Equipotential bonding
Power busbar
PE protective conductor
Standards
Theory
IEC 61439-1
The PE protective conductor contributes
to bringing all the switchboard conductive
parts to the same potential.
Appendix B
Example
Prisma
Schneider Electric proposes a table for
choosing the PE derived from the formula
provided by the standard:
It must be sufficiently sized and secured
in the switchboard to withstand heat and
electrodynamics stresses generated by a
fault current of a duration of between 0.2 s
and 5 s.
Icw
(kA eff/1 s)
< 40
40 < Icw < 85
IEC 61439-1 standard gives a method
for calculating the cross-section of the
PE conductor:
In addition to the calculation method, type tests are
conducted to ensure the performance of the protective
conductor.
Profil Linergy
Permissible current
630 A
800 A
Flat bar
cross-section
25 x 5 mm
50 x 5 mm
Icw = permissible short-time rated current
SP = √I2t/k
Where:
• SP: is the cross-section of the PE
conductor in mm2
• I: is the effective value of the phase-toearth fault current = 60 % of the phase-tophase fault current
• t: duration of the fault current in seconds
• k: a factor depending on the protective
conductor material.
Example: k = 143 for a PVC-insulated copper
conductor.
2
The cross-section of the PE conductor
must be constant throughout the
switchboard, in particular from one column
to the next.In the case of a switchboard
made up of several columns, all the PE
busbars must be connected to each other
(fish plates, bolts, etc.).
Caution: the cross-section of the
fish plates must be at least equal
to that of the PE conductor.
IEC 61439-1
§ 8.4.3.2.3
52
3
The PE conductor must never include
an insulating device.
version: 5.0
Submittal Page 20
How to assemble an electrical switchboard