signal cable

SIGNALLING CABLE

1. INTRODUCTION

A Cable can be defined as a number of insulated electrical conductors bunched in to acompact form by providing mechanical protection and electrical insulation.

Cable can be classified as Underground Cable (laid under ground), Submarine cable ( laidunder water), Aerial cable (laid over head) and Indoor cable ( laid along the walls ofbuilding. However, in Railways only Underground and Indoor Signalling Cables are used.

This handbook covers Construction. Laying, Jointing, Testing, and Maintenance ofSignalling Cables as per Indian Railway Standard Specifications No. S:63-89, S-35/93,S:76-89 and IS:1554. These Specifications cover the requirements and tests for armouredand unarmoured single core and multicore copper conductor, PVC insulated sheathed andunsheathed cables for Indoor and Outdoor Railway Signalling.

2. BRIEF DESCRIPTION

The Cable is circular throughout its length and is free from any physical defects. Themeasured length of cable on any drum should not vary by more than + 0.2% of drum length(CL.4.2 of S/63-89) Single core cables may be supplied in coils of 100 + 0.5 metres (CL.6.1of S/63-89) .

Unless otherwise specified, the multicore cable is supplied in length of 500 metres each.With the prior approval of cosignee, cable upto 9 cores may be supplied in length of 1000metres each. Non-standard lengths each not less than 100 metres shall be acceptable upto4% of the total quantity ordered (CL.6.4 of S/63-89).

The cable ends are sealed to prevent moisture entry. The length of the cable is marked in asequential manner over the outer sheath at intervals of one metre with an accuracy of +0.2%. The Cable drum number shall be legibly embossed at every one metre or less on thePVC outer sheath throughout the length of cable (CL.4.4 of S/63-89).

The following information shall be stencilled on the drum in black paint over yellowpainted background (CL.4.3 of S/63-89):

a) Manufacturer’s name, brand name or trade mark.b) IRS Specification number.c) Type of cable and voltage grade.d) Number of cores.e) Nominal cross-sectional area of conductor.f) Colour of cores (In case of single core cable).g) Number of lengths on drums/in coils ( if more than 1)h) Length of the cable on the drum/coil.i) Initial and final sequential marking for the length.j) Direction of rotation of drum (by means of arrow).k) Approximate gross weight.l) Country of manufacture.m) Month and year of manufacture.

CAMTECH/99/S/SIG-CAB/1.0 2

2.1 Advantages of Underground Cable

1. Overhead lines may come in contact with trees, bushes, etc. and cause lowinsulation.

2. Due to natural causes and ravages of humans beings, overhead lines are prone to ahigher fault incidence.

3. Due to headway considerations the maximum number of pairs on a pole route islimited to 16.

By using underground cable all these disadvantages can be minimised.

3. TYPES AND USE

3.1 Outdoor Signalling Cable Signalling cables for outdoor circuits should be laid underground. Following types ofunderground cables are normally used in Railway Signalling.

A) Main Cable

These cables are used for extending signalling circuits from cabins to location boxes andbetween location boxes. Normally 2, 4, 6, 9, 12, 18, 24, 30 and 37 cores, armoured cablesare recommended for use as main cable.

B) Tail Cable

Tail Cables are used for extending signalling circuits from location boxes to signallinggears. Cables of 5 core to 12 core are normally used as tail cables.

C) Power Cable

These cables are used for extending 230/110 Volt AC supply. Normally aluminium cables2/16 Sq.mm, 2/25 Sq.mm, 2/35 Sq.mm, 3/16 Sq.mm, 3/25 Sq.mm, 3/35 Sq.mm sizes areused. In addition, 2/10 Sq.mm. copper cable is also used.

SIGNALLING CABLE JUNE’ 1999

3.2 Indoor Signalling Cable

Indoor Signalling Cable is used for indoor wiring of signalling circuits. Following cablesare normally being used for indoor signalling applications :

TABLE 3.1 : ‘TYPES OF INDOOR CABLES & USES’

Sr.No.

Type ofCable

Use

1 16/0.2 mm Wiring of Q series and Shelf type Relays2 3/0.75 mm Wiring of shelf type Relays3 1/1.4 mm Wiring of lever lock, Circuit Controller



4 7/1.4 mm Power Supply i.e Battery Room toCharger and Busbar

5 1/ 2.5 mm Wiring of Boot leg (Track Circuit)6 40/0.6 mm

60/0.6 mmRack to Rack wiring in metal to metaltype relay installations.

7 24/1.0 mm40/1.0 mm60/1.0 mm

For wiring from control or Relay rackupto Cable termination rack for outdoorcircuits i.e signal and point.

8 1/0.6 mm From tagblock to tagblock (except Signal and Point)

9 1/1.0 mm From tagblock to tagblock For Signal and Point)

10 36/0.3 mm For wiring of track relays from MDF

Note : Busbar conductors shall be so chosen that voltage drop is not more than 0.5% ofbusbar voltage between battery terminals & busbar in equipment room.

4. CONSTRUCTION

Construction of a typical 30 core, un-screened, armoured cable is shown below:

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I. CONDUCTOR

Circular conductors are used for Railway Signalling applications.

The dimensions, nominal weights and resistance of conductors is shown in Annexure ‘A’ (Page 55 ).

II. INSULATION

PVC compound covering is provided on conductors for electrical isolation between them.Insulation should be free from any joints or repairs. It shall fit closely on the conductor butnot adhere to it so that it is possible to remove it easily without damage to the coductor.

The insulation resistance of each core shall not be less than 5.0 Megaohm /kilometre at 50deg.C. For details see Annexure ‘D’ at page No.58.

The average thickness of the insulation is shown in Annexure ‘B’ ( Page no. 56 ).

