In short
A power cable is selected by its voltage rating, current-carrying capacity under the actual installation conditions, voltage drop over the route, short-circuit withstand, conductor material, and construction such as insulation, armour and sheath. Include the standard, such as IEC 60502, and the total length.
Voltage rating
Cable voltage ratings are written as Uo/U, the voltage to earth and between phases, for example 0.6/1 kV for low voltage. Medium-voltage cables use ratings such as 6.35/11 kV or 12.7/22 kV depending on the standard and the system earthing, so state your system voltage and how it is earthed.
Current-carrying capacity
How much current a cable can carry depends on conductor size and material, insulation (XLPE runs hotter than PVC, at 90 °C versus 70 °C maximum conductor temperature), and how it is installed: in air, in ducts or buried. Grouping with other cables, ambient temperature and soil thermal resistivity all reduce the rating through derating factors.
Voltage drop
On long runs, voltage drop rather than current often decides the size. Local wiring rules commonly limit drop to a few percent of nominal voltage. Provide route lengths and load currents so the size can be checked.
Short-circuit withstand
Conductors and metallic screens must survive the fault current until protection clears it. For MV cables, give the fault level and clearing time so the screen cross-section can be specified.
Copper or aluminium
Aluminium conductors are lighter and less expensive but need a larger cross-section for the same current. Copper suits tight spaces and smaller terminations. Both are widely used; state any preference or project requirement.
Armour and sheath
Armour protects against mechanical damage when cables are buried or exposed. Multi-core cables commonly use steel wire armour, while single-core AC cables use non-magnetic aluminium wire armour to avoid heating. Sheath materials include PVC and low-smoke zero-halogen compounds where fire performance matters.
What to send with a cable enquiry
| Item | Example |
|---|---|
| Voltage rating | 0.6/1 kV or 6.35/11 kV |
| Cores and size | 4 × 95 mm², or 3 × 240 mm² |
| Conductor | Copper or aluminium |
| Insulation and armour | XLPE, SWA or AWA |
| Standard | IEC 60502-1 / IEC 60502-2 or BS 5467 |
| Length and drums | Total metres and preferred drum lengths |