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APPENDIX B
Short Circuit Rating
Table B3.1: Short Circuit Ratings for Low Voltage Cables
| Nominal Conductor Area | Short Circuit Rating for 1 second XLPE &XLSZH | Short Circuit Rating for 1 second PVC |
| (mm²) | (kA) | (kA) |
| 1.5 | 0.2145 | 0.1725 |
| 2.5 | 0.3575 | 0.2875 |
| 4 | 0.572 | 0.46 |
| 6 | 0.858 | 0.69 |
| 10 | 1.43 | 1.15 |
| 16 | 2.288 | 1.84 |
| 25 | 3.575 | 2.875 |
| 35 | 5.005 | 4.025 |
| 50 | 7.15 | 5.75 |
| 70 | 10.01 | 8.05 |
| 95 | 13.585 | 10.925 |
| 120 | 17.16 | 13.8 |
| 150 | 21.45 | 17.25 |
| 185 | 26.455 | 21.275 |
| 240 | 34.32 | 27.6 |
| 300 | 42.9 | 34.5 |
| 400 | 57.2 | 41.2 |
| 500 | 71.5 | 51.5 |
| 630 | 90.09 | 64.89 |
| 800 | 114.4 | 82.4 |
| 1000 | 143 | 103 |
The maximum permissible short circuit current of cables up to 1kV with copper conductors could be calculated with the following formula
Where I = Short Circuit Rating (kA)
S = Nominal Conductor Area (mm²)
t = Duration of Short Circuit (Sec)
K = Insulation Material Specific Constant
XLPE & Cross-linked Polyolefin (XLSZH) Insulated Cable
K= 0.143
PVC Insulated Cable
K= 0.115( S ≤300mm2) K= 0.103 ( S > 300mm2)
APPENDIX C
Rating Factor for Ambient Temperature
The current-carrying capacities in this work standard are based upon the following reference ambient temperatures:
i) For non-sheathed and sheathed cables in air, irrespective of the installation method : 30°C
ii) For buried cables, either directly in the soil or in ducts in the ground: 20°C
When the ambient temperature in the intended location of the non-sheathed or sheathed cables differs from the reference ambient temperature, please refer to the appropriate rating factors as below table (Table C1.1 and C1.2).
Table C1.1: Rating factors for ambient air temperatures other than 30°C to be applied to the current-carrying capacities for cables in free air.
| Ambient Temperature °C | PVC | XLPE |
| 25 | 1.03 | 1.02 |
| 30 | 1.00 | 1.00 |
| 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 | 0.50 | 0.71 |
| 65 | – | 0.65 |
| 70 | – | 0.58 |
| 75 | – | 0.50 |
| 80 | – | 0.41 |
| 85 | – | – |
| 90 | – | – |
| 95 | – | – |
Table C1.2: Rating factors for ambient ground temperatures other than 20°C to be applied to the current-carrying capacities for cables buried to ground.
| Ground Temperature °C | PVC | XLPE |
| 10 | 1.10 | 1.07 |
| 15 | 1.05 | 1.04 |
| 20 | 1.00 | 1.00 |
| 25 | 0.95 | 0.96 |
| 30 | 0.89 | 0.93 |
| 35 | 0.84 | 0.89 |
| 40 | 0.77 | 0.85 |
| 45 | 0.71 | 0.80 |
| 50 | 0.63 | 0.76 |
| 55 | 0.55 | 0.71 |
| 60 | 0.45 | 0.65 |
| 65 | – | 0.60 |
| 70 | – | 0.53 |
| 75 | – | 0.46 |
| 80 | – | 0.38 |