III. CORE

A core can be defined as an insulated conductor. Cores of cables shall be identified bydifferent colours of PVC insulation. Colour scheme shall be as follows (CL3.2.5 of S. 63-89 ) :

1 Core - Red, Black, Yellow, Blue or Red2 Cores - Red and Black3 Cores - Red, Yellow and Blue4 Cores - Red, Yellow, Blue and Black5 Cores - Red, Yellow, Blue , Black and Grey 6 Cores and -Two adjacentcores in each layer above shall be blue and yellow. Remaining cores shall be grey.

For a single core in the centre of a multicore cable, red or black colour is used. For 2, 3, 4or 5 centre cores the colours correspond to those specified for 2, 3, 4 or 5 core cables,respectively, as described above.

Alternatively, the cores of cables with 6 cores and above may be identified by numbers 1,2, 3, 4, 5......... printed indelibly at intervals of not more than 50mm.

In that case the insulation of cores is of grey colour and printing of number is black. Thecore is numbered sequentially in clockwise direction, starting with number 1 for the innerlayer.

The numbers are printed in Hindu-Arabic numerics on the outer surface of the cores. Thenumbers are legible and consecutive number is inverted in relation to each other.

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When the number is a single numeral, a dash is placed underneath it. If the numberconsists of two numerals, these are disposed one below the other and a dash is placedbelow the lower numeral.

LAYING UP OF CORES

The core of twin, three and multicore cables is laid up together with suitable lay. Theoutermost layer has right-hand lay and the successive layers are laid with opposite lay.

The cores of a layer is cross each other. The sequence of the cores is maintainedthroughout the length of the cable. The recommended plan for lay up of cores upto 37 isshown at Annexure ‘C’ ( Page No. 57).

Example:

A typical laying of core of 30 - core cable is shown below. As shown in Annexure ‘C’,there shall be 3 layers in 30 pairs cable. Lay up shall be 4 - 10 - 16 i.e. first layer, secondlayer and third layer shall have 4, 10 and 16 cores, respectively.

Colour Scheme

Colour scheme of a typical 30 - core cable is shown below:

IV. PVC COVER

A PVC covering called inner sheath is applied over cores for protection of cores fromarmour.

V. ARMOUR

One layer of armouring of aluminium or galvanised mild steel wires is applied forprotection. Armouring shall be applied over the insulation in the case of single core cables

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and over the inner sheath in case of multicore cables. Wire armouring is provided upto 9cores. Above 9 cores armouring can be of wires or strips.

VI. OUTER PVC COVER

A PVC cover is applied for protection from water penetration. It is also called outersheath. Galvanised steel strips armouring is not used in up to 9 core cables.

5. CABLE LAYING

5.1 Storing and Transportation of Cable

• Cable drums shall not be stacked on flat side. Suitable stoppers shall be placed forstability of the drums.

• Cable drums shall have easy access for lifting and moving.• When rolling the cable drum either for unloading or transportation, the drum shall

always be rotated in the direction of the “arrow” which is marked on the drum.• The drum shall not be rolled over objects that could cause damage to the protective

battens of the cable.• When unloading is carried out from the vehicle the drum shall not be dropped on the

ground directly to avoid damage due to impact. Fork lifter or ramp shall be used.• During all stages of storage, it is essential that the ends of the cable are effectively

sealed by end cap or in any other approved manner to avoid water entry into the cable.• It is desirable that cable drums are stored in covered shed to protect against direct

exposure to sun. 5.2 Planning

• While planning for cabling on a route, the number of conductors required, dependingupon the circuits required should be first determined. Recommended core sizes as perspecifications shall be used.

• Adequate spare conductors to a minimum of 20% of the total conductors used shall be

provided for in each main cable up to the farthest point zone, beyond this there shouldbe a minimum of 10% spare conductors of the total conductors used. No spareconductors are required if the total number of conductors used is 3 or less.

• Where a number of cables have been laid along a route, the circuits shall be so

distributed that cables can be disconnected for maintenance purpose with the leastpossible dislocation to traffic. Line wise and, if necessary, function wise cable shall beprovided. Auxiliary signals shall be taken in different cables.

• After deciding the size and the number of conductors in the different types of cables

to be used on a route, a foot survey along the track should be done to determine thebest route for the cable.

• The route shall be shown clearly on a cable route plan showing the actual alignment of

track, giving offsets from permanent way or permanent structures. The diagram shouldindicate the various road and track crossings, crossing with power cables, water andsewage mains and other points of importance. It is



preferable to chart the route on a route plan on which the existing routes of power cables, etc.are shown. Changes, if any, should be incorporated in the chart/plan.

• Cable route plan shall also be approved by Engineering and Electrical departments. • As far as possible, low lying areas, platform copings, drainages, hutments, rocky

terrains, points and crossings, etc. should be avoided. • Separate cables of suitable size shall be laid for point operation.

5.3 Paying out of the Cable • For paying out cables, the cable drums shall be mounted on the cable wheels. It should be

ensured that no kink is formed while paying out the cable. • The drum on the wheel shall be brought to one end of the trench and the end of the cable

freed. Cable should be laid along the trench.• A party of labourers shall move along the trench carrying cable at suitable intervals so that

the cable is not damaged due to dragging along the ground or bent unduly.• Before the cable is laid in the trench, a visual inspection of cable shall be made to see that

there is no damage to the cable. It shall be tested for insulation and continuity of the cores.Thereafter the cable shall be laid into the trench. Record of insulation and loop resistancemust be maintained.

