Underground Copper Cable Systems

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Questions and Answers

What is the primary function of the underground telecommunication lines mentioned in the content?

To connect railway offices, workshops, station yards, and block sections along the railway tracks.

Why is it necessary to keep spare capacity in telecom lines laid underground?

To allow for future extensions or extra connections without major alterations to the existing circuits.

What distinguishes the 1.4 mm Quad cable from the 0.9 mm Quad cable?

The 1.4 mm Quad cable is used for longer block sections, specifically over 12 km.

What type of cable is generally used for exchange subscriber lines?

Multi pair Multi Dia PIJF cable is used for exchange subscriber lines. Signup and view all the answers

Identify one type of cable that is unsuitable for underground laying.

Twisted Pair Switch Board Cable is unsuitable for underground laying. Signup and view all the answers

What should be done with RE cables containing paper insulation?

They should be planned for replacement at the earliest. Signup and view all the answers

According to IRS specifications, what cable type is suitable for control circuits and block interfaces?

Quad Cable is suitable for control circuits and block interfaces. Signup and view all the answers

How many pairs can a Multi pair cable accommodate as mentioned?

It can accommodate from 10 to 200 pairs. Signup and view all the answers

What type of jointing material is recommended for armoured PIJF cable according to the RDSO specifications?

Thermo shrinkable jointing material. Signup and view all the answers

How are the jointing kits differentiated for various sizes of cable?

They are differentiated by different kit types, such as TSF-1 and TSF-2. Signup and view all the answers

Which jointing kit should be used for quad cables as per the latest specifications?

Reinforced Thermo Shrink Jelly Filled kit (RTSF) type jointing kit. Signup and view all the answers

What should be done to the joint if it is kept inside a location box?

The EC Socket should be fixed on that location box, which should be painted with black & yellow stripes. Signup and view all the answers

Why is it essential to connect the screen and armour of copper cables before jointing?

To obtain the specified screening factor and avoid electric shock due to induction. Signup and view all the answers

What specifications must be included when defining the size of telephone exchange cables?

The number of pairs, diameter of conductor, type of insulation/sheath, and whether it is jelly filled, armoured, or unarmoured must be specified. Signup and view all the answers

Which type of cable is recommended for underground laying according to the guidelines?

Only jelly filled armoured cables are recommended for underground laying. Signup and view all the answers

What initial tests should be conducted on the cable before laying it?

Insulation and continuity of the cores should be tested before laying the cable. Signup and view all the answers

What is the use of a 0.5 mm conductor diameter twisted pair cable?

It is used for subscriber's connections up to 5 kilometers. Signup and view all the answers

What equipment is used for laying out cables according to the guidelines?

Cable drums mounted on cable-wheels are used for laying out the cables. Signup and view all the answers

What precautions must be taken when laying the cable if wheels are not available?

The drum should be mounted on an axle at one end of the trench, and the cable must be laid out and carried by labourers. Signup and view all the answers

Why is it important to check the bedding and armouring of the cable before laying?

It ensures that there has been no damage during transit or storage that could affect performance. Signup and view all the answers

Which inspector must be present when excavating trenches for cable installation?

The Permanent Way Inspector or his representative must be present. Signup and view all the answers

What type of cable is the 0.6 mm ATC Switch Board cable used for?

It is used for trunk connections. Signup and view all the answers

How does the design of 'Quad' type cables manage circuit formation?

Conductors that are diagonally opposite form one circuit in 'Quad' type cables. Signup and view all the answers

How does the specifications format facilitate cable identification for use?

It provides a clear description of the cable's attributes, allowing for easy identification of its intended use and suitability. Signup and view all the answers

What method should be employed for cable laying at busy road or rail crossings?

The Horizontal Directional Drilling (HDD) method should be used. Signup and view all the answers

What type of junction box is approved for terminating PIJF cables?

Termination should be done through a DP Box of approved type. Signup and view all the answers

What is required for proper jointing of PIJF cables?

Jointing should be done by a skilled and experienced person using the correct RDSO specified jointing kit. Signup and view all the answers

What role does video recording play in the cable laying and jointing process?

Video recording may be used to ensure quality in laying and jointing of cables. Signup and view all the answers

What should be done before utilizing concrete ducts in station sections for telecom cables?

Due precautions should be followed before utilizing the ducts for telecom cables. Signup and view all the answers

What is the maximum conductor diameter used for Quad cables suitable for longer block sections?

1.4 mm Signup and view all the answers

Describe the insulation types used for the RE cable mentioned in the content.

