CHAPTER XXII

SPECIAL REQUIREMENTS OF SIGNALLING IN 25 KV AC ELECTRIFIED AREA

22.1 General

22.1.1 The objectives of the special precautions taken with signalling equipment in AC electrified areas are:

a) to ensure that interference from the traction system cannot, under any circumstances, cause the Signalling system to exhibit false clear indications, or in any other way imperil the safe operation of trains. This objective must be achieved even if the traction or Signalling system is in a faulty or anomalous condition.

b) to ensure that signalling equipment continues to function normally in the presence of traction current.

c) to minimise danger to life from electric shock derived from the traction system.

22.1.2 Signalling is affected due to following in AC Electrified area

a) Visibility of signals due to OHE structure

b) Electrical clearances of signals due to live OHE close by

c) Traction rail-return current

d) Electrostatic and Electro-magnetic Induction

22.1.3 Visibility of Signals is taken care by the proper implantation of OHE structures during the design stage of OHE. Where electrical clearances are not possible to maintain, suitable protective shields for signal structures shall be provided.

22.1.4 The electrostatic induction is practically eliminated by transferring a circuit into underground cables protected by a metal sheath. The electromagnetic induction causes various currents and voltages to develop in conductors parallel to the track. These include the rails, traction return conductors where provided, cable sheath, any other conductors in the vicinity, and signalling and telecommunication circuits. The voltages that occur in the conductors appear as potential gradients. In addition, there are potential differences between various points along the conductors and the adjacent Earths. The value of this induced voltage depends on various factors, such as -

a) Length of parallelism between the cable conductors and the electrified track;

b) Soil conductivity;

c) Screening efficiency of the cable sheath where existing;

d) Return current through the rails and return conductor where provided;

e) Mutual inductance between catenary and the cable conductors;

f) Separation between catenary and cable;

g) The current carried by the catenary, etc. 

22.2 Signal structure

22.2.1 Colour light signal shall only be used in electrified area.

22.2.2 On electrified sections, the masts, insulators, wires and supports obstruct the visibility of Signals. In addition, the Signals have to be so erected that they maintain a minimum clearance from the live parts of the O.H.E. The instructions in this section shall be strictly followed in so far as the electrical clearance is concerned. These instructions may be taken as a rough guide in determining the location of signals, which would afford the best visibility to the drivers of approaching trains. However, the actual visibility shall in all cases, be checked by a Signal Sighting Committee and action to improve the visibility taken on the recommendations of the Committee.

22.2.3 The location of signals and the protection required shall be worked out from the following signal clearance diagram.

22.2.4 In these diagrams the un-shaded portion shown above the standard moving dimensions is the area into which a signal post or any of its fittings shall, under no circumstances, be allowed to infringe. The shaded envelope around this is the area into which a signal or its fittings shall  not normally be allowed to infringe. If due to unavoidable reasons, a portion of the signal post or its fittings has to infringe into this shaded area, special protective measures as detailed in para 22.2.6 shall be taken. The dotted outline in Drawing Nos. 22.1,2,3 for Broad Gauge and 22.4 and 22.5 for Metre Gauge tracks is applicable when there are two sets of catenary and contact wires parallel to each other in the same span, viz. insulated and un-insulated overlap locations. It is to be noted that these diagrams are not applicable to (i) anchor spans, (ii) turnouts, (iii) 3 meters on either side of masts, and (iv) in loco sheds and inspection pits. The diagrams are also not applicable when there is a feeder line running along with masts or where booster transformers and return conductors are provided.

22.2.5 The normal height of the contact wire is 5.60 meters at supports. The normal height of the catenary at its highest point is 7.05 meters. In tunnels as well as underneath bridges, where clearances are limited, the contact wire may be as low as 4.58 meters for Broad Gauge and 4.02 meters for Metre Gauge and the catenary is also lowered suitably or terminated at the face of Bridges or Tunnels. The clearance diagrams have, however, been drawn to suit the extreme positions of the catenary and the contact wire. In addition, the diagrams make allowances for the stagger as well as displacement of wires by wind.

22.2.6 In the matter of electrical clearances, the fundamental rule to be observed is that no one is allowed, under normal conditions, to approach closer than 2 meters from the extreme positions of the live parts of the O.H.E. The following protective measures shall, therefore, be adopted.

22.2.6.1 If any portion of a signal post or its fittings where signalling staff have to work, falls within 2 meters of a 25 kV live conductor, or any metal part electrically connected to this conductor such portion shall as far as practicable be protected by an iron screening of approved design solidly connected to the structural work.

22.2.6.2 If for any reason it is not practicable to provide the protective iron screening as given in para 22.2.6.1 above, a Caution Board of approved design shall be provided on the signal post at a height of 3 metres above the rail level, to caution the signal staff.

Note: Technical personnel shall exercise particular care to protect themselves while working on signal posts not provided with protective screens. If there is any likelihood of any part of their tools or equipment coming within 2 metre of live equipment, they shall take a power block as detailed in Chapter VI of the Manual of AC Traction- Volume II (Part-I). The same precautions are also required in the vicinity of return conductors, which should be treated as live.

22.2.6.3 The SSE/SE/JE (Signal) shall explain these instructions to the staff working under them and ensure that they are correctly complied with.

22.2.7 Drg. Nos 22.6 and 22.7 illustrate the location of signals on the left-hand side and right hand side of Broad Gauge track and the figures indicate the minimum heights and distances of Signal from the track to avoid electrical infringements.

22.2.8 Location of neutral section

22.2.8.1 Neutral section shall be located away from stop signals, level crossing.

22.2.8.2 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 through the neutral section without any risk of stalling.

22.2.8.3 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 meter away on section with gradient upto 1 in 300 and 2500 meter with higher gradient upto 1 in 200, if unavoidable. If PTFE type short neutral section has been used this distance can be reduced to at least 400 meter after the stop signal and 200meter 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.

22.3 Visibility of signals

22.3.1 Normally, all signals should be located on the left side of the track for which it refers. In exceptional cases the signals may be located on the right side.

To ensure adequate visibility of signals the OHE masts should be implanted as per the ACTM. In case it is not possible, off set brackets may be used for signal units without affecting the schedule of dimensions. Further the following steps should be taken to achieve adequate visibility.

a) The distance between the signal post and traction mast shall be as large as possible. In case the traction mast is located in front of the signal post, the distance between the traction mast and signal post should not be less than 30 metres. In addition, it should be ensured that no traction mast is located in advance of the signal post at a distance less than 10 metres.

b) The signal post should be sufficiently high so as to be seen clearly.

c) On tangent tracks it is desirable that the signal should be located within the OHE structure, i.e. the implantation of the signal from the track centre shall be less than the implantation of the OHE mast from the track centre. The setting of OHE masts in the vicinity of the colour light signals shall be as per para 20.5 of Appendix-I of the AC Traction Manual, Vol-II (Part-II). Relevant extracts as in Annexure-31.

d) On curved track or in areas, where other obstructions such as buildings, trees etc. exist, the site should be individually examined by the 'signal sighting committee' for deciding the most appropriate location of the signal.

22.3.2 No portion of a post or fittings of a colour light signal shall infringe with the schedule of dimensions from the centre line of the nearest track.

22.3.3 Signals without Junction Indicators outside tracks

22.3.3.1 Setting distance of OHE masts shall be in accordance with Drg..No. 22.8

22.3.3.2 The signal units shall be so fixed that the height of the centre line of the red signal shall be approximately 3.65 meters above rail level. No part of Signal without a route indicator shall normally be higher than 5.2 meters above rail level.

22.3.4 Signals without Junction Indicators between tracks

22.3.4.1 If signals are located between tracks no OHE structures shall be provided in the same track space for at least 600 m in rear of the signals.

