Transporting electrical power
Wires and cables are the most visible and essential part of the entire electricity system. They transport the electrical power from the energy source at the power station to the point of use where it is converted into mechanical movement, heat, light or digital signals. Wires and cables come in an enormous variety of cross-sections, lengths, and current carrying capacities from high-voltage undersea cables hundreds of kilometers in length down to ultra-fine wires in the micron range used for connections in advanced electronic equipment.
Direct current (DC) flows are evenly distributed over the cable length with energy losses inversely proportional to the cross-section. Alternating current (AC), however, flows more towards the surface of the cable cross-section. The higher the frequency of the electrical power, the stronger this skin effect becomes. For this reason, it is a common practice in specific applications to interweave several wires of smaller cross-sections instead of using a single wire with a larger section.
Electrical cables consist of various conductors:
- Two (one phase + return conductor)
- Three (one phase + return conductor + earthing conductor)
- Four (three phases + neutral conductor)
- Five (three phases + neutral conductor + earthing conductor)
The individual conductors and the entire cable itself are surrounded by electrical insulation for safety reasons and to avoid short circuits.