Chapter 22 Requirements Of Signalling in 25 KV AC Electrified Area PDF

Section 1: General ================== 1. Objectives ---------- a. To ensure that signalling equipment continues to function normally in the presence of traction current. b. To ensure that interference from the traction system cannot, under any circumstances, cause t...

Section 1: General ================== 1. Objectives ---------- a. To ensure that signalling equipment continues to function normally in the presence of traction current. b. To ensure that interference from the traction system cannot, under any circumstances, cause the Signalling system to exhibit false 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. c. To safeguard equipment and staff from electric shock. 2. Factors Affecting Signalling in AC Electrified Area --------------------------------------------------- d. Visibility of signals due to OHE structure. e. Electrical clearances of signals due to live OHE close by. f. Traction return current. g. Electrostatic induction and Electro-magnetic Induction. 3. Visibility of Signals shall be taken care of 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. Lay Out Plan for OHE shall be based on approved Signalling Plan. 4. The electrostatic induction is practically eliminated by transferring a circuit into underground cables protected by a metal sheath. The Electro-magnetic 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- h. Length of parallelism between the cable conductors and the electrified track. i. Soil conductivity. j. Screening efficiency of the cable sheath where existing. k. Return current through the rails and return conductor where provided. l. Mutual inductance between catenary and the cable conductors. m. Separation between catenary and cable. n. Current carried by the catenary etc. Section 2: Signal Structures in RE area ======================================= 1. Colour light signals only shall be used in electrified areas. 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 Loco Pilots 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. 3. The location of signals and the protection required shall be worked out from the following signal clearance diagram for Broad gauge. -- -- -- -- 4. In these diagrams the un-shaded portion shown above the standard moving dimensions is the area into which a signal posts 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 Drg. Nos. 22-D1, 22-D2, 22-D3 for Broad Gauge 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. 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 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. 6. Clearances for Safety --------------------- 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. a. 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. b. If for any reason it is not practicable to provide the protective iron screening as mentioned above, a Caution Board of approved design shall be provided on the signal post at a height of 3 meters above the rail level, to caution the signal staff. c. The SSE/JE (Signal) shall explain these instructions to the staff working under them and ensure that they are correctly complied with. 7. Drg. Nos. 22-D4 and 22-D5 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. 8. **Location of Neutral Section** *(Reference: Para No. 16.4 to 16.5 of ACTM, Appendix I)* -- -- -- -- Section 3: Erection of Signals in RE Area ========================================= Location of Signals in RE Area ------------------------------ 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, offset 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. 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 meters. In addition, it should be ensured that no traction mast is located in advance of the signal post at a distance less than 10 meters. b. PCSTEs and PCEEs of the zonal railways shall give dispensation for reduction in the distance of placing mast in front of the signal from c. The signal post should be sufficiently high so as to be seen clearly. d. 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-!I). Relevant extracts as in Annexure:22-A1. e. 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. 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. 3. Signals without Junction Indicators Outside Tracks -------------------------------------------------- f. Distance of OHE masts shall be in accordance with Drg. No.22-D6. g. 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. 4. Signals without Junction Indicators between Tracks -------------------------------------------------- h. If signals are located between tracks no OHE structures shall be provided in the same track space for at least 600 meters in rear of the signals. i. Portal drop arms shall not normally be located at least for a distance of 600 meters before the signal in track space where signals are located. j. 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. 5. Signals with Junction Indicators Outside Tracks ----------------------------------------------- Signals with Junction Indicators outside tracks Setting distances of OHE masts shall be in accordance with Drg.No.22-D7. 6. Signals with Junction Indicators between Tracks ----------------------------------------------- k. Precautions and parameters for location of portal drop arms shall be as specified under Para 22.3.4. l. For details of drawings, illustrating the above principles for Colour Light Signals, refer to Drg.No.22-D7. 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. 8. For Clearances for Signals for High Rise OHE (for Running Double Stack Container & Three Tier Car) , Please see Annexure: 22-A3 and Drg.No.22-D7 Section 4: Signaling Circuits in RE area ======================================== 1. As a rule, no aerial circuits shall be retained in the electrified zone. In every 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 limits prescribed by CCITT. 