Wire & Cable

 

 ⚡ Electrical Cable Installation in Building Works

Proper planning, selection, and installation of electrical cables are essential for the safety, reliability, and efficiency of building systems. The following guidelines outline best practices for cable types, handling, laying, and termination in construction projects, in accordance with relevant Indian Standards.

🧵 Type and Quality of Cables

• Insulation and Sheathing: All wiring cables should be PVC or XLPE insulated and PVC sheathed, conforming to applicable IS standards.
• Conductors: Cables may use stranded aluminium or copper conductors, as specified.
• Voltage Rating: Power cables must be 1100 volts grade, PVC insulated, PVC sheathed, and armoured.
• Approved Brands: Materials should be sourced from approved manufacturers or brands listed in the project documentation.

📦 Handling of Cables

• Moisture Protection: Seal both ends of cables to prevent moisture ingress.
• Drum Movement: Roll cable drums in the direction of the arrow marked on the drum.
• Cable Removal: Use jacks or cable wheels to mount drums securely; ensure lifting devices can bear the drum’s weight.

❌ Defective Cables

• Cables with kinks, straightened kinks, defective armouring, or other visible defects must not be installed.

🔄 Bending Radius

• Spacing and Support: Cable runs should be uniformly spaced and properly supported.
• Minimum Radius: For PVC cables, the bending radius should be at least 12 times the overall diameter. Larger radii are preferred when feasible.

📏 Cable Length and Jointing

• Continuous Runs: Cables should be laid in one continuous length without joints.
• Jointing: If unavoidable due to drum length, use standard joint boxes or kits.
• Measurement: Carefully measure required lengths before cutting, including allowances for loops and terminations.

✂️ Stripping of Outer Covering

• Use caution when stripping cable sheathing to avoid damaging inner insulation.
• Maintain protective covering as close as possible to the connecting terminal.

🚜 Cable Laying in Trenches

• Standard Practice: Follow IS:1255 for trench-laying procedures.
• Trench Dimensions:
• LT Cable: Width 460 mm, Depth 760 mm
• HT Cable: Depth 1000 mm
• Axial Spacing: 250 mm for 11 KV/6.6 KV, 150 mm for 1100 V cables
• Communication Cables: Must be laid in separate trenches.

🕳️ Excavation and Bed Preparation

• Trench Line: Should be straight with gradual curves and slopes.
• Precautions: Avoid damage to existing utilities; seek approval before proceeding near exposed installations.
• Sand Cushioning: Minimum 75 mm of fine sand at trench bottom.

🧱 Protective Covering for Direct Burial

• Brick Protection: Cables must be covered with flat-laid bricks supported by brick-on-edge lines.
• Multiple Cables: Additional brick-on-edge lines between cables; top cover must span all cables.
• Sand Cushioning: 75 mm above and below cables.

🧱 Backfilling of Trenches

• Use excavated soil, compacted in layers not exceeding 300 mm.
• Remove surplus soil as directed.
• Contractor supplies all materials (sand, bricks, clamps); rates include these provisions.

🧵 Cable Laying Procedures

• Insulation Testing: Conduct tests before laying.
• Transport and Layout: Use wheels and jacks; follow drum direction.
• Roller Support: For large cables, use rollers to prevent damage.
• Crossing Utilities: Use RC/GI pipes with minimum 750 mm depth and 300 mm clearance.
• Parallel Installations: Maintain 1000 mm clearance from structures and utilities.
• Termination Length: Pull adequate cable length into panels and boards for neat termination.

🔄 Surplus Cable

• Leave approximately 1 meter of surplus cable at entry/exit points for future adjustments or repairs.

🧱 Cables Through Pipe Sleeves

• Building Entry: Use sealed pipe sleeves for water-tight entry.
• Crossing Roads/Tracks: Minimum depth of 1000 mm through pipe sleeves.

🧲 Cables on Racks, Trays, Brackets, Hooks

• Exposed Installations: Use brackets, trays, or hooks along walls, ceilings, or walkways.
• Spacing: Saddles/hooks should be spaced ≤750 mm to keep cables straight.
• Tray Type: Ladder or perforated pre-fabricated trays with suitable bends.

🔚 Cable Termination

• Terminate cables neatly inside switchboards, control panels, and feeder pillars.
• Ensure proper stripping, secure connections, and compliance with safety standards.

🧠 Key Takeaways

• Use IS-compliant PVC/XLPE cables with proper insulation and armouring.
• Handle and lay cables with care to avoid damage, moisture, or kinks.
• Follow trench dimensions, spacing, and protective measures.
• Avoid joints unless necessary; use approved joint kits.
• Maintain clearances from utilities and structures.
• Ensure neat terminations and leave surplus cable for flexibility.