AC Electrified Areas: Signalling Factors

General Objectives

• Signalling equipment must function normally when traction current is present
• The signalling system must not give false readings
• The signalling system should not impact the safe operation of trains, even in a faulty or anomalous condition
• Equipment and staff must be protected from electric shock

Factors Affecting Signalling in AC Electrified Areas

• Signal visibility is affected by Overhead Equipment (OHE) structures
• Electrical clearances must be maintained for signals near live Overhead Equipment (OHE)
• Traction return current affects signalling
• Signalling is affected by electrostatic and electromagnetic induction

OHE Structures and Signal Visibility

• Implant Overhead Equipment (OHE) properly during the design stage
• Provide protective shields for signal structures when electrical clearances are not possible
• Layout Plans for Overhead Equipment (OHE) should be based on approved Signalling Plans

Electrostatic and Electromagnetic Induction

• Electrostatic induction is reduced via underground cables protected by a metal sheath
• Electromagnetic induction creates currents and voltages in conductors parallel to the track
• Affected conductors include rails, traction return conductors, cable sheaths, signalling, and telecommunication circuits
• Potential gradients and differences occur along conductors and adjacent Earths
• The value of induced voltage depends on:
• Length of parallelism between conductors and electrified track
• Soil conductivity
• Screening efficiency of cable sheath
• Return current through rails/return conductor
• Mutual inductance between catenary and cable conductors
• Separation between catenary and cable
• Current carried by the catenary

Signal Structures in RE Areas

• Use color light signals only in electrified areas
• Masts, insulators, wires, and supports obstruct signal visibility on electrified sections
• Signals must maintain minimum clearance from live Overhead Equipment (OHE)
• Follow electrical clearance instructions strictly
• Loco Pilots can see clearly as a result
• Signal Sighting Committee checks actual visibility, takes action based on recommendations

Signal Clearance Diagrams for Broad Gauge

• The location and protection of signals are based on signal clearance diagrams for Broad Gauge

Standard Moving Dimensions

• Signal posts or fittings should never infringe on the un-shaded portion above standard moving dimensions
• Signal posts or fittings should not infringe on the shaded envelope
• If infringement into the shaded area is unavoidable, special protective measures are required
• The dotted outline in Drg. Nos. 22-D1, 22-D2, 22-D3 applies when two sets of Catenary and Contact wires are parallel
• The diagrams do not apply to anchor spans, turnouts, areas within 3 meters of masts, or loco sheds/inspection pits
• The diagrams do not apply when there is a feeder line running along with masts, or where booster transformers/return conductors are provided

Contact Wire and Catenary Heights

• The normal height of the contact wire is 5.60 meters at supports
• The normal height of the catenary is 7.05 meters at its highest point
• In tunnels and under bridges, the contact wire may be as low as 4.58 meters for Broad Gauge
• Catenary may be suitably lowered or terminated at the face of bridges or tunnels when clearances are limited
• Clearance diagrams are designed for extreme positions of the catenary and contact wire
• Diagrams account for stagger and displacement of wires by wind

Clearances for Safety

• No one is allowed to approach closer than 2 meters from the live parts of the Overhead Equipment (OHE) under normal conditions
• These protective measures should be adopted by any signalling
• If signal posts or fittings are within 2 meters of a 25kV live conductor, protect with an iron screening connected to structural work
• If protective screening is impractical, provide a caution board at 3 meters above rail level
• The Supervisor shall explain instructions to staff and ensure compliance
• Drg. Nos. 22-D4 and 22-D5 show signal locations on Broad Gauge tracks, indicating minimum heights and distances

Location of Neutral Section

• Neutral sections should be located away from stop signals and level crossings including straight and level tracks

Location of Signals in RE Area

• Signals should be located on the left side of the track, exceptionally on the right
• OHE masts are implanted per the ACTM to ensure adequate signal visibility
• Offset brackets may be used for signal units without affecting the schedule of dimensions
• If a traction mast is in front of a signal post, the distance should be no less than 30 meters, with no traction masts less than 10 meters in advance
• The signal post must be high enough for clear visibility
• Desirably, the signal should be within the OHE structure on tangent tracks
• The implantation of the signal from the track centre should be less than the implantation of the OHE mast from the track centre
• Use individual examination when the track is curved or there are obstructions

Restrictions

• No part of a colour light signal can infringe within the schedule of dimension from the center line of the nearest track
• Where the traction mast is in front of the signal, there must be at least 30 meters distance. Additionally, there cannot be any traction mast at a distance less than 10 meters

