Insulation of Parallel Strands instead of Bunched

We make Building Cables and follow Class 2 construction of conductor (Stranded) with bunching the 14 strands of individual diameter 0.3mm for 1 Sqmm Cable.

We have seen some cables with straightly laid conductor, strands are straight without bunching , may be the lay is infinite or S Z which is not evident immediately.

Can you provide some idea whether this will have a reduction of copper content for the same passing Conductor Resistance value vis-a –vis a bunched conductor.

Dear Mr. Anbunathan,

Generally speaking, wire is bunched to provide flexibility so strands do not break when the cable is threaded through the house during construction. This could create hot spots by higher resistance where the strands are broken and a fire could ensue. Every country has specifications as to the way the the building cable is manufactured and cable manufacturing companies cannot go outside of these specifications.

Electricity follows each of the individual strands so the shorter the pitch of the bunch, the higher the weight of the conductor and the higher the resistance.

To calculate the weight of metal, look at the bunch and measure the length of the strand as the strand rotates 180 degrees and measure the angle of the strand. This is the hypotenuse of a right angle triangle so the longitudinal weight of the conductor can be easily calculated when you measure the mean diameter of the conductor (Conductor less one diameter of the strand.). This longitudinal weight will always be less than the helical weight whether it be S-Z or 360 degree bunch rotation..

The lightest longitudinal weight would be that of a solid conductor.

The whole idea of a stranded conductor is to use the longest allowable strand pitch and the nominal conductor resistance. This will give you the minimum conductor weight that the specification allows.

Dear Mr Peter

Thank you very much.

Regards
Reuben