Signalling & Telecommunication Installations Quiz

Electrostatic and electromagnetic induction from overhead lines (OHE) impacts signaling circuits near electrified tracks. Electrostatic induction is mitigated by underground cabling. Electromagnetic induction creates voltages in parallel metallic items like rails and cable sheaths.

The generation of voltage in a conductor due to a changing magnetic field near the conductor.

The transfer of charge to an object through an electric field.

Colour Light Signals (CLS) are typically used in double line electrified railway sections.

Signal visibility might be reduced when OHE masts and parts block the view.

Part of a signalling system that detects the presence or absence of a train on a section of track.

Process of determining the best signal placement in areas with obstructions (like curves, buildings, etc.)

A committee, including an electrical representative, that examines signal visibility before placement decisions.

Insulators are necessary on wires and point rods in AC electrified areas to protect them from induced voltages.

Voltage generated by OHE faults (Overhead line equipment) that could affect wires and point rods.

Another name for induced voltage. It transmits through wires to lever frames.

Essential process for AC electrified sections, using prescribed instructions, for signal posts, lever frames, metallic sheaths, cables, block instruments, telecommunication equipment, and surge arresters.

Used on signal posts to enhance safety and prevent electrical hazards in AC electrified sections.

Critical earthing of the cable sheath and armouring at both ends of underground cables to achieve screening from induced voltages.

Instruments used in signalling systems, which often use earth return circuits through block filters

Equipment used for communication within a section, and its components need to be earthed as prescribed.

Cables near traction masts must be at least 1 meter from the mast foundation edge, but a minimum of 3 meters if deeper than 0.5 meters; concrete pipes may reduce this distance.

Cables near substations must be at least 1 meter away from metallic parts and the substation earthing system. A 300m length requires concrete pipes.

Cables near switching stations must be at least 1 meter from metallic structures, and at least 5 meters from the earthing system; concrete pipes reduce this to 1 meter.

If an overhead line mast has a separate earth, cables must be kept at least 1 meter from it.

Ideally, cables should be laid on the opposite side of the track to feeding posts, and a minimum of 5.50 meters from the track center.

When cables cross tracks, concrete or GI pipes for the crossing are necessary.

Earth resistance should not exceed 10 ohms.

Main signaling cables in electrified sections are usually made from PVC insulated, screened and armoured type materials.

Metallic pipes, like galvanized iron pipes, are not allowed within 300 meters of a feeding post.

Galvanized iron pipes are forbidden near switching station grounds and traction masts.

When overhead communication lines are replaced with cables, block instruments using earth return are moved to insulated special PVC underground cables.

Different types of track circuits can be used on electrified sections, including DC single rail, AC at different frequencies, and electronic voice frequency circuits.

Track bonding for traction current needs adjusting in areas where track circuits are employed.

Overhead lines used for signalling and interlocking are replaced by underground cables due to electromagnetic interference.

Cable circuits are limited to prevent induced voltages exceeding 120 volts (3.5 km parallelism).

If the parallelism is more than 3.5 km, using a relay interrupts the cable and reduces parallelism to within the 3.5 km limit.

If a circuit exceeds 3.5km in parallelism due to it being fed from multiple batteries, it requires separate batteries for each section to limit the length to below 3.5km.

Telecommunication lines running parallel to tracks on AC electrified sections should be replaced with underground cables to prevent induced voltage issues.

Voltage created in a cable due to electrical fields/magnetic fields from the adjacent overhead lines.

Used to protect telecommunication equipment (way stations, subscribers' equipment, exchanges) from high induced voltages in underground cables.

Used to replace overhead lines in AC electrified areas because they're less susceptible to induced voltages.

The loss of signal strength over a distance in a communication line.

Used to boost signal strength in communication lines, especially those laid underground.

Connecting to a circuit for use.

A circuit used to regulate and control traction power systems.

Approval required by the Chief Electrical Engineer for tapping into specific traction power circuits.

Signals must be placed for maximum visibility and with specific electrical clearances (at least 2m) from live conductors in electrified sections.

Protective screens of wire mesh are needed when signal posts are within 2 meters of live overhead equipment (OHE) to safeguard non-technical staff.