22.3.4.2 Portal drop arms shall not normally be located in the track space where signals are located at least for a distance of 600 metres before the signal.

22.3.4.3 If a portal drop arm has to be unavoidably located in rear of signal itself, the signal shall be mounted on an offset bracket. In addition special study shall be made in each case to see whether the portal drop arm should also be offset from the centre line of the track space in the direction opposite to the offset of the signal. This special study shall be made for at least three portal drop arms in rear of the signal and shall also cover the possibility of shortening the portal drop arm.

22.3.5 Signals with Junction Indicators outside tracks

22.3.5.1 Setting distances of OHE masts shall be in accordance with Drg..No. 22.9

22.3.6 Signals with Junction Indicators between tracks

22.3.6.1 Precautions and parameters for location of portal drop arms shall be as specified under Para 22.3.4

22.3.6.2 For details of drawings, illustrating the above principles for Colour Light Signals, reference may be made to Drawing No.22.10.

22.3.7 The visibility of the signal shall be checked by day as well as by night by the Official in charge (Signal) of the section after each phase of the O.H.E work, i.e. erection of masts, provision of brackets, wiring, etc. If at any stage the official feels that the visibility is not adequate, he shall impose suitable speed restrictions and take such steps as are required to improve the visibility.

22.4 Cables and Cable Laying

22.4.1 Only unscreened cable shall be used.

22.4.2 Screened signalling cable may be used on signalling installations where screened cable is already in use and site condition demand its further use.

22.4.3 PVC insulated PVC sheathed and armoured unscreened cable to an approved specification (IRS-63) shall be used for carrying signalling circuits. Only approved type (IS-1554) power cable shall be used for signalling purposes.

22.4.4 The screened cable, if used, shall be PVC insulated, armored and to an approved specification IRS S-35.

22.4.5 The cable shall be so laid that it is not less than one meter from the nearest edge of the mast supporting the catenary or any other live conductor, provided the depth of the cable does not exceed 0.5 meters. When the cable is laid at a depth greater than 0.5 meters, a minimum distance of 3 meters between the cable and the nearest edge of the O.H.E structure shall be maintained. If it is difficult to maintain these distances, the cable shall be laid in concrete / heavy duty HDPE/Ducts or any other approved means for a distance of 3 meters on either side of the Mast. When so laid, the distance between the cable and the mast may be reduced to 0.5 meters. These precautions are necessary to avoid damage to the cable in the event of the failure of an overhead insulator.

22.4.6 In the vicinity of traction sub stations and feeding posts, the cable shall be at least one metre away from any metallic part of the O.H.E and other equipment at the sub station, which is fixed on the ground, and at least one metre away from the sub station earthing. In addition, the cable shall be laid in concrete or heavy-duty HDPE pipes/ Split RCC pipes or other approved means for a length of 300 meters on either side of the feeding point. As far as possible, the cable shall be laid on the side of the track opposite to the feeding post.

22.4.7 In the vicinity of the switching stations, the cable shall be laid at least one metre away from any metallic body of the station, which is fixed in the ground, and at least 5 meters away from the station Earthing. The distance of 5 meters can be reduced to one metre provided the cables are laid in concrete pipes/ heavy-duty HDPE pipes /ducts or any other approved means.

22.4.8 Where an independent Earth is provided for an OHE structure, i.e. where the mast is connected to a separate Earth instead of being connected to the rail, the cables shall be laid at least one metre away from the Earth.

22.4.9 Where there are O.H.E structures along the cable route, the cable trenches shall as far as possible, be dug not less than 5.5 meters away from the centre of the Track.

22.4.10 In a cable run, the number of circuits carrying 300V at any given instant shall not exceed three. Note : 300 V feed system shall not be used in future installations.

22.5 Signalling and Interlocking Circuits

22.5.1 As a rule, no aerial circuits shall be retained in the electrified zone. The only exception may arise in the case of Block Circuits coming in from a non-electrified zone. However, in each such case, it shall be ensured that the Block Wires are terminated in a suitable lead in cable upto a distance of 50 meters from the electrified track at right angle to track. In every such case, the length of parallelism and the distance of Block Wires from the nearest electrified track shall be checked to ensure that the maximum induced voltage does not the exceed 60 volts the limits prescribed by CCITT. Paras 505(e), 508(b) and 549(a) of Indian Railway Telecommunication manual (old) shall be considered for design and precautions.

22.5.2 Barring block-instrument circuits, no other earth-return circuit shall be permitted on A.C electrified territory. The Block instruments, however, shall be suitably protected by a filter of approved design as stipulated in para 22.9.5

22.5.3 The following electrical signalling equipment are not safe to withstand AC induced voltage. The coils of these equipment can only be used inside a cabin or a location box or internal circuits only. The coils of these equipment shall be worked from a separate battery and this battery shall not be connected to any external circuits going outside the cabin/ location box:

a) Luminous Indicators;

b) Telephone type relays;

c) Electrical Lever Locks;

d) Door Coil of IRS Block Instrument;

e) 250 Ohm D.C. neutral Line Relay;

f) Rotary Key Transmitter; &

g) D.C. Neutral Polar Relays.

22.5.4 All Batteries and the wiring in the equipment, location box or cabin shall be well insulated from the ground. PVC insulated wires to an approved specification (IRS-S-76) shall be used for wiring in location boxes and cabins.

22.5.5 Separate Batteries shall be provided for external and internal circuits.

22.5.6 When more than one cable is laid between two locations or cabins, it shall be ensured that as far as possible, all wires pertaining to any individual circuit are within the same cable.

22.5.7 Polarised Relays using permanent magnet shall not be used in any external circuit in 25 KV AC electrified areas as the permanent magnet in the relay tends to lose its magnetic properties due to continuous application of induced voltages. Competent authority shall authorise any exception in specific cases.

22.5.8 The relays, which release an interlocking, shall be slow acting so that the interlocking is not released inadvertently by voltage variations of short duration. Time delay may be of the order of 0.6 to 0.8 seconds.

22.5.9 No external circuit shall work in A.C. electrified area with out double cutting.

22.6 Line circuits

22.6.1 The length of any signalling line circuit must be limited to ensure that the induced voltage from the traction system does not exceed 400 Volts under normal conditions. If necessary, line circuits must be sectionalized. Where line circuits leave lineside enclosures or buildings in different directions, this could give rise to a continuous circuit of such length that the limits of induced voltage above could be exceeded. In such cases a sectionalized power supply unit should be provided for each direction.

22.6.2 Maximum length of parallelism

22.6.2.1 The induced voltage in the underground-Unscreened cable shall be reckoned as 116 volts/km on single line and 95 volts/km on Double Line.

22.6.2.2 When such circuits are terminated on relays/equipment their immunity shall not be less than 400 V AC. Length of feed cable terminated on relay shall be suitably reduced depending upon its AC immunity.

22.6.2.3 The induced voltage in the underground Screened cable may be reckoned as 35 V/km under normal conditions with a catenary current of 300 Amps on Single Line and 600 Amps on Double Line.

22.6.2.4 Maximum length of parallelism permitted on screened cable is 3.5 Km. Note: In future, screened cable shall not be used.

22.6.2.5 The length of DC Track Circuits terminated on Line Relays with unscreened cable shall be restricted to:-

 

*Maximum permissible induced voltage is restricted to 400V for human safety and factor of safety 1.5 has been considered.

22.7  Signal feed Circuitry

Signal feed system shall be of the 110V 50Hz type. 300 V signal feed system where already working may continue. 110 V feed system can replace 300V feed system as per the site requirements or when it has out lived its life.