• In cases where the wheels are not available, the drum shall be mounted on an axle at one

end of the trench and cable paid out and carried by labourers.• In no case shall the drum be rolled off on to the road for laying the cable and the cable

dragged on the ground for laying purposes.• Whenever mechanised equipment is used, the work shall be carried out by a trained

operator under the supervision of SE/JE (Signal) incharge of the work.• Where the cable drum is in damaged condition the cable may be placed on a horizontal

revolving platform.• In no case shall the cable be unwound by taking off from the side of the drum as this will

cause formation of twist in the cable.• Paying out of cable should be done by rotating the cable drum and not by pulling the cable

with excessive force. 5.4 Laying cable above ground • In AC electrified areas cables shall be laid underground only. Signalling cables for out

door circuits should not normally be laid above ground. In exceptionable cases where itbecomes unavoidable, the following precautions should be taken:

(i) The cable should be suspended in wooden cleats, from cable hangers or in any otherapproved manner so that no mechanical damage occurs to the cable even under exposedcondition. (ii) The cable supports shall be so spaced as to avoid sag.

(iii) In station yards, cable shall be laid in suitably protected ducts.



(iv) Indoor signalling cable should normally be laid on ladders, channels or in any other approvedmanner. The cable should be neatly tied/laced.

5.5 Underground cable Cables may be laid underground, either in trenchs, in ducts, in cement troughs, in pipes or in any

other approved manner. 5.51 Laying the Cables in ducts • RCC or any other approved type of ducts may be used for laying the cable. • The ducts shall have suitable covers. • The ducts shall be of such design as to prevent water collecting in the duct. • When cables are laid in rocky area, it is desirable to protect them with split RCC ducts of

suitable design. • Where it is necessary to take the cable between the tracks, it shall be carried in trunking

kept sufficiently below the ballast level. • Where several cables of different categories have to be laid in the same trench, they shall

be placed as far as possible in the following order starting from the main track side, so thatin the event of failures the maintenance staff may easily recognise the damaged cables:

i) Telecommunication Cable ii) Signalling Cable or Cables iii) Power Cable

• Cables belonging to the Department of Telecomm. or the Electrical Department must notbe laid in the same trench along with Signal & Telecom. cables. A distance ofapproximately 10 cm. must be maintained between telecommunication and signalling

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cables. The signalling cables must be separated from power cables, carrying more than110 volts, by a row of bricks between them.

5.52 Laying Cable shall be laid generally as per instructions given. However, special precautions to be taken in

the station yards etc. where a number of other utilities may be existing, may be detailed ina joint circular issued by the Civil Engineering, Signalling and Electrical departments ofthe Railway.

• The cable laid parallel to the track shall normally be buried at a depth of 0.80 metres from

ground level while those laid across the track must be 1.0 metre below the rail flanges.However, in case of rocky soil, the depth may be reduced suitably. When it concerns thelaying of tail cables which serve the track apparatus, etc, the depth should not be less than0.50 metres. In theft-prone areas the cables may be laid at a depth of 1.2 metre withanchoring at every 10 metre.

• The width of manually made cable trenches should be commensurate with number of

cables. The minimum width shall be kept as 0.3 metre. The bottom of the cable trenchshould be levelled and cleared of any sharp materials. In the soft ground, the cable shouldbe laid at the bottom of the trench previously levelled. In the rocky ground, the cableshould be laid on a layer of sand or sifted earth of 0.05 metre thickness previouslydeposited at the bottom of the trench. In both the cases the cable should be covered witha layer of sand or sifted earth of 0.10 metre thickness and thereafter a protective cover oftrough or a layer of bricks should be placed.

5.53 Cable Crossing

• When a cable has to cross the track, it should be ensured that:-

I) The cable crosses the track at right angles,ii) The cable does not cross the track under points and crossings, and

iii) The cable is laid in concrete/GI/CI/PVC pipes, suitable ducts or in any otherapproved manner while crossing the track.

• Wherever practical, the cable may be taken underground across the drain bed at a suitabledepth for crossing small culverts with low flood level.

When cables have to cross a metallic bridge, they should be placed inside a metallic trough which

may be filled, as an anti-theft measure, with sealing compound. The cable should besupported across the bridge in a manner which would involve minimum vibrations tothe cable and which will

facilitate maintenance work. Adequate cable length to the extent of 2 to 3 metres shall be madeavailable at the approaches of the bridge.

• Cable markers wherever provided should be placed at suitable intervals and at diversionpoints.

• While laying the cables in accordance with the above instructions, the followinginstructions should be adhered to for the safety of the track:

i) Outside the station limits, the cables should generally be laid at not less than 5.5 metres

from the centre of the nearest track.



ii) Within the station limits, the trenches shall preferably be dug at a distance of not less than 3

metres from the centre of the track, width of the trench being outside the 3 metresdistance.

iii) At each end of the main cable an extra loop length of 6 to 8 metres should be kept.

• It is desirable that the excavation of the trenches is not done in long lengths and does notremain uncovered for a long period. It is preferable that cables are laid and refilling doneon the same day.

• Back filling of the trenches should be done properly. The earth excavated shall be put

back in the trench, rammed and consolidated.• During excavation, the earth of the trenches should not be thrown on the ballast. The earth

should be thrown by the side of the trenches away from the track.• In places where cables are to be laid within 1 metre from sleeper end, digging beyond 0.50

metre shall be done in the presence of an official from Engg.Dept., and the laying of thecable and refilling of trench should be done with least delay.

• Cable joints of approved type shall only be used.• The work shall be supervised at site personally by an official of the Signal and

Telecommunication department not below the rank of a Sectional Engineer/JuniorEngineer(Signal).

6. WIRING OF SIGNALLING CIRCUITS The following instructions are to be followed for carrying out wiring of Signalling Circuits. • Wiring or alteration of signalling circuits shall be in accordance with approved circuit

diagrams. • Alternations to existing circuits may be resorted to at site only in emergency cases under the

direct supervision of an officer. In such cases the alteration should be immediately advised toapproving authority for approved wiring diagrams.

• “As made” circuit diagram must be submitted by divisions to HQs. on completion of

alterations to wiring and the final diagram should be as per actual wiring at site. This shouldbe signed by the Section Engineer (Signal) carrying out the works and the officer opening theworks.

