Dimensions of protective coverings

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Table A.1 Fictitious diameter of conductor

Cross-section (mm2) dL (mm)
1 0
1,5 1,4
2,5 1,8
4 2,3
6 2,8
10 3,6
16 4,5
25 5,6
35 6,7
50 8
70 9,4
95 11
120 12,4
150 13,8
185 15,3
240 17,5
300 19,5
400 22,6
500 25,2
630 28,3
800 31,9
1000 35,7
1200 39,1
1400 42,2
1600 45,1

The fictitious diameter Dc of any core is given by:

[math] D_{c} = d_{L} + 2t_{i} \,[/math]

where ti is the nominal thickness of insulation, in millimetres (see Tables 5 to 7).

The fictitious diameter over laid-up cores (Df) is given by:

  • a) for cables having all conductors of the same nominal cross-sectional area:
[math] D_{f} = kD \, [/math]

where the assembly coefficient k is as given in Table A.2.

  • b) for four-core cables with one conductor with reduced cross-section:
[math] D_{f} = \frac{2,42(3D_{c1} + D_{c2})}{4} \, [/math]

where:
Dc1 is the fictitious diameter of the insulated phase conductor, including metallic layer, if any, in millimetres;
Dc2 is the fictitious diameter of the conductor with reduced cross-section including the insulation or covering, if any, in millimetres.

Table A.2 Assembly coefficient k for laid-up cores

Cross-section (mm2) k
2 2
3 2,16
4 2,42
5 2,7
6 3
7 3,35
8 3,66
9 4
10 4
11 4
12 4,16
13 4,41
14 4,41
15 4,7
16 4,7
17 5
18 5
19 5
20 5,33
21 5,33
22 5,67
23 5,67
24 6
25 6
26 6
27 6,15
etc.. etc..