The current ratings given in Tables 2 to 9 are based on normal condition of installation described below: |
| |
|
1 |
Maximum Conductor Temperature |
700 for GP PVC Insulation & 850 C for HR Insulation |
|
2 |
Thermal Resistivity of soil |
1500 C cm/w |
|
3 |
Thermal Resistivity of PVC |
6500 C cm/w |
|
4 |
Ground
Temperature |
300 C |
|
5 |
Ambient air
Temperature |
400 C |
|
6 |
Depth of Laying (for cable laid direct in the ground) |
75 cms |
|
| |
|
Cables shall only be operated at their full rating if the minimum current at which circuit protection is designed to operate does not exceed 1.5 times (in the case of cables in air or in ducts) or 1.3 times (in the case of cables laid direct in the ground) the values tabulated, in table 2 to 9 |
| |
|
Short Circuit Rating in K. amp for One Second duration |
| |
Area of Conductor
Sq. mm |
Aluminum Conductor |
Copper Conductor |
|
GPPVC |
HRPVC |
GPPVC |
HRPVC |
|
1.5 |
0.1126 |
0.097 |
0.169 |
0.153 |
|
2.5 |
0.1878 |
0.162 |
0.283 |
0.255 |
|
4 |
0.3004 |
0.259 |
0.452 |
0.406 |
|
6 |
0.4507 |
0.389 |
0.67 |
0.612 |
|
10 |
0.7512 |
0.648 |
1.132 |
1.020 |
|
16 |
1.200 |
1.087 |
1.810 |
1.632 |
|
25 |
1.870 |
1.620 |
2.830 |
2.550 |
|
35 |
2.620 |
2.270 |
3.960 |
3.570 |
|
50 |
3.750 |
3.243 |
5.660 |
5.100 |
|
70 |
5.250 |
4.540 |
7.920 |
7.140 |
|
95 |
7.13 |
6.150 |
10.750 |
9.690 |
|
120 |
9.00 |
7.784 |
13.580 |
13.340 |
|
150 |
11.260 |
9.730 |
16.980 |
15.300 |
|
185 |
13.890 |
12.000 |
20.940 |
18.870 |
|
240 |
18.020 |
15.560 |
17.160 |
24.480 |
|
300 |
22.530 |
19.460 |
33.960 |
30.600 |
|
400 |
30.040 |
25.940 |
45.280 |
40.800 |
|
500 |
37.560 |
32.43 |
56.600 |
51.000 |
|
630 |
47.320 |
40.860 |
71.310 |
64.250 |
|
| Note. |
| For cables in air, no reduction in current rating is necessary provided that |
| |
 |
The horizontal clearance between circuits is: |
| |
(a) not less than six times the overall diameter of an individual cable, and
(b) not less than the overall width of an individual circuit, except that the horizontal clearance need not in any case exceed 150 mm |
|
The vertical clearance between circuits is not less than
150mm
|
|
If the number of circuits exceeds, they are installed in a horizontal plane.
|
|
|
