Water blocking conductors

[ItAintMe]

Anyone have any comments on water blocking conductors on HV cables? In particular, does using non conducting vs semi conducting tapes make any difference? We're looking for cables that we can joint or terminate without the need to open strands and pull out the tapes first.

thanks

 

[dpc]

If you are talking about strand fill, we do generally recommend it for UG circuits. The cost adder is not that great.

David Castor

http://www.cvoes.com

 

[alehman]

Not sure about the tape question. Can you elaborate?

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[ItAintMe]

I'm talking about using powder filled tapes or yarns to fill the gaps between strands - I think strand fill is an example of the technology. Geca tapes is another company that supplies the water blocking products.

I discussed this with cable accessory suppliers prior to writing the spec and they all said there were no problems with their accessories on blocked conductor. The concerns I had were
1) years ago, it was necessary to open out the strands and clean out all the blocking compound then reset the strands in order to make a joint. It was a nightmare. I've been assured this is no longer necessary, as the tapes are designed to disintegrate as the joint is compressed/bolted so there is still strand to strand continuity
2) whether these tapes etc, if left in the conductor, might reduce the current rating of the joint and hence the circuit.

As I say, we were assured by accessory makers it was no longer a problem. However, during recent tender evaluations for a turnkey project, on supplier said it was necessary to open out the strands! Checking details of the cable they supply, I noticed that they mention using non conductive tapes, while others talk about semi conducting tapes. I was wondering if their use of non conducting tapes might cause the 2 problems above, and be the reason they require strands to be opened out. The supplier in question seems to be fairly conservative in their designs, so maybe it's partly that too?

Any advice appreciated.

Thanks
Keith

 

[dpc]

I've never heard of any issues with terminations or other accessory equipment with strand-filled cables.

The only issue I am aware of is that the cable cure injection process into old UG cables cannot be done if the cable has conductor fill material.



David Castor

http://www.cvoes.com

 

[ItAintMe]

Ah - Strand Fill is that process for protecting aged XLPE cables by filling the strands with silicon oil - right? I'm not talking about that. This is where you buy new cables with polyethylene tapes or yarns impregnated with swellable powders, wrapped around each layer of conductors. It's another application of water swellable tapes - in addition to laying them up with your screen/neutral wires, you fill the strands of the conductor, so the water can't get into the cable in the first place - a pre-emptive sort of strand fill I guess.

 

[dpc]

No, sorry - a terminology issue I guess. Cable injection (cable cure) is done to older cables.

What I was talking about was the addition of material to fill the interstices between the conductors when the cable is manufactured. Okonite calls it "Filled Strand". So it not the same as the injection of of cable cure compound into older cables. But if the cable originally was made with the filled strand, it is not possible inject the cable cure compound in the future.


David Castor

http://www.cvoes.com