20.0 Setting of Masts

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.

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 HI. 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 Broad gauge and Table II for Metre gauge,. Normally, the standard setting distance on broad gauge main lines on curves should not be less than the values given below:


a) On outside curves  Standard settings (m)
i) Radius of curvature greater than or equal to 875 m. 2.50 
ii) Radius of curvature less  than 875 m. 2.65
b) On inside curve .
i) Radius of curvature  greater than or equal to 3500 m. 2.90
ii) Radius of curvature greater than or equal to 2350 m but less than 3500,m. 3.05
iii) Radius of curvature  greater than or equal to 1150 m but less than 2350 m. 3.25
iv) Radius of curvature  greater than equal to 300 m, but less than 1150 m. 3.30



Curve allowance for Metre Gauge

Note: See Drg. No. ETI/OHE/G/00111 Sheet 2 also for reference.


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.

20.3 Masts with counter weights

In the case of masts with counterweights, 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.

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, staircase's, gang ways shall be avoided. No live conductor should be run over platforms.

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.

20.5.1 Colour light signals located outside 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 and beyond and upto 400m respectively.

ii) Where approach signal is provided and for signals other than distant signals.

The minimum setting of masts before the signal should be 3.25, 3.10, 3.05,2.90 and 2.75m for distance upto 50m, beyond and upto 70 m, beyond and upto 115 m, beyond and upto 160 m and beyond and upto 240 m respectively. 

b) Colour light signal with route indicators: 

i) With horizontal route indicator:

The minimum setting of masts before the signal should be 3.72, 3.50, 3.25, 3.05, 2.90 and 2.75 m for distances 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 masts before the signal should be 3.50,3.25,3.05,2.90 and 2.75 m for distances upto 70 m, beyond and upto 130 m, beyond and upto 170 m, beyond and upto 215 m, and beyond and upto 280 m respectively.

Note: 1. See Drg. No. ETI/OHE/G/00112 also. The setting may be reduced in special cases, conforming to Figs. 6 to 9 of ibid.

2) Setting distance may be reduced for starter signals of loop lines and yard lines.

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 special 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.

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.

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.

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).

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.


Standard Clear Spans for 'N' type portals

(Spans in metres)

Nominal range : 10.0 m to 20.0 m


Standard Clear Span for 'O' and 'G' type Portal 

Nominal range: 20.0 m to 30.0 m

21.0 Over-line Structure

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 provide as large clearance as possible.

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.

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 intermediate point.

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.

21A Polluted zone

Double insulation or insulator for polluted zones shall be used in the following cases:

(i) In tunnels (see para 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.

22.0 25 kV Feeders

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.

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.

22.3 Clearance from 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 it shall be 2 m under all conditions. In the case of 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.

23.0 Cross-Spans at Switching Stations

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.

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.

23.3 Multiple, track

The general arrangement of connections at the switching stations on double track and multiple track section are shown in drawing No. ET1/OHE/G/05125 ancfO5126 respectively.

24.0 Tramway type overhead equipment

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:

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.

24.1.2 Span

The maximum span is restricted to 63 m. The general arrangement is shown in Drg. No. ET1/OHE/G/04203.

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.

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.

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. ET1/OHE/G/04101. The principles applicable to normal OHE are applicable to this type of unregulated equipment except as specified below.

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.

24.2.2 Where a section insulator is to be provided the provision of a structure becomes obligatory.

25.0 Booster Transformers

25.1 100 kVA Booster Transformer 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.

25.2 The Booster transformers are located at an approximate spacing of 2.66 km between each other.

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 equi-distant 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 equi-distant 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 6f insulated overlap by locomotives pantograph, within the station limits except for very big stations.

26.0 Return Conductors

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 dose 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.

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. ETT/OHE/G/05307. The clearance between the return conductor and the overhead equipment should not be less than 400 mm under the worst conditions.

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.

26.3 Return conductors at over-bridges

At over-bridges return conductor: may be run straight through, if possible, as on normal structures.

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.

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.

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 ET1/0HE/ G/05413.

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 post and sectioning post on either side of the insulated overlap/neutral section. In these cases, mid-point should not be connected to rail.

27.0 LT Supply Transformer

27.1  Low tension power supply

230 V single phase power supply required for operation of substation equipment e.g. circuit breakers, 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 posts, stations, block-huts and at other outdoor locations e.g. level crossings with gate signals.

27 2 Capacity

LT supply transformers are of 10 kVA capacity. More than one transformer are provided at large station, yard etc.

