Is damage to cable outer sheath/jacket detrimental to inner XLPE insulation?

[shlim]

Hi, I have an installation of 132kV XLPE single core copper conductor, with copper armouring (attached photo). These cables were in trefoil formation, tied/fasten with polymer rope (likely nylon). At some of these ties, the rope had "eaten" into the outer sheath, where I could see the metallic screen but no the armour (attached photo).

I would like to know if this condition would lead to water/moisture ingress into the XLPE layer; as well as whether this condition could be picked up during routine tan delta or PD testing. Thank you.

 

[7anoter4]

In my opinion there could be only a minor damage of the cable. However, I would clean the damaged jacket up to armor in order to examinate how much the armor and the shield penetrated the insulation.

 

[shlim]

Thank you 7anoter4 for your opinion and sketch, I will try to check whether there is any damage to the insulation at those locations.

 

[RRaghunath]

Sheath plays a special role in XLPE cables by keeping the water out of reach.
The phenomenon of Treeing and subsequent damage of XLPE insulation is well known when XLPE comes in contact with water.
Integrity of outersheath after the cable is laid and before energisation needs to be confirmed always to prevent water getting to the cable XLPE.
If found damaged, there are methods to repair the outersheath (cable manufacturer can guide if necessary).

 

[dpc]

At 132 kV, and a new intallation, I wouldn't accept this level of damage. This shows poor workmanship in my opinion. What other damage was inflicted during installation that you can't see? I would consult with cable manufacturer regarding recommended testing. Was cable tested on the reel prior to installation?

 

[7anoter4]

I agree with you RRaghunath. However, the actual moisture barrier it has to be directly applied on insulation and it has to be not damaged, indeed.
There are some heat shrink wraparounds to repair high voltage also.

 

[shlim]

These cables have been operated for at least 30years old. The damage to the sheath was recently discovered. I do not have direct access to the cables or the historical electrical test results hence the difficulty to identify/establish the extent of damage especially to the XLPE insulation, if any.