Derating Factors for NF C 13-200

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Air Temperature

Derating factor for cables layed in air, at temperature different from 30 oC.

oC Ambient Temperature Derating Factor
PVC PR / EPR
10 1.22 1.15
15 1.17 1.12
20 1.12 1.08
25 1.06 1.04
30 1 1
35 0.94 0.96
40 0.87 0.91
45 0.79 0.87
50 0.71 0.82
55 0.61 0.76
60 0.5 0.71
65 0.65
70 0.58
75 0.5
80 0.41
85
90
95

Soil Temperature

Derating factor for cables layed in ground, at temperature different from 20 oC.

oC Soil Temperature Derating Factor
PVC PR / EPR
10 1.1 1.07
15 1.05 1.04
20 1 1
25 0.95 0.96
30 0.89 0.93
35 0.84 0.89
40 0.77 0.85
45 0.71 0.8
50 0.63 0.76
55 0.55 0.71
60 0.45 0.65
65 0.6
70 0.53
75 0.46
80 0.38

Soil Thermal Resistivity

Soil Thermal Resistivity (K·m/W) Soil Thermal Resistivity Derating Factor
3 Single-core cables 1 Multi-core cable
0.5 1.25 1.2
0.7 1.14 1.1
0.85 1.06 1.05
1 1 1
1.2 0.93 0.95
1.5 0.85 0.88
2 0.75 0.79
2.5 0.68 0.72
3 0.62 0.68

Depth of laying for underground cables

Depth (m) Coefficient
0.5 1.04
0.6 1.02
0.8 1
1 0.97
1.25 0.95
1.5 0.93
1.75 0.91
2 0.9

Derating factor due to solar radiation

Valid for cables layed in air, exposed to direct sun rayes. If exposed, derating factor is 0.85, otherwise 1.

Grouping derating factor for cables layed in air

Grouping derating factor for cables layed in ground

Single- or multi-core cables laid directly into soil:

No. of Cables
Clearance between cables
touching 0.25 m 0.5 m 1 m
2 0,76 0,84 0,88 0,92
3 0,64 0,74 0,79 0,85
4 0,57 0,69 0,75 0,82
5 0,52 0,65 0,71 0,8
6 0,48 0,6 0,69 0,78
7 0,44 0,58 0,68 0,76
8 0,41 0,57 0,67 0,76
9 0,39 0,55 0,66 0,76
10 0,37 0,54 0,66 0,76
11 0,36 0,53 0,66 0,76
12 0,35 0,52 0,66 0,76

Single-core cables laid in ducts in soil or concrete:

Number of layers:
Number of ducts per layer
1 2 3 4 5 6
1 0,8 0,7 0,62 0,58 0,54 0,52
2 0,7 0,57 0,5 0,46 0,42 0,4
3 0,62 0,5 0,42 0,38 0,36 0,34
4 0,58 0,46 0,38 0,35 0,32 0,3
5 0,54 0,42 0,36 0,32 0,3 0,28
6 0,52 0,4 0,34 0,3 0,28 0,26

Single- and multi-core cables laid in ducts:

No. of Cables
Clearance between cables
0.25 m 0.5 m 1 m
2 0,74 0,76 0,78
3 0,7 0,73 0,76
4 0,67 0,71 0,75
5 0,65 0,7 0,74
6 0,63 0,69 0,73


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