Copper cable

Cable Diameter Standards
The metric area is the advertised area, equivalent of mm² copper. The actual diameter, when translated from AWG specification may differ.

The ampacity is the sustained current that can be transported through the wire without exceeding its temperature rating. In this case, the Ampacity at 60°C is given. For higher acceptable temperatures (75°C or 90°C), multiply by 1.5. Peak currents may be 10 times larger if they are short enough (< 10 seconds).

Note that the thickness of the cable is determined by the current (amperage), not by the voltage or power. So a lower-voltage installation requires thicker cables than a higher-voltage installation with the same power consumption. The current (in Ampere) can be calculated by dividing the Power (in Watts) by the Voltage of the appliance.

The thickness of the insulation depends on the voltage, and is not mentioned in this table.

Other considerations

 * Core: solid or flexible. A solid core is often used for fixed wiring, and for breadboard wires. Flexible wire contain multiple small strands and is used for flexible cables.
 * Material: copper of CCA (copper cladded aluminium). Copper is considered slightly better. CCA is cheaper and is consider good enough.

Shielding
When shielding is applied to a collection of pairs, it is usually referred to as screening, hence STP (Shielded Twisted Pair) is sometimes abbreviated to ScTP (Screened Twisted Pair).

Power over Ethernet
Note that there are many "Passive PoE" applications. The given 24V is common for Ubiquiti devices that support Passive PoE. Other applications carry up to 1.0 A at 24V, 48V or even 56V.

Example Calculation
The tables allow for calculations of power budget of PoE devices. Imagine an access point powered by 24V passive PoE, using a good Cat 5e cable, which has a 42 mΩ/m resistance. A 15 meter cable has 30 m wire (going forth and back) and has thus 12.6 Ω resistance in total. With a maximum current of 0.5 A (determined from either the PoE table or the Ampacity of AWG22 wire), this translated to a drop in voltage of 0.63 Volt. Thus only 23.37 Volt of the original 24 Volt is left for the access point, translating to maximum of 11.7 Watt (with the 0.5 A).

In general, you will find that there is no problem with short cable of 10 or 20 meter, but you may hit power limitations when using a cable of the maximum length of 100 meter.