The RE cable contains both paper and polythene insulation. Signup and view all the answers

What specification number is associated with multi pair cables as per the content?

IRS:TC 41/97 Signup and view all the answers

What performance parameter is crucial for planning future extensions in telecom lines?

Spare capacity Signup and view all the answers

What is the conductor diameter range for twisted pair switch board cables as per IRS/TEC specifications?

0.5 mm to 0.6 mm Signup and view all the answers

Which type of cable is specified for control circuits and block interfaces?

Quad cable Signup and view all the answers

What characteristic distinguishes multi pair cables from Quad cables in telecom applications?

Multi pair cables accommodate from 10 pairs to 200 pairs. Signup and view all the answers

Why are twisted pair switch board cables not suitable for underground applications?

They are designed for indoor use. Signup and view all the answers

Explain the significance of using different jointing kits like TSF-1 and TSF-2 for varying cable sizes.

Different jointing kits such as TSF-1 and TSF-2 are designed to accommodate specific cable sizes, ensuring proper fit and effectiveness in jointing protective mechanisms. Signup and view all the answers

Describe the precautions that must be taken when installing a joint inside a location box for a quad cable.

When installing a joint inside a location box for a quad cable, it must avoid sharp bends, and the box should be painted with black and yellow stripes for visibility and safety. Signup and view all the answers

What is the importance of earthing the copper cable screen and armour during jointing?

Earthing the copper cable screen and armour is crucial to achieving the specified screening factor and preventing electrical shocks due to induction. Signup and view all the answers

Why should the jointing of thermo shrinkable joints only be performed following RDSO's code of practice?

Adhering to RDSO's code of practice ensures that the jointing of thermo shrinkable joints is performed correctly, maintaining safety and functionality standards. Signup and view all the answers

What is the required action for the location box if a joint is placed inside it?

An EC socket should be fixed on the location box itself, facilitating easy access for maintenance and monitoring. Signup and view all the answers

What method should be used when encountering busy areas for laying cables which involve road or rail crossings?

The HDD (Horizontal Directional Drilling) method should be used. Signup and view all the answers

Which components are necessary to minimize electro-static and electro-magnetic induction in telephone cables?

A lead or aluminium sheath and twisted pairs are necessary. Signup and view all the answers

What is the requirement regarding supervision during the jointing of PIJF cables?

The jointing must be done under close supervision of telecom staff. Signup and view all the answers

In the absence of wheels, how should the drum be set up for cable laying?

The drum should be mounted on an axle at one end of the trench and carried by laborers. Signup and view all the answers

What should happen to the joint if it is kept inside a location box?

Proper precautions must be taken to ensure its integrity. Signup and view all the answers

Why is the use of a skills and experienced person essential during cable jointing?

To ensure quality and comply with the correct RDSO specified jointing kit. Signup and view all the answers

What type of termination method is specified for various sizes of PIJF cables?

Termination should be done through a DP Box of approved type. Signup and view all the answers

What precaution should be taken when utilizing large concrete ducts for telecom cables?

Due precautions must be followed to ensure proper installation. Signup and view all the answers

What specifications are included when defining the size of telephone exchange cables?

Specifications include the number of pairs, diameter of conductor, type of insulation or sheath, and the filling type. Signup and view all the answers

What are the key tests that should be performed on cables before they are laid?

Cables should be tested for insulation and continuity of the cores, as well as checked for continuity of armour and screen. Signup and view all the answers

What is the significance of using only jelly filled armoured cables for underground laying?

Jelly filled armoured cables provide protection against moisture and physical damage in underground conditions. Signup and view all the answers

How should cable drums be handled during the laying process?

Cable drums must be mounted on cable-wheels and pulled along the road or track to guide the cable into the trench. Signup and view all the answers

What materials are suggested for jointing PIJF cables according to specifications?

The specifications recommend using approved jointing kits tailored for the size and type of PIJF cables. Signup and view all the answers

What should be inspected regarding bedding and armouring of the cable before laying?

Inspection should check for any damage incurred during transit or storage of the cable. Signup and view all the answers

In what context is a 0.5 mm conductor diameter twisted pair cable used?

It is used for subscriber connections up to 5 kilometers in length. Signup and view all the answers

What precautions are necessary when laying out cables to prevent damage?

The cable must be guided carefully into the trench to avoid excessive bending or damage during placement. Signup and view all the answers

What jointing kits are used for different sizes of cables according to RDSO specifications?

Kits like TSF-1 and TSF-2 are used for varying sizes of cables. Signup and view all the answers

What specific jointing kit should be used for quad cables?