 22.7.2 The distance between the signal control relays and the signal must not exceed the prescribed limits in electrified zone, measured along the line of way. This will ensure that the voltage induced in the circuit will be inadequate to illuminate the lamps, even under the most adverse circumstances and with one or more earth faults present.

22.7.3 Maximum permitted length of direct feed of signal in various configuration shall be as per tabulation below:

 
22.7.4 When a signal is located at a distance greater than that specified in para 22.7..3 the signal shall be fed locally by controlling relays located at the location. Such signals may also be remotely fed from the cabin by using a corresponding relay at the location. Typical circuit is given in Drg. No. 22.11.

22.7.5 It shall be ensured that the power transformer for feeding circuits as per section 22.7.2 shall be different from the transformer feeding longer circuits.

22.8  Point operation and Detection

22.8.1 Point can be operated electrically or mechanically by rodding. Mechanical operation of point will require special measures for the protection of operating staff. Electric operation shall have restriction on maximum length between point control relays and point machine depending upon their immunity level.

22.8.2 Electric Operation of point

22.8.2.1 Point detection and point detection repeat circuits shall use ac-immunized relay.

22.8.2.2 The maximum permissible length for various types of commonly used Point Machines is as under:-

 
Factor of safety is 1.5

22.8.2.3 CSTE may authorize where necessary, longer permissible separation between point contacter and point machine when screened cable is used.

22.8.2.4 3 phase point machine is inherently immune to induced voltage and therefore can be used for operating point to any length subject to its own operating limitation.

22.8.3 Rod Runs

22.8.3.1 The point rods in A.C electrified areas are subject to a certain amount of induced voltage. In addition since the rods are in contact with the rails at some point or other, the rail voltage, which can be quite high in case of faults, is transmitted through them to the lever frame. Insulators shall, therefore, be provided on the rodding as per instructions in section 22.8.4 for protecting the Operating Staff from the effects of these voltages.

22.8.4 Insulated Rod Joints

22.8.4.1 The insulated rod joints shall be as per approved drawings.

22.8.4.2 Each rod shall be provided with an insulator in the lead out as close to the cabin as possible. While providing this insulator, it shall be ensured that there is no possibility of a contact between the insulated portion of one rod and the un-insulated portion of another rod or signal wires, the rail or O.H.E mast.

22.8.4.3 An additional insulator shall be provided between the last adjustable crank and the point or the lock bar. The purpose of this insulator is to prevent the rail voltage being passed on to the main run of rods.

22.8.4.4 If the distance between the two insulators at either end is greater than 300 meters, additional insulators shall be provided on each rod, so that the distance between two consecutive insulators on the same rod is not greater than 300 meters.

22.8.4.5 Each Point, Trap indicator and lockbar operated by rodding shall be electrically isolated from the track.

22.8.4.6 All insulators in a run shall be provided between the same two sets of rollers and guides, so that there is no possibility of the insulated portion of one rod coming into contact with the uninsulated portion of another rod.

22.8.4.7 The clearance between the insulator and the adjacent rod roller shall be adequate to permit normal movement of the rod.

22.8.4.8 When a rod crosses the track, the top of the rod shall not be less than 40mm from the bottom of the rail. When steel or C.I sleepers are used, the distance between the rod and the sleeper shall also be not less than 40 mm. Similarly, the distance between any O.H.E mast and the point rods shall not be less than 40 mm.

22.8.4.9 The operating rod of locally worked points on all electrified lines and of similar points taking off from two non-electrified track adjacent to the last electrified line shall also be provided with an insulator so that the point lever or point box is insulated from the rail.

22.8.4.10 When the Engineering department provides the point lever or point box, Engineering department shall provide the insulator on the operating rod.

22.9 Block working

22.9.1 In 25 KV electrified line only following type of block instrument shall be used :

Single Line :

               Neal's token instrument
               Daido's Tokenless block Instrument
               Block working with Axle Counter

Double Line :

               SGE Block Instrument
               Block working with Axle Counter

Push button type block instrument may be used on non electrified section taking off from electrified section if length of parallelism does not exceed 1.5 Kms.

22.9.2 If any other block instrument is to be used, prior approval of Railway Board shall be obtained.

22.9.3 Block instruments may use special PVC insulated quads in the aluminum-sheathed cable/ 4 or 6 quad jelly filled telecommunication cable or other suitable communication means, like OFC and radio, for their working.

22.9.4 When quad cable is used for the working of block instruments, Block Telephone and Block Bell circuits shall be worked through a transformer utilizing the two pairs of block quad. The Block circuits shall be worked on the phantom pair or by other suitable means.

22.9.5 Protective Devices of approved type consisting of two chokes connected in series with a four terminal condenser connected across the junction between two chokes and earth shall be used. A rare gas arrestor shall also be provided across the condenser to absorb surges  under faulty conditions. The arrangement is illustrated in Drg. No. 22.12

22.9.6 The Block Bell shall be worked through Block Bell equipment of approved type.

22.9.7 Separate line battery or DC-DC converter shall be used for each block instrument. This battery shall feed only the block instruments and not any other circuit.

22.9.7.1 Two different earths shall be provided for Discharger and Block. :

22.9.8 When OFC, Radio or other communication means are used for block working, fail-safe block interface (FSBI) of approved design shall be used. FSBI shall be installed in communication room and which may not be always close to the place where block instruments are installed. In case the distance between FSBI and block instrument is more than 500 metres, block filter and block bell and telephone shall be inserted in cable pairs connecting them.

22.9.9 Single Line Token Instruments

22.9.9.1 Where earth return is used, the rest contact of the instrument shall be substituted by the contacts of a slow release relay. The arrangement shall be such that the relay is energised during the operation of plunger but is dropped only after the condenser has discharged to a safe limit. The circuit details are illustrated in drawing No. 22.13.

22.9.9.2 Whenever stray DC is present in the earth, metallic return is provided for block circuit. Metallic return should be used with a modified filter circuit eliminating the condenser. The chokes and surge arrestors shall be retained and shunt resistors shall be provided across the Galvo (150 ohms) and Polarised Relay (77 ohms). The resistors shall be of substantial rating so that they do not get open circuited. The circuit details are illustrated in drawing No. 22.14. In this case, slow to release relay is not required.

22.9.9.3 Only Frequency Modulated Single Line Daido Token less Block Instrument is approved for installation in electrified sections.

22.9.10 Double Line Block Instrument

22.9.10.1 IRS type Block Instrument with Block filter shall be used for Double Line section electrified with 25 kV AC. The circuit details are illustrated in Drawing No. 22.15.

22.9.10.2 The voltage of the Battery shall be sufficient to ensure not less than 18-ma and not more than 25-mA current through the polarized relay. Needle coil resistance shall be modified to obtain this level of current

22.10 Track circuits

22.10.1 Track circuit on AC electrified section may use IRJs (Insulated Rail Joints) or ESJs (electrical separation joint) and may be configured as single rail or double rail track circuit. Track circuit which use electric separation joint shall be configured only as double rail track circuit.

22.10.2 Single Rail Track Circuit

22.10.2.1 With single rail track circuits, one of the rails is reserved for the traction return current. This rail is referred to as the un-insulated rail. Any connection from the O.H.E. mast or other structure shall be made only to the un-insulated rail. Similarly, connections for the return current at feeding points as well as from booster transformers and return conductors shall be made only to the un-insulated rail.

22.10.2.2 As far as practicable, the rail adjacent to the O.H.E Mast shall be utilised as the un-insulated rail. However, this may not always be possible, particularly in yards where there are a large number of points and crossings or where the O.H.E masts are not always on the same side or where track circuits are staggered.