6.1 Principles of Wiring • Wiring between any two points shall be done in one length and no joints shall be made in any

wire run.• Wire runs shall be as short as possible. Care should be taken to avoid damage to the conductor

while peeling off insulation. Stripper-cum-cutter of approved design shall only be used. • All wires in a wiring bunch shall be properly terminated and no loose wire shall be left in the

bunch without being terminated. Conductors and terminals shall be cleaned before makingconnections. Bunching tape & button should be used.

• Wires shall not be pulled out after lacing of wires. This can damage insulation of other wires.• Adequate spare conductors to a minium of 20% of the total conductors used shall be provided

for each main cable upto the farthest point zone. Beyond this there should be a minium of



10% spare conductors of the total conductors used. No spare conductors are required if thetotal number of conductors used is three or less.( CL 9.2 of S36-87).

• Suitable conductor sizes shall be used to ensure that the voltage drop on line is not more than10% (CL 9.3 of S 36-87).

• When cables are to be terminated or jointed underground in outside location boxes, these shallbe brought up over the ground and terminated or jointed in water-tight junction boxes (CL 9.4of S 36-87).

• At least two cores cable shall be provided between two ends of the yard to cater for telephonecommunication for maintenance purposes in non-RE area (CL 9.5 of S 36-87).

6.2 Wiring Practices The following practices shall be adopted for wiring: • The return negative of various circuit elements must be separately terminated at the negative

busbars. In no case a common return (negative) wire shall be used.• All terminals shall be screwed tight and washers shall be used under the screw head of

terminal nuts.• Ends of wires shall be bent round the terminal in clockwise direction unless an eyelet/lug is

used.• Precautions shall be taken to prevent kinks and twists in the wires used. If there is any kink it

must be removed.• Insulations must not be damaged and must be kept free from oil, grease, acid and alkali.• When cables/wires are taken through a duct in the wall, proper PVC pipes must be provided

or any other approved method should be adopted.• The duct for wiring should not be closed on either side. Rodents may settle in the closed duct

and damage the wiring.• As a safeguard against rodent attack, the wiring from Circuit Controller/Lever Lock to the

relay room should be taken through a cable without removing the PVC sheath and armour, inlieu of 16/0.2 mm. PVC wires.

• Terminal Blocks to RDSO design SA 23756 (Adv/Alt.2) shall only be used. • ARA terminals are to be properly fixed in vertical/ horizontal rows. Terminals of any special

design to be used with specific approval of CSTE. • The terminals should be fixed on standard Relay Rack.

6.3 Wiring Materials

The following wiring materials shall be used for different types of relay. 6.3.1 Wiring inside one rack (Intra-rack wiring) for shelf type and plug-in-type metal-to-carbon

contact relays (Q series): • 3/0.75 mm wire shall be used for wiring of Shelf type relays and 16/0.2 mm wire shall be used

for wiring of Q Series relays. Wiring between Shelf Type relay and Q Series relays shall bedone with 16/0.2 mm wire.

• The eyelets shall be connected to the wire on terminal by hand operated crimping tool.



• Appropriate eyelets and crimping tools shall be used. • For terminating the 16/0.2 mm wires to the connectors of plug-in-type relays (Non-proved

type) with metal to carbon contacts, the wire head shall be first tinned, inserted into theconnector and crimped. The wire shall again be soldered at the connector.

6.3.2 Wiring from one relay rack to another relay rack (Inter rack wiring) using metal to carbon

contact plug-in-type and shelf type relays: • Multicore (or alternatively single core) unarmoured cable of 1.0 mm (S-76 or S-63) shall be

used for wiring. Intermediaries like terminal blocks, tag blocks etc. shall not be used. • If the use of intermediate terminal block/tag block is unavoidable, the same shall be of

standard design of any type conforming to IRS specification No. S71/87. Spare contacts neednot be wired.

6.3.3 Wiring of proved type (Metal to Metal contact)

Relays: For rack to rack/IDF wiring 60/0.6 or 40/0.6 mm cable shall be used. For wiring from rack tocable termination rack 60/1.0, 40/1.0, 24/1.0 mm size wire shall be used. Size of conductorshall be chosen based on circuit current to be carried by it. 1/0.6 and .1/0.1 mm cable shall beused for tag block to tag block wiring.

6.4 Essentials of wiring in relay rooms and location boxes.

• All wiring used in the Cabin and Locations shall be done in a neat manner so that the wiringdoes not in any way prevent the proper functioning over working parts and is easily accessiblefor maintenance (CL 10.2 of S 36-87).

• At all locations and cabins wire entrance of adequate size, conveniently located for ease of

approach to terminals and other equipment so arranged as to protect the wires from mechanicalinjury, shall be provided. Such wire entrance shall be plugged and sealed with suitablecompound after the wiring is completed (CL 10.4 of S 36-87).

• Relay to Relay wiring on the same rack should as far as possible be direct without

intermediaries like tag blocks/terminals(CL 10.5.2 of S 36-87). • Identification Marker for Identifying the terminals and tags shall be provided at each terminal

to identify the circuits for which it is used (CL 10.6 of S 36-87). • Relay racks shall have sufficient capacity to take additional equipment to the extent of 15% of

equipment provided to permit additions and alterations (CL 10.7 of S 36-87). • Charts showing the positions of relays on relay racks and contact arrangement of relays

indicating the spare and used contacts shall be prepared and kept in the cabin (CL 10.8 of S 36-87).

Marking and Labelling



• Conductor marking and labelling shall be done by means of plastic ferrules with embossed

letters. Alternatively, a chain of pre-embossed plastic ferrules can also be used. • Terminal numbers should be properly marked. Bunching & Lacing

• All the inter-relay wirings and inter rack wiring shall be neatly bunched in a circular shape.

