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Designing thePENconductor
Power circuit
Additional information
Electrical characteristics
Size of PEN protective conductor
Practical guidelines
The size of the PEN is determined in the same manner as a neutral conductor, i.e.:
b
b
for copper single-phase circuits or sized y 16mm², it must be the same size as
the phase conductors
b
b
for copper three-phase circuits sized > 16 mm², it can be:
v
v
the same size as the phase conductors
v
v
smaller on the condition that:
-- the current likely to flow in the neutral during normal operation is less than the
permissible current for the conductor
-- the power rating of single-phase loads does not exceed 10 % of the total rating.
The conductor must be accessible to enable connections both in the factory and
on site, as well as checks on the tightness of connections.
Implementing the PEN protective conductor
Practical guidelines
According to standard IEC 61439-1 and 2, the practical guidelines for implementing
the PEN are the following:
b
b
at the entry to the assembly, the PEN connection must be next to the phase
connections
b
b
within the assembly, the PEN does not need to be insulated from the exposed
conductive parts (except on sites where there is a risk of fire or explosion)
b
b
the size of the conductor must be at least equal to that of the neutral
b
b
the size must remain constant throughout the main busbars
b
b
the change from a TNC to a TNS system must take place at a single point in the
switchboard, via a marked neutral-disconnection bar that is accessible and can be
dismantled to facilitate the impedance measurement of the fault loop
b
b
after the TNS creation point, it is forbidden to recreate a TNC system.
The PE and the neutral must meet their specific requirements.