27 3 Protection

LT supply transformers are protected only by a 25 kV, Amp. dropout fuse on the primary side and 63 A fuse (re-wireable d.c. type with 20 SWG tinned copper wire) on the secondary side.

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/PS1/036.

27.5 Substation L.T. Supply

At substation, in order to provide power to single phase transformer oil centrifuging / filtration plant, 100 kVA, 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.

28.0 Mast and Rail Bonds

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 Z9.1). 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.

28.2 Rail Bonds

The Rail bonds to connect the running rails longitudinally across a rail joint shall be in accordance with Drg. No. ETI/ OHE/P/7030. 

28.3 The cross bonds connecting two rails of track or rails of adjacent track shall be in accordance with Drg. No. ETI/ OHE/G/05251.

29.0 Earth Wires

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 aerial earth wire supported by the traction masts. The earth wire shall be divided into electrical sections not exceeding 1000m 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. ET1/OHE/G/05201.

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 1000m and shall be connected to earth electrodes provided not more than 500m apart and traction rail at both ends of the tunnel.

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.

29.4 Anchoring

Earth wires need be anchored only at termination of wire-runs.

30.0 Sections Arrangement

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.

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 has 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.

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.

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 120m away from the starting signal. This arrangement enables the trains to be received at the station. Fig.A1, 11 shows the layout.

FIG. A 1.11

30.3.2 The first loop line adjacent to the main is normally provided in the same elementary section as that of the main line. No sectioning is, therefore, required between the main line and the loop line. Only where there are group lines comprising of 2 loops or more, sectioning should be provided to include the loop lines in an independent elementary section. In case of large number of loop lines, the chances of damage to the OHE being more, they should be isolated to keep the main line operative. The arrangement is shown in Fig.A1. 12.

FIG. A 1.12

30.3.3 Stations provided with emergency cross-overs:

At the stations provided with emergency cross-overs, the diversion of trains from up-track to down-track and vice versa and also the diversion of trains coming on the wrong track to the correct track is possible. Isolation at such stations should be provided in accordance with Fig.A1. 13 so that the longest train can be pulled beyond the crossover before backing. It is advisable to keep the advance starter sufficiently away from the cross-over so that the longest train length can be accommodated between the cross-over and the advance starter. Otherwise, provision should be made in the station working rules for shunting of the trains beyond advance starter.

Fig.A1. 13

30.3.4 Stations provided with emergency cross-over and loop lines:

At stations having loop lines the isolation arrangement as shown in Fig: A1. 14 & A1. 15 should be adopted. Where space is available, the insulated over-tap and the isolator should be provided between the points, A & B as shown in Fig: A 1.14. Otherwise, the insulated overlap should be provided before the point and a section insulator provided in the loop line as shown in Fig:A1. 15.

Fig: A1. 14 & A1. 15


30.3.5 Sections having one or more common loops situated on one side of the track:

Generally the common loop is situated on one side of the main track. Such common loop can be electrically connected only to the adjoining main line. Stations with such a common loop also have a facing cross-over which can be beneficially used for diversion of trains from one line to the other without reversing. The sectioning should permit diversion of trains from one line to the other in both the directions. The sectioning given in Fig: A1.16 would meet these requirements.

FIG. A 1.18

Note : Where space is available the insulated overlap and isolator should preferably be provided between (A) & (B)

For layouts having a group of (common) loops on one side, sectioning arrangement shown in Fig. A1.17 should be followed.

Where an SSP is located the sectioning arrangement as shown in Fig. A1.18 could be adopted. However, this arrangement cannot be adopted at feeding posts because in that case the cross-over would be connected to two different sectors and in case of extension of feed, the section-insulator would be connected to two different phases and subjected to 44 kV. Passage of electric locos in such condition would result in bridging of 2 phases which may ' damage the section insulator assembly.

30.3.6 Common loop situated in between the two main lines:

At some stations, the common loop is provided in between the two main lines. Such stations provided ideal arrangements for sectioning, as the common loop can be connected to either up or down main lines through a set of inter-locked isolators. The sectioning arrangement is indicated in Fig:A1. 19.

