Chapter A General rules of electrical installation design

G - Sizing and protection of conductors
6 Protective earthing conductor
(PE)
6.4 Equipotential conductor
The main equipotential conductor
This conductor must, in general, have a c.s.a. at least equal to half of that of the
largest PE conductor, but in no case need exceed 25 mm 2 (copper) or 35 mm 2
(aluminium) while its minimum c.s.a. is 6 mm 2 (copper) or 10 mm 2 (aluminium).
Supplementary equipotential conductor
This conductor allows an exposed conductive part which is remote from the nearest
main equipotential conductor (PE conductor) to be connected to a local protective
conductor. Its c.s.a. must be at least half of that of the protective conductor to which
it is connected.
If it connects two exposed conductive parts (M1 and M2 in Figure G62) its c.s.a.
must be at least equal to that of the smaller of the two PE conductors (for M1 and
M2). Equipotential conductors which are not incorporated in a cable, should be
protected mechanically by conduits, ducting, etc. wherever possible.
Other important uses for supplementary equipotential conductors concern the
reduction of the earth-fault loop impedance, particulary for indirect-contact protection
schemes in TN- or IT-earthed installations, and in special locations with increased
electrical risk (refer to IEC 60364-4-41).
Between two exposed conductive parts
if SPE1 y SPE2
then SLS = SPE1
M1
SPE1 SPE2
SPE1
M2
Fig. G62 : Supplementary equipotential conductors
Schneider Electric - Electrical installation guide 2008
Between an exposed conductive part
and a metallic structure
SLS =
SPE
SLS SLS
2
M1
Metal structures
(conduits, girders…)
G41
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