Cable size

<....(suppose 180 sq mm 3.5 core) what does the size represent, size of sinle core or overall size of cabel (all core plus insulation)?...>

The "180sq.mm" in the above description is the cross-section area [CSA] of one of the conductors. The "3.5" suggests that one of the conductors is smaller than the other three, and this particular one would be selected as the neutral conductor in a 3-phase circuit.

<....if the current carried by a 3.5 core cable is 100 A, whether it is the current carried by each core or the overall current carried by all cores?....>

It depends upon how the circuit is wired. In an everyday 3Ø supply situation, which is what this particular cable is intended for, the current that passes down one conductor comes back along the others.

The neutral is smaller because it only needs to carry:

• the imbalance current between the other three phase conductors, or
• a fault current for a very short period of time before the circuit protective device operates

so its CSA can be smaller without the risk of damaging the cable. At these sort of CSAs, the cable is going to have a lot of copper in it, which has a high value, and is going to be quite stiff, making it more difficult to bend round things during installation. Anything that can be done to reduce these difficulties safely is therefore worth considering.

Dear Friend,

in each cable 100A ( i.e. 3 core cable having three wire with each phase 100A)

Regards

BVR

3.5 means 3 1/2 the half being size of neutral conductor. You can refer to my article on this - CABLE SIZES - at this location: http://docs.google.com/?hl=en&tab=wo&pli=1 questions? reach me on maintenance@maintenancecircle.com

it should be the overall surface area of the copper

of course not incl the insulator, visit some cable manufacturer website and download their catalog, u will have a better picture. :)