What is voltage rating?

The voltage rating of a cable is the highest voltage that may be continuously applied to a completed cable construction in compliance with the relevant cable standard or specification (refer to this link if you're not sure what the definition of a volt is). It's the voltage a cable can remain stable in operation up to. 

Voltage rating figures for cables are normally expressed in A.C. RMS. (Alternating Current Root Mean Square) and are written as a figure Uo/U (Um)

Uo = Rated voltage phase to Earth

U = Rated voltage phase to phase

Um = Maximum system

An example voltage rating would be what is often just referred to as 0.6/1kV - it would actually be written as 0.6/1 (1.2)kV, or take an example from a higher voltage cable such as the medium voltage 19/33 (36)kV cable. The section in brackets at the end is the maximum voltage the cable can remain stable and safely operate.

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