Rating of Power Cable
2.Rating of Power Cable
Short Circuit Rating
It happens frequently that the conductor size necessary for an installation is dictated by its ability to carry short-circuit current rather than sustained current. During a short –circuit, there is a sudden inrush of current for a few cycles followed by a steadier flow of current for a short period until the protection switchgear operators, normally between 0.1-0.3 seconds.
Conductor Size and Material Insulation Material Operating Maximum Temperature Short Circuit Rating
120 sq-mm Copper conductor PVC Insulation 70oC 13.80 KA/SEC
120 sq-mm Aluminium conductor PVC Insulation 70oC 9.12 KA/SEC
120 sq-mm Copper conductor PVC Insulation 85oC 12.48 KA/SEC
120 sq-mm Aluminium conductor PVC Insulation 85oC 8.28 KA/SEC
Current Carrying Capacity
Current carrying capacity is an important aspect is the selection of the optimum size of conductor. Voltage drop and short rating is also very important aspect to select the economical and optimum size of conductor. The safe current carrying capacity of an underground cable is determined by the maximum permissible temperature rise. The cause of temperature rise is the losses that occur in a cable which appear as heat.
Continous Current Rating of (Cables laid singly) 2 Core × 16 mm2 2 Core × 25 mm2
(i) In Ground (Ground Temp 30oC) 103 A 131 A
(ii) In Duct (Ground Temp 30oC) 86 A 111 A
(iii) In Air (Ambient AirTemp 40oC) 94 A 125 A
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