• Black twine or plastic strip of suitable design shall only be used for lacing of the wires. NOTE : In case power is to be fed to any outdoor equipment through common feeders fromoutside locations, a ring main shall be provided preferably in different cable and on differentroute, so that the failure of a part of the feeder or a fuse blowing off shall not affect the feed to theoutdoor equipment in the whole yard (CL 12.5 of S 36-87). 6.5 Earth connections • Separate earth shall be provided for each block instrument at a station. • The resistance of earth for signalling circuits shall not exceed 10 ohms. If it is not possible to

reduce the earth resistance below 10 ohms additional earth may be provided in parrallel. • Where more than one earth is used, the distance between earthing pipes shall not be less than

3 metre.The conductor leading to these earthings shall be electrically insulated from each other throughoutand also from metallic structures connected to different earths.

Method of obtaining Earth

• Earthing arrangement shall normally consist of one or more galvanized iron pipes of not lessthan 38 mm internal diameter and not less than 2.5 metre in length with a spike at one endand a lug at the other for connecting the earth lead or galvanized iron/steel rods of not lessthan 16 mm dia or copper rods of not less than 12.5 mm dia and of not less than 2.5 metrelength. While the pipe is embedded vertically the rod electrodes are driven vertically in theground .When a rocky soil is encounterd at a depth of less than 2.0 metres of the length ofthis electrode the electrode may be buried inclined to the vertical the inclination being limitedto 30 degrees from the vertical. Earth electrodes shall not be buried in a position likely tocause an obstruction or where it is likely to be damaged.

• The resistance of these electrodes in a soil of uniform resistivity decreases with depth but

there is little to be gained by driving the rod to more than 3 to 3.5 metres. Also the decrease inthe resistance with increase in rod diameter is not significant. It is therefore recommended touse the rod electrodes of such diameters as can easily withstand the strain of driving.



Earthing Leads • Earth wires shall be protected against mechanical damage and possibility of corrosion

particularly at the point of connection of earth electrode. • The earthing lead shall be a mild steel flat of size 35mm x 6 mm. or copper wire of 29 sq.mm

cross-sectional area (19 strands of 1.4 mm dia). In case the conductor is buried underground,it shall be protected from corrosion by an application of suitable anticorrosive paint orbitumen or varnish. The length of the cable so treated shall extend half a metre beyond theburied length.

• The earthing lead shall be soldered or crimped on a lug which shall be bolted to the earth

electrode.

6.6 Soldering Connections

6.6.1 Staff working in the installation and maintenance of S&T equipment shall be conversant inuse of soldering iron/gun for making good soldering joints.

6.6.2 Care shall be exercised to avoid dropping of solder particles and wire clipping on adjacentterminals and apparatus.

6.6.3 In addition to soldering irons of adequate wattage for the type of work done, the following

shall be on hand :

a. A small file for dressing the soldering tip.

b. A fire-proof pad for wiping the tip.

c. A mica sheet of adequate size or a suitable stand for soldering iron.

6.6.4 Electrical soldering irons shall be switched off when not in use over extended period. 6.6.5 While making a soldering joint, the surface shall be thoroughly cleaned, fluxed and tinned. 6.6.6 Use of too much solder shall be avoided to prevent lumpy connections. 6.6.7 Soldering iron shall not be held on the wire connection for too long to avoid damage to

insulation. 6.6.8 Imperfect joints are the result of any one of the following causes, which should be avoided: a. Soldering iron not sufficiently hot.

b. Soldering iron held on the connection for insufficient time.

c. Unclean terminal or wire

d. A solder of improper composition or inferior fluxing agent.

6.6.9 A newly soldered connection shall not be disturbed till the solder has thoroughly cooled.



6.7 Wire Termination

• While terminating wires, care shall be taken to bend the wire in clock wise direction.• Wire strippers shall be used for the purpose of stripping off the wire insulation. Cutting pliers

shall not be used for this purpose.• Washers and check nuts shall be used whilst fastening.• Not more than two wires shall be terminated on one terminal, if avoidable.• Multi-strand wires shall be terminated on terminal lugs and covered with insulation sleeves.• Wires of cable shall be neatly terminated and properly bunched. 6.8 Connections from and between Secondary cells • For inter connections between secondary cells, standard lead strips, supplied by the

manufacturer shall be used.• Flexible multi-strand copper cable PVC insulated single core of nominal cross sectional area

10 Sq.mm. (7/1.4 mm.) shall be used for wiring between secondary cells to battery chargers/terminal board. The ends shall be crimped with a copper ring conductor (eyelet) and thenterminated. However, the voltage drop between battery terminal and bus bar shall not exceed0.5 V under full load condition.

The following colour code of wires shall be used:

a) Between Battery charger and Red for positive Batteries/ Terminal Boardand Black for

negative

b) Earth connections Grey

c) AC side wiring Blue for neutral and Yellow for phase.

6.9 Tools for Wiring

1. Stripper and cutter suitable for wires 0.6 sq.mm to 1.5 sq.mm. and 2.5 sq.mm.2. Crimping tool.3. Soldering iron or Soldering Gun of suitable wattage.4. Socket set consisting of 19 sockets and other accessories for maintenance of point

machine.5. Socket driver tester set.6. Screw driver set7. Seven piece nut driver set of sizes 3/16”, 1/4”, 1/325/16”, 1”, 3/8”, 7/15” and 1/2”.CR 5,

6, 7, 9, 10, 11, 12 mm. for maintenance of Block Instruments.



7. JOINTING OF CABLE

Since the length of the cable in a cable drum is 500 metres, so when more than abovelength is required, two drum lengths of cable are to be jointed. This type of joint is calledstraight through joint.

