Cables are classified by the rated voltages Uo/U.
Uo: The voltage between the conductor and earth or earthed mettalic cover (concentric conductor, screen, armouring, metalsheath).
U: The voltage between two phase conductors.
The standard rated voltages employed ın three-phase systems in compliance with TSE-IEC-VDE and BS are accordingly:
Uo/U = 0,6/1; 3,6/6; 6/10; 8,7/15; 12/20; 18/30; 20,3/35 Kv
In three-phase AC installation systems, the rated voltages:
In single-phase AC systems where both conductors are insulated from earth, or DC systems, the rated voltages:
In single phase AC systems where one conductor is earthed or DC systems, the rated voltages:
In DC systems having a cable with Uo= 0,6 kV, the maximum permissible operating voltage is:
Um= 1,8 Kv
The maximum permissible operating voltages (Um) for single-phase or three-phase AC systems are described in the table on next page.