30.3.7 Sectioning for the loco sheds and major yards: Loco sheds and major yards are prone to frequent flash-over of insulators due to pollution caused by steam/diesel shunting locomotives and also due to switching surges from the loco transformer and sparking of rod-gap which result in tripping of feeder breaker affecting power supply to the main line. It is, therefore, advisable to provide a separate feeder with a circuit breaker and required protection for all major yards and electric loco sheds. If the yard/shed is within 4 km from the traction sub-station, a separate feeder can be economically run. If the yard/shed is beyond 4 km the power supply may be given by an interrupter located in the SSP with provision to supply from either UP or DOWN line. In case the circuit breaker or interrupter is out of service for maintenance, alternative arrangement is made to tap the OHE, directly through an inter-locked isolator. These arrangements are shown in drawing No. ETI/PSI/704. Major yards are normally separated in Up and Down yards. Each yard is again sub-divided as Reception yard, Despatch yard, Sorting yard, Marshalling yard etc. These yards, if electrified, should be electrically independent of each other. Each yard, if it consists of more than four lines, shall be divided into two or more elementary sections consisting of group of 3 to 4 lines each. Each elementary section should be fed by an isolator from a bus connected to the yard interrupter in such a way that interruption to any elementary section should cause minimum upset to the yard working.

31.0 Numbering of OHE Masts

31.1 Necessity

As the P&T overhead telegraph lines on the 25 kv ac electrified routes are replaced by under-ground screened cable, the OHE masts are used to indicate the kilometerage of the track. The mast number is also used for identification of the section of overhead equipment (OHE) and the line to which it belongs. There are normally 15 to 18 masts in one kilometer and each mast is given a number in serial order starting from kilometer post. The number is scribed in two parts, the kilometer being shown above the line and the mast serial number below the line. For example, (70/1) indicates the first mast from the kilometer post No. 70 on the Up line.

31.2 Single line section

In single line section where there is no chance of future doubling, numbering is done progressively in the direction of increase of kilometerage, i.e. 70/1, 70/2,etc. In case where doubling is anticipated in future the system of numbering will be according to para 31.3.

31.3 Double line section

All traction masts on Up track shall be given odd numbers, i.e. 75/1,75/3, 75/5 etc. and that on Down track even numbers as 75/2, 75/4, 75/6,etc. 1 and 2 are the serial number of the masts immediately after every kilometer post. Numbering is done progressively in the direction of increase of kilometerage.

31.3.1 Since the OHE masts on Up and Down tracks are normally located opposite each other, the mast numbers 1 & 2 would be in one line, and mast numbers 3 & 4 would be in in one line and so on.

31.3.2 In case the spans on the Up and down lines are not equal and the masts are not in one line, the masts shall be numbered in such a way that higher serial number does not occur at a lower kilometerage (see Fig:A1 .20).

31.4 Multiple section

In multiple track section, suffix 'A' is to be given to the multiple track mast. For instance, in case of a section consisting of UP main, DOWN main and up slow and Down slow track, the slow track masts shall be numbered as 75/1A, 75/3A, etc. for UP slow line and 75/2A.75/4A, etc. for DOWN slow line. Uprights of portals, erected in multiple track sections shall be numbered with reference to main line only, i.e.75/1,75/2 etc.

31.5 Numbering of masts of loops and sidings in station yards:

31.5.1 Individual masts .

Single cantilever and double cantilever mast supporting OHEs of tracks on either side ( umbrella type) for loops and sidings shall bear the station coda and serial number in one thousands series (1000).The station code shall be given on above the horizontal line and the serial number below it. Masts of UP loops and siding on UP line side shall be given odd number of 1001,1003,1005 etc. In the order of progressive chainage, irrespective of the n umber of loops and the masts on the DOWN loops and sidings on*he DOWN line side shall be given even numbers 1002,1004,1006 etc.

In case several independent cantilever masts for different loops are located at the same chainage, loop mast nearest to the main track should bear the lowest number in the series (see Fig. 10). This system of numbering is applied from one end of a yard in the kilometerag of the starting point and progressively higher numbers is given in the direction of increase in chainage whether it is UP or DOWN yard. The numbering does not indicate the kilometerage.

31.5.2 (a) In case a portal is provided, the upright of the portal nearest to the main track shall be given a number in 2000 series, the other upright of the portal shall be given a number in 3000 series. In case of 3-leg portals, the farthest leg from the main track shall be given a number in 4000 series.

31.5.2(b) In case a portal is covering both UP and DOWN main line as well as loops and siding, the numbering shall be as for the main line tracks, irrespective of the fact that it also covers loops.

31.5.2 (c) In case of a portal, covering UP main line and a number of UP side secondary tracks, the upright which is located near the main track and service the main line shall be numbered with respect to the main track. Other upright shall be given the same number with suffix 'A'.

