Chapter A General rules of electrical installation design

G10
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G - Sizing and protection of conductors
Item No. Methods of installation Description Reference method of
installation to be used to
obtain current-carrying
capacity
31 0.3 De
On perforated tray E or F
0.3 De
36 Bare or insulated conductors on G
insulators
70 Multi-core cables in conduit or in cable D
ducting in the ground
71 Single-core cable in conduit or in cable D
ducting in the ground
Fig. G10 : Examples of methods of installation (part of table 52-3 of IEC 60364-5-52)
2 Practical method for determining
the smallest allowable crosssectional
area of circuit conductors
Maximum operating temperature:
The current-carrying capacities given in the subsequent tables have been
determined so that the maximum insulation temperature is not exceeded for
sustained periods of time.
For different type of insulation material, the maximum admissible temperature is
given in Figure G11.
Type of insulation Temperature limit °C
Polyvinyl-chloride (PVC) 70 at the conductor
Cross-linked polyethylene (XLPE) and ethylene 90 at the conductor
propylene rubber (EPR)
Mineral (PVC covered or bare exposed to touch) 70 at the sheath
Mineral (bare not exposed to touch and not in 105 at the seath
contact with combustible material)
Fig. G11 : Maximum operating temperatures for types of insulation (table 52-4 of IEC 60364-5-52)
Correction factors:
In order to take environnement or special conditions of installation into account,
correction factors have been introduced.
The cross sectional area of cables is determined using the rated load current I B
divided by different correction factors, k1, k2, ...:
I
I' B
B =
k1⋅k 2 ...
I’ B is the corrected load current, to be compared to the current-carrying capacity of
the considered cable.
Schneider Electric - Electrical installation guide 2008