2. Barring block-instrument circuits, no other earth-return circuit shall be permitted in A.C electrified territory. Block instruments, however, shall be suitably protected by a filter of approved design as explained in Chapter 18 of SEM. 3. The following electrical signalling equipment are not safe to withstand AC induced voltage. The coils of this 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/DC-DC Converter and this battery/DC-DC Converter 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. 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. 5. Separate Batteries/DC-DC Converters shall be provided for external and internal circuits. 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. 7. Polarized 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. 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. 9. All external circuits in AC. electrified area shall work with double cutting. Section 5: Outdoor Signalling Circuits in RE area ================================================= 1. Maximum Length of Parallelism ----------------------------- a. 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 line side 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. b. 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 under normal conditions when the catenary current of 800 amperes for single line and 1000 amperes for double line. c. 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. d. The length of DC Circuits on Line Relays with unscreened cable shall be restricted to- **Type of Relay** ------------------------------------------------------------------------------------------------------------------------------ -- -- -- QNA1/QNNA1/QNA1K K50 B1 K50 B1-A2 K50 AC Immunized neutral relay (IHC Make) \* Maximum permissible induced voltage is restricted to 400 V for human safety and factor of safety 1.5 has been considered. Section 6: Signal Feed Circuitry in RE area =========================================== Feeding Distance ---------------- Signal feed system shall be of the 110 V 50 Hz type or any approved type. 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. 3. Maximum permitted length of direct feed of signal shall be as per Table given below. ------------ -------------- -------------- Single Track Double Track Unscreened 180 m 220 m ------------ -------------- -------------- 4. When a signal is located at a distance greater than that specified in para 22.6.3 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 controlling relay at the location. Typical circuit is given in Drg. No. 22-D9. 5. It shall be ensured that the power transformer for feeding circuits as per para 22.6.2 shall be different from the transformer feeding longer circuits. Section 7: Point Operation & Detection in RE area ================================================= 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. 2. Electric Operation of Point --------------------------- a. Point detection and point detection repeat circuits shall use ac-immunized relay. b. The maximum permissible length for various types of commonly used Point Machines is as under: ------------------------- -- -- -- Factor of safety is 1.5 ------------------------- -- -- -- c. 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. Rod Runs in RE Areas -------------------- 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 para 22.7.4 for protecting the Operating & Maintenance Staff from the effects of these voltages. 4. Insulated Rod Joints for RE --------------------------- d. The insulated rod joints shall be as per approved drawings. e. 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 f. 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. g. 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. h. Each Point, Trap indicator and lock bar operated by rodding shall be electrically isolated from the track. i. 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 un-insulated portion of another rod. j. The clearance between the insulator and the adjacent rod roller shall be adequate to permit normal movement of the rod. k. When a rod crosses the track, the top of the rod shall not be less than 40 mm from the bottom of the rail. When steel or C.I sleepers are used, the distance between the rod and the sleeper shall be also 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. l. The operating rod of locally worked points on all electrified lines and of similar points taking off from the 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. m. When the Engineering department provides the point lever or point box, Engineering department shall provide the insulator on the operating rod. 5. \(a) Please refer to SEM Chapter 16 for details of Power supply arrangements. b. Please refer to SEM Chapter 17 for details of Track Circuits, AFTC in RE area, Axle counter. c. Please refer to SEM Chapter 18, section 2 for details of Block working in RE area. d. Please refer to SEM Chapter 19, section 11 for details of Earthing. Section 8: Rules for Protection of Staff working on Signal & Telecommunication Installation =========================================================================================== Protection for Staff -------------------- 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. 2. **Proximity of a Live Conductor:** Any contact direct or indirect, with the 25 KV conductors is dangerous and shall be strictly avoided. 3. Pressure of Return Current in Rail ---------------------------------- The flow of return current in the rails will give rise to a potential difference. d. 