LT cables use stranded copper conductors. Although small conductor of cables may use solid conductors. The overall assembly may be round or flat. Non-conducting filler strands may be added to the assembly to maintain its shape. Special purpose LT cables for overhead or vertical use may have additional elements such as steel structural supports. Some LT cables for outdoor overhead use may have no outer sheath.
Design
Voltage: These cables can be used on AC voltage up to & Including 1100 V or DC up to & including 1500 V.
Size: 1.5 Sq.mm. & 2.5 Sq.mm. upto 37 Cores
Conductor: Annealed Bare Electrolytic Copper/ Aluminum Conductor conforming to IS:8130:1984
Insulation: Conductors are insulated with PVC Compound as per IS:5831:1984.
Colour Of Cores: Cores are identified with a colour scheme as per IS:1554 (pt-1):1988 as under
- 2 Cores: Red and Black
- 3 Cores: Red, Yellow, and Blue
- 5 And 4 cores: Red, Yellow, Blue & Black (Reduced Neutral Core in case of 3½ Core).
Laying of Cores: Cores are laid up with a suitable lay. The final layer direction shall be kept right hand lay
Inner Sheath: The Inner Sheath is applied over laid up of cores by extrusion/wrapping of thermoplastic material.
Armouring: It is applied over inner sheath. It may consist of galvanized Round Steel wires or galvanized Flat Steel Strips conforming to IS 3975. Round Wire armouring is provided, where the calculated diameter under armour is 13.0 mm. Above this, armouring is either round wire/steel strip.
Outer Sheath: A final covering of PVC Compound, confirming to IS:5831-1984, is applied over Armouring in case of Armoured Cable or Over Inner Sheath in case of Unarmoured cable, called as “Outer Sheath”. The Insulation, Inner Sheath or Outer Sheath can be PVC, FRLS PVC or FRHF Compound, depending upon their application.