31.5.2(d) The uprights of portals in UP yard shall have odd numbers i.e. 2001-3001, 2003-3003 etc. and the uprights in DOWN yard shall have even numbers i.e. 2002-3002, 2004-3004 etc.

31.6 Head Span mast

Procedure of numbering the mast of a head span shall be the same as that for portals detailed in 31.5.2 except that the mast of the head span shall be given numbers in 5000, 6000 and 7000 series as detailed in 31.5.2(a).

31.7 Branch line masts

All masts on branch lines taking off from the main line are to be given a prefix letter indicative of the branch line mast e.g. Pradhankanta - Pathardih which takes off from the main line at Pradhankanta is given a prefix letter 'P' which is indicating of Pathardih viz. 70/14 P. 

31.8 Alternative numbering

Mast on loop/yard lines may also be numbered with a letter/word prefixed indicating the nomenclature of the line e.g. the mast numbers on a goods line in passenger station area may be numbered as G1, G2 etc. below the station code. The mast numbers on engine run-round line may be numbered as ELI, EL2 etc. This method may be adopted when additional lines are provided or wired subsequently.

31.9 Switching station masts

Mast at the switching station are numbered with the station code of the switching station for example KGP/1 which means Kharagpur Switching Station, mast No.,1.

32.0 Numbering of Equipment

32. 1 Abbreviation of equipments

To identify the location of the equipments covering OHE and Switching stations a code for identifying the type of equipment followed by a S. No. is given.

AT: 25 kV/230V Auxiliary Transformers.
BT: Booster transformers.
BM: Interruptor for main lines.
BS: Interruptor for yard lines.
BX: Bus coupler interruptor.
BC: Bus coupler isolator.
CB: Circuit breakers.
CT: Current Transformers. 
DP: Double pole isolators. '
LA: Lightning arrester.
PT: Potential Transformer.
SF: Single pole Isolator at Switching Station.
SP: Single pole isolator at substation.
SM: Isolator for main lines.
SS: Isolator for secondary lines loops and yards.
TR: Power transformer.

32.2 Numbering circuit breakers

Each power transformer, current transformer, potential transformer is given a serial number in a Railway starting from 01 except 25 kV circuit breakers which shall be according to para 32.2.2.

32.2.1 High voltage (132/110/66 kV) circuit breakers are given two digit numbers progressively increasing in the direction of increasing kilometerage starting from 01. For example, the first high voltage circuit breaker will be numbered as CB/01, 02, 03.

32.2.2 25 kV circuit breakers are given three digit numbers - odd nos. e.g. CB/101, 103, 105 etc. for feeder breakers and even nos. CB/100, 102, 104 etc. for transformers circuit breakers.

32.3 The serial number of transformers and circuit breakers also follow geographical sequence within a substation/feeding post. Lower number is given for the equipment connecting at less kilometerage and higher number of for the equipment connected to higher kilometerage.

32.4 Interruptors

The main line 25 kV interruptors are numbered serial wise progressively increasing from a datum point on a railway, e.g. BM/01.02, 03 etc.

32.5 Yard Interruptors. The yard line interruptors are numbered serial wise on a railway i.e., BS01, 02, 03 etc. Where there are different yards for up and down direction, the interruptor for UP yard is given odd number and that for DOWN yard is given even number.

FIG. A 1.21

32.6 Other equipment.

The number of other equipments is serial wise progressively increasing irrespective of up or down line on a railway preferably according to increasing chainage.

32.7 Numbering of elementary section

Elementary section for main line are given a number beginning with the number of interruptor which feeds it (See Fig. A1.21). 

32.7.1 The first two/three digits of the number for an elementary section indicate the governing interruptor and last two digits indicate the progressive serial numbers. This progressive serial number for UP line are odd number starting with 01 for example 3401, 3403 etc. and even number for DOWN line starting with 02 such as 3502, 3504 etc.

32.7.2 Yard elementary sections.

The elementary section number of yard lines shall be provided with the number of the isolator which controls the feed of the line/s with a prefix 'X'. For example, if an isolator, no. 118 controls the feed of the lines of the receiving yard the elementary section number of the lines is 'XI18".

32.7.3 Elementary section for two sides

If the line/s are fed by an inter-locked isolator numbering of the elementary section should corresponds to the isolator number which normally feeds the line/s.

32.7.4 Type of number plates.

The number plates shall be in accordance with drawing no. RE/33/P/7501.