ref. Fig. A1.08(ii).

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. A1.08(iii).

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

FIG. A 1 .08



is available between the overhead equipment and the second mast. (See para 3.2). Cut in insulators or special anchor arrangements may be adopted in special cases (Ref. Fig. A1.08(iv)).

18.4 If masts are located on both sides of a track, they shall be staggered by 4.5 m (Ref: Fig. Al .08(v)).

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.

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.

18.7 Masts with counterweights should be avoided on platforms.

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.

FIG. A 1.10


18.9 Masts shall not be located in front of station entrances.

18.10 Masts shall not be located opposite to trolley refuges, close to culverts, subways and on bridges of length less than 50 m. 

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. A1.10).

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.

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.

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.

18.15 Support for OHE In tunnels

In the lined tunnels, stubs 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 stubs on one side.

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 sand covered with a concrete slab.

18.17 In case of wiring a petroleum siding special precaution shall be adopted as laid down.

19.0 Cantilever Arrangement

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.

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 drawing No. ET1/OHE/G/02106, Sheets 1 and 3.

19.2.1 Platform location

The arrangement of cantilever on platform shall be as per Drg. No. ETI/OHE/G/02104, Sheet 2.

19.3 Allowance for adjustment

The bracket assembly shall be such as to permit easy adjustment of the whole equipment after erection to cater for displacement of track during maintenance to the extent of 100 mm on either side of the track centre.

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.

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.

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 19.3.1 and 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.

19.4 Size of tubes

The size of stay tube and register arm tube is 28.4/33.7mm 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. Nos. ET1/OHE/G/00158 sheet 1,2 and 3 and 00159 sheet 1,2 & 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.

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.

19.7 Bridge & Tunnels

Bracket assembly of special design may be adopted on bridges and tunnels after making clearance study.

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 drawing No. ETI/OHE/P/3050 and RE/33/P/3100 shall be used.

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.

NEXT