7.1 TOOLS REQUIRED FOR CABLE JOINTING

1. Crowbar ]2. Spade ] for digging of pit3. Shovel ]4. Tent (complete set): for protection of joint5. Megger (500V) : for cable testing6. Tool Box : for keeping tools7. Hack Saw : for cutting steel armour8. Cutting Plier : for removing armour etc 9. Wire Nipper : for removing wire insulation and cutting the conductor.

10. Hack-Knife : for marking,cutting and opening ofsheath etc.

11. Clasp-Knife: for cleaning the sheath, cutting thread etc.12. File Rasp : for removing the rough

surface 13. File ( Triangular) : for smooth finish 14. Screw Driver : for terminating cable 15. Hammer Large ] 16. Hammer Small ] for cutting 17. Chisel ] 18. Adjustable Spanner : for tightening of nuts 19. Brass rule : for measurements 20. Dividers : for marking etc 21. Shave hock : for removing plumbing metal fromold joint. 22. Blow Lamp : for plumbing, heating etc. 23. Soldring Iron : for soldring the twisted joints

24. Measuring tape : for measuring the cable length.

7.2 CABLE JOINTING MATERIAL

1. Jointing Box 5. Kerosene Oil2. Jointing Kit 6. Copper Wire 3. PVC Sleeves 7.

Emery Paper4. Resin Core 8. Fire Wood

7. 3 M - SEAL JOINT



At the site of the cable jointing, a pit is to be dug up, the dimensions can be 51X 31 X 31

and a tent is to erected over the pit. Other necessary precautions should be taken to prevententry of water in to the pit in the event of rain etc.

M-seal Jointing is a technique for straight through joints. In this type of joint an epoxyResin is mixed with another liquid called Hardener. The resultant compound is pouredinto the mould fixed at the jointing portion.

7.4 JOINTING PROCEDURE

1. Cut and maintain the length of PVC outer and inner cover, armour and sheath as perrequirement according to the size of the kit.

2. Keep both ends face to face leaving some space between them. This space is called jointingspace. Jointing shall be started from first conductor of inner layer.

Insert the PVC sleeves on one end of the cable conductor and nip the insulation of both end cable

conductor about 1”. Twist both conductors. Now solder the tip of twisted conductors. Bendthe twisted and soldered portion to the opposite side of the PVC sleeve end, and draw overthe PVC sleeve such that the bare portion of the twisted and soldered conductor is coveredcompletely. Similarly, all conductors shall be jointed.

3. The PVC sleeves of adjacent conductors shall be inserted on alternate sides to reduce the

bulging at the centre. Now joint all conductors in sequence. Bind the conductors togetherwith PVC tape to obtain sufficient clearance between sleeves and mould.

4. Abrade the sheath and armour with emery paper and clean them thoroughly with a clothsoaked with mould adhesive-cum-solvent. Make earth continuity connection by tightlybinding earthing wire to sheath and armour with binding wire. Seal bedding of cable withputty.

5. Cut cable entry portions of the mould to match the diameter over outer sheath. Place bottomhalf of mould in position and support it by bricks etc. Ensure sufficient clearance betweenconductors and mould.

6. Stir the cable jointing compound to obtain a homogeneous mixture. Add hardener and mixboth to a uniform mixture for about 2-3 minutes. Allow air bubbles, entrapped while mixing, tocome up and remove them by pricking before pouring. If there is more than one container, mixand pour one by one and not all at a time. Ensure that only similarly marked and colourlabelled containers of cable jointing compound and hardener are mixed together.



7. Liberally apply mould adhesive-cum-solvent on the flanges of both halves of the mould.Immediately place top half in position and press the halves with clips.

8. Mix M-Seal putty and seal cable entry portions. If necessary, apply on the flanges also andleave undisturbed for about 15-20 minutes till putty hardens.

9. Finished M seal cable joint should be protected from mechanical damage by covering it withsand and bricks. In case it is to lie in the open or in cable trenches or cable tunnel liable toheavy trampling, some form of metal protection over the joint is recommended.

8. TERMINATION

• Main cable and Tail cable shall be serially numbered. • All cables shall be taken vertically in the location boxes with armour. The armour shall be

cut once, after taking the cable inside a location box. The de-armoured cable portion shallbe taken vertically and laced to a ladder. Cables coming from each side shall be groupedseparately.

• Cables shall be terminated in horizontal/vertical rows. Cables commencing from relay room

side shall be terminated on top side of the terminals and cables from the far end shall beterminated on bottom side of the terminals. All tail cables shall invariably be terminated onthe bottom sides of the respective row.

• Approved type of terminal shall only be used for termination. The terminals shall be fixed

vertically in horizontal rows on hylam strips. • On cable termination rack (CT-Rack), cables shall be terminated on 8-way terminal strips

procured from RDSO - approved sources. • All conductors of main and tail cables shall be terminated serially on terminals even if they

are spare. Allocation of cable cores should be done in such a fashion that spares areavailable from CT-Rack to last location as far as possible.

• The cables shall be suitably terminated in all location boxes such that far end functions are

on the top row and near end functions on the bottom row. • Before termination, cables shall be tested and record shall be maintained at all installations.



9. TESTING OF CABLE Signalling cable must be tested for continuity and insulation. The tests should be carriedout before and after cable laying. For maintenance purposes these tests shall be performedafter every one year for main cable and after every six month for tail cable.

9.1 TESTING PROCEDURE

Before commencement of cable testing necessary disconnection from traffic shall beobtained. All working circuits and power supply shall be disconnected from the cable at both ends. Communication between the ends of cable under test shall be established by magnetotelephones with other cable which is not under test if possible, otherwise by VHF sets. Competent staff, required instruments and material shall be available at both the ends. Testing shall be carried out when conductors and insulated parts like terminal blocks areclean and dry. Cable conductors shall be shorted/earthed momentarily to discharge the accumulatedcharge, if any, before the commencement and after the end of testing.

