Question

Which of the following materials is NOT employed for transmission lines?
1. Copper weld materials
2. Carbon core tantalum
3. Galvanized iron
4. Steel core copper

Answer 1

Correct Answer - Option 2 : Carbon core tantalum

Conductor Material:

• The conductor is one of the important items as most of the capital outlay is invested for it.
• Therefore, the proper choice of material and size of the conductor is of considerable importance.
• The conductor material used for transmission and distribution of electric power should have the following properties:

1. High electrical conductivity.
2. High tensile strength in order to withstand mechanical stresses.
3. Low cost so that it can be used for long distances.
4. Low specific gravity so that weight per unit volume is small.
    

All the above requirements are not found in a single material. Therefore, while selecting a conductor material for a particular case, a compromise is made between the cost and the required electrical and mechanical properties.

Commonly used Conductor Materials:

• The most commonly used conductor materials for overhead lines are copper, aluminum, steel-cored aluminum, steel-cored copper, galvanized steel, and cadmium copper.
• The choice of a particular material will depend upon the cost, the required electrical and mechanical properties, and the local conditions.
• All conductors used for overhead lines are preferably stranded* in order to increase flexibility.
• In stranded conductors, there is generally one central wire and round this, successive layers of wires containing 6, 12, 18, 24 ...... wires.
• If there are n layers, the total number of individual wires is [3n(n + 1) + 1].
• In the manufacture of stranded conductors, the consecutive layers of wires are twisted or spiraled in opposite directions so that layers are bound together.