The Reinforced Thermo Shrink Jelly Filled kit (RTSF) should be used. Signup and view all the answers

What is essential to do with the copper cable screen and armour during jointing?

They should be made through with suitable wires. Signup and view all the answers

What should be done if the joint is kept inside a location box?

An EC Socket should be fixed on the location box itself. Signup and view all the answers

Why is earthing of copper cable screen and armour important?

It helps prevent electric shock due to induction. Signup and view all the answers

What is the conductor diameter of the quad cable suitable for longer block sections?

1.4 mm Signup and view all the answers

Which specification number is associated with multi pair cables?

IRS:TC 41/97 Signup and view all the answers

What type of insulated cable is recommended for control circuits?

Quad Cable Signup and view all the answers

Why is it necessary to provide provisions for future extensions in telecom lines?

To accommodate additional connections without significant alterations. Signup and view all the answers

What insulation types are used in the RE cable mentioned?

Paper and polythene Signup and view all the answers

What size of twisted pair switch board cable is indicated for indoor applications?

0.5 mm to 0.6 mm Signup and view all the answers

What is the maximum number of pairs a multi pair cable can accommodate?

200 pairs Signup and view all the answers

Which type of cable is specifically unsuitable for underground laying?

Twisted Pair Switch Board Cable Signup and view all the answers

What size of conductor is specified for subscriber connections up to 10 km?

0.63 mm conductor diameter twisted pair PIJF. Signup and view all the answers

What type of cables should be used for underground laying?

Jelly filled armoured cables. Signup and view all the answers

What tests must be conducted on the cable before it is laid?

Testing for insulation and continuity of the cores. Signup and view all the answers

How should the cable be laid out according to the guidelines?

Using cable drums mounted on cable-wheels. Signup and view all the answers

What is the purpose of inspecting the bedding and armouring of the cable?

To ensure there has been no damage during transit or storage. Signup and view all the answers

What size conductor is used for local subscriber's connection in a building?

0.5 mm Annealed Tinned Copper (ATC). Signup and view all the answers

What specifications should be included when defining telephone exchange cables?

Number of pairs, diameter of conductor, type of insulation/sheath, and whether it is armoured or unarmoured. Signup and view all the answers

What happens to the cable-end when laying it in a trench?

The end of the cable is freed and put into the trench. Signup and view all the answers

How should the drum be set up in the absence of wheels when laying cable?

The drum shall be mounted on an axle at one end of the trench and the cable laid out and carried by labourers. Signup and view all the answers

What methods can be used for terminating cables?

Cables can be terminated using a DP Box of approved type or through direct termination. Signup and view all the answers

What precautions should be taken when using concrete ducts for telecom cables?

Due precautions must be followed when utilizing concrete large size ducts provided for signalling cables. Signup and view all the answers

What is the requirement for laying cables in busy areas with road or rail crossings?

The HDD (Horizontal Directional Drilling) method should be used to lay cables in busy areas. Signup and view all the answers

Who must be present while excavating for cable installation?

The Permanent Way Inspector or his representative must be present during excavation. Signup and view all the answers

What should be done prior to jointing PIJF cables?

Jointing should be done by a skilled and experienced person using the correct RDSO specified jointing kit. Signup and view all the answers

What is the significance of utilizing twisted pairs in telephone cables?

Twisted pairs minimize electro-static and electro-magnetic induction between different pairs of conductors. Signup and view all the answers

How can quality ensurement be maintained during cable laying and jointing?

The process should be conducted under close supervision of telecom staff and can be video recorded. Signup and view all the answers

Study Notes

Underground Copper Cable - Line Plant Systems

Railway departmental telecommunication lines are normally laid underground between railway offices, workshops, and track sections.

Spare Capacity

All lines should be laid with future expansion in mind, minimizing necessary circuit alterations or complete realignment.

Underground Copper Cable Types and Performance Parameters

Quad Cable (0.9 or 1.4 mm conductor diameter) - used for block interfaces and control circuits; 1.4 mm is preferred for distances over 12 kilometers.
Multi Pair Cable (10 to 200 pairs, 0.5, 0.63, or 0.9 mm conductor diameter) - used for exchange subscriber lines and branching off from main quads.
Twisted Pair Switchboard Cable (0.5 or 0.6 mm copper conductor diameter) - used for indoor applications like telephone subscriber distribution, MDF to exchange wiring, etc.
RE Cable (paper and polythene insulated copper quads) - ideally replaced with newer types.