22.10.2.3 In single rail track circuits, in the event of a break in the uninsulated rail, very heavy current will flow through the track relay as well as the equipment at the feed point. To avoid this the uninsulated rails of the adjacent tracks shall be cross-bonded at intervals of not more than 100 Mts. In case the track circuit is less than 100 Mts. the cross bonding shall be provided on the uninsulated rail at either end of the track circuit (ref Drg no 22.16).

22.10.2.4 In the case of adjacent track circuits, the return rail shall be staggered.

22.10.3 Double Rail Track Circuit

22.10.3.1 In double rail track circuits, since both rails are used for traction return current, impedance bonds shall be provided at the IRJs.

22.10.3.2 No O.H.E mast or any other structure shall be connected to either of the rails. The Electrical Department shall run separate earth wire for earthing the O.H.E masts.

22.10.3.3 Connections at the feeding points and from booster transformers and return conductors shall be made to the center points of impedance bonds.

22.10.4. DC Track Circuit

22.10.4.1 This track circuit can only be configured to work as single rail track circuit.

22.10.4.2 Interference Mechanism

With reference to fig. above traction return current flowing in the single traction return rails creates a longitudinal AC voltage along its length, which is a function of the current value and the impedance of the traction return rail. A wheelset at the feed end will impress this interfering voltage on the relay, whilst a wheelset at the relay end will similarly impress the interfering voltage on the feed set. The track circuit equipment must be immune both to false operation and to damage from such impressed voltages.

22.10.4.3 Immunized D.C. Track Relays to British Standard Specifications No. 1659 shall be provided in A.C Traction areas. Such immunized track relays shall satisfy the prescribed specifications so far as immunization is concerned in addition to provisions contained in British Railway Specification No. 939-A and RDSO/SPN/84/88 can also be used in A.C Traction areas. The resistance of the immunized Track Relay shall be 9 ohms.

22.10.4.4 Length of DC track circuit is restricted depending upon rail return current. With catenary current restricted to 300 ampere on single track section and 600 amperes on double track section length of DC track circuits shall be restricted depending upon the use of type of relay and sleeper.

22.10.4.5 The length of D.C single rail track circuit in AC electrified areas with AC immune 9 ohms shelf type relay shall not exceed 450 meters where wooden sleepers are used and 350 meters where concrete sleepers are used. The length of track circuit can be extended upto 450 meters when QTA 2 plug-in relay is used.

22.10.4.6 Restriction on the track circuit length due to use of concrete sleeper can be relaxed upto 450 meters by CSTE of Railway if adequate ballast resistance can be consistently obtained.

22.10.4.7 In view of the increased AC immunity due to the presence of biased magnetic arrangement, QBAT relays can be used upto a maximum length of track circuit of 750 meters using one 'B' type choke at the relay end, under minimum ballast resistance of 2 ohms/km. Operation of track circuit with this type of relay will require four cells delivering 8.8V. QBAT relays shall be used in conjunction with QSPA1 relays conforming to BRS 933A.

22.10.4.8 As an interim measure, length of DC track circuit may be retained at the existing level at higher catenary current of 800 Amperes on single-track section and 1000 Amp. on double track section by providing B type 120 ohms impedance choke in series with track relay. Audio frequency track circuit shall be used on sections where catenary current exceeds 300 Amps, on single- track section and 600Amps. on double track- section.

22.10.4.9 Before installation of single rail D.C track circuits in A.C Electrified areas, measurements of stray D.C currents shall be taken in accordance with the instructions in Annexure 32. The total stray current as measured, shall not exceed:

i) 10 milli-amperes, if length of track circuit is less than 100 meters ii) 100 milli-amperes, if length of track circuit is 100 meters and above

If measured value of current exceeds the specified limit as above, other type of track circuit suitable to work in A.C. traction area shall be used.

22.10.4.10 To protect the equipment from the effects of the rail voltage, a choke coil of approved type shall be provided in series with the feed resistance.

22.10.5 Audio frequency Track Circuit

22.10.5.1 Only approved type modulated Audio frequency Track Circuit shall be used.

22.10.5.2 Audio frequency track circuit shall be configured only as double rail track circuit and like any double rail track circuit it requires both rails to be balanced with respect to earth and with respect to current flow in each rail.

22.10.5.3 Impedance bond shall be used where there is no provision in design of Audio frequency track circuit to balance the traction rail return current.

22.10.5.4 Electric Traction Units shall be critically examined for harmonics generated by them before they are brought into service.

22.10.6. Impedance bonds

22.10.6.1 Impedance bonds used on 50 Hz electrified lines shall be of approved type.

22.10.6.2 The principles of operation of impedance bonds are equally applicable whether the traction return current is AC or DC. The traction current rating of DC impedance bonds is usually much higher than those designed for AC traction systems. Thus, impedance bonds designed for DC traction current can usually be used on AC traction systems, although their bulk and cost is greater than a purposely designed AC impedance bond. Conversely, impedance bonds designed for AC traction systems are not suitable for use on DC traction systems.

22.10.6.3 Generally, AC impedance bond shall be capable of supporting a current of 400A continuously (200A in each rail), with a peak loading of 1000A for a period of up to five minutes, without suffering damage or overheating.

22.10.6.4 Leads between impedance bonds across IRJ on the same track shall be capable of carrying the traction current. It shall be PVC sheathed cables, terminated by compression lugs of an approved type and bolted to the impedance bond termination.

22.10.6.5 The design and installation of impedance bonds should take into account the requirements for mechanised track maintenance and should not be a hazard for men walking along the track.

22.10.6.6 The provision and maintenance of connections between rail and impedance bonds, and from one impedance bond to another on the same track is the responsibility of the S&T department.

22.10.6.7 Cross bonds, earth wires, connections to sub-station current return busbars and connections to booster transformers must be terminated on the centre tap of impedance bonds. The installation and maintenance of these connections is the responsibility of the electrical department.

22.10.7 Maintenance and Installation of track circuits

22.10.7.1 There are no special methods used solely for the installation of track circuits on ac electrified areas, and reference should be made to installation instructions given relevant in manual and / SEM chapters.

22.10.7.2 It is, however, important to recognize that the operation of track circuit is dependent upon the integrity of traction return bonding. It is therefore important that attentions are given to the testing during installation and also during maintenance of traction return bonding.

22.10.8 Track Bonding

22.10.8.1 The objectives of track bonding are :

i) To provide a path for traction return current, which ensures that no component of the track/traction return network rises above 25 V to remote earth, under normal traction load conditions and 430V under traction short circuit conditions.

ii) To ensure that protective equipment operates satisfactorily,

iii) To minimize damage to installations due to traction short circuit,

iv) To maintain correct operation of track circuits.

22.10.8.2 Procedure of planning track bonding

22.10.8.3 When planning electrification schemes, base plans will be provided. The plans will be issued to the signal department showing the track layout and proposed position of all electrification and associated structures.

22.10.8.4 The signal department will then indicate on these plans the proposed position of insulated joints, impedance bonds, signal structures and track circuit bonding and in single rail track circuited areas, will identify the track circuit rail by marking with a thickened line. In double rail track circuited areas S&T department shall specifically indicate the provision of earth wire for structure earthing.

22.10.8.5 The plans must then be returned to electrical department who will indicate the position of continuity bonds, cross bonds, structure bonds and all earth connections to the traction system. The plans will then be returned to the signal department for his final agreement and issue to concerned parties.

22.10.8.6 Bonding of Single Rail Track circuits

22.10.8.6.1 The track circuit rail must be series bonded in order to ensure that defective bonding cannot cause a wrong side failure of the track circuit. Accordingly, the bonding arrangement of the track circuit rail must ensure that the conductive path between the track circuit feed connection and the relay or receiver end connection is interrupted in the event of a disconnection.

