As we know that Resistance of conductor is calculated by
where row=specific resistance of the conductor i.e
aluminium and copper(depends of material)
l=length of the conductor
a=area of cross-section of the conductor.
And as we know that the conductivity of the aluminium
conductor is <=1 (depends upon the distance of the cable
laid avg.0.8-1) and conductivity of copper is <=1.5
(depends on cable laid. avg. 1.2-1.5).
for ex.take cable length of 180 sq.mm Al. cable
if we want to know the current carryng capacity is
180*o.9=168 A approx.
Use of formula is always a cumbersome exercise.
In pactical 1.5A/sqmm for al,cable & 2.5A/sq.mm is
considered in practical way. means a 50sqmm Al cable will
carry at least 75A and same size copper cable will carry
Check the CCC by any supplier's brochure.
Derate the CCC on the following parameters
Maximum Ambient temp.
Cable buried UG / on air
Clearance between adjuscent cables.
185 mm2 4 c Alu XLPE cable's ccc = 200 Amps in the Gulf.
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