What are cable ratings?

Cable ratings determine the parameters within which a cable can be safely used. The most typical cable ratings are temperature, voltage and current.

Temperature rating is usually defined as one of the following:
- Max conductor temperature rating
- Minimum installation temperature rating  
- Minimum flexible temperature rating.

Voltage is usually defined in terms of the following:
Uo = The R.M.S value between any insulated conductor and the earth or metal covering.
U = The R.M.S value between any phase conductor and another phase conductor or system of single insulated conductors.
(Um) = Maximum system voltage

The current rating is usually defined in terms of:
- Normal maximum continuous current rating
- Short circuit current rating

Cables may also be de-rated depending on the method of installation, for example, a cable installed in a thermally insulated wall will have a lower current rating than a cable of the same size and type which is installed in free air or in an open cable tray.

Cables installed in the ground at a higher than normal ambient temperature will have a lower current rating.


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