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. e. Between the ends of a fractured rail at the fracture. f. Between an insulated rail and the non-insulated rail used for the traction return current. g. Between the rail and the surrounding mass of earth. 4. Wherever staff has to work on installations, which are in direct or indirect contact with the rails, they shall: h. Insulated tools must be used in accordance with approved instructions. i. Observe provisions of Section \'J\' of permanent way manual (extract given at Annexure: 22-A2). 5. Induction in Metallic Bodies Situated Close to OHE -------------------------------------------------- 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 AC electrified lines, they shall take the following precautionary measures: j. They shall as a general rule, wear rubber gloves and use tools with insulated handles. k. When the work to be done is of such a nature that rubber gloves cannot be used conveniently, special precautions shall be taken by splitting 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. l. 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 SSE/JE (Signal) shall explain the meaning of this painting to the maintenance staff and ensure that they correctly understand it. 6. Before any work is undertaken on Signalling/Telecommunication cables, the staff shall take the following precautionary measures: m. Reduce the length of the circuit as much as possible. n. Use Rubber gloves as far as possible or alternatively use insulated rubber mats. o. 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. 7. Staff who have to work on electrical circuits shall be equipped with insulated tools such as box spanners, pliers, screw-drivers, 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. 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 SSEs/JEs (Signal)\' offices. 9. Breakage of Catenary/Contact Wire --------------------------------- p. 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. q. 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 be-taken. r. On receipt of this intimation, the staff responsible for the maintenance of Signalling system 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 not below the rank of SSE (Signal) shall submit Certificate that everything is working all right and send it to his superiors along with a detailed test report as soon as possible. 10. 2.2 KV Charging as an Anti-Theft Measure ---------------------------------------- s. Guidelines for anti-theft charging pertaining to S&T works as prescribed in Appendix VII of ACTM Vol-II Part II shall be followed. t. 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. i. Replacement of existing DC track relays and DC line relays by AC immunized relays. ii. Provisions of wire mesh screen on the working platform of existing signals in case the requisite electrical working clearance of 2 meters is not available. No portion of signal post or its fittings shall be less than 700 mm from the live conductor. iii. Supply of insulated tools to maintenance staff. iv. Conversions of all overhead track crossings of BSNL and Railway into cables and removal of overhead wires thereof. v. Certificate of clearance from DOT regarding 2.2 KV anti-theft energisation. 11. An approved checklist of the works to be completed as per provisions of this chapter shall be issued by Principal 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. -- -- -- -- -- -- -- -- -- -- -- -- Visibility of Signals in RE Area ================================ (Extracts of Para 20.5 of Appendix-1: Manual of AC Traction - Volume II (Part-II) --------------------------------------------------------------------------------- 5. **Masts near Signals:** The visibility of signal 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. 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 up to 80m, beyond and up to 110m, beyond and up to 190 m, beyond and up to 270 m and beyond and up to 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 b. Colour Light Signal with Route Indicators: ------------------------------------------ iii. **With Horizontal Route Indicator:** The minimum setting of masts before the signal should be 3.72, 3.50, 3.25, 3.05, 2.90 and 2.75 m for distances up to 60 m, beyond and up to 125 m, beyond and up to 170 m, beyond and up to 215, beyond and up to 250 m, beyond and up to 310 m respectively. iv. **With other than Horizontal Route Indicator:** The minimum setting of masts before the signal should be 3.50, 3.25, 3.05, 2.90 and 2.75 m for distance up to 70 m, beyond and up to 130 m, beyond and up to 170 m, beyond and up to 215 m and beyond and up to 280 m respectively. *Note: 1. See Drg. No. ETI/OHE/G/00112 also. The setting may be reduced in special cases, conforming to Figs. 6 to 9 of ibid.* Colour Light Signals Located Between Tracks ------------------------------------------- a. **Signals without Route Indicators:** No OHE mast should, as far as possible be located in the same lane as the signal for a distance of at least 600 m before a signal. Drop arms of portals should also not normally be located in the lane where signals are located at least for a distance of 600 m before the signal. Where this is not possible, for any reason, the signal should be mounted on an off-set bracket. In addition, a special study should be made in each such case in respect of three drop arms before the signal, to see whether the drop arms can be off-set from the 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. 3. For semaphore signals located outside the track: The minimum settings of masts before the signal should be 3.05, 2.90 and 2.75 meters for the first, second and next three masts respectively.