Cable capacity to carry currently is dependent on many factors:
- The conductor type used in the cable manufacturing
- How much resistance is offered by the insulation
- Power losses in the form of heat dissipation and place of installation
Cables are designed according to their place of installation. Cable capacity sometimes designed to be less and sometimes designed to be higher depending upon the application in which it is used. No, doubt that the conductor type and the insulating material used in the cable manufacturing set a certain limit to its specifications. But mainly the Cable capacity is majorly affected by the place of installation in the surrounding i-e heat, moisture, water and cold temperature. If the cable is placed inside a duct, then certainly it possesses higher environmental protection but less current capacity.
Heat invokes high temperature among the atoms of the conductor. At high temperature, the conductor starts to offer high resistance due to which current capacity of the cable starts to decrease. Theoretically, Heat losses among the conductor is it means heat is the product of resistance and square of current passing through the conductor. So, the heat affects both the current rate at which the signal is being transmitted and also increases the resistance to the flow of current. The heat is dissipated in the surroundings and higher the heat is higher the resistance that is offered to the current.
Similarly, in the case of underground cables, there are other factors which are also taken into consideration for the cable capacity. The depth of the cable installation, the deeper the place of installation of the cable lower is the current carrying capacity. The Thermal resistivity of the soil also matters, the higher the thermal resistivity the lower is the current capacity. If the heat dissipation in the cable could not be released in the surrounding properly then it should not only affect the cable capacity but also affect the physicality of the cable.