R & D

R & D

Wire Drawing and Conductor

This is the most important and expensive process in the manufacture of Power Cables.

The conductor is the heart of the cable.

The entire flow of electricity is through the conductor and hence the more precise and better the conductor compaction – lower the conductor resistance.

If the compaction is improper it can lead to air gaps between the wires. These air gaps increase the resistance and result in transmission losses which may also lead to enhanced heating of the cable, again leading to further losses.

In order to reduce these Air Gaps and have a smooth and even finish, an appropriate number of strands must be used.

Now let us see how these numbers of strands can affect the shape of the conductor.

A properly designed conductor is smooth and compact. And an improperly designed conductor is sharp, has ridges and increases the resistance to flow of electricity.

A badly designed / compacted conductor could cost the user from 3-9% higher transmission losses. Also due to its sharp edges and uneven ridges the chances of failure increase considerably.

On the other hand if conductors are well compacted the connectivity increases, resulting in huge power savings over the years.

We have drawn a comparison chart for the number of strands used by us vis-à-vis various other manufacturers

Size in Sq. mm	Min no. of strands in a compact conductor				As per BIS standards. (Min no. of strands)
	Primecab	S-1	S-2	S-3	As per BIS standards. (Min no. of strands)
70	19	15	12	15	12
240	37	36	30	37	30
400	61	58	53	58	53

We can explain with the help of plain engineering the reason for why 19 strands are ideal for 70 sq. mm. conductor.

Let us consider a single strand with diameter (d) – 2.24mm

The pitch circular diameter for the first layer (d’) would thus be two times d.

d’=2x2.24 mm = 4.48 mm
And d’x4.14/d = 4.48x3.14/2.24=6

Thus the no. of strands accommodated in the first layer = 6

Similarly, the pitch circular diameter for the second layer (d’) will be four times d.

d” = 4x2.24 mm = 8.96 mm

And d” x 3.14/d = 8.96 x 3.14/2.24=12

Thus the number of strands in the second layer =12

Hence it is derived that 19[1+6+12] strands are perfectly suitable to form a uniform circle and thus a closely compacted conductor. This conductor, when shaped would have a smooth surface and thus the dielectric or insulation would be of uniform thickness.

If the thickness and eccentricity of the cable insulation is not uniform it avoids increases in charging current and lessens the voltage drop.

Also if this dielectric is not uniform, it leads to increase in the capacitance of the conductor and resultant higher temperature.

Hence, not just in terms of proper compaction and conductor resistance, but even in terms of electrical losses, an appropriate number of strands in the conductor are very essential.

Accordingly the ideal no. of strands are :

Hence users should insist on an ideal number of strands as per the table below. This does not increase raw material costs, but helps the user save in terms of transmission losses, year upon year.

1.5 to 10 sq mm [CU]	–	7 strands
6 to 10 sq mm [AL]	–	1 strands
16 to 50 sq mm [CU/AL]	–	7 strands
70 to 150 sq mm [CU/AL]	–	19 strands
185 to 300 sq mm [CU/AL]	–	37 strands
400 to 630 sq mm [CU/AL]	–	61 strands
800 to 1000 sq mm [CU/AL]	–	91 strands