Signals Outside Tracks without Junction Indicators

• Distance of OHE masts in accordance with Drg. No.22-D6
• Signal units should be fixed so that the centre line of the red signal is approximately 3.65 meters above rail level
• The Signal should be lower than 5.2 meters above rail level

Signals between Tracks without Junction Indicators

• When located between tracks, no OHE structures can be provided in the same track space for at least 600 meters behind
• Portal drop arms should not be located at least for a distance of 600 meters before the signal
• Where this is unavoidable, If a portal drop arm has to be located behind the signal is unavoidable, the signal should be on a bracket
• A special study ought to determine if the portal drop arm can be offset for at least 3 portal drop arms, to see if the portal drops arm can be shortened

Signals with Junction Indicators Outside Tracks

• Setting distances of OHE masts should be in accordance with Drg.No.22-D7

Signals with Junction Indicators between Tracks

• Precautions for portal drop arm locations are as specified under Para 22.3.4
• For details of drawings, illustrating principles above for color Light Signals, refer to Drg.No.22-D7

Visibility Checks

• The Official in charge of signalling is to confirm the the visibility of the signal by day and night after each phase of Overhead Equipment work
• Speed restrictions should be taken to improve visibility, if it is not adequate

Clearances for Signals for High Rise OHE

• See Annexure: 22-A3 and Drg.No.22-D7

Signalling Circuits in RE Areas

• In the electrifed zone, no aerial circuits are allowed
• Cable length and distance to Block Wires must ensure induced voltage does not exceed CCITT limits

Earth-Return Circuits

• No earth-return circuits, barring block-instrument circuits, are allowed in A.C. electrified territory
• Block instruments need an approved filter, as explained in Chapter 18 of SEM

Equipment Not Safe for AC Induced Voltage

• Luminous Indicators, Telephone type relays, Electrical Lever Locks, Door Coil of IRS Block Instrument are not safe to place where AC can interefere
• 250 Ohm D.C. neutral Line Relay, Rotary Key Transmitter and, D.C. Neutral Polar Relays are also not safe to place where AC can interfere
• Coils for mentioned equipment can only be used in a cabin or location box in internal circuits

Electrical Requirements

• All batteries and wiring in equipment locations should be well insulated from the ground
• IRS- S-76 will set the standard for approved PVC insulated wires to use for wiring in location boxes and cabins
• Batteries/DC-DC converters will be provided for external and internal circuits
• Multiple Cables ought to ensure that all wires pertaining to any individual circuit are in the same cable

AC Effects on Polarized Relays

• Polarized Relays using a permanent magnet cannot be used in external circuits in 25 KV AC
• The permanent magnet in the relay can lose magnetic properties
• Anthority can authorize any exception in specific cases

Relays

• Relays that release an interlocking must act slow to avoid unintended release due to momentary voltage changes
• Delay for the order be in the range from 0.6 to 0.8 seconds

Operation

• External AC circuits must work with double cutting

Outdoor Signalling Circuits Requirements

• A signaling light must be the only way to ensure that induced voltage from a traction has a limit of 400 volts if there are normal conditions
• If needed, circuits lines will need to be be sectionalized for enclosures or buildings
• If line side enclosures/buildings run in different directions circuits can have continuity, if the voltage has been exceeded, provide power for each direction

Calculating Voltages and Immunity levels

• Voltage on underground-unscreened cables must be recorded as 116 Volts/km single line and 95 Volts/km double line
• This should happen on cables with normal condtions
• Catenary has 800 amperes for single line and 1000 amperes for double line
• If the circuits terminate on relays/equipment immunity cannot drop below 400 V AC.
• Reduction of feed cable happens on relay to adjust to the proper setting and length dependent on AC immunity

DC circuits

• The length of DC Circuits on Line Relays with unscreened cable shall be restricted to based on type of relay, AC immunity level, length on single line and double line
• This is dependent on whether they are fitted to unscreened cables/wires
• Type of Relay
• QNA1/QNNA1/QNA1K
• K50 B
• 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.

