MV Power cables armor 1

[safy2004]

Hi! Every body
We want to use power cable 33 kV, XLPE,single core 1x400 mm2 to feed one substation outside the city, its long is about 6 kM, this cable will be buried under ground, it will be direct laid, blinded with cable laying sand 750mm.
My question is there any relation between the armor and the way in which we lay the cable, in above case can we use armored cable?
All the standards that I have seen saying it is possible, but one engineer have different opinion, and he said armored cables can be used in ducts and trenches but it can not be used in direct laid, blinded with cable lying sand… is that true?
Another question: If it is possible to use armored cable in our above case (buried with sand) are there any limitations in kind of formation (Flat formation - Trefoil formation)
Thx in advanced
Regards,
Safy

 

[rbulsara]

Ask the manufacturer. Usually it is clearly indicated on the data sheet, whether or not they are suitable for direct burial.

It pays to ask the question to the source who has the authentic answer.

Rafiq Bulsara

http://www.srengineersct.com

 

[Bilegan]

safy2004

All armoured cables are suitable for direct buried installations, and there are no relations of the armour on how the cable is laid (i.e. trefoil or flat formation).

Check the depth, a depth of 750mm for 33kV seems to be a violation against ANSI/NEC or IEC requirement.

The limitation on how to apply the trefoil or flat formation of the cable installation is the effect on the ampacity of the cable.

Trefoil formation will give you less cable ampacity against flat formation.

Regards,
Bilegan

Murphy's Law - If anything can go wrong..it will.

 

[safy2004]

Thanks Bilegan
But you have mentioned this phrase: "All armoured cables are suitable for direct buried installations" Is it mentioned in the standards, or it's just a conclusion?
Regards
Safy

 

[Bilegan]

For a medium voltage cable, Type MV, NEC Art. 328.10.4 uses permitted cable to be direct buried in accordance with column 1 of NEC Art. 300.50.

For a 33 kV, XLPE, 1x400mm2, single core with aluminum wire armour applied helically over an extruded PVC outer sheath is suitable for the above mentioned application.

Regards,
Bilegan

Murphy's Law - If anything can go wrong..it will.