The following limitations apply:
Green/yellow cores shall be used only as protective conductors and shall not
be converted e.g. by sleeving for use as neutral or line/phase conductors.
Blue cores shall be used only as neutral conductors and shall not be converted
e.g. by sleeving for use as protective conductors or line/phase conductors.
Brown, black or grey cores shall be used only as line/ phase conductors, and
shall not be converted e.g. by sleeving for use either
as protective conductors or as neutral conductors.
Where more than one conductor in a multi-core cable is fed from the same phase,
both shall be identified by the relevant phase colour, using sleeving as needed.
For single-core cables used for three-phase circuits, the core colours shall
be the same as for multi-core cables.
Where single-core cables are used to supply single-phase circuits fed from a
three-phase distribution board, the respective line/phase conductor colour may
be extended to the single-phase circuits fed from that phase.
Sleeving or tape used for identification purposes shall be permanent, heat resistant,
colour-fast, non-conductive, and shall comply with EN 60454 or other appropriate
standard.
Four-core cable without a blue core e.g. NYM-J shall be used only for circuits
with balanced three-phase loads e.g. three-phase motors.