Signal posts should be located as far as possible from traction masts to ensure driver visibility, with a minimum distance of 30m when the mast is in front.

Signal posts should be sufficiently tall for drivers to easily see them.

When protective screens are not feasible, caution boards must be placed on the signal post to alert personnel.

Technical personnel working on signal posts need to take extra care when live equipment is nearby, potentially using power blocks.

Prevent tools from getting too close to electrified equipment. Use power blocks as detailed in Chapter VI, near OHE and return conductors treated as live.

Metallic pipes, like galvanized iron, are not allowed within 300 meters of a feeding post.

Galvanized iron pipes are not allowed near switching station grounds and traction masts.

When overhead lines are replaced with cables, block instruments using earth return are moved to insulated PVC underground cables.

Different types of track circuits are used in electrified sections (DC single rail, AC at different frequencies, electronic).

Track bonding for traction current needs adjustment in areas with track circuits.

Overhead signalling lines are replaced with underground cables to reduce electromagnetic interference.

Cable circuits are limited to prevent induced voltages exceeding 120 volts (3.5 km parallelism).

If cable parallelism exceeds 3.5 km, a relay is inserted to break the physical continuity and reduce parallelism to within the limit.

If a circuit exceeds 3.5 km in parallelism due to multiple battery feeds, separate batteries are needed for each section.

The maximum acceptable resistance of an earth connection, which should not exceed 10 ohms.

Cables near traction masts must be at least 1 meter from the mast foundation edge, increasing to 3 meters if laid deeper than 0.5 meters; concrete pipes can reduce the distance.

Cables near substations require a minimum 1 meter distance from metallic parts and the substation grounding system, plus 300 m of concrete pipe.

Cables near switching stations must be at least 1 meter from metallic structures and 5 meters from the station grounding system; concrete pipes can reduce the distance to 1 meter.

If an overhead line mast has a separate earth, cables must be kept at least 1 meter away.

Ideally, cables should be laid on the opposite side of tracks to feeding posts, and a minimum 5.50 meters from the center of the tracks.

Where cables cross tracks, concrete or GI pipes must be used for the crossing.

Signalling cables in electrified sections are usually made of PVC-insulated, screened, and armoured type material.

At stations with reliable local power, the main power supply comes from the local source.

The backup power comes from a 25 kV/240 V auxiliary transformer connected to the catenary.

When no dependable local power exists, two 25 kV/240 V transformers are needed - each connected to the OHE (Overhead Line Equipment).

If the auxiliary transformer is near the station cabin, the 240 V supply acts as the primary power.

A second 25 kV/240 V transformer is installed on another OHE section for a standby power supply where the auxiliary transformer is near the station cabin.

Each wayside station needs two auxiliary transformers, one connected to the OHE for the up and down lines.

A 2 x 25 mm2 aluminum cable connects each auxiliary transformer to the control room.

Power is received at the CLS panel, which also has local power if available, and a manual changeover switch.

Two auxiliary transformers are required at each level crossing more than 2 km from a railway station.

In big yards, multiple cabins are grouped and served by a set of two transformers connected to the OHE for up and down lines.

The supply cable for Colour Light Signals (CLS) and the manual change-over switch

A two-position automatic switch for power supply at unmanned Isolated Block Huts (IBH).

One Automatic Train (AT) connected to Overhead Line Equipment (OHE) is used for CLS supply in single line sections.

Low Tension (LT) supply from AT to ASM's room using 2x25mm2 aluminium cable.

Power supply arrangement for wayside stations, level crossings (beyond 2km from station) and IBHs, incorporating a change-over switch using local power if available.

Emergency light points are provided at electrified wayside stations in ASM's room and cabins to ensure power in case of local supply interruptions, from AT via separate circuit with fuses.

Separate lighting circuits from the AT provide lights in ASM's room, platform, ticket window, waiting hall, and cable huts at non-electrified stations.

The Signal & Telecommunication (S&T) department lays 2x25mm2 cable from ASM room to each cabin, along with signal control cables.

Power cubicles with voltage stabilizer, inverter, and battery chargers are provided in relay rooms to supply signals and relays.

An 80 Ah battery backup is provided at each cabin and level crossing, sufficient for two hours of supply failure.