Cable Sizes

Outdoor Underground:
- 0.5 mm conductor diameter - subscriber connections up to 5 km.
- 0.63 mm conductor diameter - subscriber connections up to 10 km.
Indoor:
- 0.5 mm Annealed Tinned Copper - local subscriber connections in buildings, exchange to MDF wiring.
- 0.6 mm Annealed Tinned Copper - trunk connections.
Exchange Cables:
- Specify the number of pairs, conductor diameter, insulation/sheath type, jelly filled, armoured or unarmoured.
- Only jelly filled armoured cables are used for underground laying.

Testing Cable Before Laying

Conduct insulation and continuity tests of cores, armor, and screen.
Inspect bedding and armoring for damage during transit or storage.

Laying Out the Cable

Use cable wheels to mount drums. Start at one end of the trench and carefully guide the cable into the trench.
If wheels aren't available, mount the drum on an axle and carry the cable manually.
Avoid rolling the drum on the road or dragging the cable on the ground.

General Notes

Permanent Way Inspector should be present when excavating near tracks.
In quad cables, diagonally opposite conductors make up a circuit.
Lead or aluminum sheathing and twisted pairs minimize electromagnetic and electrostatic induction in telephone cables.
Use Horizontal Directional Drilling (HDD) to lay cables through road or rail crossings in busy areas. Utilize existing concrete ducts in station areas with caution.

Cable Termination

Terminate cables using:
- DP Box of approved type.
- Direct termination.
PIJF cables of various sizes should be terminated through DP Boxes.

PIJF Cable Jointing

Jointing should be done by a skilled person using RDSO specified jointing kits.
Close supervision of telecom staff required. Video recording can be used to ensure quality.
Use thermo shrinkable jointing material for armored PIJF cables with thermo shrinkable techniques.
Use reinforced thermo shrink jelly filled kit (RTSF) for quad cable.
Quad cable joints can be kept underground or housed in a location box.
When a joint is housed in a location box, an EC Socket should be fixed on the box and painted black and yellow stripes.
Screen and armor of copper cables should be jointed with suitable wires to achieve the specified screening factor. Earth this first to avoid electric shock.
Copper cable screen and armor should be earthed at stations with a low-resistance earth.

Underground Copper Cable for Railway Telecommunications

Railway telecommunication lines are laid underground, connecting offices, workshops, and stations.
Spare capacity is important for future extensions and connections without requiring extensive modifications.
Various types of underground cables are used:
- Quad Cable: For control circuits and block interfaces.
- Multi-pair Cable: Used for subscriber lines and branch cables.
- Twisted Pair Switch Board Cable: For indoor applications such as building distribution and exchange wiring.
- RE Cable: Should be replaced with newer types as soon as possible.
Cable sizes depend on the circuit:
- Outdoor: 0.5 mm and 0.63 mm conductor diameter cables are used for subscriber connections.
- Indoor: 0.5 mm and 0.6 mm ATC Switch Board cables are used for local subscriber connections and trunk connections.
Telephone exchange cables are specified by the number of pairs, conductor diameter, insulation/sheath type, and whether they are jelly-filled, armored, or unarmoured.
Testing and inspection are crucial before cable laying:
- Insulation and core continuity are tested.
- Armour and screen continuity are checked.
- Bedding and armoring are inspected for damage.
Cable laying procedures:
- Cables are rolled out from drums mounted on cable wheels.
- Laborers guide the cable into the trench.
- Drums should not be rolled on the road and cables should not be dragged on the ground.
General considerations regarding the cable installation:
- Permanent Way Inspector must be present during excavation near tracks.
- 'Quad' type cables have conductors forming a circuit diagonally opposite each other.
- Electrostatic and electromagnetic induction is minimized using a lead or aluminum sheath and twisted pairs.
- Horizontal Directional Drilling should be used in busy areas for road and rail crossings.
- Existing large ducts in station sections can be used for telecom cables with precautions.
Cable termination options:
- DP Box of approved type.
- Direct termination.
- PIJF cables are terminated through DP Boxes.
Jointing of PIJF Cable:
- Done by experienced personnel with RDSO specified jointing kits.
- Video recording of laying and jointing for quality assurance.
- Thermo shrinkable jointing technique is used for armored PIJF cables.
- Quad cables use Reinforced Thermo Shrink Jelly Filled (RTSF) jointing kits.
- Quad cable joints can be underground or housed inside location boxes avoiding sharp bends.
- The screen and armour of copper cables are jointed using suitable wires for screening and earthing.
- Copper cable screen and armour are earthed with low value earth.