22.10.8.6.2 Because of traction return considerations, it is not possible for the traction return rail to be series bonded. It is therefore essential to avoid bonding disconnection to minimize the risk of loss of train shunt.

22.10.8.6.3 In single rail track circuits, in the event of a break in the un-insulated rail, very heavy current will flow through the track relay as well as the equipment at the feed point. To avoid this, the un-insulated rails of the adjacent tracks shall be cross-bonded at intervals of not more than 100 meters. In case the track circuit is less than 100 meters, the cross bonding shall be provided on the un-insulated rail at either end of the track circuit.

22.10.8.6.4 On single line track circuited sections, a continuous earth wire is provided on the traction mast capable of carrying full traction return current. The un-insulated rail shall be connected to each of the traction masts by a structure bond, which shall be riveted at both ends. The arrangement for Double Line and Single Line Sections is as illustrated in Drawing No. 22.14.

22.10.8.6.5 Typical bonding examples with single rail track circuits are shown in figure.

22.10.8.7 Double Rail Track Circuits

22.10.8.7.1 No structure bonds, cross bonds or connections to earth wires or return conductors shall be connected to the running rails where double rail track circuits are in use. If necessary, an impedance bond must be specially installed to provide a neutral point for these connections.

22.10.8.8 Types of Bond and Responsibilities

22.10.8.8.1 Rail Joint Bonds : Rail joints in track-circuited areas shall be bonded using two 8SWG bare galvanized steel wires or copper bonds/ steel wires or flats secured by means of channel pins or welding/riveting. The S&T department is responsible for the installation and the maintenance of all rail joint bonds.

22.10.8.8.2 Rail bonds and Cross-bonds: Where rail bonds and cross bonds are required for traction return purposes they shall be installed by and remain the responsibility of the electrical department.

22.10.8.8.3 The longitudinal bonding on a non-track-circuited track adjacent to a track circuit shall be extended for a distance of 50 meters beyond the track circuit.

22.10.8.8.4 In addition, the two rails of the non-track circuited track outside any track circuit or in between two track circuits shall be bonded together immediately after the block joints.

22.10.8.8.5 Detailed instructions for bonding of track are given in the A.C Traction Manual.

22.10.8.8.6 It is essential that the traction return and track circuit bonding is maintained in its design condition. The Traction Foreman and CSI of section will arrange for physical inspection at six months intervals to ensure conformity with approved Bonding Plan. In the event of faulty connection or bond being found immediate remedial action will be taken to restore system Integrity. The results of the joint inspections shall be entered in a register maintained by the Supervisory Signal Inspector and put up within a month for the scrutiny of the Divisional Signal and Telecommunication Engineer/Divisional Electrical Engineer (OHE). Responsibility of maintenance of traction bonds is with electrical department.

22.11 Power Supply

22.11.1 In double line section power supply at stations including Block Huts, Intermediate Block Huts, Interlocked Level Crossings and at such locations in Automatic Signalling Territory as required shall be provided by tapping both UP and Down OHEs with an automatic change over switch. Uninterrupted Power Supply with inverter shall be provided if automatic change over switch between UP and Down OHEs is not provided. Diesel generators shall be provided at junctions and important stations where frequent shunting is involved. Where local power supply is reliable, the same may be utilized as standby. In single line electrified areas in addition to OHE supply standby generators of adequate capacity shall be provided in conjunction with UPS and inverters.

22.11.2 Where power supply is drawn from Up and Down OHEs, supply shall be provided such that at least one power is available in the event of power block in the station.

22.11.3 Signal department may provide a diesel generator set at large junction stations.

22.12 Axle counter

22.12.1 Axle counter used shall be of an approved design.

22.12.2 The wheel detector circuits used in axle counting system are galvanically decoupled from currents flowing in rails. As a result higher degree of immunity to traction current is available.

22.12.3 Leakage fields from inductors on locomotives can produce disturbance if these are mounted close to the rail. Locomotive and EMU shall be critically examined for the placement of inductor on the underframe.

22.13 ATP system

22.13.1 ATP system used shall be of approved design.

22.13.2 Balises used in ATP system are galvanically decoupled from currents flowing in rails. As a result higher degree of immunity to traction current is available.

22.13.3 Leakage fields from inductors on locomotives can produce disturbance if these are mounted close to the rail. Locomotive and EMU shall be critically examined for the placement of inductor on the underframe.

22.14 Earthing

22.14.1 Earthing of cables, equipment, buildings and structures is done for one or more of the following purposes:

a) To ensure effective and rapid operation of protective equipment in the event of earth fault currents in an electrical supply system which might otherwise cause fire; and to protect against danger to life through shock due to non-current carrying equipment and metal work being maintained at a dangerous potential relative to earth.

b) To provide an earth for telephone systems employing an earth return signalling circuit.

c) To provide a means for the earthing of metal screens of telecommunications cables and equipment for the purpose of reducing interference.

d) To provide a direct connection with earth for discharge tubes, lighting protectors, etc.

e) To provide an earth to block instrument working on earth return.

22.14.2 Installations to be earthed

22.14.2.1 Separate earthings shall be provided for the following cases :-

i) The lever frame and other metallic frames of the cabin shall be connected together to a separate earthing.

ii) The earthing shall be provided at every location box where cables terminate.

iii) It is not necessary to earth the sheath and armouring of screened cables or armouring of unscreened cables when they are used as a tail cables except in special cases where the length of the tail cable exceeds normal prescribed limits.

iv) Block circuits working on earth return through the respective Block filters,

v) The surge arrestors provided in block

vi) In case of signals falling within 2 meters from the electrified track, the protection screen shall be connected to an earth

22.14.2.2 There shall not be any possibility of simultaneous human contact with metallic bodies connected to different earths, where it is not possible to provide suitable spacing or partition between various metallic objects referred to above, they shall be connected to a common earth.

22.14.2.3 Limits of earth resistance: The maximum earth resistance specified is:

a) Earth for lightening discharger 10 ohms

b) Earth for equipment 10 ohms

c) Axle counter cable screen in ac electrified area 1 ohms 22.14.3 Installation of a standard Earth electrode system

The material required for a standard electrode system should be corrosion resistant.

If routine testing indicates that existing earth electrode system is not satisfactory, a new earth electrode system (or part of a system to supplement the existing system) shall be provided.

22.15 Rules for Protection of Staff working on Signal & Telecommunication Installation

22.15.1 Railway personnel working on Signal & Telecommunication equipment on sections provided with 25 KV A.C traction are required to take suitable precautions on account of the following: -

a) Proximity to live conductors;

b) Presence of returns currents in the rails;

c) Induction in all metallic bodies situated near the overhead equipment.

22.15.2 Proximity of a Live Conductor: - Any contact direct or indirect, with the 25KV conductors is dangerous and shall be strictly avoided.

22.15.3 Pressure of Return Current in Rail

The flow of return current in the rails will give rise to a potential difference: -

a) between adjacent rails at an insulated joint of a track circuit or at an ordinary joint in case the fish plates and bonding are broken ;

b) between the ends of a fractured rail at the fracture;

c) between an insulated rail and the non-insulated rail used for the traction return current; &

d) between the rail and the surrounding mass of earth.

22.15.4 Wherever staff has to work on installations, which are in direct or indirect contact with the rails, they shall -

i) use tools (insulated and non-insulated) in accordance with approved instructions &

ii) observe the provisions of Section 'J' of permanent way manual reproduced as Annexure 33.

