Following are the standard condition for rating of LT PVC cable:
(i)Maximum conductor temperature – 70°
(ii)Thermal resistivity of soil 150°cm/w.
(iii)Ground temperature – 30°C.
(iv)Ambient air temperature -40°C in the vicinity of cable.
(v)Depth of laying = 75 cm for LT cable.
1.The cable derating factor is the reduction from its present capacity for a certain gradual amount due to intermittent ambient temperature, insufficient space, unbalance flux, higher voltage dropped, depreciation to
2.To minimize the cause and effect conduction of proper survey and proper mining to with land on the cable loads and locations is needed.
3.Derating factor depends on ambient temperature how the cable is layed in air, duct, buried.
4.Normally the current carrying capacity of a particular cable is calculated at 40°C but if cable is layed in air then it includes the temperatures around it, if it increases more than 40°C then the conductor gets heated up by increasing the resistance in it thus the current carrying capacity of a given cable decreases, so we will derate the cable.