9.1.1 CONTINUITY TEST TOOLS & EQUIPMENTS REQUIRED 1. Multimeter 2. Wire nipper 3. Screw driver set

Multimeter Earth

E

This test is carried out to confirm that the core under test is either showing break betweenboth ends or continuous. Testing can be commenced as per the following procedure:

11 22 33 44 55 66 LLOOCCAATTIIOONN AA

1122 33 44

55 66 LLOOCCAATTIIOONN BB



A. Set the knob of multimeter to check resistance at 200 ohm range. (at Location A) B. Connect one probe of multimeter to earth and other probe to the end of cable limb as

shown in above figure. C. Instruct staff at the other end ( at Location B) to connect earth to same limb of the cable.

Deflection of multimeter needle shows that limb is OK, otherwise there is a break in limbunder test..

D. Repeat the procedures (b) and (c) for testing of other cores.

9.1.2. INSULATION TEST

TOOLS AND INSTRUMENTS REQUIRED 1. Insulation Tester (Megger) 500V DC 2. Wire nipper 3. Screw Driver set.

This test is carried out to measure the insulation resistance of the cable under test.insulation resistance measured between (1) conductor to conductor, called crossinsulation, and (2) conductor to earth. Procedure is as follows:

(1) Coductor to conductor (Cross Insulation) Conductor A Line • MEGGER 500 V DC Earth •

Conductor B

I) A 500 V Insulation Tester ( Megger ) shall be used for this test and kept at one end of the cable

under test. II) Conductors for which cross insulation is being measured shall be connected to at Lineand Earth terminals of megger as shown in figure. III) Now rotate the handle of megger or press push button of megger. The reading ofmeter will show the cross insulation between the conductors. Insulation reading shall berecorded after applying the test voltage for about a minute till a steady reading is obtained. IV) Replace the conductor connected to the earth terminal of megger by other conductor ofcable and take measurement. V) Repeat the process IV for remaining conductos. VI) Now connect next conductor to Line terminal of the megger & connect the remainingconductors one by one to earth terminal of the megger and take measurements as perprocedure III , IV & V.



VII) Record the measurements in the prescribed format as shown below.

CABLE MEGGERING CHART 1 2 3 4 5 6 7 8 9 10 11 12 1 X 2 X X 3 X X X 4 X X X X 5 X X X X X 6 X X X X X X 7 X X X X X X X 8 X X X X X X X X 9 X X X X X X X X X 10 X X X X X X X X X X 11 X X X X X X X X X X X 12 X X X X X X X X X X X X SIGNATURE II) Conductor to Earth Insulation

I) By this we can measure individual insulation of conductors w.r.t. earth. II) Connect conductor under test to the Line terminal of the megger. III) Connect earth terminal of the megger to the earth. IV) Rotate the handle of megger or press push button of megger. The reading of meterwill show the insulation resistance of the conductors. Insulation reading shall be recordedafter applying the test voltage for about a minute till a steady reading is obtained.

MMEEGGGGAARR550000VVoolltt

LLIINNEE

EEAARRTTHH

CCOONNDDUUCCTTOORR

EEAARRTTHH



V) Replace the conductor at Line terminal of the megger by another conductor under testand repeat as process IV. VI) Record the mesurements in following format:

Sr.No. CONDUCTOR No.

INSULATIONRESISTANCE

1 2 3 4 5 6

NOTE : These measurements shall be recorded in two copies. One copy each shallbe kept in SE(Sig.) and Sr.DSTE’s office.

Insulation Resistance should not be less than 5 Mega ohm per kilometre at 500C,irrespective of the size of conductor. For converting measured value of insulationresistance at any temperature to insulation resistance at 500C, multiplier constant is givenin the table at page No. 49 Annexure ‘D’.

Example:

Insulation resistance of 5 mega ohm/km at 50 degree centigrade is equivalent to 500 megaohm/km at 20 degree centigrade with multiplier constant 0.01.

9.2 GENERAL INSTRUCTIONS

1. All conductors of signalling cable must be tested for the insulation resistance every

year for Main Cable and after every 6 months for Tail Cable. 2. Low insulation of cable will lead to inadvertent energisation or de-energisation of

circuits. Check for insulation values periodically enables to ensure integrity of circuits. 3. A comparison of test results of successive tests carried on a cable under similar

conditions will give an indication of the trend towards deterioration or otherwise ofinsulating material over a period of time.

4. If a sudden fall in the value of insulation is observed during the test, the cause should

be investigated and immediate action shall be taken to repair or replace the defectivecable.

After completion of cable testing: • Ensure that all conductors have been reconnected properly. • Test the functions of Points, Tracks & Signals connected through the cable for their

correct response. • In case of signals, aspect should be verified personally.



• In case of points, verify positions at site. • Check whether any polarity of any feed taken through the cable has got earthed

inadvertently.

Insulation of signalling cable can be measured by means of Earth Leakage Detector.Description of a typical multi-channel Earth Leakage Detector as per RDSO- specificationNo.RDSO/SPN/256/1971 is given on next page.

9.3 MULTI - CHANNEL EARTH LEAKAGE DETECTOR

Introduction

It is an equipment which measures insulation of the bus bar cable w.r.t. earth and announcesthrough audio-visual alarms if the value of the insulation drops below the set value. It is of 2, 4, 6,8, 12 or 24 channels.

All the channels of the equipment continuously monitor the insulation of the cable and an alarm isactuated along with a visual indication when the leakage value reaches the preset value. The audioalarm is common for all channels while the visual indication is separate for each channel.

Each channel is in the form of a module thus making each module an independent unit whichworks alongwith the main unit. The main unit has a rotary switch for switching on a particularchannel for reading leakage on an analogue meter and for switching certain controls which arecommon to all channels.