22.15.5 Induction in metallic bodies situated close to overhead electric equipment

22.15.5.1 Induced voltage may appear in Signalling and Telecommunication Circuits when the length of parallelism to the track is appreciable. Even if there is no induced voltage in a circuit at the time of starting a work, precautionary measures listed below shall be taken, as induced voltages may develop at any time on account of an increase in current in the traction lines. It is also to be noted that in the case of equipment or circuits, which are earthed, a contact, which may normally be without danger, may give rise to an electric shock in the case of a break in the circuit or in the earth connections. Consequently, when staff have to work on Signal and Telecommunication Circuits on 25 KV A.C electrified lines, they shall take the following precautionary measures: -

a) They shall as a general rule, wear rubber gloves and use tools with insulated handles;

b) When the work to be done is of such a nature that rubber gloves cannot be used conveniently, special precautions shall be taken by spliting the circuits into sections or earthing them. In special cases, both the steps shall be taken simultaneously. If these protective measures cannot be applied, staff must insulate themselves from the ground by using rubber mats, etc. ;

c) The cable conductors pertaining to the block instruments are likely to develop heavy induced voltages and every time the staff handles the terminals of Block Circuits, they must rigidly observe the provisions of paragraphs (a) and (b) above. These cable terminals shall be printed RED to remind the Maintenance staff of the danger. The Maintenance Inspectors shall explain the meaning of this painting to the maintenance staff and ensure that they correctly understand it.

22.15.6 Before any work is undertaken on Signalling or Railway Telecommunication cables, the staff shall take the following precautionary measures :-

a) Reduce the length of the circuit as much as possible;

b) Use Rubber gloves as far as possible or alternatively use insulated rubber mats; &

c) Before cutting the armour or the metal sheath of the cable or the wires in the cables, an electrical connection of low resistance shall be established between the two parts of the armour, the Sheathing and wires that are to be separated by cutting.

22.15.7 Staff who have to work on electrical circuits shall be equipped with insulated tools such as box spanners, pliers, screwdrivers, etc. They shall, in addition, be supplied with rubber mats and rubber gloves. In regard to staff who have to work on equipment directly connected to the rails, tools with insulated handles may be supplied as far as possible and as far as practicable. A plastic sleeve on the handle will be sufficient in most cases.

22.15.8 Staff shall make themselves familiar with the instructions for treatment of persons suffering from electric shocks. Instruction Boards in English and in the regional languages describing the methods to be adopted for treatment of electric shock shall be clearly displayed in all Inspectors' offices.

22.15.9 In the event of break of catenary/contact wire of the overhead electrical equipment, the following precautions shall be taken for the safe working of the signalling equipment: -

i) The Train Controller, on receipt of an advice of a break in Traction Overhead Lines or confirmation of such an advice from the Traction Power Controller, shall immediately advise by the quickest possible means, to all the staff responsible for the maintenance and operation of the signalling equipment of the section where the catenary/contact wire has broken.

ii) The staff responsible for the operation of the Signalling equipment of the section shall immediately check whether the block and other signalling equipment are working normally. If an abnormal working of any equipment is noticed, its working shall be immediately suspended and necessary action under the Rules shall betaken.

iii) On receipt of this intimation, the staff responsible for the maintenance of Signalling of the section shall immediately proceed to the site and test all circuits and allied equipment paying particular attention to the external signalling gear to ensure that no damage to it has taken place. An authorised representative of the Signal Department shall submit Certificate that every thing is working all right and send it to his superiors alongwith a detailed test report as soon as possible.

22.15.10 2.2kV charging as an Anti-Theft measure

22.15.10.1 Guidelines for anti-theft charging pertaining to S&T works as prescribed in Appendix VII of ACTM Vol-II Part II shall be followed.

22.15.10.2 Besides, any specific works pertaining to specific section, the following S&T work shall be completed before issue of certificate for 2.2 kV charging

a) Provisions of wire mesh screen on the working platform of existing semaphore signals in case the requisite electrical working clearance of 2 metres is not available. No portion of signal post or it fittings shall be less than 700 mm from the live conductor.

b) Replacement of existing DC track relays and DC line relays by AC immunized relays

c) Supply of insulated tools to maintenance staff

d) Conversions of all overhead track crossings of BSNL and Railway into cables and removal of overhead wires thereof.

e) Certificate of clearance from BSNL regarding 2.2 kV anti theft energisation.

22.15.11 An approved checklist of the works to be completed as per provisions of this chapter shall be issued by Chief Signal and Telecom Engineer to the field offices. Compliance of this checklist shall be insured by the nominated officers responsible for issue of certificate before OHE is charged at 25 kV.

Annexure 31

Para 22.3.1 (C)

Extracts of Para 20.5 of Appendix-1

Manual of AC Traction - Volume II (Part-II)

20.5 Masts near signals

The visibility of 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 settings of mast before should be 3.25, 3.10,3.05,2.90 and 2.75 m for distance upto 80m, beyond and upto 110m, beyond and upto 190m, beyond and upto 270m 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 70m, beyond and upto 115m, beyond and upto 160m and beyond and upto 240m 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 2.75m for distances upto 60m, beyond and upto 125m, beyond and upto 170m, beyond and upto 215, beyond and upto 250m, beyond and upto 310m 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 2.75m for distance upto 70m, beyond and upto 130m, beyond and upto 170m, beyond and upto 215m and beyond and upto 280m 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.

Note: 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 600m before a signal. Drop arms of portals should also not normally be located in the lane where signals are located at least for a distance of 600m 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 center 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 signal's height may also be examined.

b) Signals with route indicators :

The principles mentioned under para 20.5.2 (a) should be observed in these case also.

Note: 1. No. part of a colour light signal without a route indicator should, as far as possible be higher than 5.2m 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 pantogaphs way zone.

2. On signal-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 2.75m for the first, second and next three masts respectively.

Note: For details see Drg. No. ETI/OHE/G/00112.

Annexure 32
Para 22.10.4.9

Detailed Instructions for measurement of stray Direct Current before installation of D.C. Single Rail Track Circuits.

1.0 Before installing a D.C. Track Circuit in areas, which are to be A.C. Electrified, stray Direct Current tests shall be carried out so as to ensure that D.C. Track Relays shall not operate with the stray currents.

2.0 These Tests shall be carried out only on non-electrified sections.

3.0 If there are already existing track circuits in the area, these shall be disconnected to safeguard against false readings being recorded in case of leakage of Block Joints.

4.0 The length of the track required being track circuited should be insulated by means of Block Joints on either end of the rails. The rail joints in the track-circuited length may or may not be bonded for purpose of these tests.

5.0 electing a suitable earth, which shall not exceed 5 ohms in resistance, test shall be carried out.

6.0 A suitable type of milli-volt meter and milli-ammeter shall be used for recording voltages.

7.0 These stray current and rail earth voltage measurements shall be recorded in accordance with the diagram for measurements indicated below: -

FIG. 1 - Measurement of Stray current

 

Note :- For measurement of stray current set up the circuit as shown above and measure the current simultaneously.

FIG.2 - Measurement of Rail -Earth Voltage

Note :- Where 9 ohms, 4 ohms or 2.25 ohms relays are used, use 9 ohms, 4 ohms or 2.25 ohms resistance and measure the voltage once at 'X' and next at ' XV.

8.0 These measurements shall be recorded at different periods of the day - one in the morning, one in the afternoon and one in the evening. These tests shall be extended for three days.

9.0 Where stray current/voltages are observed, the length of the Direct Current track circuit shall be cut down so as not to exceed the following limits for each length of Track Circuit: -

a) The Rail-Earth voltage as measured across 9 ohms, 4 ohms, or 2.25 ohms shall not exceed 0.1 volt.

b) The total stray current as measured shall not exceed 100 mA. Where all track circuits to be installed on the line are less than 100 metre long, the highest acceptable figure of stray current is 10 mA.

