A customer is insisting that he would like to have HV XLPE cables with orange coloured outer sheath which in turn should have a "transparent" conducting/semiconducting coat over it to carry out sheath integrity test at site.
Can anyone guide me on the material/process for providing "transparent" conducting/semiconducting coating over outer sheath which will be tested at site for 10 kV ?

Hello ngkotecha,

I am aware that, in your country, a thin outer coating of thermoplastic semiconducting polyethylene over the standard black thermoplastic polyethylene jacket or sheath is specified for at least all triple insulated power cables although I do not know the requirement for single insulated power cables. Perhaps it is the same. The two layers are usually applied simultaneously with a dual crosshead and, as you say, the semiconducting layer is there to verify the standard jacket or sheath integrity.

As I'm sure you know, the black color of the semiconducting compounds is a result of a sufficient amount of carbon black being mixed with the virgin (transparent) polyethylene to create the semiconducting properties of the finished compound. (A carrier of charge but not current hence the name semiconducting)

I have never heard of a transparent semiconducting compound and I wonder if your customer could provide you with the details so that you could provide us with this information.

The black color also provides the jacket layers with UV protection.

What your customer could do instead is to request a third layer of orange thermoplastic overall, once the sheath integrity test is performed but we do recommend that this cable be exclusively used either indoors or underground to prevent UV degradation.

Regards
Peter J. Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com
519 641-3212

Hello Peter,

Thank you.

The customer concerned has appreciated the problem and withdrawn this condition.

Thank you for the attention paid to the matter