To manufacture the electrical conductors it is used soft copper wire with next diameters: 0.32; 0.4; 0.5; 0.64; 0.7; 0.9; 1.2 mm. Copper wire is produced by continuous drawing of stock material – copper wire rod (7.2 – 8.0 mm in diameter), which is made by method of continuous casting and rolling; it is light and need no etching operations. The basic specifications of conducting wire:
- density γ = 8.9 t/m3;
- UTS (ultimate tensile strength) σt MPa (kgf/mm2) – 196…274.5 (20…28);
- elongation ∆l minimum % – 20…25;
- electrical resistivity ρ with temperature 20ºC – maximum 17.24 μΩ∙km;
- conductivity σ with temperature 20ºC – minimum 58.9 MOhm/m;
- TKC (temperature coefficient of resistance) αR ºC-t x 10-3 – 3.93.
As a core insulation for local network it is used spiral strip paper, solid polyethylene, pulp, foam-polyethylene insulation, and cord-styroflex insulation is used for trunk cables. The picture below shows structures of insulated cords:
There will be more detailed overvie of insulations’ types in next articles.