Annexure 33

Para 22.15.4

PROVISIONS OF PART 'J' OF PERMANENT WAY MANUAL
PART 'J'

Maintenance in Electrified areas

282 General Instructions to Staff : -

1) General knowledge of Engineering Staff

a) Every Engineering official working in electrical traction area shall be in possession of a copy of rules framed for the purpose of the operation of the Traction Power Distributions System pertaining to Engineering Department and ensure that staff working under him are also acquainted with the rules. He will ensure that rules pertaining to carrying out engineering works are strictly observed.

b) All electrical equipment, every power line or cable shall be regarded as being 'live' at all times. No work shall be commenced adjacent to any electrical equipment except on authority issued in writing by a competent official of the Electrical Department to the effect that the equipment has been made dead and earthed.

2) Defects in Overhead Equipment:- Defects or break downs in the overhead equipment including track and structure bonds noticed by the Engineering staff shall be reported immediately to the Traction Power Controller. When defects in the overhead equipment that are likely to cause damage to pantographs or trains are noticed, and it is not possible to convey information to Station Masters or Signal men to enable them to issue caution orders, the line shall be protected by the staff noticing such defects according to General Rule 3.62.

3) Traction Bonds: - In electrified areas the return current fully or partially flows through the rail. To ensure a reliable electrical circuit continuity and also to ensure proper earthing in case of leakage of current, various types of traction bonds as described below are provided at suitable places and maintained by the Electrical Traction Department: -

a) Longitudinal Rail Bonds: - In the case of D.C. traction system, practically the whole return current flows through the rail. Therefore, two flexible copper bonds offering minimum resistance to the flow of current are provided at each rail joint under the fishplates. Two solid lugs at the two ends of the copper bonds are inserted in holes drilled at the two rail ends between the fish bolt holes and are pressed by using a bend press to rivet them firmly to the rails. On points and crossings and at junction fishplates where continuity bonds of the above type cannot be provided due to space constraints, continuity of return current path is achieved by using mild steel straps or G.I. wire ropes.

Absence of such bonds may cause unsafe working condition and in extreme cases may damage the rail ends.

b) Cross Bonds (D.C):  Cross bonds are provided between adjacent tracks at regular intervals to reduce resistance of the current to the minimum. Such cross bonds are also known as transverse bonds.

c) Structure Bonds:- All structures supporting overhead equipment either in AC or D.C. track circuited areas are connected to the running rails for ensuring good earthing. Failure of insulator or leakage of current switches off the supply from the sub station so that men coming in contact with supporting structure etc., do not get electric shock. Removal or tampering of such bonds can, therefore, result in unsafe conditions. Since the structure are grouted in concrete, they are likely to become charged in case such bonds are kept disconnected. Similarly, other steel structures such as foot-over bridges, sheds, etc., in the vicinity of O.H.E lines are also connected to rails through similar structure bonds.

283 Special Instructions to Staff working in Traction area: -

1) Need for Precautions: - Precautions are required to be taken on account of following: -

a) Proximity of a Live Conductor: - The risk of direct contact with live O.H.E is ever present while working in electrified sections such as for painting of steel work of through spans of bridges and platform cover.

b) Build up of potential due to return current in rails : - The return current in the rails may cause a potential difference :-

i) Between rail and the surrounding mass of earth;

ii) Between two ends of a fractured rail;

iii) Between the two rails at an insulated joint ;&

iv) Between earth and any other metallic mass.

2) The following precautions should, therefore, be taken while working in traction areas: -

a) No work shall be done within a distance of two meters from the live parts of the O.H.E without a' permit-to-work'.

b) For work adjacent to overhead equipment the Engineering Inspect or shall apply to the proper authority sufficiently in advance for sanctioning the traffic and power block required. The Traction Power Controller through Traction Foreman will arrange to isolate and earth the section concerned on the date and at the time specified in consultation with the Traffic Controller. He shall then issue 'Permit-to-work' to the Engineering Inspector. On completion of the work the' Perm it-to-work' should be cancelled and Traction Power Controller advised, who will then arrange to remove the Earth and restore Power supply.

c) No part of a tree shall be nearer than 4 meters from the nearest live conductor. Any tree or branches likely to fall on live conductors should be cut or trimmed periodically to maintain this clearance. Authorized O.H.E staff should do cutting or trimming.

d) No fallen wire or wires should be touched unless power is switched off and the wire or wires suitably earthed. In case the wires drop at a level crossing, the Gatekeeper shall immediately make arrangements to stop all road traffic.

e) Work on Station roofs and Signal Gantries: - Staff working on station roofs and signal gantries and similar structures adjacent to live Overhead Equipment shall not use any measuring tapes, tools and materials when there is a possibility of their being dropped or carried by wind on to the live overhead equipment.

f) Earth Work: - For excavation work adjacent to tracks, the following action is taken :-

i) In D.C. traction areas, intimation should be given in writing sufficiently in advance to the concerned Traction Distribution Officer to enable him to depute the Traction Staff to be present in order to prevent possible damage in the traction underground feeder cables which are always located near the running lines.

ii) In AC traction areas, intimation should be given to the concerned officers of the Electrical General Services and also S&T Department, since all the S&T and Electrical lines are cabled on account of Electrical Induction.

In all AC and D.C. traction areas, the Traction Department provides cable markers showing location of cables. In addition, tiles and bricks protect the cables and during excavation, if workmen come across such tiles or bricks in an arranged manner, they should at once report the matter to the higher officials. Any further excavation should be carried out only in the presence of the authorized staff of Electrical Traction and or S&T Department as the case may be.

g) The relative alignments of the centerline of the track with respect to the alignment of the contact wire must be maintained within the specified tolerances. This applies to both horizontal and vertical clearances. Slewing or lifting of track must not be done outside the agreed maintenance limits unless the position of the contact wire is altered at the same time. Adjustment of cant has a magnified effect on the horizontal displacement of the centerline of the track with respect to the alignment of the contact wire.

Horizontal clearances to structures within the limits laid down in the Schedule of Dimensions must be maintained. For slewing or alterations to track involving adjustment of contact wire (outside the agreed maintenance limits) sufficient notice should be given to the traction staff  so that that they arrange to adjust the overhead equipment.

h) Alterations to Track Bonding: - All bonds removed by the staff of the Engineering Department shall be replaced by the staff of the Engineering Department and all such removals and replacements shall be reported to the Assistant Electrical Engineer, Traction Distribution in charge, concerned without delay.

j) Working of Cranes:- No crane shall be worked except on the authorized 'permit-to-work'. In every case of working of a crane, arrangement should be made for the presence of authorised overhead equipment staff to ensure that all safety precautions are taken.

k) Inspection of Tunnels: - For inspection of roofs and sides of a tunnel, the overhead equipment shall be rendered 'dead'. Special insulated apparatus should be used if sounding the unlined portions to locate loose rock in the roof and sides, is required to be carried out, when the overhead equipment is 'live'.

I) As far as possible closed wagons shall be used for material trains. In case open or hopper wagons are used, loading and unloading of such wagons in electrified tracks shall be done under the supervision of an Engineering official not below the rank of a Permanent Way Mistry, who shall personally ensure that no tool or any part of body of the worker comes within the' danger zone', i.e. within 2 meters of OHE.

m) Steel tapes or metallic tapes with woven metal reinforcement should not be used in electrified tracks. Linen tapes are safer and, therefore, should be used even though they are not accurate.

n) The top of foundation blocks in electrified structures should be kept clear of all materials.

284 Maintaining Continuity of Track: -

1) During maintenance or renewal of track, continuity of the rails serving electrified tracks shall invariably be maintained. For bridging gaps, which may be caused during removal of fish-plates or rails, temporary metallic jumpers of approved design shall be provided as under. The Electrical Department on requisition will provide the necessary jumper.

