Cable Laying Planning for Railways

Planning for Cable Laying on Railway Routes

• Cable Types and Conductor Requirements:
  • Determine the number, size, and type (quad, PIJF) of conductors needed based on the desired circuit types.
  • The Zonal Railway may allocate quad cables, including BPAC/IBS.
  • Leave at least 25% spare conductors for future expansion in cables with 5 or more pairs.
• Route Planning:
  • Choose the cable route by physically walking the track and identifying the most suitable alignment.
  • Create a route plan showing the alignment, offsets from permanent structures, and crossings (road, track, power cables, water/sewage mains).
  • Ideally, overlay the plan with existing power cable routes.
• Distribution Points:
  • Decide on locations for cable distribution points (e.g., main to smaller cables for subscriber connections, emergency socket locations).
• Cable Location and Depth:
  • Lay telecom cables within 1 meter of the railway boundary, referencing boundary pillars or seeking assistance from P.Way officials.
  • Maintain a 2-meter distance from the track and beyond the embankment.
  • Trenches in or near the track formation require P.Way consultation and must be filled and rammed the same day before sunset, especially during monsoon or in alluvial soil.
  • Keep cables at least 1 meter away from electrical power cables.
• Cable Markers:
  • Install markers at 50-meter intervals and at key locations (joints, crossings, bends, water/sewage mains, power cable).
  • Use Quad cable RCC route markers as per Drawing no. RDSO/TCDO/COP-22(a) (Chapter XIII).
  • Paint markers red and add yellow enamel to Quad joints for easy identification.
• Cable Trench Width and Depth:
  • Bury cables at least 1 meter below ground.
  • Ensure sufficient trench width for easy cleaning and cable laying.
• Safety Precautions Near Overhead Electrical Equipment (OHE):
  • Maintain a minimum 1-meter distance between cables and OHE masts.
  • If this is not possible, lay cables in concrete pipes, reducing the distance to 0.5 meters.
  • When the cable trench depth exceeds 0.5 meters, maintain a 3-meter distance between the trench edge and the OHE mast.
  • Mark cable joint locations on the nearest OHE mast with an approved legend.
• Laying Cable Near Traction Substations and OHE Switching Stations:
  • Lay cables at least 1 meter from metallic bodies of substations and substation earthing.
  • Enclose cables in concrete pipes or brick channels for 300 meters on either side of the substation.
  • Ideally, lay cables on the track side opposite the substation.
  • For OHE switching stations, maintain 1 meter from metallic bodies and 5 meters from station earthing, or use concrete piles to reduce this distance to 1 meter.
  • Lay cables at least 1 meter away from any independent earth provided for OHE structures.
• General Cable Layout Practices:
  • Outside station limits, lay cables at a standard distance of 10 meters from the track center.
  • When laying signalling and telecommunication cables in the same trench, maintain a 100 mm gap using bricks at 2-meter intervals.
  • Never lay HT/LT power cables and telecommunication cables in the same trench.
  • Bury cables parallel to the track at 1 meter deep, and 1 meter below rail flanges when crossing the track.
  • Keep power and telecommunication cable trenches as far apart as possible.
• Special Cable Laying Scenarios:
  • Lay cables along girder bridges, culverts, rocky terrain, etc., according to specific approved methods for each location.
  • Avoid sharp bends in cables, ensuring a bending radius of at least 40 times the cable diameter for aluminum sheathed armored cables.
  • Normally lay OFC and quad cables in the same trench. Refer to Chapter XIII for specific drawings.

Planning Cable Routes

• Planning stage:
  • Determine the number and types of conductors needed
    • Consider the type of circuits required (e.g., quad/PIJF)
    • Zonal Railway allocates quad cables
  • Allow for future expansion:
    • Plan for at least 25% spare conductors for cables carrying 5+ pairs
    • Consider the long life expectancy of telecommunication cables
• Route Selection:
  • Walk the route:
    • Identify the optimal alignment for the cable route
  • Document the route:
    • Produce a detailed route plan, including:
      • The actual alignment of the track
      • Offsets from permanent structures and track
      • Locations of road/track crossings
      • Crossings with power cables, water/sewage mains
      • Other points of importance
      • Existing routes of power and telecom cables
• Distribution points:
  • Locate convenient points for distribution:
    • For subscriber cabling, use a main cable to connect to smaller distribution cables
    • For emergency communication, consider the placement of emergency sockets
• Cable Placement:
  • Telecom cables should be within 1 meter of the railway boundary:
    • Use boundary pillars as reference points
    • Minimum distances from railway infrastructure:
      • At least 2 meters away from the nearest track
      • Outside the track embankment
    • Trenches near the track require P. Way consultation:
      • Fill and compact the trench on the same day before sunset
      • Take extra precaution during the monsoon and alluvial soil
    • Maintain a 1-meter separation from electrical power cables
  • Cable Markers:
    • Install markers at 50-meter intervals
    • Use additional markers for:
      • Cable joints
      • Water and sewage mains
      • Power cables
      • Crossings
      • Alignment bends/curves
    • Use Drawing no. RDSO/TCDO/COP-22(a) for the Quad cable RCC route marker
    • Paint the marker red as per the specified drawing
    • Paint the Quad joint with yellow enamel on all sides
  • Depth of Cable:
    • Standard depth: 1 meter below the surface
    • Exceptional cases:
      • Yards and limited trench depth (0.5 meters)
        • Minimum 1-meter distance from OHE mast and other potential contact points
        • Lay the cable in concrete pipes to reduce the minimum distance to 0.5 meters
      • Trench depth exceeding 0.5 meters near OHE masts
        • The nearest edge of the trench must be at least 3 meters away from the OHE mast
    • OHE Mast Marking:
      • Mark the location of cable joints on the nearest OHE mast using an approved legend
    • Vicinity of Traction Substations, OHE Switching Stations, and Earthing Systems:
      • Substations:
        • At least 1 meter from the metallic body of the substation fixed in the ground
        • At least 1 meter away from the substation earthing
        • Lay cables in concrete pipes or brick channels for 300 meters on either side of the substation
        • Preferably on the track side opposite the substation
      • OHE Switching Stations:
        • At least 1 meter from the metallic body fixed in the ground
        • At least 5 meters away from the station earthing
        • Can reduce the distance to 1 meter if the cables are laid in concrete piles
      • Independent Earthing for OHE Structures:
        • At least 1 meter from the earthing
    • Outside Station Limits:
      • Standard distance of 10 meters away from the center of the nearest track
    • Signalling and Telecommunication Cables in the Same Trench:
      • Maintain a 100 mm distance between cables by placing bricks every 2 meters
    • HT and LT Power Cables and Telecommunication Cables:
      • Do not lay in the same trench
    • Depth of Cable Relative to Track:
      • Cables running parallel to the track should be at least 1 meter below the ground
      • Cables crossing the track should be at least 1 meter below the rail flanges
  • Spacing Between Power and Telecommunication Cable Trenches:
    • Maximum separation between the trenches
  • Laying Cables Over Bridges, Culverts, Rocky Terrain:
    • Lay cables according to approved methods for each location
  • Avoiding Sharp Bends:
    • The bending radius must be at least 40 times the cable diameter for aluminium sheathed armoured cables
  • Laying OFC and Quad Cables:
    • Normally laid together in the same trench
    • Refer to Chapter XIII for drawings and specifications

