Calculation of Electrical Cable size

Will u please give the formula, for selection of cable sizing (both Copper and Aluminium) depend upon the electrical loads...

Questions by Prabakaran Balaraman

Showing Answers 1 - 12 of 12 Answers

the determination of cable size in done on cost basis. The most economical area of conductors that for which the total annual cost of transmission line is minimum. This ia also known as Kelvin's Law.

According to it the most economical size comes when
  variable part of annual charge= Annual cost of energy

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Susanta ku.dwivedi

  • Aug 16th, 2011
 

First we calculate the amp rating of the equipment.for cu we take 2.5A & for alu we take 1.5 to 1.7A for 1sqmm cable.

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It depends on a lot of factors like current density for mm^2 temperature is the cable on cable trays or buried or inclosed in PVC is that a 3 phase cable multicore or what and also depends on the voltage but in general making a current density 2 A/mm^2 for copper for simple applications is good.

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ENGR.MUHAMMAD YOUNAS KHAN

  • Mar 24th, 2014
 

CABLE SIZING FORMULA:-2 *L * I/(K*Vd) ...............FOR SINGLE PHASE
LEGEND:-
I :- LOAD CURRENT =160 AMPS
L :- LENGTH OF THE CABLE = 200 METERS
K :- CONDUCTIVITY OF COPPER = 58 AND CONDUCTIVITY OF ALUMINUM =36
Vd:- VOLTAGE DROP 3% OF 230 VOLTS=6.9 VOLT AND FOR 3PH. 3% OF 400VOLT=12 VOLTS
APPLY THE FORMULA:-
AREA(mm2) = 2 * L * I/(K * Vd) = 2 *200*160/(58*6.9) = 159.92 mm2 required(FOR SINGLE PHASE)
AREA(mm2) = 1.732*L*I/(K*Vd) =1.732*200*160/(58*12) =79.6 mm2 required(FOR THREE PHASE)

DEAR FRIENDS.
CALCULATE THE SIZE OF CABLE BY ABOVE SAID FORMULA AND ENJOY YOURSELF.

ENGR.MUHAMMAD YOUNAS KHAN
M.SC.ENGG.,MIEE(UK)
WAZIRABAD CITY,PUNJAB,PAKISTAN

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