When cables are installed close together (in trays, ladders, or buried), they mutually heat each other. The more cables in a group, the lower the individual capacity.
Here are the you must check in the standard tables: cable derating factor table as per iec
| | Derating Factor | IEC Reference | | --- | --- | --- | | Ambient temperature (30°C) | 1.00 | IEC 60364-5-52 | | Ambient temperature (40°C) | 0.87 | IEC 60364-5-52 | | Ambient temperature (50°C) | 0.71 | IEC 60364-5-52 | | Ambient temperature (60°C) | 0.50 | IEC 60364-5-52 | | Soil thermal resistivity (1.5 K.m/W) | 0.80 | IEC 60364-5-52 | | Soil thermal resistivity (2.5 K.m/W) | 0.60 | IEC 60364-5-52 | | Cable in air, free from solar radiation | 1.00 | IEC 60364-5-52 | | Cable in air, exposed to solar radiation | 0.90 | IEC 60364-5-52 | | Cable in ground, buried directly | 0.80 | IEC 60364-5-52 | | Cable in ground, in conduit or duct | 0.70 | IEC 60364-5-52 | | Cable grouped with other cables | 0.80 | IEC 60364-5-52 | | Cable in trefoil formation | 0.75 | IEC 60364-5-52 | When cables are installed close together (in trays,
This feature provides a quick and easy reference to cable derating factors as per IEC standards, which can be used to ensure safe and reliable operation of electrical systems. ) is the product of individual coefficients for
) is the product of individual coefficients for specific conditions:
For buried cables, the soil's ability to conduct heat away from the cable is critical. IEC standard tables typically assume a soil thermal resistivity of .