Answer Posted / mahesh sali

See , the formula for derated current is nothing bu derated
factor .
Mostly derated factor depends upon the following points.

Way of cable laying i.e. on cable trays / duct / pipe etc(
open to air or into the Hume pipe or under ground )

Cable laying by grouping & having distance between two
cable as per individual manufacturer recommandation .

Each manufacture gives the deration factor for the above
stated point.

Deration means your cable carry the less current below your
rated capacity due the above reason.

take example.

suppose
1.5 sq.mm. cu carrying the current around 12 amp.in open to
air at 25 deg.c ref. temp. as per cable manufacturer

after considering the above stated point

if suppose my deration factor would be around 0.6
then deration current of above cable would be - 12 *
0.6=7.2amp
it means that your cable carry the less cuurent do the way
of laying , temp. cable grouping etc.

i hope above inf. sufficient for understanding

thanks

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