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kVA X0.8 PF =Kw =W
P=RT3 V I COS fi
SO, I = P / RT3 x V x COSfi
I = /1.xx0.8= A
Now take cable table and select the suitable xlpe cable.
Cable sizing is done based on three parameters:
Step 1:
Calculate the load current from the load data available. Formula is,
I=Load (in kW)/(sqrt(3)*V(in kV)*p.f) (A)
The current obtained has to derated since the cable is designed to operate at a defined temperature. Derating factors will be available in cable catalog.
Get the cable size corresponding to this derated current from the catalog.
Step 2:
Next, find the cable size for the short circuit capacity of the system. Formula used is,
Cable size= (Fault current(in kA)*Fault clearing time)/K
where, K-constant depending on the conductor and insulation used. K=90 (for Al cables), K=140 (for Cu cables)
Choose the cable size whichever is greater in step 1 or step 2.
Step 3:
Check for voltage drop with the cable size chosen.
If the cable is connected to a HT motor load, then the voltage drop from transformer to motor should not exceed 5%.
Also, if it is a motor load, the voltage drop for motor starting has to be checked. It has to be less than 15%.