The Cable requirement calculations were carried out based on the Latest Feeder/ Load list furnished by LNVT
2
Length of cables are tentively considered as per the Layout
3
Derating factor considered for the cable Net Derating factor = Derating factor due to change in Amb.Temp (50oC) x Derating factor for method of cable laying Net Derating factor = 0.82 x 0.76 = 0.623
4
Min. cross section required for Cable to withstand short circuit withstand capacity of the system = Where,
5
K Ik t -
Material Constant of the Conductor with insulation (=143 for Cu.XLPE cable) Short circuit withstand capcity of the system Duration of Short circuit withstand capacity of the system
=
√(
(Icont2 x Tcont) + (Imax2 x Tmax) Tcont + Tmax
-
Continous current that flows through the cable Duration of flow of continous current in the scale of 600sec Maximum current that flows through the cable Duration of flow of maximum current in the scale of 600sec
Current (IRMS) calculation is given by IRMS Where,
6
Icont Tcont Imax Tmax
)
Steady state voltage drop for the cable connecting the Loads from MCC is given
3x I x L x (RcosF + XsinF) x 100 n x V x 1000
Percentage voltage drop =
Where,
L R X
Cos F Sin F I
n V 7
Ik t K
-
Cable length (estimated) Max. in meter Conductor resistance /Km per run Conductor Reactance /Km per run Power factor of the system
1-cos2F Full load current No of runs of cable System Voltage
Maximum Length of Cable upto which the voltage drop is less than the specified value (i.e 3%) is given by
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