Separation tape over Cu conductor

It is commonly seen that separation tapes (PETP or dry Paper) are applied over conductor (Cu or Tinned Cu) in Rubber Insulated cables. Kindly anyone suggest the exact reason for this application of tape? Is it to avoid material sticking on conductor or reaction between layers or to avoid material flowing inside the strands??? If it is sticking or reaction, whether it is only applicable for certain rubber material such as sulfur cured or is it for all types of rubber? Does this tape required for tin coated conductor as well??? Having said this, I have seen some rubber cables even without tape..

Hello Again,

Sorry for not answering sooner but I did not notice your query until today.

As you surmised, there a few reasons reasons for the helically applied semi-conducting separator tape to be present.

- Large conductors are not necessarily perfectly round so the separator tape rounds out the outer surface of the conductor, thereby saving material from flowing in to gaps in the conductor. This is generally referred to as "Fall-In" and wastes costly extruded dielectric material.

- Because the conductor is now round by virtue of the semi-conducting tape, the inner surface of the semi-conducting inner shield is more uniform and smooth resulting in lower electrical stress at that interface.

- The use of sulfur in the rubber certainly can create corrosion of the surface of the copper conductor but tinned copper wires will not have that problem. It is however an expensive fix unless there are other corrosive issues that must be addressed

- I am not sure about bare conductors sticking to rubber insulation.

In all, it is just good practice to have a semi-conducting tape over the conductor as a separator in rubber power cables and other large conductor XLPE insulated power cables..