Technical Specifications

AC Mains : 110V/230V/50 HZ ACSignalling supply : 110V/24V AC and

24V/60V/110V DC or as required by userLeakage setting range: 50K, 100K, 150K, 200K,

500K & 1M ohms.

Controls & Indications

Normal : Green LED glows when the insulation of the connected channel is within theset limit

Fault : Red bulb glows, indicating the insulation has reached the setlimit. The Normal light extinguishes.

Reset : Micro push switch, when pressed after the leakage fault is removed, bringsthe unit

back to Normal Mode.Counter : Counts number of reset operations.



Simulated : An inbuilt testing facility in the instrument Leakage to check its workingby simulating leakage used with Simulated Leakage Select on

individual module.

Power : Red neon on main unit indicates that power is connected to theunit.

Meter : Selectable through a rotary switch for a particular channelreads insulation value.

Mute : Mutes the buzzer announcing fault, Buzzer indicating that fault is acknowledged.

Channel : Used in conjunction with panel meter and Select Simulated Leakage Test.

10. PRECAUTIONS

In order to safeguard against any unsafe situation arising due to wrong connection of cableconductors during insulation check or changing of defective cable cores, the followinginstructions are issued with immediate effect in respect of all installations already in serviceand those to be commissioned in future:

10.1 No alteration in any cable core, either working or spare, in any installation should be doneby a maintainer independently. Changes where necessary to rectify a fault or for any re-distribution of cores shall be done only in the presence of and in conjunction with aSection Engineer (Signal).

10.2 The concerned SE (Signal) shall ensure that a disconnection memo is issued for theequipments controlled by the cable before any such work is undertaken. Propercommunication and co-ordination between the staff at either end of the cable must bemaintained either by telephone or by portable VHF to ensure that the connections aremade correctly.

10.3 Terminal markings shall be legible and core markers shall be available at the cableterminations identifying each core.

10.4 The length of the cable core leading to the individual CLS transformers mounted insidethe colour light unit must be to the exact length such that the conductor leading to the Redaspect transformer can not be shifted to the CLS transformer of less restrictive aspect. Thetail cable from the location box should be taken direct to the transformer and there shall beno other termination or joint between the transformer connection and the cable terminationin the location unit.

10.5 Correspondance between a lever/knob and the actual aspect at the CLS unit must beverified by the Maintainer and Section Engineer (Signal) during theirmaintenance/inspections and invariably after every occasion when cable cores have to bechanged.



ANNEXURE “A”

“ DIMENSIONS NOMINAL WEIGHTS & RESISTANCE OF CONDUCTOR”

Nominalcrosssectionalarea

No.ofwiresincondu-ctor

DiaOfWire

Toleran-ce ondia. ofwires

Weightper Km. Resistan

-ce perkilomet-er at 20deg. C

Maximum resistan-ce of each conduct-or per km at 20 deg.C.

mm. sq. - Mm. mm. kg. ohms. Ohms. ohms.

1.00 1 1.13 +0.020 8.89 17.241 17.689 18.04

1.5 1 1.40 +0.025-0.015

13.68 11.20 11.540 11.77

2.5 1 1.80 +0.035-0.015

22.62 6.775 6.978 7.118

2.5 3 1.06 +-0.016 23.55 6.664 6.843 6.9804 1 2.24 +0.045 35.03 4.375 4.506 4.5964 7 0.85 +0.012 35.28 4.414 4.591 4.6836 1 2.80 +0.055

-0.03554.74 2.800 2.884 2.942

10 7 1.40 +0.025-0.015

97.47 1.627 1.660 1.693

16 7 1.70 +0.030 143.70 1.104 1.124 1.14925 7 2.24 +-0.045 249.8 0.6357 0.6484 0.661435 7 2.50 +0.050 310.70 0.5103 0.5205 0.530950 19 1.80 +0.035 437.80 0.3633 0.3706 0.3780

ANNEXURE ‘B’

“AREA & THICKNESS OF CONDUCTOR”

Nominal Area ofConductor

Nominal thickness ofInsulation

in mm. Square Single Corein mm.

Multi Corein mm.

1.0 1.5 0.81.5 1.5 0.82.5 1.5 0.94.0 1.5 1.06.0 1.5 1.010.0 1.5 1.016.0 1.5 1.025.0 1.5 1.235..0 1.5 1.250.0 1.5 1.4



NNEXURE ‘C’

“LAY UP OF CORES”

No.ofCores

LAY-UP No.of Cores

LAY- UP

2 2 20 1-7-123 3 21 1-7-134 4 22 2-7-135 5 23 2-8-136 6 24 2-8-147 1-6 25 2-8-158 1-7 26 3-9-149 1-8 27 3-9-1510 2-8 28 3-9-1611 3-8 29 4-10-1512 3-9 30 4-10-1613 3-10 31 4-10-1714 4-10 32 5-11-1615 5-10 33 5-11-1716 5-11 34 5-11-1817 5-12 35 5-12-1818 0-6-12 36 0-6-12-1819 1-6-12 37 1-6-12-18



ANNEXURE ‘D’

MULTIPLIER CONSTANT FOR INSULATION RESISTANCE

Test Temp. ( in 0C )

MultiplierConstant

Test Temp. ( in 0C )

MultiplierConstant

10 0.001 31 0.08011 00012 32 0.10012 0.0016 33 0.12013 0.002 34 0.14014 0.0026 35 0.17015 0.0033 36 0.19516 0.0042 37 0.22517 0.0047 38 0.26018 0.0063 39 0.30019 0.006 40 0.34020 0.01 41 0.38021 0.0122 42 0.43022 0.015 43 0.48023 0.018 44 0.54024 0.022 45 0.60025 0.026 46 0.67026 0.031 47 0.75027 0.037 48 0.82028 0.046 49 0.91029 0.055 50 1.0030 0.064

signal cable

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