Cable Planning and Laying

• Initial Considerations: Begin by determining the number and sizes of conductors, as well as the type of cable required (quad/PIJF), based on the desired circuit types.

• Spare Conductors: Generally, allocate 25% or more spare conductors for cables with 5 or more pairs to accommodate future expansions. This is important due to the long service life of these cables.

• Route Selection:

  • Choose the optimal cable route by physically traversing the track area.
  • Clearly depict the chosen route on a plan, showing the track alignment, offsets from permanent structures, and crossings (roads, tracks, power cables, utilities).
  • Utilize existing plans that show locations of other cables.

• Distribution Points:

  • Identify convenient locations for distributing main cables to smaller cables (e.g., subscriber cabling, emergency sockets) to optimize network connectivity.

• Cable Placement:

  • Typically, telecom cables are laid within 1 meter of the railway boundary, referencing boundary pillars.
  • Place cables at least 2 meters away from the nearest track and beyond the embankment.
  • Trenches within or near the track formation should only be made after consulting with P.Way staff.
  • Fill and compact trenches after laying cables before sunset, especially during monsoon season or in alluvial soil.
  • Maintain at least 1 meter separation from electrical power cables.

• Cable Marking:

  • Install markers along the entire route at 50-meter intervals.
  • Provide additional markers for key locations like cable joints, utilities, crossings, bends, and curves.
  • Use approved markers (e.g., Drawing no. RDSO/TCDO/COP-22(a)) and paint them as specified.
  • Mark quad cable joints with yellow enamel paint on the markers above ground.

• Cable Depth:

  • Bury cables at least 1 meter below the ground surface.
  • Trench width should allow for smooth cleaning and cable laying.

• Special Considerations:

  • In limited depth situations (e.g., yards, 0.5 meter depth), maintain at least 1 meter separation between cables and overhead line (OHE) masts or other structures.
  • Lay cables in concrete pipes when the 1-meter separation is difficult to maintain.
  • When trench depth exceeds 0.5 meter near OHE masts, keep the nearest edge of the trench at least 3 meters away from the mast.
  • Mark the position of cable joints on the nearby OHE mast with an approved legend.

• Substations and Switching Stations:

  • Near traction substations:
    • Lay cables at least 1 meter away from grounded metallic substation components and substation earthing.
    • Place cables in concrete pipes or brick channels for 300 meters on either side of the substation.
    • Route cables on the side of the track opposite the substation.
  • Near OHE switching stations (feeding posts, sectioning posts):
    • Maintain at least 1 meter distance from grounded metallic station components and at least 5 meters away from station earthing.
    • Distance from station earthing can be reduced to 1 meter if cables are laid in concrete piles.
  • Near OHE structures with independent earth:
    • Lay cables at least 1 meter away from such earthing.

• Outside Station Limits:

  • Generally lay cables at a standard distance of 10 meters from the nearest track center.

• Signalling and Telecom Cables:

  • When laying these cables in the same trench, maintain a 100-millimeter separation using bricks at 2-meter intervals.

• Power and Telecom Cables:

  • Do not lay high tension (HT) or low tension (LT) power cables in the same trench as telecommunication cables.

• Cable Depth and Position:

  • Bury cables parallel to the track at 1 meter depth.
  • Bury cables crossing the track 1 meter below the rail flanges.
  • Keep the telecom cable trench as far from the power cable trench as possible.

• Special Locations:

  • Lay cables along girder bridges, over culverts, through culvert beds, over rocky terrain, and other similar locations using approved methods for each specific location.

• Cable Bending:

  • Avoid sharp bends during cable laying.
  • The bending radius should not be less than 40 times the cable diameter for aluminum sheathed armored cables.

• OFC and Quad Cables:

  • Generally lay optical fiber cables (OFC) and quad cables in the same trench.
  • Consult dedicated drawings for laying OFC/quad (chapter XIII).