2) In case of rail fracture, the two ends of the fractured rail shall be first temporary connected by a temporary metallic jumper of approved design (as shown in the sketch below). In all cases of discontinuity of rails, the two parts of the rail shall not be touched with bare hands; Gloves of approved quality shall be used.

 

3) In the case of track renewals temporary connection shall be made as showed above.

4) In the case of defective or broken rail bond, a temporary connection shall be made as shown above.

5) Before fishplates are loosened or removed temporary connections shall be made as in sub section (3) above.

285 Catch Sidings : - Normally all catch sidings except those, which are sanded, shall be kept alive. On sanded catch siding, the rails shall be kept clear of sand for a length of 21.5 meters, beyond the section insulators in the overhead lines and the switches controlling the sanded catch sidings shall be kept in the neutral position. If an electric engine or single or multiple unit train runs into the sanded length of a catch siding, it may possible be insulated from earth except through the buffers or couplings if connected to other vehicles, therefore, these sidings shall not be made alive when an electric engine or single or multiple unit train or any vehicle coupled thereto are standing in the sanded track until all staff have been moved away from positions where they are likely to make contact between the permanent way formation and any part of the locomotive or single or multiple unit train or coupled vehicles. No person shall attempt to enter, or leave or in any other way make contact between the permanent way formation and the electric engine or single or multiple unit train or any vehicles coupled thereto while one overhead equipment of the sanded length of siding is alive.

286 Additional precautions in AC Traction Area: - The following additional precautions are required to be taken in AC traction areas :-

1) Build-up of potential due to induction in metallic bodies situated close to O.H.E : - It is important to note that dangerous voltage may be induced in metallic masses such as fencing posts in the vicinity of traction conductors. To avoid possibility of shock due to such voltages, the metallic structures are bonded together and earthed.

2) Unloading of rails :- When unloading rails along tracks, care shall be taken to ensure that rails do not touch each other to form a continuos metallic mass of length greater than 300 meters.

3) Permanent way staff are advised to keep clear of the tracks and avoid contact with the rails when an electrically hauled train is within 250 meters.

287 Fire in electrified areas : - The Permanent Way Officials noticing a fire likely to result in loss of life or cause damage to property shall take all possible steps to prevent it from spreading and to extinguish it. In case the fire is on adjacent to any electrified equipment, the permanent way official shall make no attempt to extinguish the fire but shall report the occurrence of fire to the nearest Station Master by most expeditious means.

288 Permanent Way Tools :- Permanent Way tools (insulated and un-insulated) along with gloves shall be used in the manner as approved by the Chief Engineer of the Railway.

289 Treatment of persons suffering from Electric Shock :- When persons receive electric shock, practically in every case, they can be revived with the prompt application of First Aid.

Method of Resuscitation :- The method of resuscitation resorted to should be that known as artificial respiration.

Continuity of Treatment:- The efforts to restore breathing must be continued regularly and with perseverance, and must not be discontinued until a Doctor has taken charge of the case.

290 Accident to power lines of outside bodies: - The Engineering Inspector shall be in possession of the name and address of the officer-in-charge of each power line across Railway land to enable an immediate report of any defect or accident appertaining thereto being made, under advise to the Assistant Engineer/Divisional Engineer.
 

Note

(1) All Dimensions gives are in millimetres.

(2) In applying the diagram to curves it should be inclined so that the axis of the diagram is normal to the track plane.

(3) The diagram is not applicable to turnouts.

(4) This diagram is not applicable to the Anchor span where the conductors are outside the track zone.

(5) The curves are drawn for the maximum cant applicable, therefore, for lesser cant it may be economical to decide the clearance at site jointly with the Electrical department.

(6) Curves in full line are for tangent track and those in dotted line for curves track with SE.60.

SIGNAL CLEARANCE DIAGRAM TO SUIT 25 K.V., A.C. TRACTION

FOR TANGENT TRACKS AND CURVED TRACKS WITH SE. 60

SCALE 1 cm = 500mm

Drg. No. 22.1

Note

(1) All Dimensions gives are in millimetre.

(2) The diagram is not applicable to turnouts.

(3) The diagram is not applicable to the Anchor span where the conductors are outside the track zone.

(4) The curves are drawn for the maximum cant applicable, therefore, for lesser cant it may be economical to decide the clearance at site jointly with the Electrical department.

SIGNAL CLEARANCE DIAGRAM TO SUIT 25 K.V., A.C. TRACTION

FOR CURVED TRACKS 60 TO 140 S.E.
SCALE 1 cm = 500mm

Drg. No. 22.2

Note:
(1) All Dimensions gives are in millimetre.

(2) This diagram is not applicable to turnouts.

(3) The diagram is not applicable to the Anchor span where the conductors are outside the track zone.

(4) The curves are drawn for the maximum cant applicable. Therefore, for lesser cant it may be economical to decide the clearance at site jointly with the Electrical department.

SIGNAL CLEARANCE DIAGRAM TO SUIT 25 K.V., A.C. TRACTION

FOR CURVED TRACKS 140 TO 185 S.E.
SCALE 1 cm = 500mm

Drg. No. 22.3

SIGNAL CLEARANCE DIAGRAM TO SUIT 25 K.V. TRACTION FOR METRE GAUGE

TANGENT AND FLAT CURVED TRACKS (TENTATIVE)

Note

(1) All the dimensions are in mm, unless otherwise shown.

(2) The full outline is applicable to normal standard overhead equipment in other than overlap spans without allowance for track slewing.

(3) The dotted outline is applicable to overhead equipment in paralleling spans, insulated as well as uninsulated.

(4) The Diagram is applicable to tracks with small super elevation not exceeding 40mm, the axis of the diagram should be kept normal to track plane while applying the Diagram to super elevated tracks.

(5) The Diagram is not applicable to (i) Anchor spans (ii) Turnouts (iii) Two metres on either side of the structure, and (iv) Loco sheds and Inspection Pits.

Drg. No. 22.4

SIGNAL CLEARANCE DIAGRAM TO SUIT 25 K.V. TRACTION FOR METRE

GAUGE SHARP CURVES - (TENTATIVE)

Note :

(1) All the dimensions are in mm.

(2) The full outline is applicable to normal standard overhead equipment in other than overlap spans without allowance for track slewing.

(3) The dotted outline is applicable to overhead equipment in paralleling spans, insulated as well as uninsulated.

(4) The Diagram is applicable to curved tracks with super elevation between 40 and 100 mm.

(5) The Diagram is not applicable to (i) Anchor spans (ii) Turnouts (iii) Two metres on either side of the structure, and (iv) Loco sheds and Inspection Pits.

Drg. No. 22.5

COLOUR LIGHT SIGNAL LEFT HAND OR RIGHT HAND

Broad Gauge (Tangent Track)

(4) With the standard signal fittings (Ladder width 600mm & signal unit width 440mm). The C of signal post shall be at 2.844m (9'-4") from the C of track.

(3) If warranted by site conditions settings other than the recommended rationalised ones may be adopted provided these do not infringe the minimum settings represented by the full line.

(2) The dotted line represents the recommended rationalised settings of the OHE structures.

(1) The full line represents the minimum settings of OHE structures.

Drg. No. 22.8

(4) With the standard signal fittings (Ladder width 600mm & signal unit width 440mm). The C of signal post shall be at 2.844m (9'-4") from the C of track.

(3) If warranted by site conditions, settings other than the recommended rationalised ones may be adopted provided these do not infringe the minimum settings represented by the full line.

(2) The dotted line represents the recommeded rationalised settings of OHE structures.

(1) The full line represents the minimum settings of the structures.

Drg. No. 22.9

LIST OF CORRECTIONS AND ADDITIONS

LIST OF CORRECTIONS AND ADDITIONS