Signal Feed Circuitry in RE area

• The system for signal feed must be of the 110 V 50 Hz type or any approved type The distance between the signal control relays and the signal cannot be outside of the limits listed in the electrified zone
• This will occur even with earth faults in signal control relays
• This means that the amount of electrical activity is lower
• This will be adequate even when not good weather comes along
• This requires special equipment to safely traverse

Specific Requirements

• If the signal happens to be at a large distance, this needs to be regulated by what has been written
• An example would be, feed the signal by managing what the relays located
• Another example would be for signals that are managed, they can also be operated from using to which the relay comes from. Use No. 22-D9
• Ensure that the power for the above circuits has different requirements from other transformers/relays
• the length of the signals must be as written, Single Track needs 180 m, Double Track: 220

Point Operation & Detection in RE Area

• To operate a point can happen either by power or movement mechanically
• Both of these actions have regulations as they are sensitive
• Operation by powers should have max distance in electrical systems and their immunity to the environment
• Type and safety factors need to be well noted as such Factor of safety is 1.5

Machinery details

• There will be a length, both singular and with double lines, that will permit the system to be properly connected
• Type, Ac level and safety have all be written with a table with these specifications

3 Phase Design of Machinery

• The system from 3 phase point machine will be immune to voltages applied in any fashion and be operating in any limit
• Safety and care are greatly in need

Rod Runs in RE Areas

• Point rods get their electrical power running
• Given their connection that can be done with whatever the rails are placed on means this will send the power to this station
• Insulators help prevents the machine from taking in the rail's voltage in case any of the equipment fail

Joints And Installation

• The rod will be insulated based on previous knowledge
• Please use the safest procedures, to do this follow all safety requirements for installation and to get help from senior expert teams
• Rods should be put in place as quick, safe, and efficient for both parties
• Please remember that the rods should be installed in the closet spot where possible and any power/contact between rods should be avoided

Insulators

• Put another insulator between the crank as this will make sure no power be sent
• Distances that are too long greater than 300 can be a cause for concern, ensure that the insulators will be placed to make sure everything is safe
• Every trap indicator and the bar must have electrical assistance that is not from source
• Make sure to have and confirm a proper plan

More on insulating

• Every set of rollers and guides have an insulating portion Make certain that the gap between the insulator and roller is long enough and up to standards When crossing the track, always ensure that the top is 40 mm from the bottom For steel sleepers maintain 40 mm separation. Similar rule applies to any O.H.E mast and point rods Insulate points regardless of the distance or whether it is on the line

Further Notes and Requirements

• Please, do refer to the chapter that will give arrangements
• When that point happens make sure that the department ensures that everything has safely check and that no harm has happen
• See power that applies chapter 16, circuit's SEM chapther 17, blocks SEM, and EARTHING to understand the supply, areas and counters Section 8: Rules for Safely Keeping Team From Harms

Protection for Staff

• Those, who work on signals and telecommunication will need to perform precautions
• Ensure your proximity to whatever is charged to avoid risks

Conductors

• There must, at no point, be any contact
• Make sure to properly avoid and practice every proper steps on the conductors to safely pass and not injure staff/team
• Ensure to never have or cause stress for what has been made

Pressure and the Danger

• Be extra precaution and be sure that this is done with careful intention as it is a big safety issue to properly follow

Precautions

• Any tools used must be done with careful methods especially in working on the track
• Safety is the number one rule
• Do ensure the proper measure during this time to prevent any harm

Voltage

• Take the necessary precautions on what voltages appear as they can be heavily deadly
• Keep an idea on the voltage at all times or hire an outside source to come check and look
• Be very careful no to cause heavy contact on those lines and wear protection to come into contact with the lines incase they cause surges of voltage
• Make certain to wear gloves especially
• Make sure that the staff is highly train to act proper and use tools and equipment safely

Working Safely

• Ensure that all equipment has insulated tools When needed, use splint tools as well as earthing to ensure the staff/team who are going into the field safety
• Not following safety measures can lead to harm

More on what will happen in dangerous safety

• Follow the requirements and be completely prepared, those who take it lightly will be subject to face problems involving health complications and legal actions for damages
• Ensure that every action and step has zero chance of failure, to do this you must train and maintain safety in mind
• Follow all safety measures to ensure the safety of other as well as yourself

Working With Safety

• The team and staff must be protected at all times
• Be certain to work in what the safety and precautions are and please make sure that it is up to standards and prevent problems
• Work with plastic sleeves as it is more preferable in most tasks
• The team is there to give instructions and guidance and to help with what you need to ensure safety , if in trouble

Breakage of Cable

• Train will have to quickly communicate their position after receiving advice from above _ Ensure to give their position if something occurs with the lines and cables

Safety Against Theft

Get the standards for safety

• the final step after the work requires certifications to ensure that OHE is fully charged on line

Visible Areas

Make sure you can properly see where your position and equipment is Know the visibility of where signals Where mast are has high importance

Areas of Lights in Certain Sections